US20010034501A1 - Pressure sensor for therapeutic delivery device and method - Google Patents

Abstract

The present invention is an apparatus for treating a selected patient tissue or organ region, at the surface of such region. The apparatus has an accessing tool for accessing the patient region, the tool having a distal end, and a proximal end at which the tool can be manipulated to place the distal end adjacent to the patient region. The apparatus also has a probe carried on the distal end and defining a contact surface that may be urged against the patient region thereby creating contact pressure. A pressure transducer is operatively coupled to the probe and is capable of producing a measurable response to the contact pressure. A monitoring device is operatively connected to the pressure transducer, for determining the contact pressure. An effector is operatively disposed on the probe for producing a given effect on the patient region when the effector is activated, and an activator operatively connected to the effector, by which the effector can be activated.

Description

• This application claims priority of U.S. Provisional Patent Application No. 60/191,610 filed Mar. 23, 2000, which is incorporated in its entirety herein by reference.[0001]
FIELD OF THE INVENTION
• The present invention relates to an apparatus and method for affecting a body tissue, such as the heart, at the tissue surface, for purposes of injecting material into the tissue or otherwise stimulating a desired therapeutic effect on the tissue.[0002]
BACKGROUND OF THE INVENTION
• Percutaneous catheter-based treatments of cardiovascular disease require that navigation of the catheter within the body be done with a mode of visualizing the catheter as it is moved within the body. The most popular mode of visualization is X-ray fluoroscopy, where an operator is able to monitor a radiopaque device as it travels within a body lumen, such as the cardiovascular system.[0003]
• Recently, interventional procedures that require catheter navigation within the chambers of the heart have been developed; these include electrophysiological mapping and ablation and transmyocardial revascularization. These procedures also often require that the tip of the catheter be placed in contact with a wall of the beating heart in order to deliver the desired treatment safely. Potential complications of this procedure may be perforation of the wall when excessive force is applied or ineffective treatment due to poor tip contact. Under fluoroscopic guidance it is often difficult to assess when the catheter tip has reached the wall because live fluoroscopy does not visualize that wall itself, since it is not radiopaque. For the same reason, even after the catheter tip has reached the wall, it is difficult to determine whether the tip consistently remains in contact with the wall or if excessive force is applied to the wall. Finally, it is also difficult to determine whether the catheter tip is substantially perpendicular to the wall because fluoroscopy yields a two-dimensional image of the device in three-dimensional space.[0004]
• Thus, for procedures where a medical instrument must be placed in firm but not excessive contact with anatomical surface, there is an apparent need for a device which is able to provide information to the user of the instrument that is indicative of the existence and magnitude of the contact force. Furthermore, for procedures where the medical instrument must also be placed either perpendicular or at some selected angle to the anatomical surface, there is an apparent need for a device which is able to provide information to the user of the instrument that is indicative of the incident angle of the contact force with respect to the anatomical surface.[0005]
SUMMARY OF THE INVENTION
• It is therefore an object of this invention to provide such a device for overcoming the above-mentioned problems.[0006]
• It is another object of this invention to provide information to the user of a medical instrument, such as a catheter, that must be placed in contact with the surface of an anatomical structure, to increase the likelihood of safely delivering the desired treatment while reducing the possibility of inflicting perforation type injuries or providing inadequate treatment.[0007]
• It is further an object of this invention to provide a method for generating information regarding whether the tip of a medical instrument, such as a catheter or probe, is in contact with a surface of a tissue or organ, and, if so, the magnitude of the contact force and the incident angle of the contact force with respect to the anatomical surface.[0008]
• In summary, the present invention is an apparatus for treating a selected patient tissue or organ region, at the surface of such region. The apparatus has an accessing tool for accessing the patient region, the tool having a distal end, and a proximal end at which the tool can be manipulated to place the distal end adjacent to the patient region.[0009]
