Patent Application
20120158011
a. Field of the Invention
The present disclosure relates generally to a robotic control and guidance system (RCGS) for a medical device, and more particularly to a proximity/contact sensor interface in an RCGS.
b. Background Art
Electrophysiology (EP) catheters are used in a variety of diagnostic and/or therapeutic medical procedures to correct conditions such as atrial arrhythmia, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. Arrhythmia can create a variety of dangerous conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments.
In a typical EP procedure, a physician manipulates a catheter through a patient's vasculature to, for example, a patient's heart. The catheter typically carries one or more electrodes that may be used for mapping, ablation, diagnosis, and the like. Once at the target tissue site, the physician commences diagnostic and/or therapeutic procedures, for example, ablative procedures such as radio frequency (RF), microwave, cryogenic, laser, chemical, acoustic/ultrasound or high-intensity focused ultrasound (HIFU) ablation, to name a few different sources of ablation energy. The resulting lesion, if properly located and sufficiently contiguous with other lesions, disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that can lead to arrhythmias. Such procedures require precise control of the catheter during navigation to and delivery of therapy to the target tissue site, which can invariably be a function of a user's skill level.
Robotic catheter systems are known to facilitate such precise control. Robotic catheter systems generally carry out (as a mechanical surrogate) input commands of a clinician or other end-user to deploy, navigate and manipulate a catheter and/or an introducer or sheath for a catheter or other elongate medical instrument, for example, a robotic catheter system described, depicted, and/or claimed in U.S. application Ser. No. 12/347,811 entitled “ROBOTIC CATHETER SYSTEM,” owned by the common assignee of the present disclosure and hereby incorporated by reference in its entirety. Such robotic catheter systems include a variety of actuation mechanisms, such as electric motors, for controlling translation and deflection of the catheter and associated sheath. Such systems typically employ control algorithms for controlling the motion of the catheter based at least in part upon end-user input(s). While the location of the catheter, vis-à-vis target tissue site(s), can be monitored by a physician with a manually guided catheter, introducing a mechanically guided catheter system places a premium on patient safety. Despite these advancements, conventional systems still rely on the physician to determine what actions, if any, to take when the catheter is too close to the heart tissue.
There is therefore a need for improved systems and methods that enhance clinician control while reducing potential risk(s) in performing robotically-driven cardiac catheter procedures and thereby minimizes or eliminates one or more problems related thereto.
One advantage of the methods and apparatus described, depicted and claimed herein relates to the reliable detection of the proximity and active control of the medical device in relation to body tissue to avoid unintended device-to-tissue contact in a graduated manner.
The disclosure is directed to an apparatus for use in a robotic control system of the type suitable for manipulating a medical device in a body of a patient. The apparatus includes an electronic control unit (ECU) and a memory coupled to the ECU. Control logic is stored in the memory and is configured to be executed by the ECU. The control logic is configured to produce an actuation control signal to control actuation of a manipulator assembly portion of the robotic control system. The actuation control signal is produced so as to result in the navigation of the medical device in, and with respect to, a plurality of proximity zones in the body of the patient. The control logic is further configured to generate the actuation control signal, and thus control the navigation of the medical device, based on a so-called proximity signal. The proximity signal is indicative of a relative, distance between the medical device and body tissue. The effect the proximity signal has on the navigation of the medical device depends on certain navigation-altering attributes associated with each pre-defined proximity zone, and whether the medical device is in a particular zone based on the proximity signal.
In an embodiment, the control logic is arranged to control the navigation (i.e., via the robotic control system) of the medical device based on a pre-planned movement, which can have a pre-planned path and a pre-planned deployment or retraction speed or velocity (e.g., an automated catheter motion). The control logic is configured to make modifications to the pre-planned movement based on the proximity signal. The modifications can include one of (i) a reduced speed relative to the pre-planned speed and (ii) a stoppage of the device before completion of the pre-planned path. For example, when the device unexpectedly approaches an anatomical structure, the proximity signal indicates that the device will soon be or is currently “too close” to the approaching structure (i.e., a so-called RED proximity zone). Under this circumstance, the control logic terminates the operating power to the actuation units (e.g., electric motors) in the robotic control system, thereby stopping movement of the device. This response action prevents unintended device-to-tissue contact, which can have undesirable consequences (e.g., insult to cardiac wall tissue or a coronary vein or the like). As a further example, when the device unexpectedly approaches an anatomical structure, like in the first example, but is somewhat further away, the proximity signal will so indicate this relationship (i.e., a so-called YELLOW proximity zone). The control logic will reduce the navigation speed relative to the pre-planned (i.e., normal or default) speed. This reduction in speed is an appropriate response action to avoid contact. When the medical device is in a still further proximity zone, a so-called GREEN proximity zone, which is farther still from any body tissue than the YELLOW proximity zone, no modifications to the pre-planned movement of the medical device are warranted. The apparatus also provides a user interface to allow a user to specify many of the parameters that define the characteristics of each proximity zone as well as the resulting response action when a medical device enters such proximity zone.
The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.
a-3b are isometric views of a manipulator assembly shown in
a-4c are isometric views showing a sheath manipulation base of
a-5b are isometric views showing a sheath cartridge of
Before proceeding to a detailed description of the proximity/contact sensor interface for a robotic catheter system, a brief overview (for context) of an exemplary robotic control and guidance system (RCGS) for manipulating a medical device will first be described. The description of the RCGS will detail how several electric motors can be used to control the translation, distal bending and virtual rotation of a catheter and surrounding sheath. After the description of the RCGS, the present specification will then provide a brief description of proximity/contact sensing technology that can be used in certain embodiments. Then, the present specification will describe the proximity/contact sensor interface for use in an RCGS.
