Patent Application
20110270046
a. Field of the Invention
The instant invention relates to an optic-based sensing assembly. The instant invention includes an optic-based catheter assembly and related system used to monitor or determine contact between a catheter and the surrounding proximate environment, such as tissue. Such a system may be used for visualization, mapping, ablation, and/or other methods of diagnosis and treatment of tissue. The instant invention also relates to a method for sensing and calculating contact force exerted by an electrode on a tissue.
b. Background Art
The visualization and treatment of organs and tissues has been advanced through the increasing use of catheter systems. Catheter systems have been designed for the incorporation of various components to treat and diagnose ailments, as accomplished through the mapping of organs, sensing of thermal and electrical changes exhibited by a tissue (e.g., heart), as well as the application of energizing sources (such as radiofrequency (RF), cryogenics, laser, and high frequency ultrasound) to tissue. Moreover, catheter systems may be further modified to include irrigation channels that enable cooling of the electrode tip during ablation procedures.
Catheter systems generally include a portion that contacts the tissue or organ, or is inserted in an environment (e.g., heart chamber or vessel) to detect a number of parameters, such as for example, location of the tissue, contact or pressure exerted on the tissue, electrophysiological attributes of the tissue, or other type of parameters that aid in the evaluation or treatment of the organ or tissue.
It is known that sufficient contact between a catheter, in particular an electrode provided in connection with a catheter, and tissue during a procedure is generally necessary to ensure that the procedure is effective and safe. Current techniques of mapping, visualization and treatment using energizing sources, such as the use of radiofrequency energy during ablation, rely on placing of the electrode of a catheter system in consistent mechanical contact with targeted tissue. Perforation of the cardiac wall as well as lesion formation (such as lesions created by exposure to radiofrequency) partially depends upon the direction of contact between the electrode and tissue. In particular, for endocardial catheter applications, the point of electrode-tissue contact is typically 150 cm away from the point of application of force applied by the operator (whether manual or automated) of the catheter outside of the body. Coupled with the fact that a beating heart has dynamically moving walls, this gives rise to some functional and theoretical challenges such as ensuring that the electrode is in sufficiently constant mechanical contact with the myocardial wall.
Catheter systems having sensor assemblies, such as those mounted on the catheter shaft proximal to the electrode or remotely in the handle set, leave the possibility, however small, of obtaining false positive outcomes when detecting contact between the electrode and the tissue. False positive outcomes may occur, for example, when a nonconductive portion of the catheter wall, and not the electrode, is in contact with the tissue. Such condition may arise during the catheter manipulation in the heart when, for instance, the distal portion of the catheter is curled inward so much as to lose electrode contact with the tissue, while the distal portion of the catheter is in contact with the tissue. When that happens, remotely placed sensors can generate signals due to the deflection of the catheter shaft, thereby falsely indicating contact between the electrode and tissue. Accordingly, optic-based contact sensors coupled to the electrode can, among other things, help reduce the possibility of obtaining false positive outcomes when detecting contact between the electrode and the tissue.
As previously suggested, there are a number of methods used for ablation of desired areas, including, for example, radio frequency (RF) ablation. RF ablation is accomplished by transmission of radio frequency energy to a desired target area through an electrode assembly to ablate tissue at the target site. Because RF ablation may generate significant heat, which if not controlled can result in undesired or excessive tissue damage, such as steam pop, tissue pop, and the like, it is commonly desirable to include a mechanism to irrigate the target area and the device with biocompatible fluids, such as a saline solution. The use of irrigated ablation catheters can also prevent the formation of soft thrombus and/or blood coagulation.
Irrigated catheters may be used to ensure an increase in ablation efficiency, while at the same time increasing the cooling efficiency of the electrode. Moreover, irrigated ablation electrodes may be used to further enhance the performance of the catheter system. Nonetheless, in the use of an irrigated catheter in endocardial ablation applications, there remains the continued challenge in ensuring the directionality of the irrigation such that the irrigation ablation portion of the electrode faces the tissue.
For some applications, it is desirable to have an optic-based catheter system that includes an optical sensor that detects changes in reflected energy, such as light, from an optically interactive surface provided by an electrode. It is also desirable to provide a system which is insensitive to an RF field, electromagnetic interference (EMI), and thermal effects. Furthermore, it is also desirable to have a system which seeks to minimize false positives, is robust in construction and has a wide dynamic range. In an embodiment, the electrode may be subjected to a compressive force due to mechanical contact of the electrode surface with another body or surface. The optical sensor of the invention can be used to measure contact of an electrode with a dynamically moving wall, such as a beating heart.
