Force sensitive mechanism for contact detection in catheter systems

Abstract

A catheter includes a shaft and a distal portion extending distally from a distal end of the shaft and defining a longitudinal axis. The distal end portion comprises a proximal section, a distal section distal of the proximal section, the distal section being displaceable relative to the proximal section, and a force sensing mechanism comprising a proximal housing secured within the proximal section; a piezoelectric sensor mounted to the proximal housing and having a first portion fixed to the proximal housing and a second portion not fixed to the proximal housing; and a distal housing fixed within the distal section and including a protrusion contacting the second portion of the piezoelectric sensor and configured to apply an axial force to the second portion of the piezoelectric sensor when an external force is applied to the distal section.

Description

Technical Field

[0001] The present disclosure is generally directed to various force sensing catheter features. Background Art

[0002] In ablation therapy, it can be useful to assess contact between an ablation element and tissue targeted for ablation. For example, in interventional cardiac electrophysiology (EP) procedures, contact can be used to assess the effectiveness of a delivered ablation therapy. Other catheter-based treatments and diagnostics can be assisted by knowing whether components of the catheter contact the target tissue, and the extent to which components of the catheter press against the target tissue. The tissue exerts a return force on the catheter, which can be measured to assess contact and the extent to which the catheter presses against the target tissue.

[0003] There is a continuing need for improved catheter devices and corresponding methods of use that are capable of sensing forces applied by the catheter tip to target tissue. Summary of the invention

[0004] In Example 1, a catheter adapted to measure contact force includes an elongated shaft having a proximal end and a distal end, and a distal portion extending distally from the distal end of the shaft. The distal portion defines a longitudinal axis extending therethrough, and includes a proximal segment, a distal segment located distal to the proximal segment (the distal segment is separated from the proximal segment by a gap), and a force sensing mechanism. The force sensing mechanism includes a proximal housing fixed within the proximal segment; a piezoelectric sensor mounted to the proximal housing and having a first portion fixed to the proximal housing and a second portion not fixed to the proximal housing; and a distal housing fixed within the distal segment and including a protrusion that contacts the second portion of the piezoelectric sensor and is configured to apply an axial force to the second portion of the piezoelectric sensor when an external force is applied to the distal segment. The piezoelectric sensor is configured to generate an output indicating the amount of axial force applied to the second portion of the piezoelectric sensor in response to the external force being applied to the distal segment.

[0005] In Example 2, the catheter of Example 1, wherein the proximal housing includes an upper surface, a lower surface, and a cavity extending from the lower surface through the upper surface, and wherein a first portion of the piezoelectric sensor is fixedly attached to the upper surface, and wherein a second portion of the piezoelectric sensor extends at least partially across the cavity.

[0006] In Example 3, the catheter of Example 2, wherein the piezoelectric sensor has an arcuate or rectangular profile when viewed from a direction parallel to the longitudinal axis.

[0007] In Example 4, the catheter of Example 2, wherein the piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is a peripheral portion of the piezoelectric sensor, and the second portion is located radially inward of the first portion of the piezoelectric sensor.

[0008] In Example 5, the catheter of Example 2, wherein the piezoelectric sensor is substantially a disk, and wherein the second portion extends across the cavity.

[0009] In Example 6, the catheter of any of Examples 1-5, wherein the proximal shell includes a compressible backing material that is disposed within a portion of the cavity and contacts the second portion of the piezoelectric sensor relative to a protrusion on the distal shell, wherein the backing material resists deformation of the second portion of the piezoelectric sensor when an external force is applied to the distal segment.

[0010] In Example 7, the catheter of any of Examples 1-6, wherein the force sensing mechanism includes three piezoelectric sensors mounted to the proximal housing and circumferentially spaced about the longitudinal axis, each of the piezoelectric sensors having a first portion fixed to the proximal housing and a second portion deflectable relative to the first portion.

[0011] In Example 8, the catheter of Example 7, wherein the distal housing includes three protrusions, each protrusion contacts the second portion of a corresponding one of the piezoelectric sensors and is configured to apply an axial force to the second portion of the corresponding piezoelectric sensor when an external force is applied to the distal segment.

[0012] In Example 9, the catheter of Example 8, wherein each of the piezoelectric sensors is configured to generate an output indicative of an amount of axial force applied to the second portion thereof in response to application of an external force to the distal segment.

[0013] In Example 10, the catheter of Example 9, wherein the proximal housing includes three cavities extending from the lower surface through the upper surface, each of the cavities is aligned with a corresponding one of the piezoelectric sensors, and wherein the second portion of each of the piezoelectric sensors extends at least partially across the corresponding one of the cavities.

[0014] In Example 11, the catheter of Example 10, wherein each piezoelectric sensor has an arcuate or rectangular profile when viewed from a direction parallel to the longitudinal axis.

[0015] In Example 12, the catheter of Example 10, wherein each piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is a peripheral portion of the piezoelectric sensor and the second portion is located radially inward of the first portion of the piezoelectric sensor.

[0016] In Example 13, the catheter of Example 10, wherein each piezoelectric sensor is substantially a disk, and wherein the second portion of each piezoelectric sensor extends across the corresponding cavity.

[0017] In Example 14, the catheter of any of Examples 8-13, wherein a compressible backing material is disposed within a portion of each cavity and in contact with a second portion of the corresponding piezoelectric sensor relative to a corresponding protrusion on the distal housing, wherein when an external force is applied to the distal segment, the backing material resists deformation of the second portion of the corresponding piezoelectric sensor.

[0018] In Example 15, the catheter of Example 1 further includes a preload mechanism operably coupled to the proximal housing and configured to allow a user to selectively preload the piezoelectric sensor.

[0019] In Example 16, a catheter suitable for measuring contact force includes an elongated shaft having a proximal end and a distal end, and a distal portion extends distally from the distal end of the shaft. The distal portion defines a longitudinal axis extending through it, and includes a proximal segment, a distal segment located distal to the proximal segment, and a force sensing mechanism, and the force sensing mechanism includes a proximal housing fixed in the proximal segment; a piezoelectric sensor, which is mounted to the proximal housing and has a first portion fixed to the proximal housing and a second portion not fixed to the proximal housing; and a distal housing, which is fixed in the distal segment and includes a protrusion, the protrusion contacts the second portion of the piezoelectric sensor and is configured to apply an axial force to the second portion of the piezoelectric sensor when an external force is applied to the distal segment.

[0020] In Example 17, the catheter of Example 16, wherein the proximal housing includes an upper surface, a lower surface, and a cavity extending from the lower surface through the upper surface, and wherein a first portion of the piezoelectric sensor is fixedly attached to the upper surface, and wherein a second portion of the piezoelectric sensor extends at least partially across the cavity.

[0021] In Example 18, the catheter of Example 17, wherein the proximal shell includes a compressible backing material that is disposed within a portion of the cavity and contacts the second portion of the piezoelectric sensor relative to a protrusion on the distal shell, wherein when an external force is applied to the distal segment, the backing material resists deformation of the second portion of the piezoelectric sensor.

[0022] In Example 19, the catheter of Example 17, wherein the piezoelectric sensor has an arcuate or rectangular profile when viewed from a direction parallel to the longitudinal axis.

[0023] In Example 20, the catheter of Example 17, wherein the piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is a peripheral portion of the piezoelectric sensor and the second portion is located radially inward of the first portion of the piezoelectric sensor.

[0024] In Example 21, the catheter of Example 17, wherein the piezoelectric sensors are substantially disks, and wherein the second portion of each piezoelectric sensor extends through the corresponding cavity.

[0025] In Example 22, the catheter of Example 1 further includes a preload mechanism operably coupled to the proximal housing and configured to allow a user to selectively preload the piezoelectric sensor.