• The apparatus also has a probe carried on the distal end and defining a contact surface that may be urged against the patient region thereby creating contact pressure. At least one pressure transducer, wherein each pressure transducer is operatively coupled to the probe and is capable of producing a measurable response to the contact pressure experienced adjacent to the pressure transducer. A monitoring device is operatively connected to each pressure transducer, for determining contact pressure. At least one effector, wherein each effector is operatively disposed on the probe for producing a given effect on the patient region when the effector is activated, and an activator operatively connected to the effector, by which the effector can be activated.[0010]
BRIEF DESCRIPTION OF THE FIGURES
• FIG. 1 illustrates the force contact transducer attached to a probing tool and monitoring circuitry;[0011]
• FIG. 2 is an exploded view of a force contact transducer constructed in accordance with embodiments of the invention;[0012]
• FIG. 3 illustrates a view of the cap and base of the force contact transducer;[0013]
• FIG. 4 illustrates a view of the cap region of the force contact transducer;[0014]
• FIG. 5 illustrates a detailed exploded view of contact elements of the invention;[0015]
• FIG. 6 illustrates one embodiment of the invention that employs a thin film transducer array disposed around a tool shaft;[0016]
• FIGS.[0017]7A-7D illustrate embodiments of a transducer array and a single transducer;
• FIG. 8 illustrates, in simplified view, the cap region of a transducer capable of detecting both axial and lateral force components applied to the sensor; and[0018]
• FIG. 9 illustrates an embodiment of the invention of the invention that measures force movement by electrical inductance, rather than by resistance.[0019]
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 shows an[0020]apparatus44 constructed according to the invention. The apparatus provides an assembly ortool46, for accessing a patient tissue ororgan region47, and asensor device20, detailed below, for determining the pressure of the probe against the target tissue and, in some embodiments, the angle of contact between the probe and target tissue.
• In general application, the assembly is used to access an internal target region, and to provide a therapeutic stimulus, such as injection of a therapeutic compound or gene, forming a laser channel, or introducing an injury, e.g., by ultrasonic waves, infrared radiation, or mechanical injury on below the surface of the target region. E.g., to stimulate an angiogenic response in the target region. The therapeutic stimulus is preferably administered/provided through the assembly probe. The sensor device operates, in accordance with the invention, to provide information to the user about the position of the probe with respect to the target region, since the target region is generally not directly viewable by the user, e.g., physician.[0021]
• In the embodiment shown, the medical instrument includes a[0022]rigid shaft46, which may have a curved section, as shown in FIG. 1. Alternatively, the medical instrument is a flexible catheter, e.g., for delivery of a therapeutic stimulus to a target site within the vasculature or heart. The distal end of the shaft may be the base of the transducer, as shown in FIG. 1, or a separate element securely affixed to base. Ahandle48 is attached to the proximal end of the shaft or base. In one embodiment, the shaft is pivotally attached to the transducer base to permit the tip of the medical instrument to bend. The handle includes acontrol panel50 having for control of the instrument by the user. Also shown are a bridge divider, anoutput device54, such as a display device, andsignal processing circuitry56 whose operation is described below.
• While not detailed here,[0023]handle48 is designed to produce a selected therapeutic effect on target tissue, when a desired pressure and/or pressure contact angle is sensed between the probe and target tissue. The therapeutic effect may be the injection, by a needle or needleless injection system, of a solution or suspension of a therapeutic compound or gene, or a radiation or ultrasound injury produced by an light-carrying fiber or sonic device on the probe, or a mechanical injury produced by a mechanical tool on the probe, as in conventional. The apparatus is therefore equipped, according to well-known devices, to provide an extendable needle, a light fiber, an extendable mechanical-injury device, or the like to produce the desired therapeutic effect, in response to a signal applied by the user to handle48. That is,handle48 includes structure for activating the therapeutic receptor at the distal end of the apparatus. In one embodiment, the therapeutic response is activated when the distal end of the apparatus is positioned against the target tissue with a desired pressure, that is, above a selected pressure threshold or within a desired pressure range, as determined from the pressure sensor device of the invention. In addition, angle of contact as sensed by the device may be employed as a variable to be considered in an automated triggering.
• FIG. 2 is an exploded view of a force contact transducer or[0024]device20 constructed in accordance with embodiments of the invention.Device20 includes an elongate,cylindrical base22 that may be constructed of non-conductive material such as polycarbonate or a metallic conductive material such as surgical steel or similar material. The base has alarger diameter portion24 that may serve as, or be attached to, a shaft of an associated medical instrument, such as needle-delivery device or light fiber, in which the transducer is incorporated. Extending from the distal end of the larger diameter portion is a reduceddiameter portion26.
