US20210316334A1 - Method and system for generating mechanical pulses - Google Patents

Abstract

A method for generating a mechanical wave, including generating a high amplitude mechanical pulse; coupling the mechanical pulse in a proximal end of a transmission member; propagating the mechanical pulse into the transmission member from the proximal end and a distal end thereof; and transmitting the mechanical pulse at the distal end.

Description

TECHNICAL FIELD
• The present invention relates to the field of methods and systems for generating mechanical pulses.
BACKGROUND
• Cardiovascular disease remains a leading cause of death worldwide. Atherosclerosis consists of plaque accumulation along the inner wall of arteries. Chronic total occlusion (CTO) represents the complete blockage of a blood vessel. These occlusions are difficult to recanalize using traditional percutaneous transluminal angioplasty (PTA) techniques and apparatus. Procedural success is defined as the ability to pass a standard PTA device across the CTO. PTA procedural shortcomings and complications are usually higher for CTOs. The presence of calcifications and fibrotic tissues within CTO lesions together with the vessel size and tortuosity may be the cause of the potential complications. Therefore, a significant amount of CTOs are treated using an invasive bypass surgery. However, there are benefits of crossing CTOs using PTA procedures. Moreover, some experts believe that new devices and technologies in the field of PTA may improve the success rate and reduce the procedure time for CTO interventions.
• Over the years, various apparatus and methods have been developed and proposed to achieve CTO recanalization through minimally invasive procedure. For example, devices have used a mechanical impactor with or without the use of a transmission member, a narrowband ultrasonic source with a transmission wire, and various other methods of energy deposition near the CTO lesion.
• For procedures performed using a mechanical impactor, a projectile is accelerated and impacts a proximal end of a transmission member or a distal cap that is in direct contact with the occlusion. The projectile can be accelerated using a pneumatic source, a solenoid, a mechanical spring or other means. The mass of the projectile and its speed at impact produce high stresses at the impact surface and therefore require commensurate maintenance. Also, this method may offer very limited control over the parameters of the mechanical pulse that is generated. Moreover, such devices may be noisy.
• Another prior art example consists in a system comprising an ultrasonic wire excited at resonance with a horn and a stacked transducer. This constitutes a first example associated with the use of a narrowband source. This arrangement is used to amplify the displacement at the distal end of the device in contact with the occlusion. The ultrasonic wire is usually used inside a dedicated catheter with cooling fluid circulation. By doing so, the device becomes bulkier and thus is limited in its ability to reach CTOs in small and tortuous anatomy. Considerable loss (due to signal distortion and nonlinearity) and/or mode conversion (from axial to transverse) may also occur at a bend when the device is activated. The frequency of operation (typically around 20 kHz) may create large stress, strain and heat conversion at the ultrasonic wire junction with the horn and within the ultrasonic wire itself. This may contribute to weaken the ultrasonic wire resulting in higher risk of failure.
• A second example of a narrowband source is associated with the use of multiple resonant elements distributed in a phased array manner to generate and transmit ultrasonic energy along a transmission line. For example, all resonant elements transmit ultrasonic energy perpendicular to the axis of the waveguide (i.e. radial waves). As a result, most of the energy may be trapped inside the proximal end member, thus making the device inefficient. In another example, shear waves resonant elements are used to induce longitudinal propagating waves inside the waveguide wire (i.e. axial waves). The bond joint between these shear wave resonant elements and the waveguide may be an issue, as the bonding medium (e.g. epoxy) may fail rapidly and/or may add significant attenuation due to bonding material absorption. Therefore, such apparatuses may be limited in terms of power and robustness.
• Other prior art forms of energy deposition can be used near the CTO lesion. For example, electromechanical transducer(s) can be used at or near the distal end of a catheter to produce mechanical waves near the occlusion. Such a method may be limited in terms of the power that can be generated considering its miniature size. Moreover, the fabrication of this transducer may be complex and expensive especially considering that the device must be discarded after utilization to prevent contamination. Also, electrical wires are needed to drive the transducer(s) which can leak current inside the body and impact normal heart rhythm.
• Laser energy may be used with optical fibers to effectively deliver pulses of high intensity light at the occlusion lesion. However, the inherent fragility of optical fibers makes them prone to break, especially when used in tortuous anatomy. Moreover, this form of energy may be difficult to control and thus be unsafe to nearby healthy tissues; this also necessitates costly laser sources.
• Radiofrequency (RF) energy is another prior art source of energy that can be delivered at the occlusion site using electrodes and high voltage (i.e. 1 kV or higher). However, RF energy may be limited in terms of control capability and may tend to create large heat deposition resulting in damage to nearby healthy tissues. Electrical spark discharge can also be used to generate Shockwaves near the occlusion, which requires even higher voltages (i.e. greater than 2 kV). For certain designs, erosion and mechanical wear of the electrodes may represent safety and reliability issues. Furthermore, for safety issues, devices using electrical discharges in the heart need to be synchronized with the patient's heart rhythm, which must thus be predictable and constant.
• Chemical detonations can also be used to accelerate a distal hard mass causing it to impact a nearby occlusion. Chemical reactions may be difficult to control and contain, especially in in-vivo environments. Toxic and potentially hazardous products can also be associated with detonations and explosions.
• Therefore, it appears that impactors, narrowband energy sources and other prior art methods of energy deposition near vascular occlusions all present drawbacks.
• Therefore, there is a need for an improved method and system for generating mechanical waves to treat occlusions for example.
SUMMARY
• In accordance with a first broad aspect, there is provided a method for generating a mechanical wave, comprising: generating at least one high amplitude mechanical pulse; coupling the at least one mechanical pulse into a proximal end of a transmission member; propagating the at least one mechanical pulse into the transmission member from the proximal end to a distal end thereof; and transmitting the at least one mechanical pulse at the distal end of the transmission member.
• In one embodiment, the step of generating comprises generating a plurality of mechanical waves having a first amplitude and combining the mechanical waves, thereby obtaining at least one high amplitude mechanical pulse each having a second amplitude greater than the first amplitude.
• In one embodiment, the step of combining comprises focusing the mechanical waves on a focus zone.
• In one embodiment, the step of focusing comprising reflecting the mechanical waves on a parabolic surface.
• In another embodiment, the step of combining comprising propagating the mechanical waves into a temporal concentrator.
• In a further embodiment, the step of combining comprises propagating the mechanical waves in a taper.
• In still another embodiment, the step of combining comprises propagating the mechanical waves in a reverberating cavity
• In still a further embodiment, the step of combining comprises propagating the mechanical waves in a dispersive medium.
• In one embodiment, the at least one high amplitude mechanical pulse each have a center frequency fc comprised between about 20 kHz and about 10 MHz and a duration of about 1/fc.
• In one embodiment, an amplitude of the at least one high amplitude mechanical pulse when reaching the distal end of the transmission member is comprised between about 10 MPa and about 1000 MPa.
• In accordance with a second broad aspect, there is provided a system for generating a mechanical wave, comprising: a pulse generator for generating at least one high amplitude and short duration mechanical pulse; and a transmission member extending between a proximal end and a distal end, the proximal end being coupled to the pulse generator for receiving the at least one mechanical pulse therefrom, the transmission member for propagating the at least one mechanical pulse from the proximal end to the distal end and transmitting the at least one mechanical pulse at the distal end.
• In one embodiment, the pulse generator comprises: a plurality of broadband sources each for emitting a respective mechanical wave having a first amplitude; and a wave concentrator for combining the mechanical waves in order to obtain the mechanical pulse having a second amplitude greater than the first amplitude.
• In one embodiment, the wave concentrator is a spatial concentrator.
• In another embodiment, the wave concentrator is a temporal concentrator.
• In one embodiment, the wave concentrator is adapted to focus the mechanical waves on a focus zone adjacent to the proximal end of the transmission member.
• In one embodiment, the wave concentrator comprises a parabolic reflecting surface for reflecting at least some of the mechanical waves generated by the broadband sources towards the focus zone.
• In another embodiment, the wave concentrator is a taper.
• In a further embodiment, the wave concentrator comprises a spatial concentration stage and a temporal concentration stage.
• In one embodiment, the at least one high amplitude mechanical pulse each have a center frequency fc comprised between about 20 kHz and about 10 MHz and a duration of about 1/fc.
• In one embodiment, an amplitude of the at least one high amplitude mechanical pulse when reaching the distal end of the transmission member is comprised between about 10 MPa and about 1000 MPa.
• According to a third broad aspect, there is provided a concentrator for focusing mechanical waves emitted by mechanical wave sources, comprising: a body extending between a transmission face comprising a focal zone thereon and a reflection face opposite to the transmission face, the transmission face for receiving at least one mechanical wave source and transmitting at least one mechanical wave emitted by the at least one mechanical wave source within the body, the reflection face being unparallel to the transmission face so as to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone of the transmission face in order to focus the at least one mechanical wave and propagate the at least one focused mechanical wave into a transmission member positioned at the focal zone, and the focusing of the at least one mechanical wave resulting in a greater amplitude mechanical wave having an amplitude being greater than an amplitude of the at least one mechanical wave emitted by the at least one mechanical wave source.
• In one embodiment, the focal zone is located substantially at a center of the transmission face.
• In one embodiment, the reflection face comprises at least one sloped section each facing a respective one of the at least one mechanical wave source when received on the transmission face and each oriented so as to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone.
• In one embodiment, the reflection face has a substantially parabolic shape adapted to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone.
• In one embodiment, the reflection face has a truncated parabolic shape, the reflection face having a source receiving section thereon for receiving a further mechanical source for emitting a further mechanical wave to be combined at the focal zone with the at least one mechanical wave emitted by the at least one mechanical wave source.
• In one embodiment, the source receiving section substantially faces the focal zone of the transmission face.
• In one embodiment, the source receiving section is substantially planar.
• In one embodiment, the transmission face is substantially planar.
• In one embodiment, the concentrator further comprises at least one protrusion extending from the transmission face, the at least one protrusion defining at least one recess each for receiving a respective one of the at least one mechanical wave source therein.
• In one embodiment, the transmission face comprises at least one rounded section each for receiving a respective one of the at least one mechanical wave source having a rounded emission end.
• In one embodiment, a section of the transmission face containing the focal zone is substantially planar for coupling the greater amplitude mechanical wave into a waveguide having a substantially planar end.
• In one embodiment, a section of the transmission face containing the focal zone is rounded for coupling the greater amplitude mechanical wave into a waveguide having a rounded end.
• In one embodiment, the transmission face is adapted to receive at least two concentric sources of mechanical waves.
• In one embodiment, the at least one mechanical wave source comprises at least one of an annular mechanical wave source and a hexagonal annular mechanical wave source.
• In accordance with a fourth broad aspect, there is provided a connection device for connecting together two mechanical waveguides, comprising: a female connector defining a first aperture for receiving a first mechanical waveguide therein, the first mechanical waveguide comprising a first flange adjacent a first end thereof, an internal face of the female connector comprising a protrusion; a male connector defining a second aperture for receiving a second mechanical waveguide therein, the second mechanical waveguide comprising a second flange adjacent a second end thereof, the male connector having a connection end insertable into the first aperture of the female connector, a first bushing insertable around the first mechanical waveguide, the first bushing comprising a first abutment face for abutment against the first flange of the first mechanical waveguide and a second abutment face for abutment against the protrusion located on the internal face of the female connector; and a second bushing insertable around the second mechanical waveguide and comprising a third abutment face for abutment against the second flange of the second mechanical waveguide and a fourth abutment face for abutment against the connection end of the male connector.
• In one embodiment, the connection end of the male connector comprises a beveled recess and the fourth abutment face of the second bushing is beveled for abutment on the beveled recess of the male connector.
• In one embodiment, the protrusion of the female connector is beveled and the second abutment face of the first bushing is beveled for abutment against the beveled protrusion.
• In one embodiment, the male connector comprises a tubular section adjacent to the connection end and the first aperture of the female connector comprises a cylindrical section, the tubular section of the male connector being insertable into the cylindrical section of the first aperture of the female connector.
• In one embodiment, the tubular section of the male connector comprises a first thread extending on an external surface thereof and an internal face of the female connector comprises a second thread extending in the cylindrical section of the first aperture, the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, the first and second bushings are made of plastic first material being different from a second material, the male and female connectors being made of the second material.
• In one embodiment, the first and second bushings are made of plastic.
• In one embodiment, the first bushing is adapted to abut against the first flange that extends around a whole circumference of the first mechanical waveguide and the second bushing is adapted to abut against the second flange that extends around a whole circumference of the second mechanical waveguide.
• In one embodiment, one of the first and second mechanical waveguides comprises a tapering section.
• In accordance with another broad aspect, there is provided a connection device for connecting together two mechanical waveguides, comprising: a male connector defining a first aperture for receiving a first mechanical waveguide therein, the first mechanical waveguide comprising a first flange adjacent a first end thereof, the first aperture comprising a first section for receiving the first flange of the first mechanical waveguide and a second section, an internal face of the male connector comprising a first protrusion defining the second section of the first aperture, the first protrusion comprising a first abutment face for abutment against the first flange of the first mechanical waveguide, and dimensions of the second section of the first aperture being greater than dimensions of the first mechanical waveguide so that the first protrusion is not in physical contact with the first mechanical waveguide when the first mechanical waveguide is inserted into the male connector; and a female connector defining a second aperture for receiving a second mechanical waveguide therein, the second mechanical waveguide comprising a second flange adjacent a second end thereof, the second aperture comprising a third section for receiving therein the second flange of the second mechanical waveguide and a portion of the male connector, and a fourth section, an internal face of the female connector comprising a second protrusion defining the fourth section of the second aperture, the second protrusion comprising a second abutment face for abutment against the second flange of the second mechanical waveguide, and dimensions of the fourth section of the second aperture being greater than dimensions of the second mechanical waveguide so that the second protrusion is not in physical contact with the second mechanical waveguide when the second mechanical waveguide is inserted into the female connector.