In another embodiment, a contact sensing assembly for sensing contact with a target (e.g., a tissue or other organ surface) is provided. The assembly may include an elongated body having a distal section and a sensor connected to the distal section. The sensor may include a segment with a first interactive component, a tip positioned distally from the segment, and a flexible coupling member separating the segment from the tip. The tip may include an external surface and is positioned distally from the segment, the tip further including a second interactive component that is adapted to interact with the first interactive component. The flexible coupling member may separate the segment from the tip, such that the second interactive component can move relative to the first interactive component when the external surface of the tip contacts the target.
In another embodiment, a contact sensing assembly may include a catheter including a body having a proximal end and a distal end, and an electrode including a tip portion and a base portion, and a generally central axis, with a portion of the electrode being connected to the distal end of the catheter. One or more optical sensors may be provided for emitting and/or receiving an optical signal, with a part of the optical signal being transverse to the central axis. The optical sensor may be operatively connected to the electrode or the catheter body. One or more optical interference members may be operatively connected to the electrode or the catheter body for interfering with the optical signal.
In another embodiment, an irrigated contact sensing assembly may include a catheter including a body having a proximal end and a distal end, and an electrode including a tip portion and a base portion, wherein a plurality of irrigation ports are positioned on the tip portion of the electrode. Moreover, the tip portion of the electrode may be configured with a predefined length, such that the irrigation ports are disposed along the length of the tip portion of the electrode. The irrigation ports may be provided in various numbers, shapes, sizes and orientations to provide a irrigated catheter. The irrigation ports may be adapted to transport cooling fluid from a lumen to the surface of the electrode.
For the contact sensing assembly described above, in an embodiment, the optical sensor may be configured to send and receive light energy or a light-based signal. In an embodiment, the distal end of the catheter may include a coupling member having a neck portion. The neck portion of the coupling member, in an embodiment, may move relative to an external force exerted on the electrode. In an embodiment, the neck portion of the coupling member may include a twist, torsion bar, alpha, dove-tail or spring shaped elastic portion for enabling external axial and transverse forces and torques exerted on the electrode to be sensed by the optical sensor. The coupling member, in an embodiment, may include a mounting shaft that defines an internal recessed groove for receiving at least a portion of the optical sensor. In an embodiment, the tip portion of the electrode may include an irrigation port. The electrode, in an embodiment, may include a lumen provided within an internal cavity of the electrode, with the lumen being positioned adjacent to the base and tip portions of the electrode.
For the contact sensing assembly described above, in an embodiment, the optical sensor may include an emitter and a receiver for respectively emitting and receiving the optical signal. The emitter and receiver, in an embodiment, may be provided with a single optic fiber. In an embodiment, the emitter and/or receiver may be positioned to respectively emit or receive the optical signal, a part of which may be substantially parallel to the central axis. In an embodiment, a reflective surface may be provided for altering an angle of the optical signal substantially towards the optical interference member. The reflective surface may be disposed on the emitter or on a fiber mirror arrangement. The emitter and/or receiver, in an embodiment, may be positioned to respectively emit or receive the optical signal, with the optical signal being substantially transverse to the central axis.
For the contact sensing assembly described above, in an embodiment, the optical sensor may include one or more emitters and radially positioned receivers for respectively emitting and receiving the optical signal. In an embodiment, at least a part of the optical signal may be substantially parallel to the central axis. The distal end of the catheter, in an embodiment, may include a coupling member having an elastic neck portion. In an embodiment, the optical signal may be substantially transverse to the central axis. In an embodiment, the emitter and receiver may be provided with a single optic fiber. The optical interference member, in an embodiment, may be an appendage formed on the electrode base portion, and the single optic fiber may be disposed radially outboard of the appendage relative to the central axis. In an embodiment, the optical interference member may be an appendage formed on the electrode base portion, with the single optic fiber disposed radially inboard of the appendage relative to the central axis.
For the contact sensing assembly described above, in an embodiment, the optical interference member may be a structure formed on the electrode base portion or the catheter distal end (or both). In an embodiment, the optical interference member may be an appendage formed on the electrode base portion. The appendage, in an embodiment, may include a cutout for allowing passage of a predetermined amount of the optical signal.
For the contact sensing assembly described above, in an embodiment, the optical interference member may be configured to interfere with the optical signal by respectively first and second predetermined amounts related to first and second predetermined positions of the electrode relative to the catheter body. In an embodiment, the first predetermined amount of optical signal interference may be zero interference. Alternatively, the first predetermined amount of optical signal interference may be greater then zero interference. In an embodiment, the optical sensor may include a fiber optic cable including one or more lumens, and a peripheral wall surrounding the lumen, with the optical sensor connected to the peripheral wall. A plurality of optical sensors, in an embodiment, may be disposed within the body of the catheter, with each optical sensor having a means for emitting and receiving light energy. In an embodiment, the optical sensors may be circumferentially disposed within the body of the catheter. The optical sensor, in an embodiment, may include an emitter and a receiver for respectively emitting and receiving the optical signal, with the emitter and receiver being adjacent to one another and being paired. In an embodiment, the optical sensor may include an emitter and a receiver for respectively emitting and receiving the optical signal, with a plurality of emitters and a plurality of receivers being distributed about a peripheral wall of a fiber optic cable such that each emitter operatively interacts with one or more receivers.