• Attached to, or formed integrally with, the reduced diameter portion is a[0025]flange28 that has acentral opening28aand one or more notches, such asnotch28c,formed in its outer edge. Anupper surface28bof the flange is electrically conductive (by placement of a not shown conductive layer and serves as one of the electrical conductors of the transducer. The details of the base are illustrated in FIG. 4.
• [0026]Device20 further includes acap30, which is generally cylindrical in shape and has an axial bore extending therethrough to define an inner wall. A plurality ofrectangular feet30bare formed on oneend surface30cof the cap, which surface acts as the second electrical conductor of the transducer. The cap is shown in more detail in FIG. 4.
• Sandwiched between conducting[0027]surfaces30cand28bare: (i) a conductive orsemi-conductive elastomer32 that is preferably made of carbon loaded silicone rubber or other material with similar characteristics, and (ii) a thin, non-conducting insulatinglayer34 that is preferably made of mylar, polyimide or other material which exhibits similar insulating or dielectric properties. Each of thesecomponents32 and34 has anopening32aand34arespectively formed therein so that these components may be received on the reduceddiameter portion26 ofbase22. Alower surface34bof the insulating layer abuts against, but does not completely cover,conductor surface28b,so that alower surface32bof the conductive elastomer is able to selectively make contact withconductor surface28bbased on a force applied to the transducer, as will be explained in more detail below.
• In the illustrated embodiment, this is accomplished by making[0028]opening34bin the form of a slot, as seen best in FIG. 5. However, this is merely one example; other arrangements are possible. For example, the insulator may have a central opening a plurality of radial arms providing a plurality of circumferential slots through which electrical contact between in the elastomer and the confrontingconductive surface28bofflange28.
• Formed along the outer edge of[0029]insulator34 is anotch34c,which is aligned withnotch32cinelastomer32 andslot28cinflange28, as seen particularly in FIGS. 3 and 4. The notches accommodate a pair ofelectrical leads36aand36bthat are in electrical contact with conductingsurfaces28band30c,respectively, as shown in FIGS. 2 and 3.
• Formed in an[0030]upper surface32cof the conductive elastomer is a plurality of indents or footprints that correspond to thefeet30bformed onconductive surface30cof the cap. Each one of thefeet30bis adapted to fit securely within its complementary footprint to maintain constant contact between the conductive surface ofcap30 and the upper surface ofconductive elastomer32.
• It is desirable to seal the components of the contact force transducer apparatus to prevent ingress of bodily or other fluids into the electrical regions of the apparatus. Furthermore, it is highly desired to seal the invention to prevent the egress of components from the contact force transducer apparatus. Accordingly, one skilled in the art would realize that numerous means for sealing the apparatus are possible. For example, a potting material may be introduced at component junctions so as to seal the device without interfering with its intended function. Alternatively and as discussed in detail below, a shroud or tip may be employed to seal the apparatus. Such sealing means may be preformed or formed in place, for example, by dipping an appropriately masked apparatus in a sealing compound to create a tip or shroud in place.[0031]
• A[0032]tip element38 may be employed to protect the cap. In one embodiment, the tip has alower end38athat is securely attached to an upper end of the cap, as shown in FIG. 2. In another embodiment, the tip extends over the cap-conductive elastomer-insulator assembly (not shown). In either case, when the tip is used, itsouter surface38bacts as the contact surface of the transducer. When the tip is not employed, the upper end of the cap is the contact surface. The transducer components including the tip in assembled form are shown in FIG. 2. When the tip is not used,upper end30dserves as the contact surface of the transducer. The assembled transducer excluding the tip is shown in FIG. 3.
• If desired, a suitable biologically compatible coating or cover[0033]40 may be applied to the cap-conductive elastomer-insulator-flange assembly (and tip if included) to protect it and to prevent fluid ingress. Such a cover or coating, with portions broken away, is shown in FIG. 2.
• A second embodiment of the invention (not shown) is similar to the first except that it further includes a thin insulator which fits between[0034]cap30 andtip38 to reduce the friction between these components and enable them to move relative to each other as the force applied to the contact surface of the transducer is varied.