[0026] In Example 23, a catheter suitable for measuring contact force includes an elongated shaft having a proximal end and a distal end, a distal portion extending distally from the distal end of the shaft. The distal portion defines a longitudinal axis extending therethrough and includes a proximal segment, a distal segment located distal to the proximal segment, and a force sensing mechanism, the force sensing mechanism including a proximal housing fixed within the proximal segment, the proximal housing having a lower surface and an upper surface; a plurality of piezoelectric sensors mounted to the proximal housing and circumferentially spaced from each other around the proximal housing, each piezoelectric sensor having a first portion fixed to the proximal housing and a second portion not fixed to the proximal housing; and a distal housing fixed within the distal segment and including a plurality of protrusions, each of the protrusions contacting a second portion of a corresponding one of the piezoelectric sensors and configured to apply an axial force to the second portion of the corresponding piezoelectric sensor when an external force is applied to the distal segment, wherein each of the plurality of piezoelectric sensors is configured to generate an output indicating the amount of axial force applied to its second portion in response to the external force being applied to the distal segment.

[0027] In Example 24, the catheter of Example 23, wherein the proximal housing includes a plurality of cavities extending from the lower surface through the upper surface, each of the cavities being aligned with a corresponding one of the piezoelectric sensors, wherein a second portion of each of the piezoelectric sensors extends at least partially across a corresponding one of the cavities.

[0028] In Example 25, the catheter of Example 24, wherein the proximal shell includes a compressible backing material disposed within each of the cavities and in contact with a second portion of the piezoelectric sensor located thereon relative to a corresponding protrusion on the distal shell, wherein when an external force is applied to the distal segment, the backing material resists deformation of the second portion of the piezoelectric sensor.

[0029] In Example 26, the catheter of Example 24, wherein each piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is an outer radial portion of the piezoelectric sensor and the second portion is an inner radial portion of the piezoelectric sensor.

[0030] In Example 27, the catheter of Example 24, wherein each piezoelectric sensor is substantially a disk, and wherein the second portion of each piezoelectric sensor extends across the corresponding cavity.

[0031] In Example 28, the catheter of Example 24, wherein the force sensing mechanism includes three piezoelectric sensors mounted to the proximal housing and circumferentially spaced about the longitudinal axis, each of the piezoelectric sensors having a first portion fixed to the proximal housing and a second portion deflectable relative to the first portion, and wherein the distal housing includes three protrusions, each protrusion contacting the second portion of a corresponding one of the piezoelectric sensors and configured to apply an axial force to the second portion of the corresponding piezoelectric sensor when an external force is applied to the distal segment.

[0032] In Example 29, the catheter of Example 28, wherein the proximal housing includes three cavities extending from the lower surface through the upper surface, each of the cavities is aligned with a corresponding one of the piezoelectric sensors, and wherein a second portion of each of the piezoelectric sensors extends at least partially across a corresponding one of the cavities.

[0033] In Example 30, a force sensing mechanism for an ablation catheter is provided, the force sensing mechanism being suitable for measuring contact force and comprising a proximal housing having a lower surface and an upper surface, a plurality of piezoelectric sensors mounted to the proximal housing and circumferentially spaced apart from one another around the proximal housing, each piezoelectric sensor having a first portion fixed to the proximal housing and a second portion not fixed to the proximal housing, and a distal housing comprising a plurality of protrusions, each of the protrusions contacting a second portion of a corresponding one of the piezoelectric sensors and being configured to apply an axial force to the second portion of the corresponding piezoelectric sensor when an external force is applied to the distal housing, wherein each of the plurality of piezoelectric sensors is configured to generate an output indicating an amount of axial force applied to its second portion in response to the external force being applied to the distal housing.

[0034] In Example 31, the force sensing mechanism of Example 30, wherein the proximal housing includes a plurality of cavities extending from a lower surface through an upper surface, each of the cavities being aligned with a corresponding one of the piezoelectric sensors, wherein a second portion of each of the piezoelectric sensors extends at least partially across a corresponding one of the cavities.

[0035] In Example 32, the force sensing mechanism of Example 31, wherein the proximal shell includes a compressible backing material disposed within each of the cavities and in contact with a second portion of the piezoelectric sensor located thereon relative to a corresponding protrusion on the distal shell, wherein when an external force is applied to the distal segment, the backing material resists deformation of the second portion of the piezoelectric sensor.

[0036] In Example 33, the force sensing mechanism of Example 30, wherein each piezoelectric sensor has a rectangular shape.

[0037] In Example 34, the force sensing mechanism of Example 30, wherein each piezoelectric sensor has an annular shape, wherein the first portion is a peripheral portion of the piezoelectric sensor, and the second portion is located radially inward of the first portion of the piezoelectric sensor.

[0038] In Example 35, the force sensing mechanism of Example 30, wherein each piezoelectric sensor is substantially a disk, and wherein the second portion of each piezoelectric sensor extends across the corresponding cavity.

[0039] While multiple embodiments are disclosed, 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figures 1A-1C A system for measuring force with a catheter according to various embodiments of the present disclosure is shown.

[0041] Figure 2 A block diagram of circuits used to control the various functions described herein is shown.

[0042] Figure 3 A perspective view of the distal end of a catheter is shown in accordance with various embodiments of the present disclosure.

[0043] Figure 4A and 4B According to various embodiments of the present disclosure Figure 3 Perspective and front views of a force sensing mechanism in a catheter.

[0044] Figure 4C According to various embodiments of the present disclosure Figure 4A-4B A cross-sectional elevation view of the force sensing mechanism shown in FIG.

[0045] Figure 5A , 5B and 5C are respectively used for Figure 3 Perspective, front and cross-sectional views of an alternative force sensing mechanism in a catheter.

[0046] Figures 6A-6D According to various embodiments of the present disclosure, Figure 3 Perspective, front and cross-sectional views of an alternative force sensing mechanism in a catheter.

[0047] Fig. 7A and 7B Accordingly, the various embodiments of the present disclosure are used for Figure 3 Front view and cross-sectional view of an alternative force sensing mechanism in a catheter.

[0048] Although the present invention is applicable to various modifications and alternative forms, specific embodiments are shown by way of example in the accompanying drawings and are described in detail below. However, the purpose of the present invention is not to limit the present invention to the specific embodiments described. On the contrary, the present invention is intended to cover all modifications, equivalents and alternatives within the scope of the present invention defined by the appended claims. DETAILED DESCRIPTION

[0049] Various cardiac abnormalities can be attributed to inappropriate electrical activity of cardiac tissue. Such inappropriate electrical activity may include, but is not limited to, generating electrical signals, conducting electrical signals, and / or mechanically contracting tissue in a manner that does not support efficient and / or effective cardiac function. For example, during the cardiac cycle, an area of ​​cardiac tissue may become electrically active prematurely or otherwise asynchronous, thereby causing cardiac cells in the area and / or adjacent areas to contract rhythmically. The result is an abnormal cardiac contraction that is not timed for optimal cardiac output. In some cases, an area of ​​cardiac tissue may provide a faulty electrical pathway (e.g., a short circuit), which causes arrhythmias (such as atrial fibrillation or supraventricular tachycardia). In some cases, inactivated tissue (e.g., scar tissue) may be preferable to dysfunctional cardiac tissue.

[0050] Cardiac ablation is a procedure to treat cardiac tissue to inactivate the tissue. As described above, the tissue targeted for ablation can be associated with inappropriate electrical activity. Cardiac ablation can cause tissue lesions and prevent the tissue from inappropriately generating or conducting electrical signals. For example, lines, circles, or other forms of damaged cardiac tissue can prevent the propagation of erroneous electrical signals. In some cases, cardiac ablation is intended to cause cardiac tissue death and perform scar tissue reconstruction on the injury, where the scar tissue is not associated with inappropriate electrical activity. Injury treatments include electrical ablation, radiofrequency ablation, cryoablation, microwave ablation, laser ablation, and surgical ablation, among others. Although cardiac ablation treatment is used as an example herein, various embodiments of the present disclosure may relate to ablation of other types of tissue and / or non-ablative diagnostics and / or catheters for delivering other treatments.

