Disclosure of Invention
The invention aims to provide a microwave ablation catheter, which can drain a refrigerant flowing out of a first diversion opening to a second diversion opening through a capillary tube and spray the refrigerant to the inner wall of a human body cavity so as to cool the inner wall of the human body cavity and prevent non-target tissues in an ablation area from being damaged by high temperature, and meanwhile, the device can realize stable ablation and efficient energy radiation in human organs with different dielectric constants by adjusting the sizes of L1, L2 and L3, and the ablation area is expanded while a spherical heating mode is kept unchanged.
The technical scheme adopted by the invention is as follows:
The utility model provides a microwave ablation pipe, includes outer pipe, the one end of outer pipe is provided with the needle bar, the inside of needle bar is fixed with the steering control piece, a plurality of grooves of dodging have been seted up to the inside of steering control piece, and a plurality of dodging groove and a plurality of first water conservancy diversion mouth looks adaptation, the inside sliding connection of outer pipe has an inner catheter, just the one end and the needle bar fixed connection of inner catheter, the inside of inner catheter is equipped with the cooling tube, still includes:
The support net sleeve is arranged between the outer catheter and the needle bar and is positioned at the outer side of the inner catheter, the support net sleeve is formed by connecting a plurality of support rods and connecting rods, a plurality of second guide ports are formed in the outer sides of the support rods, and the support net sleeve can shrink and expand along the radial direction of the inner catheter;
the coaxial cable is assembled in the cooling pipe, one end of the coaxial cable is provided with a top capacitor loading antenna which is positioned in the needle bar, the outer side of the top capacitor loading antenna is sleeved with a retainer, and the inner ring of the retainer is provided with a plurality of diversion holes;
the control end is assembled at one end of the outer catheter, which is far away from the needle bar, a water inlet pipe and a water outlet pipe are arranged in the control end, the water inlet pipe is connected with the cooling pipe, and the water outlet pipe is connected with the inner catheter;
After the refrigerant is conveyed into the cooling pipe, the refrigerant flows to the first diversion port and the water outlet pipe, and part of the refrigerant is sprayed to the inner wall of the human body cavity through the needle bar and the second diversion port in sequence.
In a preferred scheme, the material of bracing piece and connecting rod is any one of the following materials: PTFE, FEP, PI, PEEK, elastic pieces, polymers and high molecular materials.
In a preferred scheme, a plurality of first water conservancy diversion mouth have evenly been seted up to the outside of needle bar, the bracing piece is hollow tubular product, the input has been seted up to the one end that the bracing piece is close to the needle bar, the one end that the bracing piece kept away from the needle bar is closed state, and is a plurality of be connected between the input and the a plurality of first water conservancy diversion mouth of bracing piece.
In a preferred embodiment, the number of the first conduction ports is denoted as M, and the number of the support rods is denoted as N, where M > N.
In a preferred scheme, be equipped with the choking piece between needle bar and the steering control spare, the one end and the needle bar fixed connection that the outer pipe was kept away from to the choking piece, choking piece and steering control spare sliding connection, the ripple expansion section has been seted up to the middle-end of choking piece, wherein, when ripple expansion section is in the state of stretching, choking piece is to first water conservancy diversion mouth formation cover, when ripple expansion section is in the state of shrinking, first water conservancy diversion mouth and the inside groove of dodging of steering control spare link up each other.
In a preferred embodiment, the material of the flow blocking piece is a memory alloy.
In a preferred embodiment, the phase transition temperature of the flow resistor is in the range of 35 ℃ to 60 ℃.
In a preferred embodiment, a shielding layer is provided on the outside of the flow resistor.
In a preferred scheme, the shielding layer is made of graphite;
In a preferred scheme, the coaxial cable includes microwave antenna, around the coaxial antenna dielectric layer that sets up of microwave antenna and around the coaxial antenna shielding layer that sets up of antenna dielectric layer, just microwave antenna and top electric capacity load antenna fixed connection, wherein, in the extending direction of needle bar, the distance between the one end that the top electric capacity load antenna kept away from outer pipe to the antenna dielectric layer near top electric capacity load antenna one end is recorded as L1, the distance between the one end that the antenna dielectric layer near top electric capacity load antenna and the one end that antenna shielding layer near top electric capacity load antenna is recorded as L2, the length of top electric capacity load antenna in the needle bar extending direction is recorded as L3, and L1, L2, L3's value is adjusted according to the dielectric constant of organs.