For the contact sensing assembly described above, in an embodiment, a lumen may be disposed within the body of the catheter, with at least a portion of the lumen extending into the electrode for slidably receiving one or more sensing components. In an embodiment, a lumen may be disposed within the body of the catheter, with at least a portion of the lumen extending into the electrode for slidably receiving one or more energizing components. The energizing component may be a radiofrequency current, direct current, high-intensity ultrasound, laser, cryogenic, and combinations thereof. In an embodiment, the tip portion of the electrode may include a portion configured to perform ablation. The optical sensor, in an embodiment, may be adapted to measure a parameter, such as, intensity, wavelength, phase, spectrum, speed, optical path, interference, transmission, absorption, reflection, refraction, diffraction, polarization, and/or scattering.
In another embodiment, a lumen may be disposed within the body of the catheter and extending into the electrode, in particular, the tip portion of the electrode. The lumen may be provided to allow fluid to flow within the catheter to the electrode, thereby enabling irrigation of the electrode and surrounding tissue once contact is determined by the feedback from the optical sensors of the catheter system.
In another embodiment, an optical-based catheter system may include a catheter including a body having a proximal end and a distal end. An electrode may include a tip portion and a base portion, and a generally central axis, with a portion of the electrode being connected to the distal end of the catheter. One or more optical sensors may be provided for emitting and/or receiving an optical signal, with at least a part of the optical signal being transverse to the central axis, and the optical sensor being operatively connected to one of the electrode and the catheter body. One or more optical interference members may be operatively connected to the electrode or the catheter body (or both) for interfering with the optical signal. The system may further include a light energy source, a processor, and a catheter mapping unit for use in mapping or visualizing the catheter location.
For the system described above, in an embodiment, the system may determine a displacement associated with the electrode tip portion using sensed changes in intensity of the optical signal. The optical sensor may be adapted to measure a parameter, such as, intensity, wavelength, phase, spectrum, speed, optical path, interference, transmission, absorption, reflection, refraction, diffraction, polarization, and/or scattering.
In another embodiment, a method for sensing contact force exerted by an electrode on a tissue may include directing an optical signal along at least a portion of a tubular body of a catheter having a proximal end and a distal end, and connecting an electrode including a tip portion and a base portion to the distal end of the catheter. The method may further include emitting and/or receiving an optical signal, with at least a part of the optical signal being at a predetermined angle relative to the central axis, and sensing changes in intensity of the optical signal responsive to displacement associated with the electrode tip portion based on the contact force exerted by the electrode on the tissue.
For the method described above, in an embodiment, the predetermined angle may be approximately 0°. In an embodiment, alternatively, the predetermined angle may be greater than approximately 0°. In an embodiment, the method may further include determining corresponding contact force vectors between the electrode and the tissue in contact with the electrode by evaluating the sensed changes in intensity. The contact force vectors, in an embodiment, may include an axial component of the contact force and a transverse component of the contact force. The method, in an embodiment, may further include calibrating an optical sensor that emits and receives the optical signal.
For the method described above, in an embodiment, the method may include calibrating a plurality of optical sensors that emit and receive respective optical signals. In an embodiment, the method may further include calibrating the optical sensors by measuring an intensity of the respective optical signal for each optical sensor at zero-force (I0x), measuring an intensity of the respective optical signal for each optical sensor at a force greater than zero (Ix), and determining the relative intensity (Irx) between Ix and I0x for each optical sensor as follows: Irx=Ix−I0x. The method may, in an embodiment, include determining the axial and transverse components of contact force as a function of an angle of attack of the electrode relative to the tissue. In an embodiment, the method may include determining regression curves for the axial and transverse components of the contact force for a predetermined contact force range.
For the method described above, in an embodiment, the method may further include using the calibrated optical sensor(s) to determine the axial and transverse components of the contact force. In an embodiment, the method may further include determining the contact force magnitude as a function of the axial and transverse components of the contact force. The method may, in an embodiment, include determining an angle of attack of the electrode relative to the tissue as a function of the axial and transverse components of the contact force. In an embodiment, the method may include determining an angle of rotation of the electrode relative to the tissue as a function of the change in intensity and phase angle of the optical sensor.