• In one embodiment, the first and second apertures are cylindrical, the second section of the first aperture having a diameter being greater than a diameter of the first mechanical waveguide and being less than a diameter of the first flange, and the fourth section of the second aperture having a diameter being greater than a diameter of the second mechanical waveguide and being less than a diameter of the second flange.
• In one embodiment, the portion of the male connector insertable into the female connector comprises a first thread extending on an external surface thereof, and an internal surface of the female connector comprising a second thread within the third section of the second aperture, and the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, the first protrusion is adapted to abut against the first flange that extends around a whole circumference of the first mechanical waveguide and the second protrusion is adapted to abut against the second flange that extends around a whole circumference of the second mechanical waveguide.
• In one embodiment, one of the first and second mechanical waveguides comprises a tapering section.
• In accordance with a further broad aspect, there is provided a connection device for connecting together two mechanical waveguides, comprising: a male connector defining a first aperture for receiving a first mechanical waveguide therein, an internal surface of the male connector comprising a plurality of teeth projecting therefrom; and a female connector defining a second aperture for receiving a second mechanical waveguide therein, the second mechanical waveguide comprising a flange adjacent an end thereof, an internal face of the female connector comprising a protrusion for abutment against the flange of the second mechanical waveguide, and the second aperture being adapted to receive at least a portion of the male connector therein.
• In one embodiment, the male connector comprises a tubular body extending along a longitudinal axis and having an opening extending along the longitudinal axis for allowing an insertion of the first mechanical waveguide therein.
• In one embodiment, the male connector comprises a first thread extending along portion of the male connector insertable into the female connector, and an internal face of the female connector comprises a second thread, the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, the male connector comprises two hemi-tubular bodies, wherein the teeth each project from an internal face of a respective one of the two hemi-tubular bodies.
• In one embodiment, each one of the two hemi-tubular bodies comprises a first thread on an external face thereof and an internal face of the female connector comprises a second thread, the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, the connection device further comprises securing means for securing the two hemi-tubular bodies together around the first mechanical waveguide.
• In one embodiment, the teeth are pointed.
• In one embodiment, the teeth have a pyramidal shape.
• In another embodiment, the teeth have a conical shape.
• In one embodiment, the teeth are each adapted to be received in a respective groove located on a lateral face of the first mechanical waveguide.
• In accordance with a further broad aspect, there is provided a connection device for connecting together two mechanical waveguides, comprising: a male connector defining a first aperture for receiving a first mechanical waveguide therein, the first mechanical waveguide comprising a plurality of teeth projecting from a lateral face thereof; and a female connector defining a second aperture for receiving a second mechanical waveguide therein, the second mechanical waveguide comprising a flange adjacent an end thereof, an internal face of the female connector comprising a protrusion for abutment against the flange of the second mechanical waveguide, and the second aperture being adapted to receive at least a portion of the male connector therein.
• In one embodiment, the male connector comprises a tubular body extending along a longitudinal axis and having an opening extending along the longitudinal axis for allowing an insertion of the first mechanical waveguide therein.
• In one embodiment, the male connector comprises a first thread extending along portion of the male connector insertable into the female connector, and an internal face of the female connector comprises a second thread, the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, an internal face of the tubular body comprises grooves each for receiving a respective of the teeth.
• In one embodiment, the grooves are pointed.
• In one embodiment, the grooves each have a pyramidal shape.
• In another embodiment, the grooves each have a conical shape.
• In another embodiment, the male connector comprises two hemi-tubular bodies, wherein the teeth each project from an internal face of a respective one of the two hemi-tubular bodies.
• In one embodiment, each one of the two hemi-tubular bodies comprises a first thread on an external face thereof and an internal face of the female connector comprises a second thread, the second thread matching the first thread so that the male and female connectors be threadingly securable together.
• In one embodiment, the connection device further comprises securing means for securing the two hemi-tubular bodies together around the first mechanical waveguide.
• In one embodiment, an internal face of the two hemi-tubular bodies comprises grooves each for receiving a respective one of the teeth.
• In one embodiment, the grooves are pointed.
• In one embodiment, the grooves each have a pyramidal shape.
• In another embodiment, the grooves each have a conical shape.
• In accordance with still another broad aspect, there is provided a mechanical waveguide comprising: an elongated body extending along a longitudinal axis between a proximal end and a distal end, the proximal end being adapted to receive a mechanical wave, the elongated body being adapted to propagate the received mechanical wave from the proximal end to the distal end, and the distal end being adapted to transmit at least a portion of the propagated mechanical wave into a medium surrounding the distal end.
• In one embodiment, the elongated body has a cylindrical shape.
• In one embodiment, the elongated body has a constant diameter along the longitudinal axis.
• In one embodiment, the elongated body has a varying diameter along the longitudinal axis.
• In one embodiment, the distal end is adapted to cross at least one of a fibrotic tissue and a calcified tissue contained within an occlusion.
• In one embodiment, the distal end is adapted to at least one of tunnel, cross, cleave, break, penetrate in and create a path within an occlusion.
• In one embodiment, the distal end is adapted to create a tension wave in the medium surrounding the distal end and create a cavitation effect within the medium.
• In one embodiment, at least a section of the elongated body is made of a biocompatible material.
• In one embodiment, at least a section of the elongated body is coated with a biocompatible material.
• In one embodiment, at least a section of the elongated body is dispersive.
• In one embodiment, the elongated body is non-dispersive.
• In one embodiment, at least a section of the elongated body is sized to be insertable into a blood vessel of a body.
• In one embodiment, the elongated body is made of a single material.
• In one embodiment, the elongated body is made of several materials.
• In one embodiment, at least a section of the elongated body is provided with a coating having an acoustic impedance being different from an acoustic impedance of the elongated body.
• In one embodiment, at least a section of the elongated body has a low-friction coating.
• In one embodiment, the low friction coating is made of a hydrophobic material.
• In one embodiment, the low friction coating is made of a hydrophilic material.
• In one embodiment, the low friction coating is made of polytetrafluoroethylene.
• In one embodiment, at least a section of the elongated body is provided with a surface finish adapted to reduce friction.
• In one embodiment, a section of the elongated body is adapted to be one of manipulated by a user and be secured to a grabbing tool.
• In one embodiment, at least a section of the elongated body is made of one of a flexible material and an elastic material.
• In one embodiment, at least a section of the elongated body is made of a low attenuation material.
• In one embodiment, the low attenuation material comprises one of stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, nitinol, and fused quartz.
• In one embodiment, the titanium alloy comprises one of Ti-6Al-4V and Ti-1 1.5Mo-6Zr-4.5Sn (Beta III titanium).
• In one embodiment, at least a section of the elongated body is heat treated.
• In one embodiment, the heat treatment is annealing.
• In one embodiment, at least a section of the elongated body has a low attenuation microstructure.
• In one embodiment, at least a section of the elongated body is adapted to withstand stress and strain generated by a propagation of a mechanical pulse therealong.
• In one embodiment, at least a section of the elongated body is adapted to withstand fatigue associated with repetitive passages mechanical pulses.
• In one embodiment, cross-sectional dimensions of the elongated body are less than a center wavelength of a mechanical pulse propagating therealong.
• In one embodiment, the elongated body has a circular cross-section and a diameter of the elongated body is less than the center wavelength of the mechanical pulse propagating therealong.
• In one embodiment, a diameter of the cylindrical elongated member is chosen so as to allow the cylindrical elongated body to withstand a pushing force exerted by a user.
• In one embodiment, at least a section of the elongated body is adapted to be inserted into a catheter.
• In one embodiment, a cross-section of the at least a section of the elongated body is chosen so as to minimize contact with the catheter.
• In one embodiment, a cross-section of the at least a section of the elongated body is one of rectangular and square.
• In one embodiment, the at least a section of the elongated body comprises bumps protruding from a lateral surface thereof.
• In one embodiment, the proximal end is one of fat, partially rounded and rounded.
• In one embodiment, the distal end is coated with one of a hydrophobic material and a hydrophilic material.
• In one embodiment, the mechanical waveguide further comprises an acoustic coupler secured at the distal end.
• In one embodiment, the mechanical waveguide further comprises a radiopaque marker secured adjacent to at the distal end.
• In one embodiment, the radiopaque marker comprises one of a tungsten marker, gold strips, a high-density plating, a high-density ring, a high-density coil and doped polymer jacket with dense metal powders.
• In one embodiment, the distal end is one of flat, rounded, partially rounded, and beveled.
• In one embodiment, the distal end is shaped to direct the mechanical pulse at least partially radially.
• In one embodiment, the distal end has a truncated conical shape.
• In one embodiment, the distal end is adapted to focus mechanical energy away from the distal end.
• In one embodiment, a given section of the elongated body adjacent to the distal end is one of curved, bent and bendable.
• In one embodiment, a diameter of the cylindrical elongated body is comprised between about 0.004 and about 0.035 in.
• In one embodiment, a diameter of the distal end is greater than a diameter of a section of the elongated body adjacent to the distal end.
• In one embodiment, the elongated body comprises plurality of individual wires.
• In one embodiment, the elongated body has a tubular shape.
• In one embodiment, a ratio between a length of the elongated body and a diameter of the elongated body is greater than 100.
• In one embodiment, the ratio between the length of the elongated body and the diameter of the elongated body is greater than 1000.
• In one embodiment, a length of the elongated body is comprised between about 36 in and about 200 in.
• In one embodiment, the proximal end is connectable to a source of mechanical waves or pulses.
• In one embodiment, the tubular elongated body contained one of fluid and gas.
• In one embodiment, the distal end is shaped to focus the mechanical wave away therefrom.
• In one embodiment, the distal end has a concave shape.
• In one embodiment, a section of the elongated body adjacent to the distal end is split into different regions along the longitudinal axis.
• For the purpose of the present description, the expression “narrowband bandwidth” should be understood as a fractional bandwidth smaller than about 10%, and the expression “broadband bandwidth” should be understood as a fractional bandwidth larger or equal to about 10%. The fractional bandwidth is given by the following equation:
• 
  100*Af/fc
• where fc is the center/peak frequency (i.e. the frequency at which the frequency spectrum is maximum) and Øf is the −3 dB bandwidth. The expression “−3 dB bandwidth” should be understood as the frequency bandwidth over which the magnitude of vibration is greater than half the magnitude at the center/peak frequency fc.
• Therefore, a broadband signal should be understood as a signal having a broadband frequency bandwidth. Similarly, a broadband source should be understood as a source emitting a signal having a broadband frequency bandwidth.
• The bandwidth threshold between narrowband and broadband bandwidths may also be defined in term of Q-factor (i.e. quality factor). The Q-factor is defined as the reciprocal of the fractional bandwidth, i.e.Q−fc/Af. The equivalent Q-threshold between narrowband and broadband bandwidths is equal to about 10. A narrowband source corresponds to a high Q (i.e. ringing) source, i.e. a source having a Q-factor being greater than about 10, while a broadband source corresponds to a low-Q (i.e. damped) source, i.e. a source having a Q-factor being equal to or less than about 10.
• For the purpose of the present description, a mechanical wave should be understood as a signal having an arbitrary amplitude, duration, waveform, frequency, and/or the like. For example, a mechanical wave may have a high/low amplitude, a short/long duration, different waveforms, and any frequency content.
• For the purpose of the present description, a mechanical pulse should be understood as a short duration mechanical wave. The duration of a mechanical pulse is of the order of life.
• Furthermore, a mechanical waveguide should be understood as a waveguide adapted to propagate mechanical waves or pulses along its length. In the present description, the expressions “waveguide”, “mechanical waveguide” and “transmission member” may be used interchangeably. The shape and dimension of a waveguide may vary. For example, a waveguide may have a cylindrical shape. The diameter of the waveguide may be constant along its length. Alternatively, the diameter of the waveguide may vary along its length. For example, the diameter of a waveguide may decrease along its length so that the waveguide corresponds to a taper.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
• FIG. 1 is a flow chart illustrating a method for generating a mechanical pulse, in accordance with an embodiment;
• FIG. 2 is a block diagram of a system for generating a mechanical pulse, in accordance with an embodiment;
• FIG. 3 illustrates a system for generating mechanical pulses comprising a reflecting concentrator, a time concentrator, a taper concentrator, and a transmission member, in accordance with an embodiment;
• FIG. 4 illustrates a focalized electromechanical broadband source, in accordance with an embodiment;
• FIG. 5 illustrates a phased-array electromechanical broadband source, in accordance with an embodiment;
• FIG. 6aillustrates an array of electromechanical broadband sources cooperating with an acoustic lens, in accordance with an embodiment;
• FIG. 6billustrates an array of electromechanical broadband sources cooperating with a reflector, in accordance with an embodiment;
• FIG. 7 illustrates an electromechanical broadband source cooperating with a dispersive medium, in accordance with an embodiment;
• FIG. 8 illustrates an array of electromechanical broadband sources cooperating with a multi-scattering/reverberating medium, in accordance with an embodiment;
• FIG. 9 is a perspective view of a spatial concentrator adapted to combine the mechanical waves emitted by nine electromechanical transducers, in accordance with an embodiment;
• FIG. 10 is a perspective view of the spatial concentrator ofFIG. 9 from which six electromechanical transducers have been removed;
• FIG. 11 is a cross-sectional view of the concentrator ofFIG. 9;
• FIG. 12 illustrates a connection between a rounded-end transmission member and a taper; in accordance with an embodiment;
• FIG. 13 illustrates an exemplary transmission member provided with a wave-deflecting protrusion at a distal end, in accordance with an embodiment;
• FIG. 14 is a perspective view of a connection system for removably connecting together a taper and a dispersive waveguide, the connection system being in an open position, in accordance with an embodiment;
• FIG. 15 is a cross-sectional side view of the of the connection system ofFIG. 14, when in the open position;
• FIG. 16 is a cross-sectional side view of the of the connection system ofFIG. 14, when in a closed position;
• FIG. 17 illustrates a connection system for removably connecting a transmission member and a dispersive waveguide, in accordance with an embodiment; and
• FIG. 18 illustrates a connection system for removably connecting a transmission member and a taper, in accordance with an embodiment.
• It will be noted that throughout the appended drawings, like features are identified by like reference numerals.
DETAILED DESCRIPTION
• FIG. 1 illustrates one embodiment of amethod10 for generating and propagating mechanical pulses. In one embodiment, the method may be adapted to treat vascular occlusions, i.e. to cross an occlusion present in a blood vessel such as a vein or an artery or in any other conduct present in a human body. Themethod10 may have applications in fields other than the medical field. For example, the method may be used to cross occlusions/obstructions present in a conduct that is used to propagate water or any other fluid.