Now referring to the drawings wherein like reference numerals are used to identify identical components in the various views,
Exemplary RCGS System Description. RCGS 10 can be likened to power steering for a catheter system. The RCGS 10 can be used, for example, to manipulate the location and orientation of catheters and sheaths in a heart chamber or in another body cavity or lumen. The RCGS 10 thus provides the user with a similar type of control provided by a conventional manually-operated system, but allows for repeatable, precise, and dynamic movements. For example, a user such as an electrophysiologist can identify locations (potentially forming a path) on a rendered computer model of the cardiac anatomy. The system can be configured to relate those digitally selected points to positions within a patient's actual/physical anatomy, and can thereafter command and control the movement of the catheter to the defined positions. Once at the specified target position, either the user or the system can perform the desired diagnostic or therapeutic function. The RCGS 10 enables full robotic navigation/guidance and control.
As shown in
Displays 12 are configured to visually present to a user information regarding patient anatomy, medical device location or the like, originating from a variety of different sources. Displays 12 can include (1) an ENSITE VELOCITY™ monitor 16 (coupled to system 14—described more fully below) for displaying cardiac chamber geometries or models, displaying activation timing and voltage data to identify arrhythmias, and for facilitating guidance of catheter movement; (2) a fluoroscopy monitor 18 for displaying a real-time x-ray image or for assisting a physician with catheter movement; (3) an intra-cardiac echo (ICE) display 20 to provide further imaging; and (4) an EP recording system display 22.
The system 14 is configured to provide many advanced features, such as visualization, mapping, navigation support and positioning (i.e., determine a position and orientation (P&O) of a sensor-equipped medical device, for example, a P&O of a distal tip portion of a catheter). Such functionality can be provided as part of a larger visualization, mapping and navigation system, for example, an ENSITE VELOCITY system running a version of NavX™ software commercially available from St. Jude Medical, Inc., of St. Paul, Minn. and as also seen generally by reference to U.S. Pat. No. 7,263,397 entitled “METHOD AND APPARATUS FOR CATHETER NAVIGATION AND LOCATION AND MAPPING IN THE HEART” to Hauck et al., owned by the common assignee of the present disclosure, and hereby incorporated by reference in its entirety. System 14 can comprise conventional apparatus known generally in the art, for example, the ENSITE VELOCITY system described above or other known technologies for locating/navigating a catheter in space (and for visualization), including for example, the CARTO visualization and location system of Biosense Webster, Inc., (e.g., as exemplified by U.S. Pat. No. 6,690,963 entitled “System for Determining the Location and Orientation of an Invasive Medical Instrument” hereby incorporated by reference in its entirety), the AURORA® system of Northern Digital Inc., a magnetic field based localization system such as the gMPS system based on technology from MediGuide Ltd. of Haifa, Israel and now owned by St. Jude Medical, Inc. (e.g., as exemplified by U.S. Pat. Nos. 7,386,339, 7,197,354 and 6,233,476, all of which are hereby incorporated by reference in their entireties) or a hybrid magnetic field-impedance based system, such as the CARTO 3 visualization and location system of Biosense Webster, Inc. (e.g., as exemplified by U.S. Pat. Nos. 7,536,218, and 7,848,789 both of which are hereby incorporated by reference in its entirety). Some of the localization, navigation and/or visualization systems can involve providing a sensor for producing signals indicative of catheter location and/or orientation information, and can include, for example one or more electrodes in the case of an impedance-based localization system such as the ENSITE VELOCITY system running NavX software, which electrodes can already exist in some instances, or alternatively, one or more coils (i.e., wire windings) configured to detect one or more characteristics of a low-strength magnetic field, for example, in the case of a magnetic-field based localization system such as the gMPS system using technology from MediGuide Ltd. described above.
The input control system 100 is configured to allow a user, such as an electrophysiologist, to interact with the RCGS 10, in order to control the movement and advancement/withdrawal of both a catheter and sheath (see, e.g., commonly assigned U.S. patent application Ser. No. 12/751,843 filed Mar. 31, 2010 entitled “ROBOTIC CATHETER SYSTEM” (docket no. 0G-043516US) and PCT/US2009/038597 entitled “ROBOTIC CATHETER SYSTEM WITH DYNAMIC RESPONSE” (docket no. 0G-043513WO), published as WO 2009/120982; the entire disclosure of both applications being hereby incorporated by reference). Generally, several types of input devices and related controls can be employed, including, without limitation, instrumented traditional catheter handle controls, oversized catheter models, instrumented user-wearable gloves, touch screen display monitors, 2-D input devices, 3-D input devices, spatially detected styluses, and traditional joysticks. For a further description of exemplary input apparatus and related controls, see, for example, commonly assigned U.S. patent application Ser. No. 12/933,063 entitled “ROBOTIC CATHETER SYSTEM INPUT DEVICE” (docket no. 0G-043527US) and U.S. patent application Ser. No. 12/347,442 entitled “MODEL CATHETER INPUT DEVICE” (docket no. 0G-043508US), the entire disclosure of both applications being hereby incorporated by reference. The input devices can be configured to directly control the movement of the catheter and sheath, or can be configured, for example, to manipulate a target or cursor on an associated display.
The electronic control system 200 is configured to translate (i.e., interpret) inputs (e.g., motions) of the user at an input device or from another source into a resulting movement of the catheter and/or surrounding sheath. In this regard, the system 200 includes a programmed electronic control unit (ECU) in communication with a memory or other computer readable media (memory) suitable for information storage. Relevant to the present disclosure, the electronic control system 200 is configured, among other things, to issue commands (i.e., actuation control signals) to the manipulator assembly 300 (i.e., to the actuation units—electric motors) to move or bend the catheter and/or sheath to prescribed positions and/or in prescribed ways, all in accordance with the received user input and a predetermined operating strategy programmed into the system 200. In addition to the instant description, further details of a programmed electronic control system can be found in commonly assigned U.S. patent application Ser. No. 12/751,843 filed Mar. 31, 2010 entitled “ROBOTIC CATHETER SYSTEM” (docket no. 0G-043516US), described above. It should be understood that although the exemplary ENSITE VELOCITY System 14 and the electronic control system 200 are shown separately, integration of one or more computing functions can result in a system including an ECU on which can be run both (i) various control and diagnostic logic pertaining to the RCGS 10 and (ii) the visualization, mapping and navigation functionality of system 14.