For the method described above, in an embodiment, the electrode may perform RF ablation, HIFU ablation, laser ablation, cryo ablation, ultrasonic imaging, electrical pacing, EP pacing, electrical sensing, and/or EP sensing. In an embodiment, the sensed contact force may be utilized for automatically limiting a maximum contact force, warning of a high or unacceptable contact force, giving visual or audible feedback to a practitioner regarding a tissue contact force, warning of a loss of contact force or contact, and/or warning of a contact force which may be too low.
In another embodiment, a method of manufacturing an optical sensing assembly, in accordance with the present invention, may further include providing an optical sensor having a proximal end and distal end, including an emitter and a receiver, each having a distal end and a proximal end, for respectively emitting and receiving an optical signal. The method further includes advancing the distal end of the optical sensor towards a proximal end of an electrode. The method includes retracting the optical sensor from the proximal end of the electrode to dispose the distal end portion of the optical sensor within a base portion of the electrode. Moreover, the method includes coupling the proximal end of the optical sensor to an amplifier, and positioning the optical sensor within the base portion of the electrode by utilizing optical signals processed by the amplifier. The method further includes securing the optical sensor relative to the base portion of the electrode.
The foregoing and other aspects, features, details, utilities, and advantages of the invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.
Referring now to the drawings wherein like reference numerals are used to identify like components in the various views,
The contact sensing assembly 10 may be used in the diagnosis, visualization, and/or treatment of tissue (such as endocardial tissue) in a body. Contact sensing assembly 10 may be used in a number of diagnostic and therapeutic applications, such as for example, the recording of electrograms in the heart, the performance of cardiac ablation procedures, and/or various other applications. The assembly may be used in connection with a number of applications that involve humans, or other mammals, for tissue observation, treatment, repair, or other procedures. Moreover, the invention is not limited to one particular application, but rather may be employed by those of ordinary skill in the art in any number of diagnostic and therapeutic applications. Throughout the disclosure, various embodiments of assembly 10 are disclosed, including alternate embodiments of catheter shaft 12, electrode 14, and optical sensor 16. Each of the components of the assemblies may be used interchangeably, as recognized by one of ordinary skill in the art.
The catheter shaft 12 of the assembly includes a body 18 having a distal end 20 and a proximal end 22. The body 18 of the catheter shaft 12 is generally tubular in shape, although other configurations of the catheter shaft may be used as known in the industry. The distal end 20 of catheter shaft 12 is connected to the electrode 14. The body 18 of shaft 12 may house the optical sensor 16, as well as other components used in the diagnosis and/or treatment of tissue. If desired, the outer portion of the catheter shaft 12 may have a braided outer covering thereby providing better torque transfer, and increased flexibility and strength. The catheters of the invention vary in length and are attached to a handle, handle assembly or any other type of control member that allows a surgeon, an electrophysiologist, or any other type of operator of the catheter assembly to manipulate the relative position of the assembly within the body from a remote location, as recognized by one of ordinary skill in the art. This type of manipulation and/or movement may be accomplished either manually (i.e., by a surgeon) or automatically (i.e., through the use of a robotically operated device).
In accordance with an embodiment of the assembly, as reflected in
The electrode 14 includes a tip portion 24 and a base portion 26. In one embodiment, electrode 14 may be configured to include a means for irrigating. For example, without limitation, at least one irrigation port 28 may be incorporated within or through the electrode 14, thereby providing an irrigated electrode tip. An irrigated electrode tip allows for the cooling of the electrode 14, for instance, through the transporting of fluid through the electrode 14 and around the surface of the tissue. A number of different types of electrodes, irrigated and non-irrigated, may be connected and incorporated for use as the electrode 14 according to embodiments of the invention depending on the type of procedures being performed. Such irrigated electrodes include, but are not limited to, those disclosed in U.S. patent application Ser. Nos. 11/434,220 (filed 16 May 2006), 10/595,608 (filed 28 Apr. 2006), and 11/646,270 (filed 28 Dec. 2006) 11/647,346 (filed 29 Dec. 2006), and international patent application no. PCT/US2007/080920 (filed 10 Oct. 2007), each of which is hereby incorporated by reference as though fully set forth herein.
The electrode 14 may further include an optically interactive surface 30, 30′ (see, e.g.,
As stated, the optically interactive surface 30 may be provided on or in connection with a surface associated with electrode 14. The relative position of the interactive surface 30 (which has a known position with respect to the electrode) allows sufficient interaction and/or functional communication with the optical sensor 16 such that a change in the communication (e.g., optical signal, light intensity) can provide a means for determining the contact force and/or orientation of the electrode with the tissue or surrounding area. In one embodiment, the electrode cavity 36 includes the optically interactive surface 30 (see, e.g.,
The optical sensor 16 may be positioned within the distal end 20 of the catheter shaft 12. The optical sensor 16 may include at least one optic fiber that transmits and receives an optical signal, such as light energy. The optical sensor may also be manufactured to transmit and/or receive various types of signals including those associated with electromagnetic radiation, lasers, x-rays, radiofrequency, etc. In an embodiment, the optical sensor 16 may use light energy to determine the relative contact (e.g., force, stress, and/or orientation) between electrode 14 and an external surface in operational contact with the outer surface of the electrode—for example, tissues and surrounding environments, including organs, heart chambers, and the interior of vessels. Moreover, the optical sensor may be adapted to measure one or more parameters, including, for example, intensity, wavelength, phase, spectrum, speed, optical path, interference, transmission, absorption, reflection, refraction, diffraction, polarization, and scattering.