• Atstep12, at least one mechanical pulse is generated. Each mechanical pulse has a high amplitude and a short duration.
• In one embodiment, the outputs of several sources covering adjacent frequency bands are combined together to generate the mechanical pulse. In one embodiment, the outputs of at least two broadband sources, i.e. the mechanical pulses generated by the at least two broadband sources, are combined together. In another embodiment, the outputs of at least one broadband source and at least one narrowband source are combined together.
• In another embodiment, the mechanical pulses are generated by focusing, via a spatial concentrator, the output of a large broadband source toward a focal zone. It should be understood that the outputs of more than one large broadband source may be concurrently focused on the same focal zone.
• In a further embodiment, a high amplitude mechanical pulse may be generated by spatially and/or temporally combining mechanical pulses or waves sequentially emitted by a single broadband source using a reverberating cavity. It should be understood that the mechanical pulses generated by more than one broadband source may be spatially and/or temporally combined together by a reverberating cavity to provide the high amplitude mechanical pulse.
• In still another embodiment, high amplitude mechanical pulses may be generated by using a dispersive medium to combine the component waves (introduced below in the context of the temporal wave concentrator62) emitted sequentially by a single broadband source. It should be understood that the mechanical pulses generated by more than one source may be combined together using the dispersive medium.
• Atstep14, each mechanical pulse is propagated along a transmission member such as a waveguide adapted to propagate mechanical pulses or waves, i.e. a mechanical waveguide. The transmission member extends between a proximal end and a distal end. The transmission member receives the generated mechanical pulse at the proximal end and the mechanical pulse propagates along the transmission member up to the distal end. When it reaches the distal end, the mechanical pulse is transmitted at the distal end, which creates a displacement of the distal end and a mechanical pulse that propagates in the medium surrounding the distal end of the transmission member away from the distal end. In one embodiment, substantially all of the mechanical pulse is transmitted at the distal end of the transmission member. In another embodiment, only a portion of the mechanical pulse is transmitted at the distal end of the transmission member depending, among other things, on the acoustical impedance continuity at the interface between the distal end and the surrounding medium.
• In one embodiment, the mechanical pulse has a center frequency fc comprised between about 20 kHz and about 10 MHz. In one embodiment, the amplitude of the mechanical pulse when reaching the distal end of the transmission member is comprised between about 10 MPa and about 1000 MPa. In one embodiment, the duration of the mechanical pulse when reaching the distal end of the transmission member is in the order of 1/fc.
• In one embodiment, the method may be adapted to treat vascular occlusions, i.e. to cross an occlusion present in a blood vessel. In this case, at least a section of the transmission member is positioned within the vessel so that its distal end be adjacent to the occlusion. For example, the distal end of the transmission member may be in physical contact with the occlusion. When a mechanical pulse reaches the distal end of the transmission member, the distal end will impact onto the occlusion and transmits the mechanical pulse in the occlusion itself. If the distal end of the transmission member is not in physical contact with the occlusion, the mechanical pulse is transmitted in the medium present between the occlusion and the distal end, e.g. blood, and the transmitted mechanical pulse can propagate up to the occlusion. The mechanical pulse allows cracking, eroding cleaving, tunneling and/or breaking the occlusion and further allows the distal end of the transmission member to cross the occlusion as the distal end is moved farther within the vessel.
• In one embodiment, the method further comprises a step of amplifying the amplitude of the mechanical pulse. In an embodiment in which a temporal concentrator is present, the mechanical wave becomes a mechanical pulse of which the amplitude is greater than that of each component wave of the mechanical wave. In an embodiment in which a spatial concentrator is present, the amplitude of a mechanical pulse or wave is increased while propagating through the spatial concentrator. In another embodiment in which a spatial concentrator is present, different mechanical waves or pulses combine together to generate a greater amplitude mechanical wave or pulse, i.e. the different mechanical waves or pulses add to each other.
• FIG. 2 illustrates one embodiment of asystem20 that may be used to perform themethod10. The system comprises abroadband generator22, aconcentrator24 operatively connected to themechanical pulse generator22, and atransmission member26 operatively connected to theconcentrator24.
• Thebroadband generator22 comprises at least one broadband source adapted to generate mechanical waves. The generated mechanical waves are broadband and each have a substantially low amplitude. The mechanical waves are propagated through theconcentrator24 in which their amplitude increases so that theconcentrator24 outputs mechanical pulses which have a greater amplitude than that of the mechanical waves. If theconcentrator24 is a temporal concentrator, at least two component waves of the mechanical waves interact together while propagating along the temporal concentrator to generate at least one mechanical pulse at the output of the temporal concentrator so that the amplitude of the mechanical pulse is greater than that of the mechanical waves and the duration of the mechanical pulse is shorter than that of the mechanical waves. The mechanical pulses are then transmitted into thetransmission member26 at a proximal end thereof and they propagate along thetransmission member26 up to the distal end thereof. The transmission of the mechanical pulses at the distal end of thetransmission member26 creates mechanical pulses that displace the distal end of thetransmission member26 and then propagate in the medium surrounding the distal end of thetransmission member26 away from the distal end of thetransmission member26.
• In one embodiment, thetransmission member26 is adapted to be inserted into a blood vessel, a catheter, or the like. In this case, thetransmission member26 is sized and shaped to slide into the blood vessel or the catheter. In one embodiment, thetransmission member26 is made of a flexible material so that it may be bent to follow curvatures of the blood vessel or the like.
• In one embodiment, theconcentrator24 comprises at least two concentration stages. For example, a first concentration stage may consist of a spatial wave concentrator while a second concentration stage may consist of a temporal wave concentrator. It should be understood that any adequate concentrator adapted to increase the amplitude of the mechanical pulses may be used. It should also be understood that when no temporal concentrator is present, the broadband sources are adapted to generate mechanical pulses. It should also be understood that, when a temporal concentrator is present, the broadband sources are adapted to generate mechanical waves which become a mechanical pulse after propagating in theconcentrator24. It should be understood that the order of the concentration stages may be reversed so that the first concentration stage comprises a temporal concentrator and the second concentration stage comprises a spatial concentrator.
• In an example in which no temporal concentrator is present, a spatial wave concentrator may be adapted to focus the mechanical pulse emitted by a large broadband source on the input of thetransmission member26 which has a cross-sectional size that is less than the emission surface of the large broadband source. In another example, a spatial wave concentrator may be adapted to combine and focus the mechanical pulses generated by at least two different broadband sources. The emission time of the mechanical pulses emitted by the broadband sources are chosen so that the mechanical pulses combine together so as to create a single mechanical pulse of which the amplitude is greater than that of the mechanical pulses generated by the broadband sources.
• In another example, a spatial wave concentrator may comprise a tapered waveguide.
• An example of an adequate temporal mechanical wave concentrator is described in US Patent Application No. 2013/0158453. The temporal wave concentrator comprises an elongated waveguide having dispersive properties that are chosen so that the component waves of a mechanical wave, having a given amplitude and a given duration, propagates therein and combine together at the end of the elongated waveguide to create a pulse having an amplitude that is greater than the given amplitude of the mechanical wave and a duration that is less than the given duration of the mechanical wave.
• While in the illustrated embodiment, it is positioned between thebroadband generator22 and thetransmission member26, the person skilled in the art will understand that thewave concentrator24 may be positioned at the distal end of thetransmission member26. For example, a spatial concentrator such as a taper may be positioned at the distal end of thetransmission member26. The taper may be integral with thetransmission member26, i.e. thetransmission member26 may comprise a tapered section at its distal end.
• FIG. 3 illustrates oneexemplary system50 for generating and propagating mechanical waves. In this example, thesystem50 is adapted to treat anocclusion52 that may be present in a blood vessel (not shown) and the mechanical pulses generated by thesystem50 are adapted to crack, erode, cleave, tunnel and/or break theocclusion52.
• Thesystem50 comprises three broadband sources54-58, a firstspatial wave concentrator60, atemporal wave concentrator62, a secondspatial wave concentrator64, and a transmission member such as anultrasound waveguide66 adapted to propagate mechanical pulses. The system further comprises at least one controller (not shown) for powering and controlling the broadband sources54-58 so as to control the characteristics of the mechanical waves generated by the broadband sources54-58. In one embodiment, theelements54 and56 are part of a same broadband source having an annular shape.
• The firstspatial wave concentrator60 comprises areflector68 that extends between a distal ortransmission face70 and a proximal orreflection face72. In the illustrated embodiment, thetransmission face70 is substantially planar and thebroadband sources54 and56 are operatively connected to thetransmission face70. It should be understood that thetransmission face70 may not be planar.
• The reflection face72 comprises three sections, i.e. sections74-78. Thesections74 and76 are sloped and they each face a respective one of the first andsecond broadband sources54 and56. The angle between thefirst section74 and thetransmission face70 is chosen so that mechanical waves emitted by thefirst broadband source54 are reflected towards a focal zone such as the center of thetransmission face70. It should be understood that the focal zone may be located on thetransmission face70 at a location other than the center of thetransmission zone70. Similarly, the angle between thesecond section76 and thetransmission face70 is chosen so that mechanical waves emitted by thesecond broadband source56 are reflected towards the focal zone of thetransmission face70. Thesection78 is substantially planar and parallel to thetransmission face70. It should be understood that thesection78 may not be planar. Furthermore, thesection78 faces the center of thetransmission face70. The size and shape of thethird section78 are chosen so as to receive thethird broadband source58. For example, thethird section78 may be rounded such as concave or convex to accommodate a rounded source such as a source having an emission end being convex or concave, respectively.
• While the illustratedtransmission face70 is planar, it should be understood that other configurations may be possible. For example, thetransmission face70 may comprise rounded sections such as concave sections and/or convex sections to accommodate rounded sources. For example, thetransmission face70 may comprise rounded recesses defining concave receiving sections each for receiving arespective source54,56 having a convex emission end. In another example, thetransmission face70 may comprise rounded protrusions defining convex receiving sections each for receiving arespective source54,56 having a concave emission end.
• Similarly, thefocal zone82 may be planar for accommodating awaveguide80 having aplanar end82. In another embodiment, the focal zone may be rounded for coupling the combined mechanical waves into awaveguide80 having arounded end82. For example, thetransmission face70 may comprise a rounded recess at the focal zone defining a concave coupling section for accommodating awaveguide80 having aconvex end82. In another example, thetransmission face70 may comprise a rounded recess at the focal zone defining a convex coupling section for accommodating awaveguide80 having aconcave end82. Thetemporal wave concentrator62 is adapted to receive and combine together at least two component waves of a mechanical wave having a given amplitude into at least one mechanical pulse having an amplitude that is greater than the given amplitude. In one embodiment, thetemporal wave concentrator62 comprises adispersive waveguide80 such as the ultrasound waveguide described in the US Patent Application No. 2013/0158453. Thedispersive waveguide80 extends between aproximal end82 and adistal end84. Theproximal end82 is adjacent to thespatial wave concentrator60 so as to be operatively connected thereto, and substantially faces the center of thepropagation face70. The properties of thedispersive waveguide80 are chosen so that thewaveguide80 be adapted to combine component waves of the mechanical wave emitted by the broadband sources54-58 into greater amplitude mechanical pulses, as described below.
• Thetemporal wave concentrator62 comprising thedispersive waveguide80 operates as follows. Any mechanical wave can be decomposed into a finite sum of component waves. The component waves each include a function in time and a function in space. Specifically, each component wave has an associated frequency, magnitude, phase in time and an associated deformation field in space. A specific shape of the deformation field corresponds to a mode of the waveguide. In the present description we consider that a component wave has an associated frequency, an associated magnitude, an associated phase, and an associated mode of the waveguide. As a consequence, two component waves may have a same frequency and excite different modes. Two component waves may also have different frequencies and excite a same mode. In another example, two component waves may have different frequencies and excite different modes. For a mechanical wave traveling in thewaveguide80, a component wave has an associated propagation velocity. When the propagation velocity in thewaveguide80 is function of the frequency and the mode of the component wave, the waveguide is qualified as dispersive. Thus, a dispersive waveguide compels a relative phase difference of the component waves of a mechanical wave, which transforms a pulse into a mechanical wave having a lower amplitude and a longer duration.
• When the dispersive properties of awaveguide80 are adequately chosen, dispersion may be used to generate at one end a mechanical wave of which the component waves have associated phases such that, once phase shift is introduced by thedispersive waveguide80, the component waves recombine at the other end of thewaveguide80 into a desired mechanical wave such as a greater amplitude mechanical pulse.
• Referring back toFIG. 3, the secondspatial wave concentrator64 is operatively connected to thedistal end84 of thedispersive waveguide80. The secondspatial wave concentrator64 is adapted to increase the amplitude of mechanical pulses that propagate therethrough. In one embodiment, the secondspatial wave concentrator64 comprises a taper which consists of a non-dispersive ultrasound waveguide of which the cross-sectional area decreases along a length thereof. A first or proximal end of thetaper64 is operatively connected to thedistal end84 of thetemporal wave concentrator62 so as to receive mechanical pulses therefrom. As a mechanical pulse propagates along thetaper64, its amplitude increases, and the amplified mechanical pulse exits the taper at a second end thereof.
• Thetransmission member66 extends between a first orproximal end86 that is operatively connected to the second or distal end of the secondspatial wave concentrator64, and a second ordistal end88. Thetransmission member66 is adapted to receive mechanical pulses at itsfirst end86 and propagate the mechanical pulses up to itssecond end88. When it reaches thedistal end88, the mechanical pulse is at least partially transmitted to generate a transmitted pulse that propagates outside of thetransmission member66. It should be understood that a pulse may also be reflected by theend88 and propagates back in thetransmission member66 towards thefirst end86. The transmitted mechanical pulse corresponds to a mechanical pulse that propagates in the medium surrounding thesecond end88 of thetransmission member66 up to theocclusion52. The transmitted pulse further propagates into theocclusion52, which creates cracks within theocclusion52, and eventually cleaves or breaks theocclusion52 into pieces. Also, as the pulse propagates along the transmission member, radial and longitudinal motion is induced at the surface of the transmission member which reduces the friction between the transmission member and surrounding medium and facilitates the longitudinal displacement of the transmission member into the medium, such as when crossing fibrotic tissue within an occlusion.
