Patent Application
20180042518
The present invention relates to medical devices and methods for delivering a therapy to the body. More specifically, the invention relates to devices and methods for detecting a position of the device within the body.
Cardiac arrhythmia and/or other cardiac pathology contributing to abnormal heart function may originate in cardiac cellular tissue. One technique that may be utilized to treat the arrhythmia and/or cardiac pathology may include ablation of tissue substrates contributing to the arrhythmia and/or cardiac pathology. Ablation by heat, chemicals or other means of creating a lesion in the tissue substrate may isolate diseased tissue from normal heart circuits. In some instances, electrophysiology therapy may involve locating tissue contributing to the arrhythmia and/or cardiac pathology using a mapping and/or diagnosing catheter and then using an ablation electrode to destroy and/or isolate the diseased tissue.
Prior to performing an ablation procedure, a physician and/or clinician may utilize specialized mapping and/or diagnostic catheters to precisely locate tissue contributing and/or causing an arrhythmia or other cardiac pathology. It is often desirable to precisely locate the targeted tissue prior to performing an ablation procedure in order to effectively alleviate and/or eliminate the arrhythmia and/or cardiac pathology. Further, precise targeting of the tissue may prevent or reduce the likelihood that healthy tissue (located proximate the targeted tissue) is damaged.
Several methods and/or techniques may be employed to precisely locate targeted tissue where an ablation or other therapeutic procedure may be performed. An example method may include utilizing an ablation, mapping and/or diagnostic catheter to determine how close the catheter is to targeted tissue. Further, the ablation, mapping and/or diagnostic catheter may include one or more sensing electrodes located on a distal portion of the catheter. The electrodes may sense, measure and/or provide a processor with information relating to electrical characteristics of the cardiac tissue and surrounding media. Using the sensed and/or measured information, the processor may be able to correlate the spatial location of the distal portion of the catheter to the cardiac tissue. For example, electrodes may sense the impedance, resistance, voltage potential, etc. of the cardiac tissue and/or surrounding media and determine how far a distal portion of a diagnostic and/or ablation catheter is to cardiac tissue.
To locate the catheter and electrodes within the body, the catheter may include a position sensor configured to provide an indication of a location within a multidimensional magnetic field.
A position sensor assembly comprising a base member, a first magnetic field sensor and a second magnetic field sensor. The base member has a substantially linear longitudinal axis, a proximal portion oriented in a first plane along the longitudinal axis, a distal portion oriented in a second plane along the longitudinal axis, the second plane being substantially orthogonal to the first plane, and an intermediate portion extending between the proximal and distal portions in a twisted configuration to operate as a transition between the proximal and distal portions. The base member includes a first base member element defining the proximal portion, and a second base member element defining the distal portion, and further wherein the first and second base member elements are mechanically and electrically coupled together at a joint. The first magnetic field sensor is disposed on the proximal portion of base member, the first magnetic field sensor including a first magnetic field sensing element, the first magnetic field sensor being oriented on the proximal portion of the base member so that the first magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a first axis. The second magnetic field sensor is disposed on the distal portion of base member, the second magnetic field sensor including a second magnetic field sensing element, the second magnetic field sensor oriented on the distal portion of the base member so that the second magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a second axis.
In another embodiment, a medical probe comprising a flexible catheter body having a distal end, an active element coupled to the distal end of the flexible catheter body, and a position sensor assembly carried by the catheter body proximate the active element. The position sensor assembly comprises a base member, a first magnetic field sensor and a second magnetic field sensor. The base member has a substantially linear longitudinal axis, a proximal portion oriented in a first plane along the longitudinal axis, a distal portion oriented in a second plane along the longitudinal axis, the second plane being substantially orthogonal to the first plane, and an intermediate portion extending between the proximal and distal portions in a twisted configuration to operate as a transition between the proximal and distal portions. The base member includes a first base member element defining the proximal portion, and a second base member element defining the distal portion, and further wherein the first and second base member elements are mechanically and electrically coupled together at a joint. The first magnetic field sensor is disposed on the proximal portion of base member, the first magnetic field sensor including a first magnetic field sensing element, the first magnetic field sensor being oriented on the proximal portion of the base member so that the first magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a first axis. The second magnetic field sensor is disposed on the distal portion of base member, the second magnetic field sensor including a second magnetic field sensing element, the second magnetic field sensor oriented on the distal portion of the base member so that the second magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a second axis.