In an embodiment, one or more force vectors may be used to determine the contact force and/or orientation of the electrode in connection with the surrounding tissue or other external surfaces. In particular, the change of intensity of the optical signal received by at least one of the optical sensor 16 may be correlated to the contact force exerted on electrode 14 by an external surface. The intensity of the optical signals received by optical sensor 16 is proportional to the structural displacement of the distal end 20 of the catheter shaft 12. As discussed in more detail below, the displacement of the distal end 20 is governed by a factor (k) (such as a spring constant) exhibited by the material comprising the portion 21 of distal end 20. Accordingly, the factor (k) may be equated to the external force (F), either laterally or axially, exerted on electrode 14, divided by the unit displacement (d) (either axially or laterally) of electrode, which may be generally expressed as k=F/d. Since the change in intensity of the optical signals is proportional to the displacement of the electrode, the external force exerted on the electrode may be determined.
In order to determine light or optical intensity, optical sensor 16 may include at least one receiver 32 and at least one emitter 34 for receiving and emitting light energy, respectively. The receiver 32 and the emitter 34 may be included in a single fiber optic cable or in two separate fiber optic cables, as shown in
Referring to
In particular,
As further exemplified in the combination of
The mounting shaft 54 may further include at least one recessed groove 62 for receiving and mounting optical sensor 16. The recessed groove 62 may position optical sensor 16 so that the distal end of the optical sensor 16 is flush with the distal surface of the mounting shaft 54 (see, e.g.,
As further shown in
As can be seen in
An alternate embodiment of assembly 10′″ is shown in
During operation, once or after the electrode is placed in contact with tissue targeted for ablation and the relative orientation of the electrode is detected, the directional irrigation ports 28″ may be targeted toward the tissue. Subsequently, upon energizing the electrode, such as through the application of RF power, the directional irrigation ports 28″ may provide directed cooling of the electrode-tissue interface.
As previously suggested, various embodiments of the present invention further define a gap/area 64. In general, the volume of the area generally defined by the gap/area 64 may also be filled, in whole or in part, with a medium 33 (see, e.g.,
As can be seen in
A fiber assembly may be further provided by the invention. The fiber assembly includes a supply fiber and a return fiber. The supply fiber (not shown) is connected to emitter 34 and carries light energy from a light source to emitter 34. The return fiber (not shown) carries reflected light from receiver 32 back to a processor and display unit. The light energy emitted by the optical sensor 16 is compared to the light received by the optical sensor 16 and used to determine the relative force exerted on the electrode 14.
In another embodiment, the assembly 10 further provides a first interactive component and a second interactive component, such interactive components may include optical sensors and optically interactive surfaces in various combinations. For example, in an embodiment, that assembly does not necessarily include an electrode, but may provide a sensor that includes a segment with an interactive component and a tip with another interactive component adapted to interact with one another when an external surface of the tip contacts a target.
Referring to
Referring to
Specifically, referring to
Referring to
In operation, with coupling member 72 installed onto base portion 224 of electrode 222 (see
Referring to
As shown in
Referring to
As shown in
Referring to
Referring next to
Referring to
Referring next to
Referring to
Referring to
Referring to
As shown in
In order to determine the magnitude |F| of force and angle of attack α, contact sensing assembly may first be calibrated to obtain a priori calibration curves for {right arrow over (F)}x and {right arrow over (F)}y. In order to do so, for an exemplary contact sensing assembly 700 including three sets of emitters/receivers (e.g. sensors) such as those illustrated in
I
1r
=I
1
−I
01
I
2r
=I
2
−I
02
I
3r
=I
3
−I
03
The force {right arrow over (F)} may then be resolved at any angle of attack a into axial component {right arrow over (F)}y and transverse component {right arrow over (F)}x as follows:
{right arrow over (F)}y={right arrow over (F)} Sin α
{right arrow over (F)}x={right arrow over (F)} Cos α
Referring to
Either IR=(I1+I2+I3), as shown in
Thus, IR=ay1 {right arrow over (F)}y+ay0, where ay1 is a slope of a linear curve and ay0 is the offset.