• In operation, an electrical excitation signal is generated in a bridge or divider circuit[0035]52 (FIG. 1) and applied to the conductive surfaces or other electrical elements of the sensor described below. If a force below a predetermined threshold is applied to the contact surface of the transducer, the excitation signal will remain the same. However, if the applied force is just above the predetermined threshold,conductive elastomer32, which is in constant contact withconductive surface30c,will extend or be pushed through the openings or perforations in insulatinglayer34 to make contact withconductive surface28b.This causes the impedance between the two conductive surfaces to decrease, producing a change in the excitation signal which indicates that minimum contact has been made. As the applied force is further increased, the conductive elastomer compresses causing a further proportional drop in the impedance that, in turn, produces corresponding change in the excitation signal. Thus, the impedance and therefore the excitation signal varies with the magnitude of the applied force.
• The bridge/divider circuit is in electrical communication with an[0036]output device54 which may be in the form of audio or visual device adapted to provide an information signal to the user indicative of whether the outer surface of the transducer has made contact, and, if so, the magnitude of the contact. The output device may take a variety of different forms. For example, an LED bar graph or other display capable of rendering a graphical or visual representation may be used to provide a continuous, quasi-continuous or discrete indication of the magnitude of a force applied to the contact surface of the transducer, from a minimum applied force indicative of minimum contact to a predetermined maximum. Alternatively, or in addition to, a speaker or other audio device may be used to emit a sound when minimum contact is made and emit proportionally louder sounds as the firmness of the contact increases.
• The sensitivity of the excitation signal and hence the information signal may be adjusted in a number of different ways. One way is by using an elastomer with a different conductivity and/or compressibility. Another way is with electronic signal processing circuitry with adjustable amplification and filtering. Such a signal processing circuit ([0037]56) may be physically integrated with the bridge/divider circuit, or may be a separate circuit that is in electrical communication with the bridge/divider circuit, as illustrated in FIG. 1. The sensitivity of the signals (excitation and information) may also be adjusted by varying the size of the openings or perforations in the insulating layer, or by varying the thickness of the insulating layer. Larger perforations increase the sensitivity. In any case, the sensitivity of the transducer is set based on the desired contact force threshold and the minimum magnitude of change to be detected.
• A flat transducer contact surface will generate less of an output signal if the tip is in contact with tissue surface at an oblique angle. On the other hand, a rounded or tapered contact surface will generate a greater output signal at an oblique angle of contact. Thus, the geometry of the contact surface may be tailored to provide feedback about the perpendicularity of the contact between the medical instrument tip and the tissue surface. Optionally, the friction coefficient of the tip or exposed cap material at the contact surface may be altered to provide for shear force as the probe is situated upon a tissue surface in a way that a lateral force vector component manifests, assuming at least some of the thrust force applies creates a later force component. The less the friction between the contact surface and the tissue surface, the less the shear or lateral force component realized.[0038]
• In another embodiment, a plurality of discrete transducers can be distributed on the tip of a medical instrument to provide further information regarding the perpendicularity of the contact. In the case of two transducers, each covers 180 degrees of the tip surface; in the case of three transducers, each covers 120 degrees, etc. The combined signal from the multiple transducers may be processed to provide, in addition to contact and magnitude information, angle of contact of information as well.[0039]
• In another particularly preferred embodiment, a transducer, or transducers if contact angle sensing is sought, may comprise a thin double mylar film layered sandwich as described in Krivopal, U.S. Pat. No. 5,989700, herein incorporated in its entirety by reference. Looking at FIG. 6, the instant invention differs from Krivopal in that[0040]sensor60 hassensor elements68 on a support70 having anaperture76 disposed in the center to permittool shaft64 to be disposed at a normal angle through the sensor or sensor array. Each individual sensor area is electrically accessible by leads66.
• The sensor support[0041]70 which can either be rigid, or elastic depending on the degree of flexibility sought in the device. Disposed above the sensor support is a resilient orelastomeric cap72 which mechanically communicates the probe tip contact surface incident angle and total contact force downward tosensor60.Cap72 may further includeprotuberances78 to focus the communicated force ontosensors68.
• The entire probe tip may be covered by a sheath, not shown. Alternatively, a transducer, such as a thin film transducer, may be positioned directly on the contact surface, thereby creating a superior contact surface. Alternatively, the probe may lack a cap element and thus directly expose a transducer, such as a thin film transducer, to a tip surface opposite the tip contact surface, or the transducer may itself comprise the tip surface, and thus the contact surface as well. Each of these embodiments just described may include one or more transducers so that incident angle as well as force may be detected.[0042]