The manipulator assembly 300, in response to such commands, is configured to maneuver the medical device (e.g., translation movement, such as advancement and withdrawal of the catheter and/or sheath), as well as to effectuate distal end (tip) deflection and/or rotation or virtual rotation. In an embodiment, the manipulator assembly 300 can include actuation mechanisms/units (e.g., a plurality of electric motor and lead screw combinations, or other electric motor configurations, as detailed below) for linearly actuating one or more control members (e.g., steering wires) associated with the medical device for achieving the above-described translation, deflection and/or rotation (or virtual rotation). In addition to the description set forth herein, further details of a manipulator assembly can be found in commonly assigned U.S. patent application Ser. No. 12/347,826 titled “ROBOTIC CATHETER MANIPULATOR ASSEMBLY” (docket no. 0G-043503US), the entire disclosure of which is hereby incorporated by reference.
A device cartridge 400 is provided for each medical device controlled by the RCGS 10. For this exemplary description of an RCGS, one cartridge is associated with a catheter and a second cartridge is associated with an outer sheath. The cartridge is then coupled, generally speaking, to the RCGS 10 for subsequent robotically-controlled movement. In addition to the description set forth herein, further details of a device cartridge can be found in commonly owned U.S. patent application Ser. No. 12/347,835 entitled “ROBOTIC CATHETER DEVICE CARTRIDGE” (docket no. 0G-043504US) and U.S. patent application Ser. No. 12/347,842 “ROBOTIC CATHETER ROTATABLE DEVICE CARTRIDGE” (docket no. 0G-043507US), the entire disclosure of both applications being hereby incorporated by reference.
In the Figures to follow,
a is an isometric view, with portions omitted for clarity, of manipulator assembly 302. Assembly 302 includes a catheter manipulator mechanism 304, a sheath manipulator mechanism 306, a catheter manipulation base 308, a sheath manipulation base 310, a first (catheter) drive mechanism 312, a second (sheath) drive mechanism 314, and a track 356. As further shown, assembly 302 further includes a catheter cartridge 402 and a sheath cartridge 404, with a catheter 406 having a proximal end opening 408 coupled to the catheter cartridge 402 and a sheath 410 coupled to the sheath cartridge 404.
Catheter and sheath manipulator mechanisms 304, 306 are configured to manipulate the several different movements of the catheter 406 and the sheath 410. First, each mechanism 304, 306 is configured to impart translation movement to the catheter 406 and the sheath 410. Translation movement here refers to the independent advancement and retraction (withdrawal) as shown generally in the directions designated D1 and D2 in
Each manipulator mechanism 304, 306 further includes a respective manipulation base 308, 310 onto which are received catheter and sheath cartridges 402, 404. Each interlocking base 308, 310 can be capable of travel in the longitudinal direction of the catheter/sheath (i.e., D1, D2 respectively) along a track 356. In an embodiment, D1 and D2 can each represent a translation of approximately 8 linear inches. Each interlocking base 308, 310 can be translated by a respective high precision drive mechanism 312, 314. Such drive mechanisms can include, for example and without limitation, an electric motor driven lead screw or ball screw.
The manipulator mechanisms 304, 306 are aligned with each other such that catheter 406 can pass through sheath 410 in a coaxial arrangement. Thus, sheath 410 can include a water-tight proximal sheath opening 408. Overall, the manipulator mechanisms 304, 306 are configured to allow not only coordinated movement but also relative movement between catheter and sheath cartridges 402, 404 (and thus relative movement between catheter and sheath).
b is an isometric view of manipulator assembly 302, substantially the same as
a is an isometric, enlarged view showing manipulation base 308 (and base 310) in greater detail. Each cartridge 402, 404 has an associated manipulation base 308, 310. Each base 308, 310 can include a plurality of fingers 316, 318, 320 and 322 (e.g., one per steering wire) that extend or protrude upwardly to contact and interact with steering wire slider blocks (i.e., such as slider blocks 412, 414, 416, 418 are best shown in
b is an isometric, enlarged view of base 308 (and base 310), substantially the same as
c is an isometric, enlarged view of base 308 (and base 310) that is taken from an opposite side as compared to
a is an isometric, enlarged view showing, in greater detail, sheath cartridge 404. It should be understood that the description of sheath cartridge 404, except as otherwise stated, applies equally to catheter cartridge 402. Catheter 406 and sheath 410 can be substantially connected or affixed to respective cartridges 402, 404 (e.g., in the neck portion). Thus, advancement of cartridge 404 correspondingly advances the sheath 410 and retraction of cartridge 404 retracts the sheath 410. Likewise, although not shown, advancement of cartridge 402 correspondingly advances catheter 406 while a retraction of cartridge 402 retracts catheter 406. As shown, sheath cartridge 404 includes upper and lower cartridge sections 428, 430.
b is an isometric, enlarged view showing, in greater detail, sheath cartridge 404, with upper section 428 omitted to reveal interior components. Cartridge 404 can include slider blocks (e.g., as shown for cartridge 404, slider blocks 412, 414, 416, 418), each rigidly and independently coupled to a respective one of a plurality of steering wires (e.g., sheath steering wires 420, 422, 424, 426) in a manner that permits independent tensioning of each steering wire. Likewise, cartridge 402 for catheter 406 also includes slider blocks for coupling to a plurality (i.e., four) steering wires. Device cartridges 402, 404 can be provided as a disposable item that is capable of being easily positioned (e.g., snapped) into place (i.e., onto a respective base 408, 410). Sheath cartridge 404 can be designed in a similar manner as the catheter cartridge 402, but will typically be configured to provide for the passage of catheter 406.