• In an embodiment in which thedistal end88 of thetransmission member66 abuts against theocclusion52, thetransmission member66 may further be used to break theocclusion52 and/or drill a hole into theocclusion52. The transmission of the mechanical pulse at thedistal end88 of thetransmission member66 creates a movement of thedistal end88 of thetransmission member66. During this movement, thedistal end88 of thetransmission member66 nominally first moves towards theocclusion52 and then moves back into its initial position. It should be understood that the movement may be inversed (i.e. thedistal end88 may first move away from theocclusion52 and then towards the occlusion52) depending on the polarity of the mechanical pulse reaching thedistal end88 of thetransmission member66. It should also be understood that the movement could be a complex combination of back and forth motions. When a plurality of distinct mechanical pulses are successively transmitted at thedistal end88 of thetransmission member66, the movement of thedistal end88 may be seen as a jack-hammer movement which may be used to cross theocclusion52.
• As thedistal end88 of thetransmission member66 recesses (i.e. goes away from the occlusion), a tension wave is created in the medium surrounding thedistal end88 which may create a cavitation effect. If the medium is a fluid and since a fluid cannot withstand tensile forces, the fluid changes phase and vaporizes into microscopic bubbles (void and/or vapor). These bubbles are unstable and may collapse violently inducing powerful shock waves and velocity jets. The erosion capability of the induced shock waves and velocity jets may contribute to the ablation of theocclusion52.
• While in the above description thewaveguide80 is dispersive and thetaper64 and thetransmission waveguide66 are non-dispersive, it should be understood that other configurations may be possible. For example, both thewaveguide80 and thetaper64 may be dispersive. In this case, the person skilled in the art will understand that the component waves combine together to provide a high amplitude mechanical pulse at the distal end of thetaper64 instead of the distal end of thedispersive waveguide80. In another example, thewaveguide80, thetaper64, and thetransmission member64 are all dispersive. In this case, the component waves combine together to provide a high amplitude mechanical pulse at thedistal end88 of thetransmission member66. In another example, thetransmission waveguide66 and thewaveguide80 are both dispersive while thetaper64 is non-dispersive.
• It should be understood that a first section of thetransmission member66 is inserted within the blood vessel which contains theocclusion52 and a second section of thetransmission member66 is located outside the blood vessel. In one embodiment, at least the first section of thetransmission member66 is adapted to be inserted into a blood vessel. For example, the first section of thetransmission member66 may comprise a biocompatible coating or be made of a biocompatible material.
• The following describes the operation of thesystem50. A first section of thetransmission member66 is inserted into a blood vessel containing anocclusion52 so that thedistal end88 of thetransmission member66 is adjacent to theocclusion52. In one embodiment, thetransmission member66 is positioned so that itsdistal end88 substantially abuts against theocclusion52.
• The broadband sources54-58 are each adapted to emit at least two different component waves, e.g., at least a slower component wave and a faster component wave (relative to the dispersive waveguide). Each component wave emitted by thebroadband source54 propagates from thetransmission face70 within thereflector68, reflects at thesection74 of thereflection face72, and propagates back towards a focal zone located at the center of thepropagation face70. Similarly, each component wave emitted by thebroadband source56 propagates from thetransmission face70 within thereflector68, reflects at thesection76 of thereflection face72, and propagates back towards the focal zone. Each component wave emitted by thebroadband source58 propagates through thereflector68 towards the center of the focal zone. Since theproximal end82 of thedispersive waveguide80 is positioned at the focal zone, the component waves emitted by the broadband sources54-58 are transmitted into thedispersive waveguide80.
• The broadband sources54-58 are operated so that the component waves have substantially the same waveform when reaching the focal zone. It should be understood that the amplitude of the component waves emitted by the broadband sources54-58 may be different when reaching the focal zone. The emission time for each broadband source54-58 is chosen so that the component waves reach the center of thetransmission face70 substantially at the same time and are transmitted into theproximal end82 of thedispersive waveguide80 substantially at the same time. As a result, the individual component waves emitted by the broadband sources54-58 combine together at theproximal end82 of thedispersive waveguide80 to create a component wave having a greater amplitude than that of the individual component waves. Different greater amplitude component waves emitted by the broadband sources54-58 propagate along thedispersive waveguide80 and combine together at thedistal end84 of thedispersive waveguide80 to form a first mechanical pulse.
• For example, the broadband sources54-58 each emit a first component wave, such as a slower component wave, at an adequate time so that the first component wave combine together to create a first greater amplitude component wave, such as a greater amplitude slower component wave, when reaching theproximal end82 of thedispersive waveguide80. After emitting the first component wave, the broadband sources54-58 each emit a second component wave, such as a faster component wave, at an adequate time so that the second component wave combine together to create a second greater amplitude component wave, such as a greater amplitude faster component wave, when reaching theproximal end82 of thedispersive waveguide80.
• A constructive recombination occurs when the greater amplitude slower component wave is sent in thedispersive waveguide80 before the greater amplitude faster component wave, at time intervals that compensate for the relative phase shift introduced by thedispersive waveguide80. The slower and the faster greater amplitude component waves interact with each other up to thedistal end84 of thedispersive waveguide80. When the interaction is constructive (i.e. when the component waves have both a positive magnitude or both a negative magnitude), the resultant mechanical wave consists of a greater amplitude mechanical pulse.
• As described above, the mechanical waves emitted by the broadband transducers are synchronized so that they combine precisely as they travel down the single or plural concentration stages to generate the high-amplitude mechanical pulse at thedistal end84 of thetransmission member66. The broadband transducers are driven accordingly to produce these timed mechanical waves. The required electrical driving signals can be computed knowing the system behavior or obtained from experimental measurements.
• It should be understood that more than two greater amplitude component waves may combine together at thedistal end84 of thedispersive waveguide80 to create a mechanical pulse. Each of at least two of the component waves has a unique predetermined propagation velocity through thedispersive waveguide80. It should also be understood that the characteristics of the component waves emitted by the broadband sources54-58 and the characteristics of thedispersive waveguide80 are chosen as a function of the desired properties of the mechanical pulse to be generated at thedistal end84 of thedispersive waveguide80.
• In some embodiments, the at least two component waves have an associated frequency and an associated propagation mode of the waveguide. The at least two component waves have different associated frequencies. The at least two component waves have a same associated mode.
• In some embodiments, the same associated mode is a single mode of thedispersive waveguide80.
• In some embodiments, the single mode is a fundamental longitudinal mode of thedispersive waveguide80.
• In other embodiments, the at least two component waves have different associated modes. The at least two component waves have a same associated frequency.
• Referring back toFIG. 3, the first mechanical pulse propagates from thesecond end84 of the dispersive waveguide to thetaper64. In the illustrated embodiment, thetaper64 is a non-dispersive waveguide of which the cross-sectional surface area decreases along a length thereof. Because thetaper64 is non-dispersive, the component waves forming the first mechanical pulse do not separate from one another and the first mechanical pulse propagates along thetaper64. Furthermore, the amplitude of the mechanical pulse increases while it propagates therealong due the decreasing cross-sectional surface area of thetaper64. As a result, a second mechanical pulse is emitted by thetaper64 and the amplitude of the second mechanical pulse is greater than that of the first mechanical pulse.
• The second mechanical pulse is coupled into thenon-dispersive transmission member66 in which it propagates up to thedistal end88 where a transmitted mechanical pulse is transmitted in the surrounding medium. As described above, the transmitted pulse propagates up to theocclusion52 and if thedistal end88 of thetransmission member66 abuts against theocclusion52, the jackhammer movement created by the multiple mechanical pulses at theend88 may be used to cross theocclusion52.
• In one embodiment, at least two of the elements constituting thesystem50, i.e. thereflector68, thedispersive waveguide80, thetaper64, and thetransmission member66, are permanently secured together. For example, a least two of the elements may be welded together.
• In the same or another embodiment, at least two of the elements constituting thesystem50 are removably secured together using an adequate connector. For example, thetaper64 and thetransmission member66 may be integral together or welded together, and thetaper64 may be removably secured to thetemporal concentrator62. In this case, the assembly formed of thespatial concentrator64 and the transmission waveguide6 may be disposable so that this assembly is changed after a procedure while the broadband sources54-58, thespatial concentrator60, and thetemporal concentrator62 are used from one procedure to another. It should be understood that other configurations may be possible. For example, only thetransmission member66 may be disposable and removably secured to thespatial concentrator64.
• In one embodiment, an impedance matching element/material may be positioned between two components in order to reduce coupling losses between the two components. For example, one or more layers of impedance matching material may be positioned between the broadband sources54-58 and thereflector68. In yet another embodiment, the impedance matching element is positioned between the distal end of thetransmission member66 and the surrounding medium.
• In one embodiment, thereflector68, thedispersive waveguide80, thetaper64, and thewaveguide66 are all made of a same material in order to reduce losses from impedance mismatches.
• It should be understood that at least one of theconcentrator60,62, and64 may be omitted and/or the relative position of theconcentrator60,62, and64 may be changed. For example, thespatial concentrator64 may be omitted. In this case, thetransmission member66 may be permanently or removably secured to thetemporal concentrator62. Alternatively, the temporal concentrator may be further omitted and thetransmission member66 may be secured to thespatial concentrator60. In another example, thespatial concentrator64 may be positioned at the end of thetransmission member66. In a further embodiment, thetemporal concentrator62 may be omitted and thespatial concentrator64 may be secured to thespatial concentrator60. In this case, the broadband sources54-58 emit mechanical pulses that combine at the input of thespatial concentrator64 into a greater amplitude mechanical pulse of which the amplitude is further increased while propagating through thespatial concentrator64 before propagating along thetransmission member66.
• While thesystem50 uses broadband sources54-58 such as ultrasound transducers in connection with theconcentrator60 to generate mechanical waves, it should be understood that other configurations may be possible. For example, electromechanical energy such as piezoelectric energy, electromagnetic energy, or magnetostriction energy may be used. As described above, the energy may be concentrated in space, time or both in order to increase the amplitude of the mechanical waves generated by the energy source(s). Spatial concentration configurations may include one or more larger planar/focalized transducer. The transducer(s) can be distributed in a phased array configuration and used with an acoustic lens or an acoustic reflector. Temporal concentrator configurations can use one or more planar/focalized transducer(s) with a dispersive medium or a dispersive waveguide. A reverberating cavity can also be used to combine both spatial and temporal concentration. Any combinations or arrangements of the previous configurations can also be used to achieve similar results. Each transducer composing thebroadband generator22 can have the same bandwidth of operation or can have various bandwidths to achieve the desired level of control.
• The followings describe exemplary configurations for thewave concentrator24.
• In one embodiment, one may usc a focalized transducer comprising a hemispherical concave emitting surface to direct mechanical waves toward a common focal zone, as illustrated inFIG. 4.
• In another embodiment, a phased-array transducer composed of multiple emitting elements that can be individually controlled and disposed in various ways may be used as illustrated by two examples inFIGS. 5aand 5b. Each element can be fired with a different phase/delay to steer, focus and combine the resulting mechanical wavefront. The emitting elements can also be of different shapes. While they are positioned according to a linear configuration inFIG. 5a, the emitting elements are positioned according to a curved configuration inFIG. 5b.
• In a further embodiment, an acoustic lens may be used to take advantage of the difference in wave velocity between two media to redirect mechanical waves, as illustrated inFIG. 6a. In order to focus mechanical waves using an acoustic lens, the interface between the two media has a shape similar to the one described for a focalized transducer.
• In one embodiment, an acoustic reflector adapted to reflect incident mechanical waves toward the same focal zone may be used as illustrated inFIG. 6b.
• In another embodiment, one may use a temporal concentrator configuration taking the form of a dispersive medium having a gradient in acoustic wave velocity which is obtained by the generation of a gradient in at least one of its mechanical property, as illustrated inFIG. 7. By properly timing the emission of the component waves composing the input mechanical wave, it is possible to produce a high amplitude mechanical pulse at a desired location by constructive interference. In one embodiment, the dispersive properties of the dispersive medium are due to the geometry of the waveguide instead of the properties of the medium.
• In a further embodiment, a configuration combining a spatial concentrator and a temporal concentrator can also be used. This configuration can take the form a reverberating cavity such as a multi-scattering medium, as illustrated inFIG. 8. A reverberating cavity takes advantage of the multiple reflections inside a cavity to spatially and temporally focus mechanical waves toward a desired location using a single or an array of transducers.
• FIGS. 9-11 illustrate an exemplaryspatial concentrator91 that is adapted to combine together mechanical waves emitted by nine broadband sources such as nine piezoelectric transducers. It should be understood that theconcentrator91 may be used to combine mechanical waves emitted by sources other than broadband sources and that the number of sources is exemplary only. In this example, thespatial concentrator91 comprises a truncatedparabolic section92 and acylindrical section94, and is adapted to receive fivepiezoelectric transducers96 and97 of a first type and fourpiezoelectric transducers98 of a second and different type. For example, thepiezoelectric transducers96 and97 may be cylindrical transducers having a diameter of about 2 inches while thepiezoelectric transducers98 may be cylindrical transducers having a diameter of about one inch. It should be understood that the number of transducers may vary as long as the system includes at least one transducer. For example, the system may comprise two or more concentric annular transducers. It should also be understood that the number of transducer types may also vary. For example all of the transducers may be identical.
• As illustrated inFIG. 10, protrusions project from the top face of thecylindrical section94 to define fourrecesses100 and fourrecesses102. Eachrecess100 is sized and shaped to receive a correspondingpiezoelectric transducer96 while eachrecess102 is adapted to receive a correspondingpiezoelectric transducer98. Awaveguide103 such as a dispersive waveguide is secured to thecylindrical section94.
• It should be understood that therecesses100 and102 may be omitted. For example, the top face of thecylindrical section94 may be substantially planar and any adequate means for securing removably or not thetransducers96 and98 to the planar top face of thecylindrical section94 may be used.
• As illustrated inFIG. 11, theparabolic section92 comprises atruncated portion104 located at the apex of theparabolic section92. Thetruncated portion96 is substantially flat, and it is sized and shaped to receive thepiezoelectric transducer97. Thepiezoelectric transducer97 is positioned on thetruncated portion106 so that its longitudinal axis be substantially aligned with the longitudinal axis of thewaveguide103. As a result, mechanical waves emitted by thepiezoelectric transducer97 propagate through theconcentrator91 and are transmitted into thewaveguide104. The curvature of the parabolic face of theparabolic section92 and the position of therecesses100 and102 are chosen so that the mechanical waves emitted by eachpiezoelectric transducer86,88 propagate through theconcentrator91, reflect at the parabolic face of theparabolic section92, and then propagate towards afocal zone105. A first end of thewaveguide103 is positioned at thefocal zone105 so that the mechanical waves generated by apiezoelectric transducer96,98 be coupled into thewaveguide103.