In the particular examples of
A regression curve of {right arrow over (F)}x may then be obtained as a function of Min(I1r,I2r,I3r), e.g. the minimum value between I1r, I2r, and I3r, as shown in
Min(I1r,I2r,I3r)=ax1{right arrow over (F)}x+ax0
Referring to
Referring to
After obtaining the a priori calibration curves for {right arrow over (F)}x and {right arrow over (F)}y as discussed above with particular reference to
Specifically, first the intensity I01, I02, I03 at zero-force (e.g. force {right arrow over (F)}=0) may be measured. Thereafter, the intensity I1, I2, I3 at force {right arrow over (F)}>0 at any angle of attack, e.g. α=0° to 90° may be measured. From these values, the Intensity change relative to zero-force may be calculated as follows:
I
1r
=I
1
−I
01
I
2r
=I
2
−I
02
I
3r
=I
3
−I
03
Thereafter, the resultant intensity IR may be calculated as follows: IR=(I1+I2+I3), or IR=(I1r+I2r+I3r). The axial force {right arrow over (F)}y may be obtained from the a priori regression curve of {right arrow over (F)}y as a function of either IR=(I1+I2+I3) or IR=(I1r+I2r+I3r). Thus axial force {right arrow over (F)}y is:
{right arrow over (F)}y=(IR−ay0)/ay1, with ay0 and ay1 previously obtained as discussed above.
The minimum value between I1r, I2r, and I3r may then be calculated (e.g. Min(I1r,I2r,I3r)).
The transverse force {right arrow over (F)}x may also be obtained from the a priori regression curve of {right arrow over (F)}x as a function of Min(I1r,I2r,I3r). Thus transverse force {right arrow over (F)}x is:
{right arrow over (F)}x=[Min(I1r,I2r,I3r)−ax0]/ax1, with ax0 and ax1 previously obtained as discussed above
From the axial and transverse components of force, the force IFI may be calculated as follows:
|F|=[{right arrow over (F)}x2+{right arrow over (F)}y2]1/2
The angle of attack a may be calculated as follows:
α=arctan({right arrow over (F)}y/{right arrow over (F)}x)
With the magnitude of force |F| and angle of attack α calculated as discussed above, the algorithm for calculating the angle of rotation θ will be discussed.
At any Force {right arrow over (F)}, and at any angle of attack α, the intensity values for the three Sensors (e.g. Sensor 1, Sensor 2 and Sensor 3, as discussed above), I1, I2, and I3 as well as I1r, I2r, and I3r undergo sinusoidal variations with the rotation of a catheter around its own axis as shown in
Thus:
I
1
=I
01
+A
1 Sin(θ+Φ1), or I1r=A1 Sin(θ+Φ1)
I
2
=I
02
+A
2 Sin(θ+Φ1+Φ12), or I2r=A2 Sin(θ+Φ1+Φ12)
I
3
=I
03
+A
3 Sin(θ+Φ1+Φ13), or I3=A3 Sin(θ+Φ1+Φ13)
Φ1 is the phase angle of Sensor 1 at angle of rotation θ=0 (Φ1=90° in
Φ12 is the phase angle difference between Sensor 1 and Sensor 2 (Φ12=−120° in
Φ13 is the phase angle difference between Sensor 1 and Sensor 3 (Φ13=120° in
For the above equations, A1, A2, and A3 depend on the sensitivity of the Sensors (e.g. Sensor 1, Sensor 2 and Sensor 3), in that when the sensitivity of the Sensors are matched such that A1=A2=A3, then I1r, I2r, and I3r, are related as follows:
I
1r
+I
2r
+I
3r=0, and
Angle of rotation θ may be determined from I1r, I2r, and I3r as follows:
θ=arctan [(2I2r+I1r)/(√3I1r)], or
θ=arctan [(I3r−I2r)/{√3(I3r+I2r)}], or
θ=arctan [−(2I3r+I1r)/(√3I1r)]
Based on the discussion above, referring to
The invention further discloses an optic-based catheter system 100, as shown in
As previously described, the invention provides a method of sensing contact force and/or orientation as provided by the contact sensing assembly and system. The inventive method includes directing light or energy from a source through an optical sensor within a catheter; emitting light or energy from the optical sensor across a spaced gap for interacting with an optically-interactive surface provided in connection with an electrode; and receiving reflected light or energy by the optical sensor. The reflected light or energy may be processed by a processor to determine a change between the light or energy emitted from the optical sensor and the reflected light energy correspondingly received by the optical sensor. The changes may be correlated to, among other things, force vectors exerted by the electrode on a adjacent tissue.