Referring to
In operation, a user first manually positions catheter 406 and sheath 410 (with catheter 406 inserted in sheath 410) within the vasculature of a patient. Once the medical devices are roughly positioned in relation to the heart or other anatomical site of interest, the user can then engage or connect (e.g., “snap-in”) the catheter and sheath cartridges into place on respective bases 308, 310. When a cartridge is interconnected with a base, the fingers fit into the recesses formed in the slider blocks. For example, with respect to the sheath cartridge 404 and sheath base 310, each of the plurality of fingers 316, 318, 320 or 322 fit into corresponding recesses formed between the distal edge of slider blocks 412, 414, 416, 418 and a lower portion of the cartridge housing (best shown in
The actuation unit 600 also includes a rotary motor position encoder 616 that is coupled to the motor 614 and is configured to output a signal indicative of the position of the motor 614. The encoder 616 can comprise an internal, optical encoder assembly, integral with motor 614, configured to produce a relatively high accuracy output. The motor position sensor can operate in either absolute or relative coordinates. In an embodiment, a second motor position sensor (not shown) can also be provided, such as a potentiometer (or impedance-based), configured to provide a varying voltage output proportional to the motor's rotary position. The output of the secondary position sensor can be used as an integrity check of the operating performance of the primary position sensor (encoder) during start-up or initialization of the actuation unit.
Actuation unit 600 also includes one or more local controllers including a bus interface 618 to facilitate exchange of information between actuation unit 600 and electronic control system 200 (via the bus). The controller communicates with the main electronic control system 200 via the bus interface and is configured, among other things, to (1) receive and execute motor actuation commands issued by the electronic control system 200 for controlling the movements of motor 614; and (2) receive and execute a command (issued by the electronic control system 200) to take a motor position sensor reading, for example, from encoder 616 and subsequently report the reading to system 200.
Proximity/Contact Sensing. A proximity/contact sensor on the catheter provides a proximity signal indicating how close (i.e., distance) the catheter is to the nearest body tissue (e.g., heart tissue). Embodiments are configured to monitor this proximity/contact signal periodically, e.g., every input/output cycle of the RCGS, and take appropriate response action, to ensure that the location of the catheter is always kept at a prudently safe distance from any unexpected anatomical structures, so as to avoid catheter-to-tissue contact at speed. Embodiments are configured to automatically implement such response actions, such as to alter (i.e., reduce) device speed or alternatively to cut power to the RCGS motors.
A variety of proximity/contact sensors can be used, for example, an optical force sensor or a mechanical force sensor, either being suitable for determining proximity/contact. For example, one such optical force sensor can be found in an ablation catheter commercially available under the trade designation TactiCath from Enclosense, Geneva, Switzerland (see also U.S. patent application Ser. No. 12/352,426 filed 12 Jan. 2009 hereby incorporated by reference in its entirety as though fully set forth herein). Further examples can be seen by reference to U.S. patent application Ser. No. 11/941,073 filed 15 Nov. 2007 (the '073 application) entitled “OPTIC-BASED CONTACT SENSING ASSEMBLY AND SYSTEM” and U.S. patent application Ser. No. 12/893,707 filed 29 Sep. 2010 (the '707 application). The '073 and the '707 applications are each being incorporated by reference in their entirety as though fully set forth herein. In one embodiment, a so-called electrical coupling index (ECI), or a derivative thereof such as a rate of change of ECI, can be used to indicate proximity of an electrode on the catheter to the nearest tissue. The ECI is a figure of merit derived or otherwise computed using, among other things, components of the measured complex impedance between the catheter electrode and the body tissue. The relationship between ECI and components of the complex impedance can be determined empirically. A brief description of such a process will be set forth below.
Referring now to
Z=R+jX (1)
where R is the resistance component (expressed in ohms); and X is a reactance component (also expressed in ohms). Complex impedance can also be expressed through polar coordinates as set forth in equation (2):
Z=r·e
jθ
=|Z|·e
j∠Z (2)
where |Z| is the magnitude of the complex impedance (expressed in ohms) and ∠Z=θ is the phase angle expressed in radians. Alternatively, the phase angle can be expressed in terms of degrees where
Phase angle will be preferably referenced in terms of degrees. The three terminals comprise: (1) a first terminal designated “A-Catheter Tip” which is the tip electrode 26; (2) a second terminal designated “B-Patch 1” such as the source return patch electrode 36; and (3) a third terminal designated “C-Patch 2” such as the sense return patch electrode 34. In addition to the ablation (power) signal generated by the source of the ablation generator 38, an excitation signal generated by the source 50 in the tissue sensing circuit 40 is also being applied across the source connectors (SOURCE (+), SOURCE(−)) for the purpose of inducing a response signal with respect to the load that can be measured and which depends on the complex impedance. In one embodiment, a 20 kHz, 100 μA AC constant current signal is sourced along a path 54, as illustrated, from one connector (SOURCE (+), starting at node A) through the common node (node D) to a return patch electrode (SOURCE (−), node B). The complex impedance sensor 52 is coupled to the sense connectors (SENSE (+), SENSE (−)), and is configured to determine the impedance across a path 56. For the constant current excitation signal of a linear circuit, the impedance will be proportional to the observed voltage developed across SENSE (+)/SENSE(−), in accordance with Ohm's Law: Z=V/I. Because voltage sensing is nearly ideal, the current flows through the path 54 only, so the current through the path 56 (node D to node C) due to the excitation signal is effectively zero. Accordingly, when measuring the voltage along the path 56, the only voltage observed will be where the two paths intersect (i.e., from node A to node D). Depending on the degree of separation of the two patch electrodes (i.e., those forming nodes B and C), an increasing focus will be placed on the tissue volume nearest the tip electrode 26.