• Thepiezoelectric transducers96,97, and98 emit a respective mechanical wave each at a time chosen so that the different mechanical waves arrive substantially concurrently at the focal zone. The mechanical waves emitted by thetransducers96 and98, after reflecting at the parabolic face, focus at the focal zone and combine together with the mechanical wave emitted by thetransducer97 to generate a mechanical wave having a greater amplitude than that of the mechanical wave emitted by eachpiezoelectric transducer96,97, and98 alone.
• In an embodiment in which thewaveguide103 is a dispersive waveguide acting as a temporal concentrator, thepiezoelectric transducers96,97, and98 may be controlled to first emit slower component waves which combine at thefocal zone105 to generate a greater amplitude slower component wave which is transmitted into thedispersive waveguide103 and propagate therealong. Thepiezoelectric transducers96,97, and98 are further controlled to subsequently emit faster component waves which combine at thefocal zone105 to generate a greater amplitude faster component wave which is coupled into thedispersive waveguide103 and propagate therealong. The faster and slower greater amplitude component waves combine together at the second end of the dispersive waveguide to create a desired mechanical pulse having an amplitude that is greater than that of the faster and slower greater amplitude wave components.
• In one embodiment and in order to maximize the spatial concentration of the mechanical waves at thefocal zone105, the distance of propagation of the mechanical wave within theconcentrator91 is minimized, the incident angle at the parabolic surface of thesection82 is minimized, the surface emission is maximized, and/or the operating wavelength is kept as short as possible for the following reasons. The spatial focusing gain is related to the emitting surface A divided by the distance of propagation d and the operative wavelength λ, i.e. Gain≈A/({dot over (α)}λ). Other wave propagation phenomena may be considered when mechanical waves travel in a solid medium. For example, mode conversion (e.g., longitudinal into shear) may occur in a solid medium when a mechanical wave is reflected by a boundary interface such as the parabolic surface of thesection92. This mode conversion is related to the angle between the incident wave and the boundary interface. Since they are reflected at an angle different than longitudinal waves, shear waves do not focus at the same zone than that of the longitudinal waves. Therefore, part of the input signal may be lost or trapped when mode conversion is present at a certain extent. Also, at some operative wavelengths the mechanical wavefront does not travel in a straight line but spreads in space due to diffraction. The longer distance a wavefront travels, the more it spreads in space. Therefore and in order to maximize the spatial concentration, the distance of propagation may be kept as short as possible to limit the spreading of the wavefront. Similarly, the incident angle at a parabolic surface may be kept as low as possible to limit mode conversion. The surface emission may also be large. Furthermore, the operative wavelength may be reduced when possible to minimize the aforementioned deleterious effects.
• In one embodiment, thetransducers96,97, and98 are planar piezoelectric transducers, i.e. their emission surface is planar. Such planar piezoelectric transducers are less expensive than piezoelectric transducers having a non-planar emission surface. Furthermore, it is easier to couple their emission face with thespatial concentrator91. Moreover taking advantage of a parabolic geometry of thespatial concentrator91 and by distributing the transducers86-88 on the top surface symmetrically around the main axis, the person skilled in the art will understand that the control electronics is simplified since the same emitting electronic signal may be used by similar transducers and since there is no need for introducing any phase delay. For example, a same electronic signal may be used to control the fourtransducers96 as they constitute a single channel.
• In another embodiment, the transducers96-98 may not be planar. For example, they may be focused transducers. In another example, they may be asymmetrically distributed about the axis of theconcentrator91. In a further example, thetransducers96 and98 may not be on the same planar surface.
• In one embodiment, truncating an area of the parabolic surface reduces the focalization gain for the component waves emitted by thetransducers96 and98. However, the addition of thetransducer97 on the truncated portion of thesection92 allows increasing the focalization gain with respect to the focalization gain that would be obtained if thetransducer97 would not be present and theparabolic section92 would not be truncated. In one embodiment, the distance between thefocal zone105 and thetruncated section104 together with its surface area are adequately chosen. Indeed, according to the operative wavelength and the size of the targeted focal zone, there are an optimal distance and surface area that will maximize the spatial concentration of the transducer used on the truncated section.
• In one embodiment, theconcentrator91 is designed using the geometric relations of a parabola and the theory of light propagation as a first hypothesis. Then, a numerical finite element model is developed. Once the proper parameters (such as propagating medium, boundary conditions, excitation conditions, and/or meshing) have been determined, this model is used to evaluate the impact of various geometrical parameters on the amplification factor at the focal zone. For example, different shapes, parabolic or not, emission surface area, emission zones distribution and concentrator thickness are evaluated. Furthermore, subsequent numerical models can be developed and used to evaluate the interaction and integration of the concentrator with other components of the system.
• In one embodiment, a layer of impedance matching material such as glycerin may be introduced between the concentrator91 and the transducers96-98 to reduce coupling losses. Furthermore, thewaveguide103 is mechanically connected to theconcentrator91 at thefocal zone105. For example, welding may be used as a mechanical connection.
• WhileFIGS. 9-1I illustrate cylindrical transducers having a planar emission surface, it should be understood that transducers having a different shape may be used. For example, the shape of the transducers may be annular, hexagonal, square, triangular, circular, or the like.
• It should also be understood that the number and location of the transducers96-98 relative to the concentrator may vary. For example, while theconcentrator91 comprises a single planar portion located on the parabolic surface for receiving thetransducer97, i.e. the truncated portion, the person skilled in the art will understand that the parabolic surface may comprise more than one planar portion. Each planar portion is adapted to receive a respective transducer that will emit mechanical waves towards thefocal zone105. The portions of the parabolic surface located between planar portions may then be used to reflect mechanical waves emitted by transducers positioned on top of the concentrator towards thefocal zone105.
• It should be understood that theconcentrator91 may be made of any adequate material in which mechanical waves may propagate. For example, theconcentrator91 may be made of glass, lead, fluid, gas, liquid metal, stainless steel, titanium, nitinol, etc.
• While the transducers96-98 are provided with a planar emission surface, it should be understood that other configurations are possible. For example, the transducers may be provided with a concave emission surface. In this case, the recesses also have a convex shape matching that of a respective concave transducer to accommodate their respective concave transducer. The transducers96-98 can also be used with an acoustic lens.
• Referring back to thetransmission member66, the person skilled in the art will understand that the function of thetransmission member66 is to propagate high amplitude mechanical pulses from itsproximal end86 to itsdistal end88. Theproximal end86 is located outside a patient and is permanently or removably connected to thespatial concentrator64. Thedistal end88 is to be inserted into a blood vessel of the patient with or without a catheter.
• In one embodiment, thetransmission member66 is made of a single material. In another embodiment, thetransmission member66 may be made of different materials. For example, thetransmission member66 may comprise a first section adjacent to theproximal end86 and adapted to remain outside of the patient, and a second section adjacent to thedistal end88 and adapted to be inserted into a blood vessel of the patient. In this case, the first section may be made of a first material adapted to propagate high amplitude mechanical pulses while the second section may be made of a second and different material that is also adapted to propagate high amplitude pulses and that is also biocompatible.
• In one embodiment, the second section of the transmission member comprises a low-friction coating (e.g., a hydrophobic coating, a hydrophilic coating, polytetrafluoroethylene (PTFE) coating, etc.) or specialized surface finish to reduce friction.
• In one embodiment, the second section of the transmission member comprises a low/high acoustical impedance coating, as compared to the acoustical impedance of the transmission member core, to entrap energy in the transmission member core and prevent, or at least reduce, energy leakage. Examples of low/high acoustical impedance materials comprise tungsten, aerogel, gas entrapping jacket and the like.
• In one embodiment, the second section of the transmission member comprises a low/high acoustical impedance coating and a low-friction coating, the low-friction coating covering completely or partially the low/high acoustical impedance coating.
• In one embodiment, thetransmission member66 may further comprise a third section located between the first and second sections. The third section is adapted to be manipulated by a user such as an interventional physician or to receive a grabbing tool such as a torquer.
• In one embodiment, the first, second and/or third section are made of a flexible or elastic material presenting substantially no plastic deformation as the second section follows the tortuous path within the blood vessel leading to the occlusion or as the third section is manipulated by the user.
• In one embodiment, thetransmission member66 is made of the same material as that of the element to which its proximal end is secured to ensure an improved coupling of the mechanical pulses into thetransmission member66 and therefore reduce coupling losses.
• In one embodiment, thetransmission member66 is made of a low-attenuation material such as stainless steel, aluminum or aluminum alloys, titanium or titanium alloys such as Ti-6Al-4V or, Ti-11.5Mo-6Zr-4.5Sn (Beta III titanium), nitinol, fused quartz or the like. In one embodiment, a heat treatment such as annealing may be applied to at least a portion of thetransmission member66.
• In one embodiment, thetransmission member66 has a low-attenuation microstructure that is achieved through one or a series of heat treatment and heat or cold working.
• In one embodiment, thetransmission member66 is made of a material having good mechanical properties such as good tensile strength and good torque transmission and good kink resistance.
• In one embodiment, thetransmission member66 is adapted to withstand the high stress/strain generated by the mechanical pulse propagating therealong. In the same or another embodiment, thetransmission member66 is adapted to withstand the fatigue associated with the repetitive passage (cycling) of the mechanical pulses.
• In one embodiment, the cross-sectional dimension of thetransmission member66 such as the diameter of a cylindrical waveguide is small compared to the center wavelength of the mechanical pulse propagating therealong so that thetransmission member66 is non-dispersive or weakly dispersive in order to reduce energy leakage.
• In one embodiment, the cross-sectional dimension of thetransmission member66 such as the diameter of a cylindrical transmission member is large enough to allow thetransmission member66 to withstand a pushing force exerted by a user and required to advance thedistal end88 along the blood vessel or within the catheter and into the occlusion, and to allow a safe and effective control of thedistal end88.
• In one embodiment, the outer surface of thetransmission member66 or at least the second section of thetransmission member66 features microscopic details such as fine threads or has some kind of coating, which could entrap micro-bubbles acting as a shielding layer preventing energy leakage.
• In an embodiment in which thetransmission member66 is inserted into a catheter, the cross-sectional shape of thetransmission member66 is adapted to minimize the physical contact within the catheter to minimize energy leakage and/or friction. For example, if the catheter comprises a circular cavity in which thetransmission member66 is inserted, thetransmission member66 may have a square cross-section to reduce the contact with the catheter to the four corners of the square. In another embodiment, the external surface of thetransmission member66 could be provided with small features such as bumps along its length to minimize the contact with the catheter.
• In one embodiment, theproximal end86 of thetransmission member66 and/or the first section of thetransmission member66 is not coated and is surrounded by ambient air since there is substantially no boundary friction or energy leakage to prevent or reduce.
• It should be understood that theproximal end86 of thetransmission member66 may be provided with any adequate shape. For example, theproximal end86 may be substantially flat. In another embodiment, the proximal end may be rounded as illustrated inFIG. 12 which illustrates awaveguide106 having a roundedproximal end107 which protrudes from thewaveguide106. Theelement108 to which thewaveguide106 is to be secured comprises an inwardlyrounded end109 which match therounded end107 of thewaveguide106. Such a configuration improves the mating of thewaveguide106 to theelement108 and may compensate for misalignment.
• In one embodiment, theproximal end86 of thetransmission member66 serves as an entry point to slide in an over-the-wire equipment such a catheter, a balloon or a stent.
• In one embodiment, theproximal end86 of thetransmission member66 is made of a material presenting an acoustical impedance that is compatible with that of the element to which it is secured, such as thespatial concentrator64.
• Thedistal end88 of thetransmission member66 is used to emit the mechanical pulses from thetransmission member66 core toward theocclusion52. Thedistal end88 may also be used to create a path and navigate through theocclusion52, enlarge the diameter of the path, and/or orient the direction of the emitted mechanical pulses.
• In an embodiment, in which thetransmission member66 is to be inserted into a catheter, thedistal end88 of thetransmission member66 may be designed as to facilitate its introduction into the catheter toward the occlusion. In one embodiment, a hydrophobic coating may be applied at thedistal end88 of the transmission member to flush the blood out of the catheter as thedistal end88 advances toward theocclusion52 and thereby reduce the quantity of blood that surrounds thetransmission member66 which could contribute to energy leakage.
• In one embodiment, a hydrophilic coating is added at thedistal end88 of thetransmission member66 to facilitate its introduction in a catheter.
• In one embodiment, an acoustic coupler is secured to thedistal end88 of thetransmission member66 in order to increase the energy transmission from thetransmission member66 towards theocclusion52.
• In one embodiment, radiopaque markers such as tungsten, gold strips, high-density plating, high-density ring, high-density coil or doped polymer jacket with dense metal powders are secured to thedistal end88 of thetransmission member66 to serve as references points in order to visualize via X-rays the position of the distal end relative to theocclusion52 and to other PTA devices.
• In one embodiment, thedistal end88 of thetransmission member66 is substantially flat. In one embodiment, the flat surface of thedistal end88 is substantially orthogonal to the outer longitudinal surface of thetransmission member66 that extends along the length thereof in order to maximize the energy output along the longitudinal axis along which thetransmission member66 extends. In another embodiment, the flat surface of theend88 is beveled or at an angle with respect to that longitudinal axis. Such shape may also propel the wire sideways resulting in a slapping effect that may be used to enlarge the path created within the occlusion or have vessel preparation intention before the use of a balloon during PTA intervention. It should be understood that thedistal end88 may be provided with any adequate shape other than a flat shape. For example, the distal end may be provided with a rounded shape such as a hemi-spherical shape. The surface of thedistal end88 may be provided with any adequate shape between a rounded shape and a flat shape. For example, the surface of thedistal end88 may be substantially planar with a smoothed or rounded edge to be as atraumatic as possible for biological tissues. In another example, the distal end maybe provided with a shape to focus the mechanical energy away from thedistal end88. This focusing shape could be a concave shape, for example a circular or parabolic shape. This focusing shape could be such as to focus the mechanical pulse along the longitudinal axis of the transmission member, or away from this same axis.
• In one embodiment, thedistal end88 of thetransmission member66 may be shaped so as to direct the mechanical pulse at least partially radially. This configuration may be used to create a path in theocclusion52 with a diameter larger than that of thedistal end88. Moreover, such embodiment may be used to prepare the lesion site prior the use of balloon during a PTA intervention.