The invention has the technical effects that:
According to the invention, the first guide port and the second guide port are respectively arranged on the outer sides of the needle bar and the supporting net sleeve, the refrigerant flowing out of the cooling pipe is guided to the second guide port through the capillary tube, and the refrigerant is sprayed to the inner wall of the human body cavity through the second guide port, so that the temperature of the tissue of the inner wall of the human body cavity is reduced, and the non-target tissue in the ablation area is prevented from being damaged by high temperature;
according to the invention, by adjusting the sizes of L1, L2 and L3, the device can realize stable ablation areas and high-efficiency energy radiation when performing ablation operations on human organs with different dielectric constants, so that the spherical heating mode is kept unchanged while the ablation areas are enlarged;
According to the invention, the number of the first diversion openings is adjusted, so that the device can synchronously cool the inner wall of the human body cavity through the second water outlet and the supporting net sleeve, and the area of a cooling area, the cooling effect and the cooling efficiency are improved;
The supporting net sleeve with the net structure is arranged, so that the device can be kept centered in the human body cavity, deflection of the device is avoided, the tumor focus part can not be symmetrically covered in an ablation operation, meanwhile, the supporting net sleeve made of a high polymer material can be effectively prevented from being ignited in the ablation process, surrounding tissue injury is avoided, and the phenomenon of unsmooth blood flow or unsmooth breathing of a patient is avoided;
according to the invention, the flow blocking piece made of the memory alloy is arranged in the needle bar, the first diversion port is covered by the flow blocking piece in a normal temperature environment, and the temperature of the environment is sensed by the flow blocking piece, so that the refrigerant is prevented from flowing out in advance in the process of melting and heating, and the heating time is prolonged.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one preferred embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
In describing the embodiments of the present invention in detail, the cross-sectional view of the device structure is not partially enlarged to a general scale, and the schematic drawings are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Example 1
Referring to fig. 1 to 6, in a first embodiment of the present invention, a microwave ablation catheter is provided, which includes an outer catheter 100, a needle shaft 101 is disposed at one end of the outer catheter 100, a plurality of first conduction ports 102 are uniformly disposed at the outer side of the needle shaft 101, a steering control member 103 is fixed inside the needle shaft 101, a plurality of avoiding grooves are disposed inside the steering control member 103, the plurality of avoiding grooves are adapted to the plurality of first conduction ports 102, an inner catheter 104 is slidingly connected inside the outer catheter 100, one end of the inner catheter 104 extends to the inside of the needle shaft 101 and is fixedly connected with the needle shaft 101, and a cooling tube 105 is disposed inside the inner catheter 104, and the microwave ablation catheter further includes:
The supporting net sleeve 110 is assembled between the outer catheter 100 and the needle rod 101 and positioned at the outer side of the inner catheter 104, the supporting net sleeve 110 is formed into a net structure by connecting a plurality of supporting rods and connecting rods, the supporting net sleeve 110 of the net structure can reduce the resistance of blood or gas passing through the supporting net sleeve 110, a plurality of second guide openings 111 are formed in the outer side of each supporting rod, and the supporting net sleeve 110 can shrink and expand along the radial direction of the inner catheter 104;
The coaxial cable 120, the coaxial cable 120 is assembled in the cooling tube 105, one end of the coaxial cable 120 and located in the needle bar 101 is equipped with a top end capacitor loading antenna 121, the top end capacitor loading antenna 121 can emit microwaves conveyed by the coaxial cable 120, the outer side of the top end capacitor loading antenna 121 is sleeved with a retainer 122, the retainer 122 can prevent the top end capacitor loading antenna 121 from deflecting, the inner ring of the retainer 122 is provided with a plurality of diversion holes 123, wherein the top end capacitor loading antenna 121 not only can shift the resonance frequency of microwaves emitted by the coaxial cable 120 to a lower frequency band, impedance matching is achieved, electromagnetic waves which are reversely propagated along the coaxial cable are reduced, standing waves of the radiation antenna can be regulated, radiation efficiency is improved, and an ablation area is increased;