An ECU (not shown in
The ECI can be computed using an equation (e.g., equation 3 below) but particular coefficients, or in other words, the relationship to the measured complex impedance components can vary depending on, among other things, the specific catheter used, the patient, the equipment, the desired level of predictability, the species being treated, and disease states.
Validation testing relating to the coupling index was performed in a pre-clinical animal study. The calculated coupling index was compared to pacing threshold as an approximation of the degree of coupling. Pacing threshold was used for comparison because it is objective and particularly sensitive to the degree of physical contact between the tip electrode and tissue when the contact forces are low and the current density paced into the myocardium varies. In a study of seven swine (n=7, 59+/−3 kg), a 4 mm tip irrigated RF ablation catheter was controlled by an experienced clinician who scored left and right atrial contact at four levels (none, light, moderate and firm) based on clinician sense, electrogram signals, three-dimensional mapping, and fluoroscopic images. Several hundred pacing threshold data points were obtained along with complex impedance data, electrogram amplitudes and data relating to clinician sense regarding contact. A regression analysis was performed using software sold under the registered trademark “MINITAB” by Minitab, Inc. using the Log 10 of the pacing threshold as the response and various impedance parameters as the predictor. The following table summarizes the results of the analysis:
As shown in the table, it was determined that a mean value for resistance accounted for 43.5% of the variation in pacing threshold while a mean value for reactance accounted for 35.5% of the variation in pacing threshold. Combining the mean resistance and mean reactance values increased the predictive power to 46.90% demonstrating that an ECI based on both components of the complex impedance will yield improved assessment of coupling between the catheter electrode 26 and the tissue 28. As used herein, the “mean value” for the resistance or reactance can refer to the average of N samples of a discrete time signal xi or a low-pass filtered value of a continuous x(t) or discrete x(ti) time signal. As shown in the table, adding more complex impedance parameters such as standard deviation and peak to peak magnitudes can increase the predictive power of the ECI. As used herein, the “standard deviation” for the resistance or reactance can refer to the standard deviation, or equivalently root mean square about the mean or average of N samples of a discrete time signal xi or the square root of a low pass filtered value of a squared high pass filtered continuous x(t) or discrete x(ti) time signal. The “peak to peak magnitude” for the resistance or reactance can refer to the range of the values over the previous N samples of the discrete time signal xi or the kth root of a continuous time signal [abs(x(t))]k that has been low pass filtered for sufficiently large k>2. It was further determined that, while clinician sense also accounted for significant variation in pacing threshold (48.7%)—and thus provided a good measure for assessing coupling—the combination of the ECI with clinician sense further improved assessment of coupling (accounting for 56.8% of pacing threshold variation).
Because of the processing and resource requirements for more complex parameters such as standard deviation and peak to peak magnitude, and because of the limited statistical improvement these parameters provided, it was determined that the most computationally efficient ECI would be based on mean values of the resistance (R) and reactance (X), and more specifically, the equation: ECI=a*Rmean+b*Xmean+c.
From the regression equation, and using a 4 mm irrigated tip catheter, the best prediction of pacing threshold—and therefore coupling—was determined to be the following equation (3):
ECI=Rmean−5.1*Xmean (3)
where Rmean is the mean value of a plurality of resistance values and Xmean is the mean value of a plurality of reactance values. It should be understood, however, that other values associated with the impedance components, such as a standard deviation of a component or peak to peak magnitude of a component which reflect variation of impedance with cardiac motion or ventilation, can also serve as useful factors in the ECI. Further, although the above equation and following discussion focus on the rectangular coordinates of resistance (R) and reactance (X), it should be understood that the ECI could also be based on values associated with the polar coordinates impedance magnitude (|Z|) and phase angle (φ) or indeed any combination of the foregoing components of the complex impedance and derivatives or functional equivalents thereof. Finally, it should be understood that coefficients, offsets and values within the equation for the ECI can vary depending on, among other things, the specific catheter used, the patient, the equipment, the desired level of predictability, the species being treated, and disease states. However, the coupling index will always be responsive to both components of the complex impedance in order to arrive at an optimal assessment of coupling between the catheter electrode 26 and the tissue 28.
The above-described analysis was performed using a linear regression model wherein the mean value, standard deviation, and/or peak to peak magnitude of components of the complex impedance were regressed against pacing threshold values to enable determination of an optimal ECI. It should be understood, however, that other models and factors could be used. For example, a nonlinear regression model can be used in addition to, or as an alternative to, the linear regression model. Further, other independent measures of tissue coupling such as atrial electrograms could be used in addition to, or as an alternative to, pacing thresholds.
Proximity/Contact Sensor Interface in the RCGS. An apparatus for use in the RCGS 10 as described herein minimizes or eliminates unintended contact of a robotically-controlled medical device (e.g., catheter), thereby reducing or eliminating unintended tissue trauma (e.g., perforation). Embodiments of the disclosure establish a plurality of so-called proximity zones. Each proximity zone can have an associated set of proximity criteria which, if met by the position, speed and deflection/rotation of the medical device being monitored, results in predetermined response actions being taken. Embodiments are configured to obtain specifications from the user to establish multiple proximity zones (e.g., “GREEN”, “YELLOW” and “RED” proximity zones, A-Z proximity zones, 1-10 proximity zones, etc.). For example, the RCGS 10 can guide the catheter in the patient's body at “normal” speeds (i.e., a default speed) while in the GREEN proximity zone, since the GREEN proximity zone is sufficiently spaced from nearby anatomical structures. However, the RCGS 10 can guide the catheter at only a reduced speed while in the YELLOW proximity zone. This action is based on the premise that the catheter has moved “close enough” to an anatomical structure, based on a proximity signal, to trigger a more cautious, reduced speed. When the catheter enters the RED proximity zone, embodiments of the apparatus will terminate power to the actuation mechanisms (i.e., motors) in the RCGS to prevent unintended catheter-to-tissue contact. Termination of power is based on the apparatus' determination, based on the proximity signal, that the catheter is “too close” to the anatomical structure and immediate action must be taken to avoid contact. In a related embodiment, when the proximity signal crosses a threshold, or nears a threshold, the control signal to the actuation mechanism(s) of the RCGS 10 can temporarily reverse or return to a prior location known to be free of obstacles or undesired contact with anatomical structure(s).