• FIG. 13 illustrates such a configuration in which a transmission member orwaveguide110 is provided with a distal end adapted to partially emit a radial mechanical wave. Aprotrusion112 having a truncated conical shape protrudes from the distal end of thewaveguide112. Theprotrusion112 extends between a circular distal wall located away from thewaveguide110 and a circular proximal wall secured to thewaveguide110. A truncated conical wall extends between the circular proximal and distal walls. In the illustrated embodiment, thewaveguide110 and theprotrusion112 are coaxial.
• In another configuration, the distal tip of the transmission member could be split into regions along a direction essentially parallel to its longitudinal axis, such that when the mechanical pulse reaches this region it forces the various regions away from the split interface, enabling some redirection of some of the energy in the radial direction. In another configuration, the distal tip of the transmission member could be alternately curved along the longitudinal axis so as to redirect some of the mechanical energy in the radial direction. However, the person skilled in the art will understand that other configurations may be possible.
• As illustrated inFIG. 13, the central portion of the mechanical energy schematically represented byarrow114 propagates through theprotrusion112 to generate a longitudinal mechanical wave schematically represented byarrow116 that propagates substantially along the longitudinal axis of thewaveguide110 outside of thewaveguide110 towards theocclusion52. The outer portion of the mechanical energy schematically represented byarrow118 and adjacent to the outer surface of thewaveguide110 propagates outside of thewaveguide110 and is reflected by the truncated conical wall of theprotrusion112 to generate a radial mechanical wave.
• While in the illustrated embodiment, the propagation direction of the radial mechanical wave is substantially orthogonal to that of the longitudinal mechanical wave, it should be understood that other configurations are possible by varying the angle between thewaveguide110 and the truncated conical wall of theprotrusion112. Moreover, such configuration does not need to be symmetrical around the main axis of the ultrasound waveguide.
• The person skilled in the art will understand that the amount of energy converted into a radial mechanical wave may be adjusted by adequately varying the surface area of the distal and/or proximal walls of theprotrusion112.
• In one embodiment the section of thetransmission member66 adjacent to thedistal end88 may be bent or bendable so a user may apply a permanent or temporary curvature with his fingers, a metallic needle introducer or a tool. A bent at thedistal end88 may be used to steer the transmission member (i.e. to give the transmission member a direction) as it is pushed forward in the blood vessel or in the occlusion and/or to redirect the emitted mechanical pulse.
• In one embodiment, thetransmission member66 has a cross-sectional shape and/or cross-sectional dimensions that are substantially constant along a length thereof. For example, thetransmission member66 may have a circular cross-sectional shape of which the diameter is substantially constant along the length thereof. In one embodiment, the diameter of thewaveguide66 is between about 0.004 and about 0.035 in.
• In another embodiment, the cross-sectional shape and/or the dimensions of thetransmission member66 may vary along a length thereof. For example, the first section of thetransmission member66 that is adjacent to theproximal end66 and/or the second section of thetransmission member66 that is adjacent to thedistal end88 may have a cross-sectional shape and/or a dimension different from a third section located between the first and second sections. In another example, thetransmission member66 may comprise at least one tapering section for amplifying mechanical pulses.
• For example, theproximal end86 may be provided with a circular cross-sectional shape having a first diameter while the third section of thetransmission member66 may be provided with a circular cross-sectional shape having a second and different diameter. For example, the first diameter may be greater than the second diameter. In another example, the second diameter may be greater than the first diameter. In one embodiment, the diameter of thetransmission member66 smoothly varies from the first diameter to the second diameter along a given section of thetransmission member66.
• In another example, theproximal end86 may be provided with a first cross-sectional shape while the third section of thetransmission member66 may be provided with a second and different cross-sectional shape. For example, theproximal end86 may be provided with a square cross-sectional shape while the third section of thetransmission member66 may be provided with a circular cross-sectional shape. In another example, theproximal end86 may be provided with a hexagonal cross-sectional shape while the third section of thetransmission member66 may be provided with a circular cross-sectional shape. In one embodiment, the shape of thetransmission member66 smoothly varies from the first cross-sectional shape to the second cross-sectional shape along a given section of thetransmission member66.
• In one embodiment, the dimension of thedistal end88 is less than that of the third section of thetransmission member66 to increase the flexibility of thedistal end88.
• In another embodiment, the dimension of thedistal end88 is greater than that of the third section of thewaveguide66 to flush the blood out of the catheter in which thedistal end88 of thetransmission member66 is inserted as thedistal end88 is moved toward the occlusion.
• In a further embodiment, the dimension of thedistal end88 is greater than that of the third section of thetransmission member66 to maximize the opening size in the occlusion while maintaining great flexibility at thedistal end88.
• In one embodiment the transmission member can be comprised of a plurality of individual wires. In another embodiment the transmission member can be of generally tubular shape.
• In one embodiment, the transmission member such aswaveguide66 is adapted to be used with traditional PTA devices. In one embodiment, the transmission member has a diameter that is less than about 0.125 inches, and preferably less than about 0.035 inches.
• In one embodiment, the aspect ratio (defined as: length/diameter) of the transmission member is chosen to be greater than 100, and preferably greater than 1000. In one embodiment, the transmission member has a length comprised between about 60 in and about 120 in. In another embodiment, the transmission member has a length comprised between about 36 in and about 200 in.
• In one embodiment, at least the distal section of the transmission member is flexible so as to be bent or curved substantially easily during the intended application. For example, the aortic arch can have a radius of curvature of about 1 in. Therefore, the flexible transmission member may be bent to present a radius of curvature of about 1 in or less.
• In one embodiment, the transmission member may have a proprietary interface at its proximal end so that only the latter can be connected to the energy source. This can take the form of added features at the proximal end of the transmission member. Also, a proprietary acoustic signature of the transmission member can be detected using a pulse-echo technique at the beginning of the procedure. An electronic chip that can only be recognized by the proprietary connector may also be used.
• In one embodiment, the transmission member may be made of nitinol, stainless steel, titanium alloy, fused quartz or the like. These materials provide an adequate amount of acoustic wave transmission, stiffness and torque transmissibility. However, a fluid or a gas transmission member may also be used.
• As described above, two components or elements of thesystem50 may be removably secured together.FIGS. 14-16 illustrate such as a configuration in which ataper150 is removably secured to adispersive waveguide152. It should be understood that thewaveguide152 may also be non-dispersive.FIGS. 14-16 further illustrate atransmission member154 that is integral with thetaper150. Alternatively, thetaper150 and thetransmission member154 may be welded together. Afemale connector160 and amale connector162 form a connection device that is used for removably connecting together thetaper150 and thedispersive waveguide152. It should be understood that the connection device illustrated atFIGS. 14-16 may be used for connecting together any king of mechanical waveguides having a flange at the connecting end such as tapers, waveguides having a constant diameter, and/or the like.
• Theproximal end164 of thetaper150 is provided with aflange166 which extends radially and outwardly from thetaper150 along the circumference of theproximal end164. Abushing168 is inserted around thetaper150 and positioned at a position that is adjacent to theproximal end164 thereof. It should be understood that thetaper150 is received in thebushing168 and thebushing168 may translate along thetaper150. Similarly, thedistal end170 of thedispersive waveguide152 is provided with aflange172 which extends radially and outwardly from thedispersive waveguide152 along the circumference of thedistal end170. Abushing174 is inserted around thedispersive waveguide152 and positioned at a position that is adjacent to thedistal end170 thereof. It should be understood that the taper is received in thebushing168 and may translate along thetaper150. Thebushings168 and174 are used for alignment purposes and they may be made of a plastic or a metallic material in order to reduce energy leakage.
• While in the illustrated embodiment, theflanges166 and172 extend along the whole circumference of theproximal end164 and thedistal end170, respectively, it should be understood that at least one of the twoflanges166 and172 may extend only along a portion of the circumference of itsrespective end164,170. It should be understood that the diameter of theflanges166 and172 may vary as long as it is greater than the diameter of theproximal end164 of thetaper150 and the diameter of thedistal end170 of thedispersive waveguide152, respectively. While in the illustrated embodiment, theflanges166 and172 have substantially the same diameter, other configurations may be possible.
• Thefemale connector160 comprises atubular body180 provided with anaperture182 which extends between proximal and distal ends thereof and in which thetaper150 and optionally thetransmission member154 are inserted. The cross-sectional dimension of theaperture182 is greater than that of the assembly formed by thetaper150 and thetransmission member154 so that thetaper150 may slide within theaperture182 and thefemale connector160 may rotate about thetaper150. Thesection184 of the internal wall of thebody180 that is adjacent to the proximal end of thefemale connector160 is threaded.
• Themale connector162 comprises atubular body190 provided with anaperture192 which extends between proximal and distal ends thereof and in which thedispersive waveguide152 is inserted. The cross-sectional dimension of theaperture192 is greater than that of thedispersive waveguide152 so that thedispersive waveguide152 may slide within theaperture192 and themale connector162 may rotate about thedispersive waveguide152. Thesection194 of the internal wall of thebody190 that is adjacent to the distal end of themale connector162 is threaded and its thread matches that of thesection184 of the female connector so that the threadedsection194 of themale connector162 may be screwed into the threadedsection184 of thefemale connector160.
• In order to secure the female andmale connectors160 and162 together, thetaper150 is inserted into thefemale connector160 until the distalbeveled end196 of thebushing168 abuts abeveled surface198 of a protrusion that extends from the internal wall of thebody180, as illustratedFIG. 16. Thedistal end170 of thedispersive waveguide152 is inserted into the female connector until it abuts against theproximal end164 of thetaper150. Then the threadedsection194 is screwed into the female connector. By screwing themale connector162 into thefemale connectors160, the proximal beveled end of thebushing174 abuts a beveled surface of the internal wall of thebody190.
• The beveled surface of thebushing168 and the corresponding beveled surface of the internal wall of thebody180 cooperate together to center thetaper150 within theaperture182 of thefemale connector160 so that thefemale connector160 is not in physical contact with thetaper150 or thetransmission member154 to prevent or at least reduce energy leakage. Similarly, thebeveled surface197 of thebushing174 and the correspondingbeveled surface199 of the distal end of thebody190 cooperate together to center thedispersive waveguide152 within theaperture192 of themale connector162 so that themale connector162 is not in physical contact with thedispersive waveguide152 to prevent or at least reduce energy leakage.
• In one embodiment, an impedance matching material may be inserted between thedispersive waveguide152 and thetaper150. Furthermore, a glycerin film may be added between thedispersive waveguide152 and thetaper150 to ensure an optimal coupling between the two and to ensure that the longitudinal mechanical wave may be transmitted. In another example, a film of ultrasonic gel is inserted between thedispersive waveguide152 and thetaper150.
• It should be understood that theconnectors160 and162 may be made of any adequate material such as stainless steel, titanium alloy, plastic, or the like.
• In one embodiment, theflanges166 and172 have a thickness that is less than the central wavelength of the mechanical pulse to minimize diffraction of the mechanical pulse in theflanges166 and172.
• In one embodiment, theflanges166 and172 may be omitted and replaced by notches provided in thetaper150 and thedispersive waveguide152. In this case, the holding mechanism may comprise a grip. With respect to the configuration comprising flanges, the notches allow not increasing the overall diameter of thedispersive waveguide152 and that of thetaper150.
• While in the illustrated embodiment, threaded sections are used to removably secure the twoconnectors160 and162 together, it should be understood that any adequate securing means adapted to removably secure the two connectors together may be used.
• FIG. 17 illustrates an exemplary configuration of aconnection device230 for removably connecting a firstmechanical waveguide231 such as a dispersive waveguide to a secondmechanical waveguide232 such as transmission member. In this embodiment, the proximal end of thetransmission member232 is provided with aflange233 and the distal end of thedispersive waveguide231 is also provided with a flange234.
• Theconnection device230 comprises amale connector235 defining anaperture236 for receiving thefirst waveguide232 therein. Thefirst aperture236 comprises a first section for receiving theflange233 of the firstmechanical waveguide232 and a second section. The internal face of themale connector235 comprises aprotrusion237 defining the second section of theaperture236. Theprotrusion237 comprises an abutment face for abutment against theflange233 of themechanical waveguide232, The dimensions of the second section of theaperture236 are greater than the dimensions of themechanical waveguide232 so that theprotrusion237 is not in physical contact with the lateral face of themechanical waveguide232 when thewaveguide232 is inserted into themale connector235.
• Theconnection device230 further comprises afemale connector238 which defines anaperture239 for receiving themechanical waveguide231 therein. Theaperture239 comprising a first section for receiving therein the flange234 of themechanical waveguide231 and a portion of themale connector235, and a second section. The internal face of thefemale connector238 comprises aprotrusion240 which defines the second section of theaperture239. Theprotrusion240 comprises an abutment face for abutment against the flange234 of themechanical waveguide231. The dimensions of the second section of theaperture239 are greater than the dimensions of themechanical waveguide231 so that theprotrusion240 is not in physical contact with themechanical waveguide231 when themechanical waveguide231 is inserted into thefemale connector238.
• In one embodiment, theapertures236 and239 are cylindrical. In this case, the second section of theaperture236 has a diameter that is greater than that of themechanical waveguide232 and that is less than that of the flange of themechanical waveguide232. The second section of theaperture239 has a diameter that is greater than that of themechanical waveguide231 and that is less than that of the flange of the second mechanical waveguide.
• In one embodiment, the portion of themale connector235 that is insertable into thefemale connector238 comprises a first thread extending on its external surface. The internal surface of thefemale connector238 comprises a second thread within the first section of theaperture239, and the second thread matches the first thread so that the male andfemale connectors235 and238 be threadingly securable together.
• In one embodiment, theflange233 extends around a whole circumference of themechanical waveguide232 and the flange234 extends around a whole circumference of themechanical waveguide231.
• It should be understood that theconnection device230 may be used for connecting any kind of waveguides provided with a flange. For example, theconnection device230 may be used for connecting together a taper and a cylindrical waveguide.
• Once secured together, the male and female connectors are only in physical contact with the flange of the waveguides. Such a configuration allows reducing the surface of contact between the connectors and the dispersive waveguide and the transmission member so as to reduce energy leakage.
• In another embodiment, the proximal end of the transmission member may be threaded and the distal end of the dispersive waveguide is provided with a threaded recess in which the transmission member is screwed in order to removably secure the transmission member and the dispersive waveguide together. It should be understood that such a connection may be used for removably securing a taper to a dispersive waveguide, a transmission member to a taper, etc.