[0051] Ideally, ablation therapy can be delivered in a minimally invasive manner, such as using a catheter introduced into the heart through a blood vessel, rather than surgically opening the heart for direct access (e.g., as in a maze procedure). For example, a single catheter can be used to perform electrophysiological studies of the inner surface of the heart to identify patterns of electrical activation. Based on these patterns, clinicians can identify areas of inappropriate electrical activity and ablate cardiac tissue in a manner that kills or isolates tissue associated with inappropriate electrical activation. However, the lack of direct access in catheter-based procedures may require clinicians to interact with cardiac tissue only through a single catheter and track all information collected by the catheter or otherwise associated with the procedure. In particular, it may be challenging to determine the location of the treatment element (e.g., proximity to the tissue), the amount of damage, and whether the tissue is completely damaged, insufficiently damaged (e.g., still able to generate and / or conduct unwanted electrical signals) or excessively damaged (e.g., burning through or otherwise weakening the heart wall). The amount of damage may depend on the degree of contact between the ablation element and the target tissue. For example, an ablation element that barely contacts the tissue may not be adequately positioned to deliver effective ablation therapy. Conversely, an ablation element that is pressed too hard into tissue may deliver too much ablation energy or cause perforations.

[0052] Among other things, the present disclosure relates to methods, devices, and systems for assessing the degree of contact between a portion of a catheter (e.g., an ablation element) and tissue. Understanding the degree of contact (such as the magnitude and direction of the force generated by the contact between the catheter and the tissue) helps determine the extent of damage to the target tissue. Among other things, information about the extent of damage to cardiac tissue can be used to determine whether the tissue should be further damaged or whether the tissue has been successfully ablated. Additionally or alternatively, indicators of contact can be useful when navigating a catheter because the user may not feel the force that the tissue is exerting on the catheter as the catheter is advanced within the patient, causing damage or perforation of the vessel or cardiac tissue.

[0053] Figures 1A-1C An embodiment of a system 100 for sensing data from inside the body and / or delivering therapy is shown. For example, the system 100 can be configured to map cardiac tissue and / or ablate cardiac tissue, among other options. The system 100 includes a catheter 110 connected to a control unit 120 via a handle 114. The catheter 110 can include an elongated tubular member having a proximal end 115 connected to the handle 114 and a distal end 116 configured to be introduced into the heart 101 or other areas of the body. Figure 1A As shown, the distal end 116 of the catheter 110 is positioned within the left atrium of the heart 101 .

[0054] like Figure 1B As shown, the distal end 116 of the catheter 110 includes a proximal section 111, a force sensing mechanism 112, and a distal section 113. Figure 1BAs shown, the proximal segment 111 and the distal segment 113 can be coaxially aligned with each other in the base orientation, and the force sensing mechanism 112 bridges the proximal segment 111 and the distal segment 113. Specifically, in the illustrated embodiment, each of the proximal segment 111 and the distal segment 113 is coaxially aligned with the common longitudinal axis 109. In one embodiment, the longitudinal axis 109 can extend through the radial center of each of the proximal segment 111 and the distal segment 113, and can extend through the radial center of the distal end 116 as a whole. In some embodiments, the coaxial alignment of the proximal segment 111 and the distal segment 113 can correspond to the base orientation. As shown, the distal end 116 extends straight along at least the proximal segment 111 and the distal segment 113. In some embodiments, this straight arrangement of the proximal segment 111 and the distal segment 113 can correspond to the base orientation.

[0055] The distal segment 113 or any other segment may be in the form of an electrode configured to sense electrical activity, such as cardiac electrical signals. In other embodiments, such electrodes may additionally or alternatively be used to deliver ablative energy to tissue.

[0056] In various embodiments, the force sensing mechanism 112 provides force sensing capabilities to the catheter 110. For example, Figure 1B and 1C As shown, the catheter 110 is configured to sense the force applied to the distal segment 113 due to the engagement of the distal segment 113 with the tissue 117 of the heart 101. In various embodiments, the distal segment 113 can be relatively rigid so that when the distal segment 113 engages the tissue 117, the force applied to the tissue 117 by the tip of the distal segment 113 can be transmitted to the proximal segment 111, and the magnitude and (in some embodiments) direction of the applied force can be sensed by the force sensing mechanism 112. Figure 1B and 1C As shown, the applied force from the tissue causes a relative displacement between the proximal segment 111 and the distal segment 113 (based on this disclosure, one skilled in the art will recognize that such relative displacement, which may be on the order of microns, is Figure 1C 117). One or more sensors within the distal end 116 of the catheter 110 can sense the extent of bending or axial movement of the distal segment 113 relative to the proximal segment 111 to determine the magnitude and (in some embodiments) direction of the applied force, as further discussed herein. When the distal segment 113 is no longer engaged with the tissue 117, the proximal segment 111 and the distal segment 113 move toward Figure 1B Base orientation shown.

[0057] The control unit 120 of the system 100 includes a display 121 (e.g., a liquid crystal display or a cathode ray tube) for displaying information. The control unit 120 also includes a user input 122 that may include one or more buttons, switches, trackballs, mice, touch pads, or the like for receiving user input. The user input 122 may be additionally or alternatively located on the handle 114. The control unit 120 may include control circuits for performing the functions described herein. Some or all of the control circuits may alternatively be located within the handle 114.

[0058] Figure 2 A block diagram showing an example of a control circuit that can perform the functions described herein is shown. This or other control circuits can be housed within a control unit 120, which can include a single housing or multiple housings in which components are distributed. The control circuit can additionally or alternatively be housed within a handle 114. The components of the control unit 120 can be powered by a power source (not shown) known in the art, which can power the control unit 120 and any component of the system 100. Among other options, the power source can be plugged into an electrical outlet and / or powered from a battery.

[0059] The control unit 120 may include a catheter interface 123. The catheter interface 123 may include a plug that receives electrical wires from the handle 114. The catheter 110 may include a plurality of conductors (not shown, but known in the art) to transmit electrical signals between the distal end 116 and the proximal end 115, and further to the catheter interface 123. Through the catheter interface 123, the control unit 120 (and / or the handle 114, if the control circuit is included in the handle 114) may send electrical signals to any element within the catheter 110 and / or receive electrical signals from any element within the catheter 110. The catheter interface 123 may conduct the signals to any component of the control unit 120.

[0060] The control unit 120 may include hardware and software for imaging the tissue being mapped and / or treated. For example, in one embodiment, the control unit 120 may include an ultrasound subsystem 124 including components for operating the ultrasound functions of the system 100. Figure 2The illustrated example of the control circuit shown in includes an ultrasound subsystem 124, but it should be understood that not all embodiments may include an ultrasound subsystem 124 or any circuit for imaging tissue. The ultrasound subsystem 124 may include a signal generator configured to generate a signal for ultrasound transmission; and a signal processing component (e.g., a high-pass filter) configured to filter and process the reflected ultrasound signal received by the ultrasound sensor in the sensing mode and conducted to the ultrasound subsystem 124 through the conductor in the catheter 110. The ultrasound subsystem 124 can send signals to elements within the catheter 110 via the catheter interface 123 and / or receive signals from elements within the catheter 110 via the catheter interface 123.

[0061] However, it should be emphasized that the ultrasound subsystem 124 or other type of imaging subsystem is strictly optional and need not be included in the control unit 120 .

[0062] Control unit 120 may include ablation subsystem 125. Ablation subsystem 125 may include components for operating the ablation functionality of system 100. Figure 2 The illustrated example of the control circuit shown in includes an ablation subsystem, but it should be understood that not all embodiments may include an ablation subsystem 125 or any circuit for generating an ablation therapy. The ablation subsystem 125 may include an ablation generator to provide different treatment outputs depending on the specific configuration. In one embodiment, the ablation generator is configured to generate a high-frequency alternating current signal for delivering radiofrequency ablation energy to one or more electrodes. Alternatively, the ablation subsystem 125 and the corresponding ablation generator may be configured to provide relatively high voltage pulses (monophasic or biphasic) to achieve pulsed field ablation, thereby generating the desired damage in the target tissue via irreversible electroporation. The ablation subsystem 125 can support any other type of ablation therapy, such as microwave ablation. The ablation subsystem 125 can deliver signals or other types of ablation energy to the catheter 110 via the catheter interface 123.