As described above, when the approach of the catheter relative to a body structure (e.g., cardiac wall) meets the most serious proximity criteria (i.e. RED proximity zone), the ECU 202 will terminate operating power to the electric motors 6141, 6142, . . . , 614n as a safety precaution (i.e., to avoid potential tissue damage). To this end, the RCGS 10 can include a mechanism for selectively terminating operating power, for example only, a mechanism that includes a watchdog timer 212 or the like. The watchdog timer 212 is configured to have a countdown time interval which counts down (or up if so configured). The timer 212, which is coupled to a controlled power source 216, is configured to automatically generate a power termination signal 218 when the countdown time interval expires. The power source 216, in response to the power termination signal 214, will terminate operating power 220 provided to the motors. While the timer 212 and the power source 216 are shown separately, they can be integrated into a single unit.
To prevent the watchdog timer 212 from terminating power during normal operation, the ECU 202 is programmed (e.g., in an operating control routine) to generate, at times less than the countdown time interval, a set (or reset) signal 214 in order to refresh the countdown time interval. For example, this refresh can occur every I/O cycle of the RCGS 10. The I/O is described below in connection with
The UI logic 226 performs the general functions of outputting information (visual, textual, aural, etc.) for the user as well as querying for or otherwise permitting entry of inputs from the user 224. This general function applies to both core operations of the RCGS 10 as well as for the proximity sensor interface. For example, the UI logic 226 displays information regarding a currently displayed (rendered) scene (e.g., the view angle, the mouse location, the catheter tip location, etc.). The UI logic 226 is also configured to receive user inputs with respect to an anatomical model of a body portion of the patient, for example, for setting up a pre-planned path for the catheter, for initiating and conducting diagnostic and therapeutic procedures, or the like. With respect to the proximity sensor interface, the UI logic 226 receives inputs from the user 224 to define the plurality of proximity zones (e.g., distance, speed, etc.), an operating mode of the proximity sensor interface (e.g., OFF, MONITOR, ACTIVE, etc.), control actions (e.g., speed reductions) and response actions (e.g., alerts, terminating power, etc.).
The control logic 228 is configured, generally, to implement a predetermined operating control strategy (i.e., higher level control algorithms) for the RCGS 10, as described in greater detail in U.S. application Ser. No. 12/751,843 filed Mar. 31, 2010 entitled “ROBOTIC CATHETER SYSTEM” that was referred to above. The operating control logic 228 is configured to process incoming data from a plurality of sources, including the UI logic 226, the human interface device 234, a proximity signal 240 from the proximity sensor 236, location data 238, as well as the current motor states from the motor state model 230. Based on these inputs, the apparatus 222 generates actuation control signals 218 destined for the plurality of motors in the manipulator assembly to achieve desired catheter and sheath movements (i.e., translation, deflection or virtual rotation).
The human interface device 234 facilitates communication of inputs by the user 224 (i.e., directions) to the apparatus 222. For example, for a controller type device, the control logic 228 can receive a current handle position as well as current button states for those devices having buttons. For example only, the handle location can be specified in a frame of reference (i.e., a 2-dimensional or 3-dimensional coordinate system) that is specific to the device (e.g., x, y, z).
In an embodiment, the proximity signal 240 can take the form of an ECI as described above in connection with
Location data from source 238 can comprise position and orientation information associated with the manipulated catheter (e.g., such as the catheter tip). In an embodiment where an impedance-based positioning system (e.g., ENSITE VELOCITY) 14 is used as the source 238, the location data can comprise at least an electrode coordinate (x, y, z) for specified electrodes on the catheter.
The motor state model 230 contains information about the current states for each of the motors in the RCGS 10 (i.e., reflects the current physical states of the physical motors). States can include motor position, motor speed, tension (i.e., pull wire tension—see
An exemplary use case involves the user 224 specifying a number of so-called waypoints to describe a movement path having a predetermined, default or specified speed (or speed profile along the path) for the catheter. The pre-planned movement is then executed by the RCGS 10. However, the catheter, as guided by the RCGS 10 in accordance with the pre-planned movement, can unexpectedly encounter an anatomical structure. The apparatus 222 is configured to monitor proximity, based on the proximity signal 240, speed, and deflection/rotation, throughout the catheter's pre-planned movement. When predetermined proximity criteria are met, the apparatus 222 selectively adjusts the pre-planned movement consistent with the likelihood of a potential contact, for example, by either reducing speed or terminating power to the motors, thereby stopping the catheter before completion of the pre-planned path.
The apparatus 222 uses a construct referred to herein as a proximity zone, a descriptor that is used to refer to a number of individual pieces of information that collectively define proximity criteria for each zone. Each proximity zone also has an associated set of response actions, which are fulfilled by the apparatus 222 when the catheter's movement in relation to any nearby tissue meets the criteria for that proximity zone. To setup the proximity zone, the user 224 interacts with the UI logic 226 to obtain the needed data. Several categories of such data are thus provided by the user 224 and are collectively shown in block 242 in
A proximity zone table 244 includes a plurality of records 2461, 2462, 2463 identifying the criteria associated with each of a plurality of proximity zones (i.e., a physical representation of multiple proximity zones is shown in
Each record 246i (where i=1 to n—the number of proximity zones) has a respective plurality of fields associated therewith, such as a proximity-to-tissue distance 248, a device speed 250 (user-specified), and a deflection/rotation, for example, which can include a deflection angle 252 and a virtual rotation angle 254. The UI logic 226 is configured to receive inputs from the user 224 to set values for some of these fields, depending on the embodiment.