• Considering now the embodiments shown in FIGS.[0043]7A-77D, asandwich112 has atop mylar film112a,an upperconductive ink layer112bapplied to the lower surface region of thetop mylar film112a,an uppersemiconductive ink112capplied to the upperconductive ink layer112b,anair gap112d,a lowersemiconductive ink layer112edisposed upon a lowerconductive ink layer112fwhich is disposed on the upper surface of abottom mylar film112g.
• There may be an insulting ring or sections surrounding the above described ink sandwich to separate the upper mylar layer from the lower mylar layer thus creating the air-gap between the upper and lower semi-conductive ink layers. In the case of a[0044]multiple transducer array100,several sandwich regions102,104,106 may be arranged upon the plane created by the mylar film, each region being in electrical communication with the monitoring unit, and each region is independently responsive to the contact force present at the corresponding region of the contact surface of the probe thus providing a means of determining the incident angle of the contact force with respect to the tissue surface by comparing the individual responses of each transducer sandwich region.
• Alternatively, each[0045]sandwich region114 may be a separatemylar film sandwich116, with eachelectrode118,120 individually in electrical communication with the monitor device.
• In another embodiment, the pressure transducers may be a combination to of a purely mechanical resilient device such as an elastomeric spacer, and a mechanical or electrical device for measuring the effect of the force upon the resilient device. Measurement may include a mechanical deflection of mechanically communicated information to a portion of the tool distal from the patient surface, or may be a switch or potentiometer mechanically operating is above its inherent mechanical (frictional) resistance. Mechanically communicated deflection may be monitored and displayed to a user as described below.[0046]
• FIG. 8 shows another embodiment of a[0047]sensor device80 for use in the apparatus of the invention. The device shown here is designed to measure both axial pressure, along an axis normal to the contact face of the probe, and lateral direction, i.e., force applied to a side region of the probe. The device includes a rigidmechanical support81 which is attached at its lower end in the figure to the distal end of the accessing tool, and which provides acentral opening82 through which the therapeutic effector, e.g., needle or optical fiber is received.
• The device has a[0048]flexible cap83 that is rigidly attached to a radially extendingannular ring91 in the support. The cap is formed of a flexible polymer or elastomer material or other flexible material that permits the cap to deform when pressure is applied to the cap, when the probe is in contact with the target tissue. Carried on inner, upper surface of the cap is a preferably segmentsannular electrode ring84 positioned to contact an annularconductive elastomer member86 of the type described above, when an axial pressure acts and distorts the upper surface of the cap. The elastomer member, in turn, is seated on ainsulative spacer85 that provides an electrical barrier between the elastomer and support, but which provides openings or notches through which the elastomer can be pressed, when an axial force acts on it, as described with reference to FIGS.1-4.
• In operation, when an axial force is applied to the cap, the cap is distorted to bring[0049]electrode ring84 into contact withelastomer member86, pushing the elastomer through spaces in theinsulative spacer85. This changes the resistance of a circuit containing the two electrodes and the elastomer member in proportion to the total contact area that the elastomer makes with the support electrode, and this change in resistance is recorded and displayed to the user.
• Carried on the annular side region of the support is a plurality of insulative members, such as[0050]elastomeric members88a,88b,arranged circumferentially about the support. Typically, the device includes three such members, each member being carried on an insulative spacer, such asspacers89a,89b.Similarly, carried on the inner confronting surface of the cap is asegmented electrode87 which is disposed to make contact withindividual elastomer members84 when side regions of the cap are distorted by side pressure and brought against the confronting elastomeric segments. Thus, side-directed pressure is detected, as above, by a change in the resistance in one or more or the side elastomer members, as the cap electrodes push against the elastomer member(s), forcing surface portions of the member(s) through openings in the spacers, and lowering the resistance of each associated circuit containing the affected elements. The user thus has information about axial pressure, from the change in resistance (impedance) in the upper-cap circuit, and information about angle of contact by the extent of asymmetry in measured resistances of the three side circuits.