In another embodiment, a medical system comprising a medical probe, a magnetic field generator and a processor. The medical probe comprises a flexible catheter body having a distal end, an active element coupled to the distal end of the flexible catheter body, and a position sensor assembly carried by the catheter body proximate the active element. The position sensor assembly comprises a base member, a first magnetic field sensor and a second magnetic field sensor. The base member has a substantially linear longitudinal axis, a proximal portion oriented in a first plane along the longitudinal axis, a distal portion oriented in a second plane along the longitudinal axis, the second plane being substantially orthogonal to the first plane, and an intermediate portion extending between the proximal and distal portions in a twisted configuration to operate as a transition between the proximal and distal portions. The base member includes a first base member element defining the proximal portion, and a second base member element defining the distal portion, and further wherein the first and second base member elements are mechanically and electrically coupled together at a joint. The first magnetic field sensor is disposed on the proximal portion of base member, the first magnetic field sensor including a first magnetic field sensing element, the first magnetic field sensor being oriented on the proximal portion of the base member so that the first magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a first axis. The second magnetic field sensor is disposed on the distal portion of base member, the second magnetic field sensor including a second magnetic field sensing element, the second magnetic field sensor oriented on the distal portion of the base member so that the second magnetic field sensing element has a sensitivity to a component of the multi-dimensional magnetic field along a second axis. The magnetic field generator is configured to generate a multi-dimensional magnetic field in a volume including the medical probe and a patient. The processor is operable to receive outputs from the magnetic field sensors to determine a position of the position sensor assembly within the volume.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.
While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
In the illustrated embodiment, the system 10 includes a mapping catheter or probe 14. Each probe 14 may be separately introduced into the selected heart region 12 through a vein or artery (e.g., the femoral vein or artery) using a suitable percutaneous access technique. Alternatively, the system 10 may include one or more probes that have both mapping and therapeutic capabilities (e.g., a radiofrequency (RF) ablation catheter having one or more sensing electrodes for acquiring electrical signals from the patient's heart).
In the illustrated embodiment, the mapping probe 14 may include flexible catheter body 18, the distal end of which carries a three-dimensional multiple electrode structure 20. In the illustrated embodiment, the electrode structure 20 takes the form of a basket formed from a plurality of splines together defining an open interior space 22, although other electrode structures could be used. The electrode structure 20 carries a plurality of mapping electrodes 24 each having an electrode location on a respective spline of the electrode structure 20 (for ease of illustration, the electrodes 24 are depicted only on a single spline in
The electrodes 24 may be electrically coupled to the processor 32. A signal wire (not shown) may be electrically coupled to each electrode 24 on structure 20. The signal wires may extend through body 18 of probe 14 and electrically couple each electrode 24 to an input of the processor 32. Electrodes 24 may sense electrical characteristics correlated to an anatomical region adjacent to their physical location within the heart. The sensed cardiac electrical characteristic (e.g., voltage, impedance, etc.) may be processed by the processor 32 to assist a user, for example a physician, by generating processed output—e.g. an anatomical map (e.g., 3D map of heart chamber)—to identify one or more sites within the heart appropriate for a diagnostic and/or treatment procedure, such as an ablation procedure.
The processor 32 may include dedicated circuitry (e.g., discrete logic elements and one or more microcontrollers; application-specific integrated circuits (ASICs); or specially configured programmable devices, such as, for example, programmable logic devices (PLDs) or field programmable gate arrays (FPGAs)) for receiving and/or processing the acquired physiological activity. In some examples, processor 32 may include a general purpose microprocessor and/or a specialized microprocessor (e.g., a digital signal processor, or DSP, which may be optimized for processing activation signals) that executes instructions to receive, analyze and display information associated with the received physiological activity. In such examples, the processor 32 can include program instructions, which when executed, perform part of the signal processing. Program instructions can include, for example, firmware, microcode or application code that is executed by microprocessors or microcontrollers. The above-mentioned implementations are merely exemplary, and the reader will appreciate that processor 32 can take any suitable form for receiving electrical signals and processing the received electrical signals. The processor 32 further includes code for determining a location of the position sensor within the multidimensional magnetic field.