[0063] The control unit 120 may include a force sensing subsystem 126. The force sensing subsystem 126 may include components for measuring the force experienced by the catheter 110. Such components may include a signal processor, an analog-to-digital converter, an operational amplifier, a comparator, and / or any other circuit for conditioning and measuring one or more signals. The force sensing subsystem 126 may provide a signal to a sensor (such as a piezoelectric sensor (see below)) within the catheter 110 via the catheter interface 123. Figure 3-7B The discussed) sends current and receives signals from sensors within catheter 110 via catheter interface 123.

[0064] Each of the ultrasound subsystem 124 (when present), the ablation subsystem 125, and the force sensing subsystem 126 can send signals to and receive signals from the processor 127. The processor 127 can be any type of processor for performing computer functions. For example, the processor 127 can execute program instructions stored in the memory 128 to perform any of the functions involved herein, such as determining the magnitude and direction of the force experienced by the catheter 110.

[0065] The control unit 120 also includes an input / output subsystem 129 that can support user input and output functions. For example, the input / output subsystem 129 can support a display 121 to display any information referenced herein, such as a graphical representation of tissue, catheter 110, and the magnitude and direction of forces experienced by catheter 110, among other options. The input / output subsystem 129 can record key and / or other input entries via user input 122 and route the entries to other circuits.

[0066] A single processor 127 or multiple processors can perform the functions of one or more subsystems, so the subsystems can share control circuits. Although different subsystems are presented herein, the circuits can be divided between a greater or lesser number of subsystems, which can be accommodated separately or together. In various embodiments, the circuits are not distributed between the subsystems, but are provided as a unified computing system. Whether distributed or unified, the components can be electrically connected to coordinate and share resources to perform functions.

[0067] Figure 3 1 is an isometric illustration of a distal portion of a cardiac ablation catheter 300. In an embodiment, the cardiac ablation catheter 300 corresponds to the ablation catheter 110 described in FIG. 1 and includes a distal accessory 302. As shown, the distal accessory 302 is arranged along the axis ( Figure 2 303 is axially disposed about a longitudinal axis 303 defined by the distal accessory 302 (not shown). The distal accessory 302 includes a proximal segment 304, a distal segment 305, and a force sensing mechanism 306. The distal accessory 302 also includes a tip electrode 312 and a ring electrode 314, wherein the tip electrode 312 is located at the distal end of the distal accessory 302, and the ring electrode 314 is located proximal to the tip electrode 312 and spaced apart therefrom. In an embodiment, the distal accessory 302 may include additional electrodes, such as electrodes 316, 318, disposed proximal to the electrodes 312 and 314 and longitudinally spaced apart therefrom. More or fewer electrodes may be employed in other embodiments within the scope of the present disclosure.

[0068] The specific operation of the various electrodes (or electrode pairs) can vary depending on the specific clinical use of the ablation catheter 300. In an embodiment, the electrodes 312, 314, 316 and 318 can be configured to operate as ablation electrodes, sensing electrodes, or both. For example, any one or all of the electrodes 312, 314, 316 and 318 can be configured to be operable to deliver ablation energy to the target tissue. Additionally or alternatively, any one or all of the electrodes 312, 314, 316 and 318 can be operated as a sensing electrode that is configured to sense electrical signals (e.g., intrinsic cardiac activation signals and / or electric fields generated by injected current for impedance-based position tracking, tissue proximity or contact sensing, etc.). In one embodiment, the electrodes 312, 314 can be configured to operate as ablation electrodes, such as for bipolar delivery of ablation energy, and in particular for bipolar delivery of pulsed field ablation energy for focal ablation of cardiac tissue. In embodiments, electrodes 316, 318 may be used as sensing electrodes, or alternatively as ablation electrodes. In some cases, electrodes 316, 318 are configured to measure local impedance, and may act as position sensors for sensing local electric fields in 5 degrees of freedom (e.g., 5 different motions—x, y, z, acceleration, and rotation). In embodiments, except as specifically described herein, electrodes 312, 314, 316, and 318 may be configured according to those described in co-pending and commonly assigned U.S. Patent Application No. 63 / 194,716, the entire contents of which are incorporated herein by reference.

[0069] However, it should be emphasized that the present disclosure is not limited to Figure 3 Rather, those skilled in the art will appreciate that additional variations in electrode configurations, number of electrodes, etc., may be employed within the scope of the present disclosure.

[0070] In an embodiment, the distal fitting 302 further includes an insulating material 330 that encapsulates and forms the outer insulating surface of the proximal segment 304 and the distal segment 305. In an embodiment, the insulating material 330 is formed by an overmolding process. Alternatively, the insulating material 330 can be formed using a reflow process in which one or more tubular insulating material segments are positioned around the partially assembled distal fitting 302 and then heated, as is known in the art. In an embodiment, employing an overmolding process to provide the insulating material 330 can have certain advantages, such as reducing or even eliminating the need for subsequent processing (such as injecting a medical adhesive to complete the assembly process and provide a fluid-tight connection between the various components). The insulating material can be a commercially available 55D and 55D. Both materials can be used in overmolding processes and bonded to “epoxy bondable” wire insulation. Pellethane can be used with a primer (e.g., Sivate TM E610) and plasma bonded to the tip insulator. Pebax can be bonded to the tip insulator without plasma using an adhesive (e.g., Thermedics 1-MP).

[0071] Those skilled in the art will appreciate that although Figure 3 100 . Although not shown, in various embodiments, the ablation catheter 300 may include additional components to achieve its functionality. For example, in embodiments where the ablation catheter 300 is of a deflectable or steerable type, the ablation catheter 300 may include structures (e.g., steering wires and one or more associated anchors) to facilitate controlled deflection of the distal portion of the ablation catheter 300 by a user. In addition, the ablation catheter 300 includes electrical conductors disposed within the catheter shaft to electrically couple the electrodes 312, 314, 316, and 318, the piezoelectric sensors 340, 342, 344, and other electrical components (e.g., one or more magnetic navigation sensors (when present)) to the associated functional components of the system 100. In general, construction techniques and structures for implementing steerability or deflectability of an ablation catheter and electrically coupling the electrical components to a control unit of an ablation system are well known, and thus, those skilled in the art will recognize that a wide range of such techniques may be employed in the ablation catheter 300.

[0072] In various embodiments, the proximal segment 304 and the distal segment 305 are spaced apart from each other to allow for a small deflection of the distal segment 305 relative to the proximal segment 304 when an external force is applied to the distal segment 305 by the patient tissue, it being understood that such movement can be very small (e.g., on the order of microns). The force sensing mechanism 306 is operably connected to the proximal segment 304 and the distal segment 305, and in the illustrated embodiment comprises a plurality of piezoelectric sensors 340, 342, 344 circumferentially spaced apart from each other about the longitudinal axis 303. The sensors 340, 342, 344 are configured to generate a variable output based on the force applied to the target tissue by the distal segment 305, the output being calibrated to indicate the magnitude of such force.

[0073] exist Figure 3In the embodiment of the present invention, the three piezoelectric sensors 340, 342, 344 are at evenly spaced azimuths around the longitudinal axis 303 (evenly arranged circumferentially around the longitudinal axis 303) and have the same radial distance from the longitudinal axis 303. If the force applied to the distal segment 305 of the catheter 300 is coaxial with the longitudinal axis 303, the output of each of the piezoelectric sensors 340, 342, 344 will be substantially equal. Based on these equal changes, the control circuit can calculate the magnitude of the force applied to the distal segment 306. The control circuit can also determine that the force is coaxial with the longitudinal axis 303 because the output of each of the three piezoelectric sensors 340, 342, 344 is the same.

[0074] If the force is not coaxial with the longitudinal axis 303, the output of each of the piezoelectric sensors 340, 342, 344 will not be equal. Based on this, the magnitude and direction (eg, unit vector) of the force can be determined by the control circuit.