• In a purely mechanical device there may be disposed between the probe and the proximal end of the tool an elastic resilient support. Absent any surface contact, the probe's contact surface remains perpendicular to the thrust axis of the tool because of the elastic resilient support. Attached to the tool side of the probe are the ends of at least 3 or more flexible shafts running parallel or coherently through the tool length. These shafts run slidably through and protrude beyond lumens within the tool body beginning at the probe facing side of the proximal end of the tool and terminating as openings at the distal or user end of the tool. As the contact surface is deflected away from the thrust axis of the tool, the distance between the probe contact surface and the tool varies depending on the angle of deflection. The shaft, beneath where the distance between the contact surface of the probe and the proximal end of the tool is least, will protrude out more from the distal or user end of the tool, whereas the shafts opposite will recede into the tool at the distal or user end. Consequently, a user will be able to observe angular relation of the probe to the tool by observing the protrusion or withdrawal of the shafts, thereby the user could adjust the incident angle of the tool to achieve a balanced shaft display. One skilled in the art would readily recognize that many variations of this embodiment are possible, especially with respect to how the angular information is displayed to the user.[0051]
• In another multi-transducer embodiment, each pressure transducer is independently elastically and resiliently related to the contact surface, and another embodiment provides for each pressure transducer being mutually elastically and resiliently related to the contact surface.[0052]
• In yet another embodiment, the monitor is operatively connected to the activator such that at a pre-selected measurement, the activator is activated thus causing the effector to activate. In a related embodiment, the monitor is operatively connected to the activator such that the activator can only be manually activated by the user when the monitor measures a predetermined measurement from the pressure transducer. In yet another related embodiment, the monitor does not affect the operability of the activator.[0053]
• In yet another embodiment, the pressure transducer may respond to deflection by varying capacitance rather than resistance. Capacitance can be varied by sandwiching a pressure sensitive dielectric material between two electrodes. Alternatively, changes in pressure can be measured by varying inductance with[0054]inductor transducer device90 illustrated in FIG. 90. As seen, the device includes acap94 which can move in an axial direction (the direction of arrow100) toward and away from the relaxed (no-pressure) position shown in the figure, mounted for such axial movement on asupport92 which is carried on the distal end of the apparatus tool. The support provides aninduction coil99 formed ofconductive wire windings98 which are positioned adjacent a cylindricalpermanent magnet96 mounted on the cap.
• Movement of the cap in the direction of[0055]arrow100caries magnet96 past the inductive wires, producing a change in the inductance of the coil. Such changes can be monitored by incorporating the inductor into a LC or inductor-capacitor oscillating circuit and monitoring the change in the resonant frequency of the LC circuit.
• In yet another embodiment, any transducer described herein may be combined with an ultrasonic transducer capable of detecting tissue density or thickness. For example, the ultrasonic transducer of Zanelli, et al., U.S. Pat. No. 6,024,703, herein incorporated in its entirety by reference, discloses an ultrasound device for axial ranging. This would provide for the ability to limit the throw or depth that an effector element is permitted to penetrate into the patient tissue underlying the tissue surface thus avoiding either to shallow, thus ineffective penetration, or to deep and thus harmful penetration of the effector element.[0056]
• As should be apparent from the foregoing description, the present invention, unlike fluoroscopic methods provides force information such as but not limited to, force contact, magnitude and direction or incident angle with respect to the patient tissue surface, for catheter-based surgical procedures or other medical procedures where the degree of contact between the medical instrument and a surface of an anatomical structure is useful to know. In addition, such information may be provided in real-time and in a variety of formats using a low cost, disposable force contact transducer of the type disclosed herein. Such a transducer may be easily integrated into existing catheter tools, eliminating the need for extensive hardware/software interfaces.[0057]
• While various embodiments of the invention have been illustrated and described, it will be evident to those skilled in the art in light of the foregoing disclosure that many further alternatives, modifications and variations are possible. For example, the insulator need not be a separate element but may be in the form of an insulative coating that is selectively applied to the conductive surface of the flange to permit the lower surface of the conductive elastomer to make contact with that conductive surface in accordance with the teachings of the invention. The invention disclosed herein is intended to embrace all such alternatives, modifications, and variations as may fall within the spirit and scope of the appended claims.[0058]