The mapping probe 14 including a position sensor (not shown in
The position sensor is communicatively coupled to the processor 32 by a wired or wireless communications path such that the processor 32 sends and receives various signals to and from the position sensor. As is known in the art, a position tracking system (not shown) including a magnetic field generator is configured to generate one or more magnetic fields that are sensed by the position sensor on the probe 14. The processor 32 is configured to process the output signals from the position sensor to resolve the location of the position sensor, and consequently, the distal portion of the probe 14, within the volume defined by the multi-dimensional magnetic field.
The processor 32 may output data to a suitable device, for example display device 40, which may display relevant information for a user. For example, the display device 40 may provide to the user a three-dimensional electroanatomical map of the cardiac chamber in which the mapping probe 14 is deployed. In some examples, device 40 is a display (e.g. a CRT, LED), or other type of display, or a printer. In addition, the processor 32 may generate position-identifying output for display on device 40 that aids the user in guiding an ablation electrode or other therapeutic device into contact with tissue at the site identified for ablation.
As further shown, the intermediate portion 120 extends between the proximal and distal portions 112, 116 in a twisted configuration to operate as a transition between the proximal and distal portions 112, 116. In various embodiments, the intermediate portion 120 has a reduced stiffness with respect to the proximal and/or distal portions 112, 116, for example by reducing a thickness and/or a width of the transition zone base member. Alternatively, the intermediate portion 120 may be formed from a material having a lower stiffness than that of the proximal and/or distal portions 112, 116. In some embodiments, the axis of rotation about which the intermediate portion is twisted substantially corresponds to the longitudinal axis 108.
The position sensor assembly 100 further includes a first magnetic field sensor 124 having a first magnetic field sensing element 128, and a second magnetic field sensor 132 having a second magnetic field sensing element 136. As will be understood by those skilled in the art, the first and second magnetic field sensing elements 128, 136 are each configured to have a sensitivity to a component of a multi-dimensional magnetic field generated by an external field generator (as described previously) along a predetermined direction or axis.
In the illustrated embodiment, the first magnetic field sensor 124 is disposed on the proximal portion 112 of base member 104, and consequently, in the first plane. Additionally, the second magnetic field sensor 132 is disposed on the distal portion 116 of base member 104, and consequently, in the second plane, which as described and shown, is oriented generally orthogonal to the first plane.
In various embodiments, the position sensor assembly 100 may also include a third magnetic field sensor (not shown) having a third magnetic field sensing element substantially similar to the first and second magnetic field sensing elements. In such embodiments, the third magnetic field sensor may be disposed on the proximal portion 112 of the base member 104, but oriented thereon such that its axis of sensitivity is orthogonal to that of the first magnetic field sensing element 128. Alternatively, the third magnetic field sensor may be disposed on the distal portion 116 of the base member 104, but oriented thereon such that its axis of sensitivity is orthogonal to that of the second magnetic field sensing element 136.
In some embodiments, one or both of the first magnetic field sensor 124 and the second magnetic field sensor 132 may be a dual-axis sensor having two magnetic field sensing elements disposed on or within a single die, each magnetic field sensing element being oriented so that the axes of sensitivity of the respective magnetic field sensing elements are mutually orthogonal to one another. For example, in one embodiment, the first magnetic field sensor 124 may include both the first magnetic field sensing element 128 as well as the third magnetic field sensing element (not shown). Alternatively, in one embodiment, the second magnetic field sensor 132 may include both the second magnetic field sensing element 136 as well as the third magnetic field sensing element. Thus, the respective individual magnetic field sensing elements need not necessarily all be located on a separate die.
In the various embodiments, the position sensor assembly 100 is configured to sense the generated external magnetic fields and provide tracking signals indicating the location and orientation of the position sensor assembly 100 in up to six degrees of freedom (i.e., x, y, and z measurements, and pitch, yaw, and roll angles) when the first, second and third magnetic field sensors are present and oriented along mutually orthogonal axes.