In particular, under normal conditions of zero-contact force (e.g. when the electrode is not subjected to external forces), the plane of reflection as provided by either optically interactive surface 30, media 31 or medium 33, alone or in combination with one another as the case may be, is generally parallel to the plane of emitters 34 as previously described. Accordingly, the amplitude or intensity of the optical signal (e.g., light) received by receivers 32 is substantially the same or proportionally constant depending on the properties of the interactive surface. When the electrode contacts a surface, the contact force modifies the plane of reflection provided by the respective interactive surface (30, 31, or 33). In particular, upon the exertion of axial force (Fa) on the electrode, the plane of reflection is pushed closer to the place of emitters due to the spring-like configuration and/or flexibility exhibited by distal end 20 of catheter 12. Similarly, upon the exertion of lateral force (F1), the plane of reflection is tilted with respect to the plane of emitters. The change in amplitude or intensity of the reflected optical signal (e.g. light) received by each of the receivers relative to one another results in the calculation of the lateral force exerted on the external surface of the electrode. The change in amplitude or intensity of the reflected light relative to the zero-axial-force condition can be used to determine the axial force being exerted on the electrode. As a result, the net contact force is given by the vector sum of the axial and lateral force, and the direction relative to the axis may be calculated. Overall, the force, either axial, lateral or a combination of both, is determined based on the change of intensity of the optical signal received by the receivers which is proportional to the displacement and/or movement of the distal end 20 of catheter 12.
The invention also provides a contact sensing assembly (see
During manufacturing or fabrication of the contact sensing assemblies, such as those various embodiments described above, optic fibers may be positioned in connection within the base portion of the electrode and coupled to the coupling member for connection to a catheter shaft. One particular method of fabrication and aligning of the optical fibers, may include positioning the emitter/receiver into an assembly fixture such that the angle of the end portions of the fibers may be cleaved or cut to the desired angled (such as, for example, approximately 45 degrees). As previously suggested, the end portions of the emitter/receiver may further be partially or fully metalized, such as with a reflection-enhancing material, as recognized by those of ordinary skill in the art. Alternatively, the end portions of the optical fibers may be polished, such that an angle of approximately 45 degrees is obtained.
A number of various manufacturing or fabrication methods may be utilized in preparing the embodiments of the optical contact sensing assemblies of the present disclosure. With regards to one method of manufacturing, as previously discussed, the optical sensor having a proximal end and distal end is provided for incorporated within the contact assembly. As previously suggested, the optical sensor, includes an emitter and a receiver each having a distal and a proximal end, for emitting and receiving an optical signal. The end portions of the emitter and receiver may be provided at a desirable angle, such as, for example, approximately 45 degrees. In general, the distal end of the optical sensor is advanced towards the proximal end of an electrode. More specifically, the end portions of the emitter and receiver may be placed through the base portion of the electrode (such as seen in
The alignment of the emitter and receiver in connection with one another may further include positioning the optical sensor within the base portion of the electrode by utilizing optical signals. In particular, the distal end of the emitter may be rotated until an optical signal is in contact with the receiver (such as, for example, a visible light is shinning at the receiver thereby indicating alignment). The receiver may then be rotated until a peak voltage is obtained from the amplifier. The peak voltage may be measured by a digital voltage meter, such that the receiver is rotated until a highest voltage meter reading is detected, such as for example, at least 3Vdc. Once a peak voltage is obtained, the receiver may be secured in position, such as for example, by tightening a set screw or any other securing mechanism known by one of ordinary skill in the art. Similarly, the emitter may be rotated until a peak voltage is obtained, such that the digital voltage meter reading reaches its highest voltage level, such as for example, at least 3Vdc. The emitter and receiver may then be advanced proximally and distally in relation to one another to detect a sensed voltage obtained by the amplifier. Furthermore, the emitter and receiver may be moved proximally or distally uniformally in relation to the base portion of the electrode to obtain a sensed voltage. The sensed voltage is preferably in the range of approximately 5.1Vdc to approximately 5.2Vdc. Once the sensed voltage is obtained and the approximately 50% of the angled end portions of the emitter and receiver are within the base portion of the electrode, the emitter and receiver (i.e., optical sensor) may be secured relative to the base portion of the electrode. In particular, an adhesive may be disposed within the opening of the base of the electrode for securing the optical sensor within the electrode. The adhesive may comprise an ultraviolet adhesive. Ultraviolet light may be provided to cure the adhesive. Alternately, other types of methods may be used to harden the adhesive. Once the emitter and receiver are secured within the base portion of the electrode, various distinguishing markings may be provided on the proximal ends of the receiver and emitter to distinguish the two. The optical sensor may then be released from any sort of assembly used during the process and the electrode may be rotated to another position for an additional optical sensor to be coupled to the electrode. In one embodiment, the process may be continued for a total of three optical sensors. The alignment of each of the fibers may be continued for each of the other pairs of the fibers for the contact sensing assembly, such as for example, fibers 230, 232, and 234, as shown in
The assembly may further be configured to include a reference structure. The reference structure may comprise acoustic, electromagnetic, optical, or any other type of structural elements capable of detecting and localizing the structure within the body, and hence the orientation of the catheter electrode relative to the body. One particular example of a reference structure, may include a fluoro-opaque marker. The fluoro-opaque marker may be provided as a coating on the surface of the assembly or integrated within the assembly (such as, for example, a coating or thin wire) having a known relationship to the optical sensors of the assembly and optionally to the directional irrigation ports. The reference marker may, in general, allow for visual rendering of the assembly through the use of a machine. Moreover, the sensor assembly may include other structural components and materials such as a magnetic material to enable sensing of the assembly through use in connection with various systems, such as, for example, and without limitation, the Carto™ System available from Biosense Webster, and as generally shown with reference to U.S. Pat. Nos. 6,498,944 entitled “Intrabody Measurement” and 6,788,967 entitled “Medical Diagnosis, Treatment and Imaging Systems,” both of which are incorporated herein by reference in their entireties; commonly available fluoroscopy systems; or a magnetic location system, such as, for example, the gMPS system from MediGuide Ltd., and as generally shown with reference to U.S. Pat. No. 7,386,339 entitled “Medical Imaging and Navigation System,” the disclosure of which is incorporated herein by reference in its entirety.