• FIG. 18 illustrates a further example for aconnector250 between ataper252 and atransmission waveguide254. The connector assembly comprises afemale connector256 having a tubular shape and being movably mounted on the taper, and amale connector258 mounted on the transmission member. The distal end of the taper is provided with aflange260 that radially and outwardly extends around the circumference thereof.
• Thefemale connector256 comprises a tubular body having an internal threaded face and aprotrusion261 having anabutment face262. Themale connector258 comprises two hemi-tubular bodies264 that are clamped about thetransmission member254. Each hemi-tubular body264 is provided withteeth266, e.g. sharp or pointed protrusions, extending from its internal face, and a threaded outer surface threadingly engageable with the internal threaded surface of thefemale connector256. The two hemi-tubular bodies264 may be clamped about thetransmission member254 using any adequate clamping means. In this case, theteeth266 create notches in thetransmission member254 and the two clamped hemi-tubular bodies254 are fixedly secured together and fixedly secured to thetransmission member254 to form a threaded bolt. Once the hemi-tubular bodies264 have been clamped about thetransmission member254, the threaded bolt is screwed into thefemale connector256. While the threaded bolt is screwed into the female connector, theabutment face262 of thefemale connector256 abuts against theflange260 of thetaper252 and the distal end of thetaper252 abuts against the proximal end of thetransmission member254.
• In another embodiment, the two hemi-tubular bodies264 may not be clamped together. In this case, the two hemi-tubular bodies264 are pushed against thewaveguide254 and the assembly formed of the two hemi-tubular bodies264 and thewaveguide254 is screwed into thefemale connector256
• In one embodiment, the use of theteeth266 for securing thetransmission member254 to themale connector258 allows minimizing the surface area of thetransmission member254 that is in physical contact with themale connector258, thereby minimizing the propagation losses for mechanical pulses propagating in thetransmission member254.
• In one embodiment, the external surface of thetransmission member254 is provided with grooves that are each shaped and sized for receiving arespective tooth266 therein. For example, the shape and dimensions of the grooves may substantially correspond to those of the teeth so each tooth may be snuggingly inserted into its respective groove. In this case, the insertion of theteeth266 in their respective grooves allows preventing any translation of thetransmission member254 along the longitudinal axis thereof relative to themale connector258.
• In one embodiment, the grooves may result from the clamping of the two hemi-tubular bodies264 which pushes theteeth266 into thetransmission member254, thereby creating the groves. In this case, theteeth266 may be made of a material having a greater hardness than that of the material of which thetransmission member254 is made.
• In another embodiment, the grooves may be made prior to the securing of themale connector258 thereon.
• While in the illustrated embodiment, the teeth of the two hemi-tubular bodies264 are aligned together, i.e. each tooth of one of the two hemi-tubular bodies264 is aligned with a respective tooth of the other one of the two hemi-tubular bodies264, it should be understood that the teeth of the two hemi-tubular bodies264 are misaligned.
• It should also be understood that the number, position, and orientation of theteeth26 on each one of the two hemi-tubular bodies264 may vary. For example, the distance between two following teeth may vary along the internal face of the hemi-tubular bodies264.
• It should be understood that theteeth266 may be provided with any adequate shape. In one embodiment, theteeth266 may be sharp or pointed. For example, the teeth may have a pyramidal shape, a conical shape, or the like. In another example, the teeth may be rounded.
• While in the illustrated embodiment themale connector258 comprises two hemi-tubular bodies264, it should be understood that themale connector258 may comprise a single hemi-tubular body264. In this case, securing means are used to fixedly secure the hemi-tubular body264 to thetransmission member254. For example, a cable tie may be used.
• In one embodiment, theteeth266 are made of the same material than that of which thetransmission member254 is made. In another embodiment, theteeth266 and thetransmission member254 are made of different materials. For example, theteeth266 may be made of a material having a greater hardness than that of the material of which thetransmission member254 is made.
• While in the illustrated embodiment, theteeth266 project from the hemi-tubular bodies264, the person skilled in the art would understand that theteeth266 may be omitted and replaced by teeth that project radially and outwardly from the lateral surface of thetransmission member254. In this case, the teeth projecting from thetransmission member254 create notches in the internal surface of the two hemi-tubular bodies264 when the two hemi-tubular bodies264 are secured or clamped together, thereby securing the two hemi-tubular bodies264 to thetransmission member254.
• In one embodiment, the bandwidth of the energy source used in the present system, which is expressed as a percentage of the center frequency f_c, is greater than about 10%, and preferably between about 40% and about 120%. The center/main frequency f_cof the broadband energy source may vary between about 20 kHz and about 10 MHz and is preferably between about 0.1 MHz and about 1 MHz.
• The broadband source power and the level of control over the output of the broadband source can be characterized by the pulse duration, repetition rate, pressure amplitude, polarity and waveform type. In one embodiment, the mechanical pulse duration at the distal end of the transmission member is usually of the order of 1/f_c. For example, an energy source having a center frequency of 500 kHz will generate a mechanical pulse having duration of about 2 ∝s, when a bandwidth of 100% (i.e. a Q factor of 1) is considered. In one embodiment, the mechanical pulse duration can be varied by changing the center frequency or the bandwidth (i.e. Q factor) of the energy source; the pulse duration is preferably less than about 1 ms.
• The pulse repetition rate is associated with the number of pulses that can be transmitted during a certain amount of time. In one embodiment, the repetition rate can be varied between about 0.1 Hz and about 1000 Hz and is preferably between about 10 Hz and about 200 Hz.
• In one embodiment, the output pressure amplitude of the mechanical pulse generated at the output of the transmission member is greater than about 10 MPa in both compression and tension. In one embodiment, the output pressure amplitude is comprised between about 10 MPa and about 1000 MPa in compression and between about 10 MPa and about 500 MPa in tension, when measured at the distal end of the transmission member in a fluid medium.
• The amplitude of the generated mechanical pulse may be modified using different methods. For example, increasing or decreasing the driving voltage of at least one of the transducers would cause the mechanical pulse amplitude to vary accordingly. In another example, clipping the electric signals amplitude anywhere between no clipping (original signal) and 100% clipping, where only the sign (polarity) of the driving signal is preserved, would cause the mechanical pulse amplitude to increase accordingly, albeit with an increase of the amplitude of the parasitic mechanical waves preceding and following the mechanical pulse.
• The polarity is defined as the ability to reverse the sign of the pressure amplitude profile of the output mechanical pulse. The control over the waveform type can be defined as the ability to generate more than one pulse shape. For example, it may be useful to lengthen only the tensile part of the waveform or to add oscillations to treat a specific occlusion type.
• The polarity of the generated mechanical pulse may be reversed without the need of re-calibrating the system for that particular mechanical pulse. Indeed, for a linear system (as opposed to a non-linear system), the polarity of the generated pulse may be reversed by negating, i.e. multiply by −1, the transducer driving signals.
• The shape or temporal signature of the generated mechanical pulse may also be controlled electronically. In one embodiment, the system would keep in its memory sets of driving signals for the transducers, each set corresponding to a unique pulse shape. In another embodiment, the shape of the mechanical pulse may be modified by making algebraic combination(s) of the electrical driving signals with themselves such that the same algebraic combination(s) would then be impacted on the pulse itself. The workflow would be as follows. A first mechanical pulse would be measured at the distal end of the transmission member. Next, modified version(s) of the acquired first mechanical pulse would be digitally constructed and serve as building blocks and summed to create the pulse of altered shape. The modified versions are created by delaying and/or multiplying (by a given factor) the first mechanical pulse. Finally, equivalent version(s) would be made from the electrical driving signal(s) and their summation would become the new driving signals. These composed driving signals would then generate the pulse of altered shape at the distal end of the transmission member.
• In order to achieve at least some of the above-listed characteristics, thesystem50 may be used. However, the person skilled in the art will understand that other configurations are possible.
• In one embodiment, thesystem50 illustrated inFIG. 3 allows achieving an amplification factor greater than 1OOx. The amplification factor is defined as the maximum output pressure ratio between thesystem50 and a single electromechanical broadband transducer. These pressures are usually measured in water, at the same distance, on the same surface area and using the same output waveform for both configurations. In one embodiment, an amplification factor of this order of magnitude may provide the ability to reduce the input electrical power and/or the electromechanical emitting surface area. Therefore, the cost of goods and/or the apparatus overall footprint could be downsized accordingly.
• In one embodiment, the sources54-58 are electromechanical broadband sources. By doing so, the device has the capability of working in a pulse-echo mode to image/characterize biological tissues located just in front of the distal end of the transmission waveguide. Moreover, an electromechanical broadband source may provide an adequate level of control desired to cross vascular occlusion efficiently and safely.
• The following presents a specific exemplary implementation for thesystem50 illustrated inFIG. 3 in which the concentrator81 illustrated inFIGS. 4-6 are used. Nine broadband piezoelectric transducers are used, comprising four 1 inch diameter transducers and five 2 inches diameter transducers. These transducers have a bandwidth of 80% (corresponding to a Q factor of about 1.25). Eight transducers, i.e. four 1 inch diameter transducers and four 2 inches diameter transducers, are distributed symmetrically on the propagation face of the concentrator81, and a single 2 inches diameter transducer is positioned on the reflection truncated face of the concentrator81. The concentrator81 has the following dimensions: a diameter of about 6.25 inches and a thickness of about 2 inches. The concentrator81 is made of a titanium alloy. Also, the focal zone is located at the same plane where the eight transducers are positioned. The concentrator81 produces an amplification factor of about 4× when compared to a single piezoelectric transducer having the same size as the useful focal zone. Thetemporal concentrator62 has a cylindrical shape and is made of the same titanium alloys as the concentrator81. Furthermore, thetemporal concentrator62 has the following dimensions: a diameter of about 0.25 in and a length of about 50 feet. In order to limit its footprint, the spatial concentrator is coiled to a radius of curvature of about 14 in. The geometry, dimension and medium of the temporal concentrator are selected accordingly to the wavelength of operation in order to maximize the amplification factor. Taking advantage of the dispersive properties of thetemporal concentrator62, an amplification factor of at least 15× is achieved between the input and the output end of thetemporal concentrator62. The proximal end of thetemporal concentrator62 is welded at the focal zone of the spatial concentrator81 to allow an optimal wave transmission between the two parts. At the distal end of thedispersive waveguide62, a second stage spatial concentrator is added. This spatial concentrator takes the form of a taperingwaveguide64 having a proximal end diameter of about 0.25 inches and a distal end diameter of about 0.014 inches. The taperingwaveguide64 is about 3 inches long and is made of the same titanium alloy.
• The amplification factor associated with the taperingwaveguide64 is about 2×. The proximal end of theconcentrator64 can be welded to the distal end of thedispersive waveguide62 or removably connected using the above-described connector. Theproximal end86 of the elongated andflexible transmission waveguide66 is secured to the distal end of theconcentrator64. Similar securing methods may be used, e.g., welding, using a removable connector, or the like. The overall amplification factor of the device is about 120× after theconcentrator64. Thetransmission member66 is a wire made of suitable alloy like Ti-11.5Mo-67r-4.5Sn (Beta III titanium) and having a diameter comprised between about 0.040 inches and about 0.004 inches and a length of about 120 inches. A person skilled in the art will understand that different geometry, configuration, component, energy source, wavelength of operation, propagating medium, and/or the like can be used to achieve the above-described system/method for crossing occlusions using a broadband energy source that generates and transmits short, high pressure and customizable pulses up to the distal end of a transmission member.
• In one embodiment, the present method and system allow crossing vascular occlusions using a broadband source with a transmission member. This method and system are most likely to be safer and more effective compared to traditional PTA techniques. A broadband energy source that is external to the body of the patient is used to generate mechanical waves that propagate across an elongated and flexible transmission member up to the site of the vascular occlusion. Pulsed and controlled mechanical wave emission at the distal end of the transmission member may crack, cleave, erode, tunnel and/or break parts of the occlusion. By doing so, the occlusion is easier to cross using the present system and method than traditional PTA devices.
• In one embodiment, the use of a broadband source to cross vascular occlusions provides the ability to tailor the treatment according to the lesion specific composition and characteristics. Treatment customization can be achieved by varying the pulse duration, repetition rate, pressure amplitude, polarity, and/or waveform type. Adjustments of the output mechanical pulse can be made once at the beginning or live during the procedure.
• In one embodiment, because it is external to the patient body, the energy source may be used multiple times without risk of contamination. Moreover, because it is situated outside of the patient body, the energy source is not constrained in power, size or geometry.
• In one embodiment, the elongated and flexible transmission member can be used with or without traditional PTA devices such as guidewire, micro-catheter, catheter, over-the-wire balloon, or the like to facilitate accessing, guiding and crossing of the vascular occlusion. By doing so, the present system may be inserted into the workflow of standard PTA procedures.
• While they are described in a medical context, i.e. for crossing vascular occlusions, it should be understood that the above methods and systems may be used for other medical or non-medical applications. For example, the methods and systems may be used to fragment kidney stones, enhance and improve the delivery of chemicals and drugs, increase the mechanical compliance of vascular lesions prior to the use of balloon, and/or unclog and recanalize shunt catheter, catheter, micro-catheter, endoscope and/or other medical tubular instruments. The above-described method and system may also be used to soften calcified cardiac valves, free pacemaker leads and other medical device embedded in calcified and/or fibrotic tissue. The methods and systems may also have applications in other medical fields. For example, they may be used for dental and orthopedic drilling, anchor (bolt, sealant, crown, etc.) removing, and/or surface cleaning.
• The above-described methods and system of generating mechanical pulses may have applications in fields other than the medical field. For example, they may be used for machining and shaping materials such as brittle materials, for solution mixing and homogenization, unclogging pipes, hole drilling, and/or the like.
• In one embodiment, the above-describedsystem20 can be used to image or characterize an object, tissue or a surrounding area located in front of the distal end of the transmission member. To do so, a broadband source that can work both as an emitter and as a receiver may be used. In order to image an object, a mechanical pulse is first delivered at the distal end of the transmission member. Following transmission into the surrounding medium, parts of the mechanical pulse are reflected back into the transmission member. These echoes travel back thesystem20 and are converted into an electrical signal by the broadband source. Post-processing analysis can be performed to treat this signal and convert it into useful information. To perform imaging, the broadband mechanical source ofsystem20 can be the same as the one use for emission or can be a different one. For example, one can want to use a broadband mechanical source at a higher center frequency (>10 MHz) so to increase the spatial resolution of the imaging.
• The embodiments of the invention described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims (21)