The control end 200 is assembled at one end of the outer catheter 100 far away from the needle bar 101, a water inlet pipe 201 and a water outlet pipe 202 are arranged in the control end 200, the water inlet pipe 201 is connected with the cooling pipe 105, the water outlet pipe 202 is connected with the inner catheter 104, a microwave input port 203, a mesh adjusting key 204, a first steering handle 205 and a second steering handle 206 are also assembled in the control end 200, the microwave input port 203, the coaxial cable 120, the mesh adjusting key 204 and the outer catheter 100 are all connected with each other, the mesh adjusting key 204 can drive the outer catheter 100 to move relative to the inner catheter 104, the distance between the outer catheter 100 and the needle bar 101 is changed, the supporting mesh 110 is further driven to shrink or expand, the first steering handle 205, the steering control 103, the second steering handle 206 and the steering control 103 are all connected through traction ropes, a plurality of traction ropes are annularly arranged in the steering control 103, the steering control 103 can be driven to bend through the cooperation of the first steering handle 205, the second steering handle 206 and the traction ropes, the steering control 103 can be driven to bend, the needle bar 101 is driven by the steering control 103 to bend, and the needle bar 101 can be driven by the steering control 103 to bend along the shape of a human body 101 to reach the focal position along the needle bar 101;
After the refrigerant is fed into the cooling tube 105, the refrigerant flows to the first guide port 102 and the water outlet pipe 202 according to a predetermined path, and a part of the refrigerant flows out of the needle bar 101 through the first guide port 102.
Further, the device is also matched with a refrigerant conveying device and a microwave control module, the refrigerant conveying device can convey a refrigerant into the cooling pipe 105 and drive the refrigerant to circularly flow, the input end of the refrigerant conveying device is connected with the water inlet pipe 201, and the input end of the refrigerant conveying device is connected with the water outlet pipe 202, wherein the refrigerant can be one of the following substances: normal saline and pure water, in this embodiment, the refrigerant is preferably normal saline, and the microwave control module is connected to the microwave input port 203, and the microwave control module can transmit microwaves to the coaxial cable 120 and regulate and control the frequency of the microwaves.
It should be noted that, the one end that the needle bar 101 kept away from outer pipe 100 is provided with the guide surface, and the shape of guide surface is semi-circular or arc, through this scheme setting, can avoid needle bar 101 to get into inside the human cavity after the needle bar 101 causes fish tail or damage to human cavity inner wall.
In this embodiment, when the tumor focus or the target tissue is ablated, the needle rod 101 is conveyed to a preset position through the guidance of the imaging device, the microwave control module is started, microwaves are conveyed through the coaxial cable 120, the microwaves are emitted through the top capacitor loading antenna 121, the polar molecules in the tumor focus or the target tissue are rotationally vibrated to generate a thermal effect through microwave radiation, the cells in the tumor focus or the target tissue are coagulated and necrotized through a heating mode, an ablation area is finally formed, in this process, the top capacitor loading antenna 121 is arranged, standing waves of the radiation monopole antenna can be effectively adjusted, the radiation efficiency is improved while smaller standing waves are obtained, the ablation area is increased, the ablation antenna is enabled to perform excellent performance at a desired frequency, in the process of ablating the tumor focus or the target tissue, the refrigerant conveying device is started, the refrigerant is conveyed into the cooling tube 105, and is split after flowing out of the cooling tube 105, part of the refrigerant flows into the water outlet tube 202 through a gap between the inner conduit 104 and the cooling tube 105, and flows into the cooling tube conveying device through the inner part of the cooling tube through the flow holes 123 and the needle rod 101 in turn, the other refrigerant flows into the inner support tube, and the inner wall 111 is sprayed onto the inner wall of the human body cavity through the second guide channel, so that the human body is prevented from damaging the inner wall of the human body cavity.
In a preferred embodiment, the support rod and the connecting rod are made of any one of the following materials: PTFE, FEP, PI, PEEK, an elastic member, a polymer, and a polymer material, in this embodiment, the supporting rod and the connecting rod are preferably made of a polymer material.