In an embodiment, the apparatus 222 is pre-configured with a predetermined number of proximity zones (e.g., three), each of which are pre-defined in terms of a respective distance-from-tissue value (i.e., field 248) as well as with respect to the response action to be taken when the respective criteria are met (e.g., reduce speed in the Yellow zone, cut power in the Red zone). In other words, in this embodiment, while the number of zones, the distances and response actions are configurable (i.e., at the design time of the RCGS 10), they are not user configurable through UI logic 226. Additionally, however, in this embodiment, the user 224 can specify other criteria associated with the proximity zones (e.g., catheter speed).
In another embodiment, however, the UI logic 226 is configured to receive inputs to set the number of zones, the respective characteristics or criteria (i.e., the distance 248, speed 250, deflection angle 252, virtual rotation parameter 254), control actions (below) and response actions (below). In a further embodiment, the apparatus 222 is configured to use a combination of pre-configured and user-specified values (obtained through UI logic 226).
With continued reference to
The distance-to-tissue, speed threshold, and deflection/rotation values appropriate for any particular RCGS 10 can take a wide range of values. For example, it should be appreciated that mechanical inertia of the components of the RCGS 10 can be considered in selecting distance/speed combinations for the plurality of proximity zones (i.e., a “stopping distance” to avoid contact of a moving catheter with tissue). The deflection angle and/or rotation/virtual rotation value can also come into play as distal end shape affected by these parameters can in turn affect the angle of approach. In any event, for exemplary purposes only, the first proximity zone 266 can be set up to span distances from 0 mm to 2 mm from the tissue boundary 262, the second proximity zone 270 can be set up to span distances greater than 2 mm but less than 4 mm from the tissue boundary 262 and the third proximity zone 272 can be set up to cover distances greater than 4 mm from the tissue boundary 262. Of course, as described, these distances are exemplary only and the actual values will vary. For exemplary purposes only, a “normal” device speed (e.g., in the GREEN proximity zone) within the RCGS 10 can be 5 mm/second, but the particular speed threshold for the YELLOW and RED proximity zones would be reduced, and will vary from system to system.
It should be understood that while
Referring again to
In the OFF mode 280, the apparatus 220 will inhibit reading of proximity sensor 236 or if such sensor is read, its effect on the operation of RCGS 10 will be suppressed. For example, in the case of an ablation procedure, the user 224 can wish to disable the proximity sensor interface feature of the RCGS 10 by selecting the OFF mode 280.
In the MONITOR mode 282, the apparatus 220 will inhibit the specified response action even when proximity criteria are satisfied and a response action (e.g., reduce speed, cut power) would otherwise be taken by apparatus 222. However, when the proximity criteria associated with a particular zone have been met, the apparatus 220 will generate an alert. Such an alert can be an audio alert, a visual alert, a haptic alert, or a pop-up window displaying a warning or error message. In the ACTIVE mode 284, the apparatus 220 will implement the specified response actions, provided the proximity criteria have been met.
As shown in
A response action associated with a proximity zone can also modify the behavior of the UI logic 226. In an embodiment, certain functions available in the user interface can be disabled once the proximity zones have been established. For example, the UI logic 226 can be modified to prevent the user 224 from specifying a way point, as part of an overall pre-planned catheter movement, in or through a RED proximity zone.
In another embodiment, the response action can also entail (i) a reversal of movement of the medical device, and/or (ii) a return of the medical device to a prior location within a different proximity zone (e.g., return back to a GREEN zone upon entering a YELLOW zone).
The apparatus 222 is also configured with adaptive logic to dynamically redefine proximity zones. In both the MONITOR mode 282 and the ACTIVE mode 284, the apparatus 222 keeps track of the number of times the catheter entered either the Yellow or Red proximity zones. Using this information, adaptive diagnostic logic (not shown) automatically redefines parameters associated with the proximity zones (e.g., adjust the distance parameter, increase the degree to which the catheter's speed is reduced, etc.). These adjustments are made in a way so as to reduce or eliminate instances of operating power to the motors being terminated.
The control table 286 stores information specifying how and to what extent catheter speed (column 288) or a range of catheter deflection and/or translation (column 292) can be scaled down when the catheter enters the YELLOW proximity zone. The available speed control steps for scaling speed, NORMAL, MINOR, MID, and MAJOR are referred to collectively as steps 290. These steps are selected by the user 224 via interaction through the UI logic 226. The NORMAL step can be the default, normal speed for catheter movement within the RCGS 10, for example only, 5 mm/second. The MINOR step can correspond to a minor reduction, for example, a 25% reduction relative to normal speed. The MID step can correspond to a mid-level reduction, for example, a 50% reduction relative to the normal speed. The MAJOR step can correspond to a large reduction, for example a 75% reduction, relative to normal speed. The speed control step parameters can be selected by the user 224 as the desired response action associated with the YELLOW proximity zone Likewise, the NORMAL, MINOR, MID, and MAJOR steps associated with deflection step control parameter and translation step control parameters (not shown) can be configured and user selected in a like manner. In another embodiment, the control table 286 may include information to specify a relaxation control step. The relaxation step specifies an amount that any tension force or compression force imparted to the medical device is reduced. For example, the reduction may be one of either wholly released or partially released.