[0075] Once assembled, the catheter 300 can be subjected to a calibration step at the factory or just before use by a physician. In such a step, a plurality of forces of known magnitude and direction can be sequentially placed on the distal segment 306, and the outputs of the piezoelectric sensors 340, 342, 344 can be calibrated based on the known magnitude and direction of the applied forces.

[0076] Amplitude can be represented by a gram or other measure of force. Amplitude can be represented as a running line graph, a bar graph or a graphic symbol, which shows the new force value and the most recent force value with a color or intensity change that moves over time. Direction can be represented as a unit vector in a three-dimensional reference system (e.g., relative to the X, Y and Z axis coordinate system). In some embodiments, a three-dimensional mapping function can be used to track the three-dimensional position of the distal end of the catheter 300 in a three-dimensional reference system. A magnetic field can be generated outside the patient and sensed by a sensor (not shown) sensitive to the magnetic field in the distal end of the catheter 300 to determine the three-dimensional position and specific orientation of the distal end of the catheter 300 in a three-dimensional reference system. The direction can be represented relative to the distal end of the catheter 300. For example, a line protruding toward or extending from the distal segment 306 can represent the direction of the force relative to the distal segment 306. Similarly, a graphic symbol with a changing color and / or intensity and / or shape can be used to represent the amplitude and / or direction of force. As described herein, such representation can be performed on a display.

[0077] Among other options, the magnitude and direction of the force can be used to navigate by providing an indicator when the catheter encounters tissue, and / or to assess the damage of the tissue by determining the degree of contact between the damaging element and the tissue. In some embodiments, a force below 10 grams is suboptimal (e.g., due to being too small) for damaging tissue, and a force exceeding 40 grams is also suboptimal (e.g., due to being too large) for damaging tissue. Therefore, a window between 10-40 grams can be ideal for damaging tissue, and the output of the force during the injury can provide feedback to the user to allow the user to stay within the window. Of course, other force ranges that are ideal for damage can also be used.

[0078] Figure 4A , 4B 4A and 4C are perspective, front, and cross-sectional views, respectively, of a force sensing mechanism 406 for use in a catheter 110 according to an embodiment of the present disclosure. The force sensing mechanism 406 corresponds functionally to the force sensing mechanism 306 described above. In the illustrated embodiment, the force sensing mechanism 406 includes a plurality (three in this case) of piezoelectric sensors 440, 442, 444, a rigid proximal housing 450, and a rigid distal housing 454. As shown, the piezoelectric sensors 440, 442, 444 are disposed in and attached to the proximal housing 450. In the illustrated embodiment, the piezoelectric sensors 440, 442, 444 have a generally rectangular shape when viewed in a direction parallel to the axis of the catheter, although other embodiments utilize piezoelectric sensors having different shapes or form factors.

[0079] In various embodiments, the proximal housing 450 is securely attached to the proximal section (111, 112 in FIG. 1 ) of the catheter 110, 300 described above. Figure 3 304 in FIG. 1 ), and the distal housing 454 is securely attached to the distal section (113 in FIG. 1 , 300 in FIG. 2 ) of the catheter 110 , 300 . Figure 3 306 in). In addition, in the absence of external forces on the distal segments of the respective catheters, the proximal housing 450 and the distal housing 454 are separated by a gap 456 that limits the maximum axial movement of the distal segment relative to the proximal segment under external forces. In addition, in the illustrated embodiment, a lumen 457 extends longitudinally through the proximal housing 450 and the distal housing 454 to accommodate the passage of catheter components (e.g., guide wires, irrigation tubes, etc.) to the distal segment of the catheter.

[0080] Figure 4C is a cross-sectional elevation view bisecting the force sensing mechanism 406 through the piezoelectric sensor 440 . Figure 4C The specific structural details shown in FIG. 4 represent the arrangement of the piezoelectric sensors 442, 444. Figure 4CAs shown, the proximal housing has a proximal end face 458, an opposite distal end face 459, a longitudinal cavity 460, and a distal recess 470 formed in the distal end face 459, the recess 470 defining a shoulder 475. As further shown, the distal housing 454 has a proximal end face 478, an opposite distal end face 479, and includes an axial projection 480 extending proximally from the proximal end face 478.

[0081] like Figure 4C As shown, piezoelectric sensor 440 includes an upper layer 488, a lower layer 490, and a piezoelectric layer 492 disposed therebetween. Piezoelectric sensor 440 also defines a fixed portion 494 and a free portion 496. As further shown, an optional backing member 498 is disposed within longitudinal cavity 460 adjacent to lower layer 490. Although only piezoelectric sensor 440 is shown in detail for ease of illustration, it should be emphasized that each of piezoelectric sensors 442 and 444 has the same structure as piezoelectric sensor 440. In addition, the overall configuration of force sensing mechanism 406 with respect to the location of piezoelectric sensors 442, 444 is similar to Figure 4C , i.e., a cross-sectional elevation view bisecting the piezoelectric sensors 442, 444 would appear the same as Figure 4C The structure is the same as described in, including the presence of recesses, longitudinal cavities and protrusions and the corresponding relationship with corresponding piezoelectric sensors.

[0082] The upper layer 488 and the lower layer 490, or at least a portion thereof, are electrically conductive and serve as electrode layers during operation of the piezoelectric sensor 440. In addition, the piezoelectric layer 492 includes a piezoelectric material, such as a piezoelectric ceramic such as lead zirconate titanate (PZT) or a piezoelectric polymer such as polyvinylidene fluoride (PVDF). As is well known in the electromechanical arts, a piezoelectric sensor produces a measurable electrical characteristic when subjected to a mechanical stress.

[0083] It should be emphasized that the specific (e.g., 3-layer) structure of the piezoelectric sensor 440 described herein is exemplary only and is not intended to limit the range of potential piezoelectric designs suitable for use with the force sensing mechanism 406. For example, in embodiments, the piezoelectric element itself can be a multi-layer or multi-piece structure. In addition, the upper layer 488 and the lower layer 490 can themselves be formed of a multi-layer or multi-component structure. In embodiments, all or part of the piezoelectric sensor used herein can be coated with a protective and / or insulating outer coating such as an epoxy resin.

[0084] Special reference Figure 4C, the piezoelectric sensor 440 is located in the distal recess 470 of the proximal housing 450, wherein the fixed portion 494 is located on the shoulder 475 and the free portion 496 extends above the longitudinal cavity 460. As further shown, the backing element 498 is adjacent to the lower layer 490 along the free portion 496 of the piezoelectric sensor 440. In addition, the axial protrusion 480 of the distal housing 454 is located above and pressed against the upper layer 488 in the free portion 496 of the piezoelectric sensor 440. Relative to the piezoelectric sensor 440, the piezoelectric sensors 442, 444 each have the same positional relationship and each have a configuration as shown in FIG. Figure 4C The distal recess, shoulder and longitudinal cavity in the proximal housing 450 and the axial protrusion in the distal housing 454 are shown. Figure 4C The same arrangement as shown is arranged in the longitudinal cavity adjacent to the piezoelectric sensors 442, 444.

[0085] In an embodiment, the fixed portion 494 of the piezoelectric sensor 440 is rigidly attached to the shoulder 475 of the proximal housing 450, and the free portion 496 of the piezoelectric sensor 440 is effectively cantilevered over the longitudinal cavity 460. Because the rigid axial protrusion 480 of the distal housing 454 is in direct contact with the upper layer 488 of the piezoelectric sensor 440, the pressure applied to the distal segment 305 ( Figure 3 ) will be transmitted to the free portion 496 of the piezoelectric sensor 440. In addition, the cantilever arrangement of the free portion 496 will maximize the piezoelectric effect exhibited by the piezoelectric sensor 440 in response to the transmitted force (i.e., the stress induced in the piezoelectric layer 492 and the sensor output caused by the corresponding piezoelectric effect will be significantly greater than an arrangement in which the piezoelectric sensor is rigidly fixed along its entire length).