In this embodiment, by the above arrangement, the supporting mesh 110 made of metal material can be effectively prevented from striking fire during the ablation process, which causes damage to surrounding tissues.
In a preferred embodiment, referring to fig. 3, the coaxial cable 120 includes a microwave antenna 124, an antenna dielectric layer 125 coaxially disposed around the microwave antenna 124, and an antenna shielding layer 126 coaxially disposed around the antenna dielectric layer 125, the microwave antenna 124 and the top capacitive loading antenna 121 are fixedly connected, and the microwave antenna 124 and the microwave input port 203 are electrically connected, wherein, in the extending direction of the needle shaft 101, a distance between an end of the top capacitive loading antenna 121 far from the outer catheter 100 and an end of the antenna dielectric layer 125 near the top capacitive loading antenna 121 is denoted as L1, a distance between an end of the antenna dielectric layer 125 near the top capacitive loading antenna 121 and an end of the antenna shielding layer 126 near the top capacitive loading antenna 121 is denoted as L2, and lengths of the top capacitive loading antenna 121 in the extending direction of the needle shaft 101 are denoted as L3, and values of L1, L2, L3 are adjusted according to dielectric constants of organs.
In the embodiment, as the difference of organs and tissues such as liver, kidney, pancreas, lung and the like is large, the water content of the liver tends to be isotropic, the water content of the lung tissue is less, the protein is fluffy, the air is more, the difference of tissue dielectric constants is large, the size of an ablation area can be changed along with the difference, and according to the tissues and organs with different dielectric constants, the antenna size is adjusted, stable ablation area and efficient energy radiation can be realized, so that the spherical heating mode is kept unchanged while the ablation area is enlarged.
In a specific embodiment, as shown in fig. 9, in the renal artery denervation ablation procedure, the relative dielectric constant of the renal tissue is 40, the conductivity is 1.23S/m, the density is 1165Kg/m3,, and the microwave ablation catheter with a corresponding model is selected according to the above data to perform simulation experiment and electromagnetic radiation SAR distribution diagram observation, and the test shows that when l1=6mm, l2=8mm and l3=3.8mm, the emitted signal is smaller, the standing wave of the monopole antenna is effectively reduced, and a stable radiation area with a larger range is formed.
In another specific embodiment, referring to fig. 10, when performing an ablation operation on lung tissue, the relative dielectric constant of the lung tissue is 30, the electrical conductivity is 1.1S/m, the density is 1005Kg/m3,, and a corresponding model of microwave ablation catheter is selected according to the data to perform simulation experiment and electromagnetic radiation SAR distribution diagram observation, and the result is that when l1=16 mm, l2=18 mm and l3=6 mm, the emitted signal is smaller, the standing wave of the monopole antenna is effectively reduced, and a stable radiation area with a larger range is formed.
In another specific embodiment, as shown in fig. 11, when performing an ablation operation on liver tissue, the relative dielectric constant of the liver tissue is 43, the electric conductivity is 1.69S/m, the density is 1036Kg/m3,, and a corresponding model of microwave ablation catheter is selected according to the data to perform simulation experiment and electromagnetic radiation SAR distribution diagram observation, and the test shows that when l1=11mm, l2=10.5 mm and l3=4.8 mm, the emitted signal is smaller, the standing wave of the monopole antenna is effectively reduced, and a stable radiation area with a larger range is formed.
The sizes of L1, L2 and L3 are adjusted, so that the device can realize stable ablation area and high-efficiency energy radiation when performing ablation operation on human organs with different dielectric constants, and the spherical heating mode of the ablation area is kept unchanged while the ablation area is enlarged.
Furthermore, in the above embodiment, the simulation software is the Comsol software, and the simulation experiment can be performed by other simulation software according to the use environment and the use requirement, and of course, the test results may also have differences, which will not be further described herein.
Referring to fig. 4, the supporting rod is a hollow tube, an input end is provided at one end of the supporting rod close to the needle rod 101, one end of the supporting rod far away from the needle rod 101 is in a closed state, and the input ends of the supporting rods are connected with the first guide ports 102 through capillaries (not shown).