In another embodiment, the invention provides a method for sensing contact force exerted by an electrode on a tissue. The method may include directing an optical signal along at least a portion of a tubular body of a catheter having a proximal end and a distal end (see
An optical contact sensor assembly as disclosed may be further adapted to detect and quantify events that may occur either during or as a result of ablating tissue. Moreover, such an assembly may be adapted to detect and quantify, or sample, events (such as, for example, physiological events) at or during a discrete time interval, such as, for example a temporal duration ranging from approximately a few hundredths of a second to approximately sub-millisecond intervals. The events may be further detected within the frequency domain in a range from approximately 10 Hz to approximately 10 kHz. In general, many events may occur during the ablation of tissue. However, with some traditional systems and methods, such events may go undetected by an operator. In contrast, such events may be detected by manipulating the sensitivity of the sensor assembly. For instance, the sensitivity of the sensor assembly may be adjusted by manipulating at least one of the stiffness of the coupling member, the interference of the optical signal, the gain of the amplifiers, and the frequency of the acquired signal. Thus, due to the increased sensitivity of a sensor assembly of the type disclosed in connection with the present teachings, various sub-millisecond events may be recorded and identified. These events may include, but are not limited to, tissue pop, steam pop, identification of regions impacted by either tissue or steam pop, and any other type of event that may generate either an electrical or surface change in the region of interest as detected by the sensor assembly. For instance, changes in optical intensity associated with the contact of the sensor assembly, or the force readings recorded by the assembly, may be used as a basis for identifying events at a discrete level. These types of events, and all associated parameters (e.g., for example, power settings, irrigation levels, ablation settings, force, time/date, and relative location (3D or 4D location)) may be recorded and stored in the connection with known systems, such as the system having the model name EnSite NavX™ and commercially available from St. Jude Medical, Inc., or any other mapping and/or navigational system. Moreover, a robotic surgical system may collectively store the event information, as well as the associated parameters, and use such information to modifying the surgical procedure or relevant operational settings. Accordingly, the assembly may be coupled or integrated with a processor for processing the collected physiological signals. Moreover, the signals may be stored in a memory structure for further processing, reference, or collecting of the physiological signals. As suggested, various physiological signals may be processed and/or stored and collected, including but not limited to, the occurrence of, the spatial co-ordinates for, the ablation generator settings for, and the magnitude of the physiological signals.
One particular event that may be detected at a sub-millisecond level is the instance of tissue pop during an ablation procedure, such as shown in
As shown in
Another embodiment, as shown in
As previously indicated, all embodiments of the present invention may be incorporated into a machine-based or robotically manipulated system, such as in a closed-loop control configuration.
Although a number of embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. For example, all joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 61/142079 | Dec 2008 | US | national |
This application claims priority to and the benefit of U.S. provisional application No. 61/142,079 filed 31 Dec. 2008 (the '079 application). For purposes of U.S. patent prosecution, this application is also a continuation-in-part of U.S. non-provisional application Ser. No. 11/941,073, filed 15 Nov. 2007 (the '073 application), which in turn claims the benefit of U.S. provisional application No. 60/915,387, filed 1 May 2007 (the '387 application). The entire contents of each of the '079, the '073, and the '387 applications are hereby incorporated by reference as though fully set forth herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US09/69857 | 12/30/2009 | WO | 00 | 6/30/2011 |