In the various embodiments, the magnetic field sensors of the position sensor assembly 100 can include any magnetic field sensing technologies now known (e.g., anisotropic magneto-resistive (AMR) sensing elements, giant magneto-resistive (GMR) sensing elements, tunneling magneto-resistive (TMR) sensing elements, colossal magneto-resistive (CMR) sensing elements, extraordinary magneto-resistive (EMR) sensing elements, spin Hall sensing elements, and the like), or later developed.
As further shown, the position sensor assembly 100 includes a encapsulating element 140 (i.e., a housing) surrounding the base member 104 and the magnetic field field sensors disposed thereon. In embodiments, the encapsulating element 140 can be an epoxy material. Additionally, the position sensor assembly 100 includes conductors 150 for coupling the magnetic field sensors to electrical connection components (not shown) at or near the proximal portion 112 of the base member 104.
In various embodiments, position sensor assembly 100, particularly the base member 104 and the conductors 150 and associated electrical interconnects, may be constructed according to known, or later-developed, printed circuit board construction technologies. For example, the conductors 150 may be constructed as electrical traces formed on the body 104. Similarly, the body 104 may also be formed of any materials used for flexible printed circuit substrates. In other embodiments, the conductors 150 may be conductor wires that are separately bonded to the body 104 and the respective magnetic field sensors, either before or after forming the twist in the intermediate portion 120. As will be appreciated, the magnetic field sensors may discrete dies that are mounted to the base member 104 and electrically coupled to the conductors 150 according to known techniques.
In embodiments, the conductors 150 are disposed, at least within the intermediate portion 120, as near as possible to the longitudinal axis 108, which also constitutes the axis of rotation about which the intermediate portion 120 is twisted. In doing so, rotational and torsional stresses and strains on the conductors 150 disposed along the intermediate portion 120 of the base member 104 can be minimized.
In the particular embodiment illustrated, the intermediate portion 320 has an “hourglass” shape, such that it has concavely-curved outer edges resulting in a width at the middle of the intermediate portion 320 that is smaller than the width of either of the proximal or distal portions 312, 316. The illustrated shape of the intermediate portion 320 provides that portion with a lower torsional stiffness than either of the proximal or distal portions 312, 316, thus facilitating twisting the intermediate portion 320 so that the proximal and distal portions 312, 316 can be oriented in different, mutually orthogonal planes. In embodiments, the conductors 350 (e.g., electrical traces) connected to the second magnetic field sensor 332 can be disposed on or proximate the longitudinal axis 308 along the intermediate portion 320 so as to minimize torsional stress and strain on those conductors.
In the particular embodiment illustrated, the intermediate portion 420 has a “serpentine” configuration when in the flat, untwisted state as depicted in
The base member 504 differs from those described in the previous embodiments in that it is a two-piece construction and includes a proximal base member element 560 and a distal base member element 564 mechanically and electrically coupled together at a joint 568, which can include one or more bond pads 570, 574 or other conventional structures for joining PCB components. In the illustrated embodiment the twisted intermediate portion 520 is located on the distal base member element 564. In other embodiments, the intermediate portion 520 may be located on the proximal base member element 560. The two-piece construction of the base member 504 can advantageously minimize stresses induced in the base member 504 substrate as well as in the electrical conductors 550 formed on the base member 504. In various embodiments, the intermediate portion 520 can have an hourglass or serpentine configuration as previously described.
The position sensor assembly 600 differs from the previously described embodiments in that the conductors 650 constitute lead wires that are structurally separated from (i.e., not formed on) the base member 604. In particular, the conductors 650 connected to the magnetic field sensor 632 located on the distal portion 616 of the base member 604 are carried by the encapsulating element 644 at least across the intermediate portion 620, to bond pads 660, 664 located at the distal tip of the base member 604 and electrically coupled to the magnetic field sensor 632 via short electrical traces (not shown) formed on the distal portion 616. In this configuration, the conductors 650 extending across the intermediate portion 620 are not exposed to the torsional stresses imposed on the intermediate portion 620 during the manufacturing step of forming the twist in the intermediate portion 620.
Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.
This application claims priority to Provisional Application No. 62/374,559, filed Aug. 12, 2016, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62374559 | Aug 2016 | US |