In the embodiment, in the process of ablating tumor lesions or target tissues, a refrigerant conveying device is started, a refrigerant is conveyed into the cooling tube 105, after the refrigerant flows out of the cooling tube 105, the refrigerant starts to flow, part of the refrigerant flows to the water outlet tube 202 through a gap between the inner guide tube 104 and the cooling tube 105 and flows back into the refrigerant conveying device, and the rest of the refrigerant is sprayed onto the inner wall of the human body cavity tract through the flow dividing hole 123, the first flow guide opening 102 and the second flow guide opening 111 in sequence, so that the inner wall of the human body cavity tract in an ablation area is cooled, the damage to the inner wall of the human body cavity tract in the ablation operation process is avoided, and the damage to tissues except the target tissues can be effectively avoided in non-tumor ablation operations (such as nerve removal operation, pulmonary ground glass nodule ablation, digestive tract biliary tract ablation and the like).
It should be noted that, the target tissue refers to a tissue to be ablated, such as: pulmonary hair glass nodule in pulmonary hair glass nodule ablation, mucous membrane lesion tissue in digestive tract biliary tract ablation, internal nerve tissue in kidney part in renal nerve removal operation, etc.
Example two
The present embodiment is further optimized based on the first embodiment, and the difference between the present embodiment and the first embodiment is that the number of the first conduction ports 102, specifically:
the number of the first flow guiding ports 102 is denoted as M, and the number of the supporting rods is denoted as N, M > N.
It should be noted that, since the number of the first conduction ports 102 is greater than the number of the support rods, only a part of the first conduction ports 102 are connected through the capillaries and the input ends of the support rods, in order to better describe the working process of the device in this embodiment, the first conduction ports 102 connected with the second conduction ports 111 through the capillaries are denoted as first water outlets, and the first conduction ports 102 not connected with the capillaries are denoted as second water outlets.
In this embodiment, since the number of the first diversion ports 102 is greater than the number of the support rods, after the refrigerant conveying device is started, the flow path of the refrigerant flowing out through the cooling pipe 105 increases, wherein a part of the refrigerant flows to the water outlet pipe 202 through the gap between the inner conduit 104 and the cooling pipe 105 and flows back into the refrigerant conveying device, a part of the refrigerant is sprayed onto the inner wall of the human body cavity channel sequentially through the diversion port 123, the first water outlet and the second diversion port 111, and the rest of the refrigerant is directly sprayed onto the inner wall of the human body cavity channel through the second water outlet, and the area of cooling is increased through the cooperation of the second water outlet and the second diversion port 111, so that the cooling efficiency is improved, and further, the protection can be better provided for tissues other than the target tissues.
Example III
This embodiment is further optimized based on the second embodiment, and differs in that the inside of the needle shaft 101 in this embodiment is equipped with a flow blocking member 106, specifically:
Referring to fig. 7 and 8, a flow blocking member 106 is assembled between the needle shaft 101 and the steering control member 103, one end of the flow blocking member 106 away from the outer catheter 100 is fixedly connected with the needle shaft 101, the flow blocking member 106 is slidably connected with the steering control member 103, the material of the flow blocking member 106 is a memory alloy, the middle end of the flow blocking member 106 is provided with a corrugated expansion section, when the corrugated expansion section is in an extended state, the flow blocking member 106 covers the first flow guiding port 102, and when the corrugated expansion section is in a contracted state, the first flow guiding port 102 and an avoidance groove inside the steering control member 103 are mutually communicated.
Further, at normal temperature, the choke 106 is in an extended state.
It should be noted that, the memory alloy is a current mature material, and after plastic deformation occurs in a certain temperature range, the memory alloy can recover the original macroscopic shape in another temperature range, and it can be mainly divided into: one-way memory effect alloy, two-way memory effect alloy, and one-way memory effect alloy, in this embodiment, the flow resistor 106 is preferably one-way memory effect alloy.