1.-20. (canceled)

21. A concentrator for focusing mechanical waves emitted by mechanical wave sources, comprising:

a body extending between a transmission face comprising a focal zone thereon and a reflection face opposite to the transmission face, the transmission face for receiving at least one mechanical wave source and transmitting at least one mechanical wave emitted by the at least one mechanical wave source within the body, the reflection face being unparallel to the transmission face so as to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone of the transmission face in order to focus the at least one mechanical wave and propagate the at least one focused mechanical wave into a transmission member positioned at the focal zone, and the focusing of the at least one mechanical wave resulting in a greater amplitude mechanical wave having an amplitude being greater than an amplitude of the at least one mechanical wave emitted by the at least one mechanical wave source.

22. The concentrator ofclaim 21, wherein the focal zone is located substantially at a center of the transmission face.

23. The concentrator ofclaim 21, wherein the reflection face comprises at least one sloped section each facing a respective one of the at least one mechanical wave source when received on the transmission face and each oriented so as to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone.

24. The concentrator ofclaim 21, wherein the reflection face has a substantially parabolic shape adapted to reflect the at least one mechanical wave emitted by the at least one mechanical wave source towards the focal zone.

25. The concentrator ofclaim 21, wherein the reflection face has a truncated parabolic shape, the reflection face having a source receiving section thereon for receiving a further mechanical source for emitting a further mechanical wave to be combined at the focal zone with the at least one mechanical wave emitted by the at least one mechanical wave source.

26. The concentrator ofclaim 25, wherein the source receiving section substantially faces the focal zone of the transmission face.

27. The concentrator ofclaim 25, wherein the source receiving section is substantially planar.

28. The concentrator ofclaim 21, wherein the transmission face is substantially planar.

29. The concentrator ofclaim 21, further comprising at least one protrusion extending from the transmission face, the at least one protrusion defining at least one recess each for receiving a respective one of the at least one mechanical wave source therein.

30. The concentrator ofclaim 21, wherein the transmission face comprises at least one rounded section each for receiving a respective one of the at least one mechanical wave source having a rounded emission end.

31. The concentrator ofclaim 21, wherein a section of the transmission face containing the focal zone is substantially planar for coupling the greater amplitude mechanical wave into a waveguide having a substantially planar end.

32. The concentrator ofclaim 21, wherein a section of the transmission face containing the focal zone is rounded for coupling the greater amplitude mechanical wave into a waveguide having a rounded end.

33.-128. (canceled)

129. The concentrator ofclaim 21, wherein the transmission face is adapted to receive at least two concentric sources of mechanical waves.

130. The concentrator ofclaim 21, wherein the at least one mechanical wave source comprises at least one of an annular mechanical wave source and a hexagonal annular mechanical wave source.

131. (canceled)

132. The concentrator ofclaim 21, wherein the transmission face comprises a section having one of a convex shape and a concave shape.

133. The concentrator ofclaim 29, wherein the at least one recess is provided with a rounded shape.

134. The concentrator ofclaim 30, wherein the rounded emission end is provided with one of a concave shape and a convex shape.

135. The concentrator ofclaim 21, further comprising a transition element positionable between the transmission face and the transmission member.

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