[0086] In an embodiment, the backing element 498 (when present) is made of a compressible material (e.g., an elastomer) and its function is to provide some support to the free portion 496 of the piezoelectric sensor 440 to resist its deformation when external forces are applied, while not rigidly resisting all such deformation. In an embodiment, the mechanical properties of the backing element 498 can be tailored to fine-tune the piezoelectric effect exhibited by the piezoelectric sensor 440.

[0087] Those skilled in the art will appreciate that because the piezoelectric sensor 440 is an electromechanical device, electrical leads (not shown) are attached to the electrode structures on the upper layer 488 and the lower layer 490. In embodiments, the electrical leads may be routed through the longitudinal cavity 460, may be routed to the lumen 457, or through some other access feature within the proximal housing 450. Figure 4CAs further shown, in embodiments, a potting material 499 may be disposed within the open space within the proximal housing 450, which may be used to hermetically seal the internal components of the catheter and the force sensing mechanism 406, and may also enhance the structural attachment between the proximal and distal segments of the catheter. In embodiments, the potting material 499 and the backing element 498 may be formed of the same compressible material and may be formed in a single manufacturing step, although this is not strictly required. In some embodiments, the potting material 499 (or some other compressible material) may be disposed in the gap 456. In some embodiments, the backing element 498 and / or the potting material 499 may be omitted entirely.

[0088] Once again, Figure 4C The arrangement shown with respect to piezoelectric sensor 440 represents piezoelectric sensors 442 and 444.

[0089] As is generally recognized in the electromechanical arts, piezoelectric sensors 440, 442, 444 will exhibit electrical properties that vary depending on the stresses generated within their respective piezoelectric layers. Figure 1A ) can be delivered to electrodes in the upper and lower layers of each piezoelectric sensor 440, 442, 444, and the response change of the electrical response exhibited by the piezoelectric layer in each sensor due to changes in its internal stress (which is caused by the force transmitted thereto by the distal segment of the catheter 110) can be measured relative to the calibrated force amplitude. Exemplary changes in electrical properties measured in such embodiments may include resonant frequency, electrical impedance, or decay time constant. In other embodiments, changes in the piezoelectric capacitance of the piezoelectric sensor 440, 442, 444 caused by changes in the induced stress in the piezoelectric sensor can be directly measured. The latter embodiment eliminates the request to provide an excitation signal from the control unit 120, but may have lower sensitivity relative to embodiments that utilize such an excitation signal.

[0090] Figure 5A , 5B 5C are perspective, front, and cross-sectional views, respectively, of a force sensing mechanism 506 for use in a catheter 110 according to an embodiment of the present disclosure. The force sensing mechanism 506 corresponds functionally to the force sensing mechanism 306 described above. In the illustrated embodiment, the force sensing mechanism 506 includes a plurality (three in this case) of annular piezoelectric sensors 540, 542, 544, a rigid proximal housing 550, and a rigid distal housing 554. As shown, the piezoelectric sensors 540, 542, 544 are disposed in and attached to the proximal housing 550.

[0091] In various embodiments, the proximal housing 550 is securely attached to the proximal section (111, 112 in FIG. 1 ) of the catheter 110, 300 described above. Figure 3 304 in FIG. 1 ), and the distal housing 554 is securely attached to the distal segment (113 in FIG. 1 , Figure 3 306 in). In addition, in the absence of external forces on the distal segments of the respective catheters, the proximal housing 550 and the distal housing 554 are separated by a gap 556 that limits the maximum axial movement of the distal segment relative to the proximal segment under external forces. In addition, in the illustrated embodiment, a lumen 557 extends longitudinally through the proximal housing 550 and the distal housing 554 to accommodate passage of catheter components (e.g., guide wires, irrigation tubes, etc.) to the distal segment of the catheter.

[0092] Figure 5C is a cross-sectional elevation view bisecting the force sensing mechanism 606 through the piezoelectric sensor 540. Figure 5C The specific structural details shown in FIG. 5 represent the arrangement of the piezoelectric sensors 542, 544. Figure 5C As shown, the proximal housing has a proximal end face 558, an opposite distal end face 559, a longitudinal cavity 560, and a distal recess 570 formed in the distal end face 559, wherein the recess 570 defines a shoulder 575. As further shown, the distal housing 554 has a proximal end face 578, an opposite distal end face 579, and includes an axial projection 580 extending proximally from the proximal end face 578.

[0093] like Figure 5C As shown, the piezoelectric sensor 540 includes an upper layer 588, a lower layer 590, and a piezoelectric layer 592 disposed therebetween. The annular shape of the piezoelectric sensor 540 further defines: a fixed portion 594 corresponding to an outer peripheral region of the piezoelectric sensor 540, and a free portion 596 radially inward of the fixed portion 594 and corresponding to an inner radial region of the piezoelectric sensor 540. As further shown, the annular shape of the piezoelectric sensor defines a hole 597 substantially centrally located through the piezoelectric sensor 540. As further shown, an optional backing element 598 is disposed within the longitudinal cavity 560 adjacent to the lower layer 590. Although only the piezoelectric sensor 540 is shown in detail for ease of illustration, it is emphasized that each of the piezoelectric sensors 542 and 544 has the same structure as the piezoelectric sensor 540. In addition, the overall construction of the force sensing mechanism 506 relative to the position of the piezoelectric sensors 542, 544 is the same as Figure 5C , i.e., a cross-sectional view bisecting the piezoelectric sensors 542, 544 would appear the same as Figure 5C The structure shown in is the same as that shown in, including the presence of recesses, longitudinal cavities and protrusions and the corresponding relationship with the corresponding piezoelectric sensors.

[0094] The upper layer 588 and the lower layer 590, or at least a portion thereof, are electrically conductive and serve as electrode layers during operation of the piezoelectric sensor 540. In addition, the piezoelectric layer 592 includes a piezoelectric material, such as a piezoelectric ceramic such as lead zirconate titanate (PZT) or a piezoelectric polymer such as polyvinylidene fluoride (PVDF). As is well known in the electromechanical arts, a piezoelectric sensor produces a measurable electrical characteristic when subjected to a mechanical stress.

[0095] Special reference Figure 5C , the distal recess 570 is axially aligned with the longitudinal cavity 560, and the piezoelectric sensor 540 is located in the distal recess 570 of the proximal housing 550, wherein the fixed portion 594 is located on the shoulder 575 and the free portion 596 extends above the longitudinal cavity 560. As further shown, the backing element 598 is adjacent to the lower layer 590 along the free portion 596 of the piezoelectric sensor 540. In addition, the axial protrusion 580 of the distal housing 554 is located above and across the hole 597, so that the axial protrusion presses on the upper layer 588 in the free portion 596 of the piezoelectric sensor 540. Relative to the piezoelectric sensor 540, each of the piezoelectric sensors 542, 544 has the same positional relationship and each has a distal recess, shoulder and longitudinal cavity in the proximal housing 550, and an axial protrusion on the distal housing 554, as shown. Figure 5C In addition, in an embodiment, the optional backing element is Figure 5C The same arrangement as shown is disposed in the longitudinal cavity adjacent to each piezoelectric sensor 542, 544.

[0096] In an embodiment, the fixed portion 594 of the piezoelectric sensor 540 is rigidly attached to the shoulder 575 of the proximal housing 550, and the free portion 596 of the piezoelectric sensor 540 extends above the longitudinal cavity 560. Because the rigid axial protrusion 580 of the distal housing 554 is in direct contact with the upper layer 588 of the piezoelectric sensor 540, the pressure applied to the distal segment 305 ( Figure 3 ) will be transmitted to the free portion 596 of the piezoelectric sensor 540. In addition, the arrangement of the free portion 596 extending above the longitudinal cavity 560 will maximize the piezoelectric effect exhibited by the piezoelectric sensor 540 in response to the transmitted force (i.e., the stress induced in the piezoelectric layer 592 and the sensor output caused by the corresponding piezoelectric effect will be significantly greater than an arrangement in which the piezoelectric sensor is rigidly fixed along its entire length).