In this embodiment, when performing an ablation procedure on a target tissue, microwaves are transmitted to the top capacitor loading antenna 121 through the coaxial cable 120, and the microwaves are transmitted to form a radiation area through the top capacitor loading antenna 121, the target tissue in the radiation area is ablated, the temperature of the target tissue gradually rises in the ablation process, the choking piece 106 also absorbs heat through heat transfer, the temperature gradually rises, at this time, the choking piece 106 is in an extended state, the first conduction port 102 is covered by the choking piece 106, the cooling medium in the cooling tube 105 is prevented from flowing out through the first conduction port 102, the temperature of the target tissue can be enabled to reach a preset temperature rapidly through the scheme, the purpose of ablation is achieved, after the temperature of the choking piece 106 is increased to a phase-change temperature, the extended state is changed to a contracted state, the first conduction port 102 is not covered, at this time, part of the cooling medium flowing out of the cooling tube 105 is sprayed onto the inner wall of a cavity outside the target tissue through the supporting net sleeve 110 and the second water outlet, the purpose of cooling is achieved, the cavity outside the target tissue is prevented from being damaged by heating, the cooling medium outside the target tissue is prevented from being damaged by the cavity, the cooling medium can not reach the temperature of the inner wall of the target tissue due to the preset temperature, the temperature can be prevented from being reduced, the cooling medium can not reach the temperature of the target tissue due to the preset temperature, and the temperature can be prevented from being reduced.
In a preferred embodiment, the phase transition temperature of the flow resistor 106 is in the range of 35 ℃ to 60 ℃, and in this embodiment, the phase transition temperature of the flow resistor 106 is preferably 50 ℃.
In this embodiment, the phase transition temperature of the choke 106 can be adjusted according to the actual use environment, and the main purpose of the present invention is to sense the ambient temperature through the choke 106, and after the ambient temperature reaches the phase transition temperature, the choke 106 is changed from the extended state to the contracted state, so as to avoid the damage of the human tissues other than the target tissues.
In a preferred embodiment, the outside of the flow resistor 106 is provided with a shielding layer.
In this embodiment, the shielding layer is configured to prevent the choke piece 106 from absorbing microwaves emitted by the top capacitive loading antenna 121, prevent the choke piece 106 from absorbing microwaves to cause temperature rise, and not sense the temperature in the cavity of the human body, so that the coolant cools the inner wall of the cavity in advance.
In a preferred embodiment, the shielding layer is made of graphite.
Further, the form of the shielding layer made of graphite material may be any one of the following forms: a coating, film or other form capable of providing a barrier effect, in this embodiment a graphite barrier coating is preferred.
In this embodiment, graphite has good shielding performance to microwaves, can effectively avoid the choke piece 106 absorbing microwaves and causing self-heating, and simultaneously, graphite also has good heat conducting performance, and can rapidly transfer heat in the environment to the choke piece 106, so that the choke piece 106 senses the temperature in the cavity of the human body and the state changes according to the temperature in the cavity of the human body.
The working principle of the invention is as follows:
When the tumor focus or target tissue is ablated, the needle bar 101 is conveyed to a preset position through the guidance of the imaging equipment, the microwave control module is started, microwaves are conveyed to the top capacitive loading antenna 121 through the coaxial cable 120, the resonance frequency of the microwaves is moved to a lower frequency band through the top capacitive loading antenna 121, impedance matching is achieved, electromagnetic waves which are restrained from counter-propagating along the coaxial cable are reduced, radiation efficiency is improved, an ablation area is increased, polar molecules in the tumor focus or target tissue are rotationally vibrated through microwave radiation to generate a thermal effect, cells in the tumor cells or target tissue are coagulated and necrotized through a heating mode, finally an ablation area is formed, in the process of ablating the tumor focus or target tissue, the refrigerant conveying device is started, refrigerant is conveyed into the cooling tube 105, after the refrigerant flows out of the cooling tube 105, the refrigerant flows to the water outlet tube 202 through a gap between the inner guide tube 104 and the cooling tube 105, the rest of the refrigerant flows into the inside the refrigerant conveying device through the separation tube 123 and the needle bar 101 in sequence, the other refrigerant is sprayed onto the inner wall of a human body cavity through the second guide opening 111, and the human body cavity inner wall is cooled outside the target tissue is prevented from damaging the human body tissue.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention. Structures, devices and methods of operation not specifically described and illustrated herein, unless otherwise indicated and limited, are implemented according to conventional means in the art.