Claims (16)

what is claimed:

1. Apparatus for treating a selected patient tissue or organ region, at the surface of such region, comprising

an accessing tool for accessing the patient region, said tool having a distal end and a proximal end at which the tool can be manipulated to place the distal end adjacent such patient region,

a probe carried on said distal end and defining a contact surface that may be urged against said patient region thereby creating contact pressure,

a pressure transducer operatively coupled to said probe and capable of producing a measurable response to the contact pressure,

a monitoring device operatively connected to said pressure transducer, for determining the contact pressure,

an effector operatively disposed on said probe for producing a given effect on the patient region when effector is activated,

an activator operatively connected to said effector, by which said effector can be activated.

2. The apparatus of

claim 1

, wherein said monitor is operatively connected to a user readable display.

3. The apparatus of

claim 1

, wherein said activator is operatively connected to said monitor and activates said effector at a pre-selected range.

4. The apparatus of

claim 1

, wherein said monitoring device is operable to measure the range over which the pressure transducer is responsive to changes in the force applied to the transducer, and to determine from such range, a contact-pressure range within which activation of the effector is optimized for treatment effect.

5. The apparatus of

claim 1

, wherein said pressure transducer is responsive to the magnitude and direction of force applied to the transducer, and said monitor is operable to determine both the contact pressure and the approximate incidence angle of said tool with respect to the surface of the patient region.

6. The apparatus of

claim 5

, wherein said pressure transducer includes a plurality of pressure-transducer units, each carried on the probe's contact surface, and said monitoring device is operable to determine from the force applied to each unit, the orientation of the said tool with respect to the surface of patient tissue with which said is in contact.

7. The apparatus of

claim 5

, wherein said pressure transducer defines an axis of least strain along which force can be applied to the tool's head, and the transducer is responsive to force components applied along the axis and off axis.

8. The apparatus of

claim 5

, wherein said probe is movably mounted on the distal end of said tool, and the pressure transducer includes position-sensing means for sensing the position of the probe with respect to the distal end of the tool.

9. The apparatus of

claim 1

, wherein said pressure transducer includes (i) first and second conductors, (ii) an insulating layer adjacent the first conductor, said layer having perforations therein, and (iii) a conductive elastomer disposed between the insulating layer and the second conductor and in constant contact with the second conductor; wherein, during operation of the transducer, an electrical excitation signal applied to the two conductors and the impedance therebetween varies with a force applied to the contact surface of the transducer to generate an information signal indicative of whether or not the force applied to the contact surface is above a predetermined threshold, and, if so, the magnitude of the applied force.

10. The apparatus of

claim 9

, wherein said conductive elastomer temporarily flows through the perforations in the non-conductive layer and makes contact with the first conductor, when the applied force is above the predetermined threshold.

11. The apparatus of

claim 1

, wherein said monitoring device is operably connected to said activator, to activate said effector when such contact pressure is within a selected pressure range.

12. The apparatus of

claim 1

, for use in promoting angiogenesis in an under-oxygenated region of a patient's heart, wherein the accessing tool is designed to access an exterior or interior surface of such heart region from an external body site, and said effector is designed to produce an angiogenic stimulus in the myocardial layer of such region, upon activation of the effector.

13. A pressure transducer comprising

means defining a contact surface,

first and second conductors;

an insulating layer having perforations therein, the non-conductive material being adjacent to the first conductor; and

a conductive elastomer between the insulating layer and the second conductor and in constant contact with the second conductor;

wherein, during operation of the transducer, an electrical excitation signal applied to the two conductors and the impedance therebetween varies with a force applied to the contact surface of the transducer to generate an information signal indicative of (i) whether or not the force applied to the contact surface is above a predetermined threshold, and, if so, (ii) the magnitude of the applied force.

14. The transducer of

claim 13

, wherein the information signal is provided continuously and in real-time.

15. The transducer of

claim 13

, wherein the conductive elastomer temporarily flows through the perforations in the non-conductive layer and makes contact with the first conductor, when the applied force is above the predetermined threshold.

16. The transducer of

claim 15

, wherein the electrical excitation signal remains substantially unchanged when the applied force is below the predetermined threshold.

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