[0097] In an embodiment, the backing element 598 (when present) is made of a compressible material (e.g., an elastomer) and its function is to provide some support to the free portion 596 of the piezoelectric sensor 540 to resist its deformation when external forces are applied, while not rigidly resisting all such deformation. In an embodiment, the mechanical properties of the backing element 598 can be tailored to fine-tune the piezoelectric effect exhibited by the piezoelectric sensor 540.

[0098] Those skilled in the art will appreciate that because the piezoelectric sensor 540 is an electromechanical device, electrical leads (not shown) are attached to the electrode structures on the upper layer 588 and the lower layer 590. In embodiments, the electrical leads may be routed through the longitudinal cavity 560, may be routed to the lumen 557, or through some other access feature within the proximal housing 550. Figure 5C As further shown, in embodiments, a potting material 599 can be disposed within open spaces within the proximal housing 550, including within the aperture 597 as shown, which can be used to hermetically seal the internal components of the catheter and the force sensing mechanism 506, and can also enhance the structural attachment between the proximal and distal segments of the catheter. In embodiments, the potting material 599 and the backing element 598 can be formed from the same compressible material and can be formed in a single manufacturing step, although this is not strictly required. In some embodiments, the potting material 599 (or some other compressible material) can be disposed in the gap 556. In some embodiments, the backing element 598 and / or the potting material 599 can be omitted entirely.

[0099] Once again, Figure 5C The arrangement of piezoelectric sensor 540 shown in FIG. 5 represents piezoelectric sensors 542 and 544 .

[0100] Furthermore, in embodiments, the piezoelectric sensors 540, 544, and 542 can have configurations other than the annular configuration shown. In particular, in embodiments, the piezoelectric sensors 540, 544, and 542 can be configured as substantially circular disks without a central hole, and the respective free portions are defined by the central portion of the disk located above the corresponding longitudinal cavity.

[0101] Figures 6A-6D An alternative force sensing mechanism 606 for use in catheter 110 is shown in accordance with an embodiment of the present disclosure. Fig. 6A and 6B is an exploded perspective view of the force sensing mechanism 606 . Figure 6C is a front view of the force sensing mechanism 606, and Fig.6D is along Figure 6C FIG. 6 is a cross-sectional elevation view of the force sensing mechanism 606 taken along line 6D-6D in FIG. 6A .

[0102] The force sensing mechanism 606 corresponds in function to the force sensing mechanism 306 described above. In the illustrated embodiment, the force sensing mechanism 606 includes a single annular piezoelectric sensor 640, a rigid proximal housing 650, and a rigid distal housing 654. As shown, the piezoelectric sensor 640 is disposed in and attached to the proximal housing 650.

[0103] In various embodiments, the proximal housing 650 is securely attached to the proximal section (111, 112 in FIG. 1 ) of the catheter 110, 300 described above. Figure 3 304 in FIG. 1 ), and the distal housing 654 is securely attached to the distal section (113 in FIG. 1 , 300 in FIG. 1 ) of the catheter 110 , 300 . Figure 3 306 in). In addition, in the absence of external forces on the distal segments of the respective catheters, the proximal housing 650 and the distal housing 654 are separated by a gap 656 that limits the maximum axial movement of the distal segment relative to the proximal segment under external forces. In addition, in the illustrated embodiment, a lumen 657 extends longitudinally through the proximal housing 650 and the distal housing 654 to accommodate passage of catheter components (e.g., guide wires, irrigation tubes, etc.) to the distal segment of the catheter.

[0104] As shown, the proximal housing 650 has a proximal end face 658, an opposite distal end face 659, and a distal recess 670 formed in the distal end face 659. Figure 6C As shown in the cross-sectional view of , the distal recess 670 defines a shoulder 675. In addition, the distal housing 654 has a proximal face 678, an opposite distal face 679, and an annular axial protrusion 680 extending proximally from the proximal face 678.

[0105] like Figure 6C As shown, the piezoelectric sensor 640 includes an upper layer 688, a lower layer 690, and a piezoelectric layer 692 disposed therebetween. The annular shape of the piezoelectric sensor 640 further defines a fixed portion 694 corresponding to an outer peripheral region of the piezoelectric sensor 640 and a free portion 696 radially inward of the fixed portion 694 and corresponding to an inner radial region of the piezoelectric sensor 640. As further shown, an optional backing element 698 is disposed within the recess 670 adjacent to the lower layer 690.

[0106] The upper layer 688 and the lower layer 690, or at least a portion thereof, are electrically conductive and serve as electrode layers during operation of the piezoelectric sensor 640. In addition, the piezoelectric layer 692 includes a piezoelectric material, such as a piezoelectric ceramic such as lead zirconate titanate (PZT) or a piezoelectric polymer such as polyvinylidene fluoride (PVDF). As is well known in the electromechanical arts, a piezoelectric sensor produces a measurable electrical characteristic when subjected to a mechanical stress.

[0107] Special reference Figure 6C, the piezoelectric sensor 640 is positioned with a fixed portion 694 located on the shoulder 675, and a free portion 696 extending above the lower portion of the recess 670. As further shown, the backing element 698 is adjacent to the lower layer 690 along the free portion 696 of the piezoelectric sensor 640. In addition, the axial protrusion 680 of the distal housing 654 is positioned so that the axial protrusion 680 presses on the upper layer 688 in the free portion 696 of the piezoelectric sensor 640.

[0108] In an embodiment, the fixed portion 694 of the piezoelectric sensor 640 is rigidly attached to the shoulder 675 of the proximal housing 650, and the free portion 696 of the piezoelectric sensor 640 extends above the recess 670. Because the rigid axial protrusion 680 of the distal housing 654 is in direct contact with the upper layer 688 of the piezoelectric sensor 640, the pressure applied to the distal segment 305 ( Figure 3 ) will be transmitted to the free portion 696 of the piezoelectric sensor 640. In addition, the arrangement of the free portion 696 extending above the longitudinal cavity 660 will maximize the piezoelectric effect exhibited by the piezoelectric sensor 640 in response to the transmitted force (i.e., the stress induced in the piezoelectric layer 692 and the sensor output caused by the corresponding piezoelectric effect will be significantly greater than an arrangement in which the piezoelectric sensor is rigidly fixed along its entire length).

[0109] In an embodiment, the backing element 698 (when present) is made of a compressible material (e.g., an elastomer) and its function is to provide some support for the free portion 696 of the piezoelectric sensor 640 to resist its deformation when external forces are applied, while not rigidly resisting all such deformation. In an embodiment, the mechanical properties of the backing element 698 can be tailored to fine-tune the piezoelectric effect exhibited by the piezoelectric sensor 640.

[0110] like Figure 6C As further shown, in embodiments, a potting material 699 can be disposed within the open space within the proximal housing 650, including within the aperture 697 as shown, which can be used to hermetically seal the internal components of the catheter and the force sensing mechanism 606, and can also enhance the structural attachment between the proximal and distal segments of the catheter. In embodiments, the potting material 699 and the backing element 698 can be formed of the same compressible material and can be formed in a single manufacturing step, although this is not strictly required. In some embodiments, the potting material 699 (or some other compressible material) can be disposed in the gap 656.

[0111] In operation, the annular piezoelectric sensor 640 is configured to operate similarly to each of the annular piezoelectric sensors 540, 542, 544 discussed elsewhere herein. However, because the force sensing mechanism 606 includes only a single piezoelectric sensor, the force sensing mechanism 606 is configured to sense only the magnitude (not the direction) of the applied external force.

[0112] Fig. 7A and 7B Respectively, according to various embodiments of the present disclosure, Figure 3 FIG. 7 is a front view and a cross-sectional view of an alternative force sensing mechanism 706 in a catheter of FIG. The force sensing mechanism 706 is constructed in many respects in the same manner as the force sensing mechanism 606 and includes a single annular piezoelectric sensor 740, a proximal housing 750 and a distal housing 754 separated by a gap 756. The proximal housing 750 includes an annular recess 770 and the piezoelectric sensor 740 is disposed therein with a fixed portion 794 and a free portion 796 in the same manner as the piezoelectric sensor 640. In addition, the distal housing 754 includes an annular axial protrusion 780 that presses on the free portion 796 of the piezoelectric sensor 740 in the same manner as described above in conjunction with the other various embodiments. The illustrated embodiment also includes a backing element 798 that supports the free portion 796 of the piezoelectric sensor 740, although in other embodiments the backing element 798 may be omitted.

[0113] The force sensing mechanism 706 differs from the previous embodiments in that it also includes a semi-annular preload collar 720 operably coupled to the proximal housing 750 and the distal housing 754. The preload collar 720 is configured to facilitate application of an initial load to the piezoelectric sensor 740 and a corresponding stress therein, or alternatively to facilitate assembly of the force sensing mechanism 706 by ensuring intimate contact between the annular axial protrusion 780 and the piezoelectric sensor 740.

[0114] The preload collar 720 has a generally semicircular shape that is complementary to the shapes of the proximal housing 750 and the distal housing 754. As shown, the preload collar 720 has a distal body portion 722 having an upper surface 724 and a lower surface 726, and a handle 730 extending proximally from the lower surface 726.

[0115] As further shown, in Figure 7A-7BIn the embodiment of the present invention, the distal housing 754 has an annular groove 732 extending radially inwardly around its circumference, and the shape of the annular groove is generally rectangular to complement the cross-sectional shape of the distal body portion 722 of the preload collar 720. The annular groove 732 defines a radial support surface 734 that is adjacent to the lower surface 726 of the distal body portion 722 of the preload collar 720. In addition, an annular wall 736 is defined in the outer circumference of the proximal housing 750 radially outward from the recess 770.

[0116] In an embodiment, the outer surface of the handle 730 is rotatably engaged with the inner surface of the annular wall 736 at the connection member 738 ( Figure 7B ). Figure 7B The connector 738 schematically shown in FIG. 7 is configured such that rotation of the preload collar 720 relative to the distal housing 754 causes the preload collar 720 to move axially relative to the proximal housing 740 and the distal housing 754. In an exemplary embodiment, the connector 738 can be configured as a threaded connector including internal and external threads that cooperate on the annular wall 736 and the handle 720, respectively.

[0117] Figure 7B The force sensing mechanism 706 is depicted in a substantially unloaded state, wherein the protrusion 780 is in contact with the piezoelectric sensor 740 but exerts minimal or no force on the piezoelectric sensor 740, and the lower surface 726 of the body portion 722 of the preload collar 720 is axially spaced from the radial support surface 734 of the distal housing 754. Those skilled in the art will recognize that, from the illustrated state, due to the configuration of the connector 738, selective rotation of the preload collar 720 relative to the proximal housing 720 causes the preload collar 720 to translate axially to move the lower surface 726 of the body portion 722 of the preload collar 720 into contact with the radial support surface 734 of the distal housing 734. Once the lower surface 726 of the body portion 722 of the preload collar 720 and the radial support surface 734 of the distal housing 734 are in contact, further rotation of the preload collar 720 in the same direction will drive the distal housing 754 toward the proximal housing 750 and cause the annular protrusion 780 to apply a force to the free portion 796 of the piezoelectric sensor 740. In this way, during assembly of the force sensing mechanism 706, the preload collar 720 can be operated to confirm the desired contact between the protrusion 780 and the piezoelectric sensor 740, and if necessary, a selective preload can be applied to facilitate tuning of the piezoelectric sensor 740.

[0118] Various embodiments of the present disclosure demonstrate significant advancements over conventional catheter force sensing technology. In particular, the embodiments described herein eliminate the need for complex spring mechanisms used in prior art catheters. Similarly, the piezoelectric sensors of various embodiments are relatively low cost compared to the electrical inductive position sensors used in prior art catheters.

[0119] 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 above-described embodiments relate to specific features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Therefore, the scope of the present invention is intended to include all such substitutions, modifications and variations that fall within the scope of the claims, and all equivalents thereof.

Claims

1. A catheter suitable for measuring contact force, the catheter comprising: an elongated shaft having a proximal end and a distal end; a distal portion extending distally from the distal end of the shaft, the distal portion defining a longitudinal axis extending therethrough and comprising: proximal segment; a distal segment located distal to the proximal segment, the distal segment being separated from the proximal segment by a gap; and A force sensing mechanism, comprising: a proximal housing secured within the proximal segment; a piezoelectric sensor mounted to the proximal housing and having a first portion secured to the proximal housing and a second portion not secured to the proximal housing; and a distal housing fixed within the distal segment and comprising a protrusion, the protrusion contacting the second portion of the piezoelectric sensor and configured to apply an axial force to the second portion of the piezoelectric sensor when an external force is applied to the distal segment, Wherein the piezoelectric sensor is configured to generate an output indicative of an amount of the axial force applied to the second portion of the piezoelectric sensor in response to the external force being applied to the distal segment.

2. A catheter according to claim 1, wherein the proximal housing includes an upper surface, a lower surface, and a cavity extending proximally from the upper surface, and wherein a first portion of the piezoelectric sensor is fixedly attached to the upper surface, and wherein a second portion of the piezoelectric sensor extends at least partially across the cavity.

3. The catheter according to claim 2, wherein: The piezoelectric sensor has an arcuate or rectangular profile when viewed from a direction parallel to the longitudinal axis.

4. The catheter according to claim 2, wherein: The piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is a peripheral portion of the piezoelectric sensor and the second portion is located radially inward of the first portion of the piezoelectric sensor.

5. The catheter of claim 2, wherein the piezoelectric sensor is a substantially circular disk, and wherein the second portion extends across the cavity.

6. The catheter according to any one of claims 1 to 5, wherein: The proximal shell includes a compressible backing material, which is disposed within a portion of the cavity and contacts the second portion of the piezoelectric sensor opposite the protrusion on the distal shell, wherein the backing material resists deformation of the second portion of the piezoelectric sensor when the external force is applied to the distal segment.

7. A catheter according to any one of claims 1-6, wherein the force sensing mechanism includes three piezoelectric sensors mounted to the proximal housing and circumferentially spaced around the longitudinal axis, each of the piezoelectric sensors having a first portion fixed to the proximal housing and a second portion deflectable relative to the first portion.

8. A catheter according to claim 7, wherein the distal housing includes three protrusions, each protrusion contacts the second portion of a corresponding one of the piezoelectric sensors and is configured to apply an axial force to the second portion of the corresponding piezoelectric sensor when the external force is applied to the distal segment.

9. The catheter of claim 8, wherein each of the piezoelectric sensors is configured to generate an output indicative of an amount of axial force applied to a second portion thereof in response to the external force being applied to the distal segment.

10. A catheter according to claim 9, wherein the proximal housing includes three cavities extending proximally from the upper surface, each of the cavities is aligned with a corresponding one of the piezoelectric sensors, and wherein the second portion of each of the piezoelectric sensors extends at least partially across a corresponding one of the cavities.

11. The catheter of claim 10, wherein each piezoelectric sensor has an arcuate or rectangular profile when viewed from a direction parallel to the longitudinal axis.

12. The catheter according to claim 10, wherein Each piezoelectric sensor has an annular shape when viewed from a direction parallel to the longitudinal axis, and wherein the first portion is a peripheral portion of the piezoelectric sensor and the second portion is located radially inward of the first portion of the piezoelectric sensor.

13. The catheter of claim 10, wherein each piezoelectric sensor is a substantially circular disk, and wherein the second portion of each piezoelectric sensor extends across the corresponding cavity.

14. The catheter according to any one of claims 8 to 13, wherein: A compressible backing material is disposed within a portion of each cavity and in contact with a second portion of the corresponding piezoelectric sensor opposite a corresponding protrusion on the distal housing, wherein the backing material resists deformation of the second portion of the corresponding piezoelectric sensor when the external force is applied to the distal segment.

15. The catheter of Claim 1, further comprising a preload mechanism operably coupled to the proximal housing and configured to allow a user to selectively preload the piezoelectric sensor.

Images