In step 1402, the apparatus 222 monitors at predetermined time intervals the catheter's proximity to nearby tissue. In an embodiment, the predetermined time interval can be the I/O cycle time, although other time intervals can be suitable depending on the particular configuration of the RCGS. The RCGS 10 operates in accordance with a system wide input/output (I/O) cycle, which can be on the order of between about 30-50 milliseconds, and can be about 50 milliseconds. The I/O cycle is the “heartbeat” of the RCGS 10, establishing a timing reference for a variety of functions. This deterministic approach ensures that a situation where the catheter unexpectedly approaches an anatomical structure will not go undetected for any more than one I/O cycle's worth of time. The method proceeds to step 1404.
In step 1404, the control logic 228 obtains an updated proximity reading from the proximity sensor 236. As described above, in an embodiment, a value of an ECI can be used, or a derivative of the ECI (e.g., the rate of change of ECI over time). The method proceeds to step 1406.
In step 1406, the control logic 228 determines whether the operating mode has been set to OFF (e.g., by the user, for instance, when conducting ablation where it is desirable to maintain the ablation electrode in good contact with the tissue). If the answer in step 1406 is YES, then no further processing is done and the method branches to step 1402, to await the next I/O cycle. If the answer in step 1406 is NO, then the operating mode is either the MONITOR mode or the ACTIVE mode and in either case, the method proceeds to step 1408.
In step 1408, the control logic 228 determines whether the proximity criteria specified for the GREEN proximity zone has been met. This step can be performed by comparing the defined criteria discussed above to current values for proximity-to-tissue distance, speed, deflection/rotation, etc. For example only, if the distance criterion associated with the GREEN proximity zone specifies that the catheter can be no closer than 4 mm to any anatomical structure (tissue), then the control logic 228 will compare the current proximity reading with a threshold set to correspond to a distance equal to or greater than 4 mm. As shown in
In step 1410, the control logic 228 determines whether the proximity criteria is met for the YELLOW (caution) proximity zone. Again, this step can be performed by comparing the defined criteria discussed above to current values for proximity-to-tissue distance, speed, deflection/rotation, etc. If the answer in step 1410 is NO, then the method proceeds to step 1412. Otherwise, if the answer in step 1410 is YES, then the method proceeds to step 1418.
In step 1412, the control logic 228 determines that proximity criteria for the RED proximity zone has been met in the same way as described above for the GREEN and YELLOW proximity zones. The control logic 228, to determine what response action to take, determines whether the operating mode has been set to the ACTIVE mode or to the MONITOR mode. If the control logic 228 determines that the operating mode has been set to the ACTIVE mode, then the method branches to step 1414; otherwise, the method branches to step 1420 (MONITOR mode).
In step 1414 (RED zone, ACTIVE mode), the control logic 228, for example through suppression of the refresh signal 214 (
In step 1416, the control logic 228 updates an internal register or the like that stores the number of times that power has been terminated (i.e., RED zone). In addition, the control logic 228, given the severity of the response action, is configured to disable further operation of the RCGS 10 until the user 224 specifically intervenes, thereby acknowledging the incident (e.g., a pop-up error message can be displayed through the UI logic 226, and disables further operation of the RCGS 10 until the user clicks to dismiss or otherwise indicates acknowledgement of the error message).
In step 1418, the control logic 228 determines whether the operating mode has been set to the ACTIVE mode. If the answer in step 1418 is NO, then the operating mode has been set to the MONITOR mode, and the method branches to step 1420. Otherwise, the method proceeds to step 1426.
In step 1420 (“MONITOR mode”), the control logic 228 outputs an alert in accordance with the specified alert in the response table 296 (
In step 1426 (YELLOW zone, ACTIVE mode), the control logic 228 reduces the navigation speed of the catheter (or other device) specified for the pre-planned movement, all in accordance with the speed control (step down) parameters set forth in the control table 286 (
It should be understood that the sequence of steps in the method of
As described herein, the control logic 228 is configured to keep track of the number of times a reduction in speed was implemented (i.e., YELLOW zone) or that a termination of power was commanded (i.e., RED zone) for the purpose of automatically redefining the proximity zones or response actions associated with a proximity zone. For example, when the number of RED proximity zone entries exceed a predetermined threshold, the control logic 228 can increase a YELLOW proximity zone speed reduction from a MINOR setting to a MAJOR setting. For example, the reason for entry into the RED zone can involve “overshoot” of the catheter into the RED zone from the YELLOW zone due to excessive speed. A reduction in speed in the YELLOW zone can reduce the occurrence of such “overshoot” situations. In another embodiment, the YELLOW zone can be expanded and the RED zone reduced from a dimensional perspective. Other variations are possible.
The proximity sensor interface enhances the experience of the electrophysiologist by providing additional safeguards within the RCGS 10. The capabilities described herein also enhance the safety of the patient by anticipating and avoiding unintended device-to-tissue contact.
While the RCGS 10 as described herein employed linear actuation (i.e., fingers, slider blocks), the spirit and scope of the disclosures contemplated herein is not so limited and extends to and covers, for example only, a manipulator assembly configured to employ rotary actuation of the control members. In further embodiments, the ECU can be configured to cause the manipulator assembly to either linearly actuate and rotary actuate one or more control members associated with the medical device for at least one of translation, rotation, virtual rotation and deflection movement.
Additional apparatus can be incorporated in or used in connection with the RCGS 10, whether or not illustrated in
Further configurations, such as balloon-based delivery configurations, can be incorporated into catheter embodiments consistent with the disclosure. Furthermore, various sensing structures can also be included in the catheter, such as temperature sensor(s), force sensors, various localization sensors (see description above), imaging sensors and the like.
As used herein “distal” refers to an end or portion thereof that is advanced to a region of interest within a body (e.g., in the case of a catheter) while “proximal” refers to the end or portion thereof that is opposite of the distal end, and which can be disposed outside of the body and manipulated, for example, automatically through the RCGS 10.
It should be understood that an electronic controller or ECU as described above for certain embodiments can include conventional processing apparatus known in the art, capable of executing pre-programmed instructions stored in an associated memory, all performing in accordance with the functionality described herein. To the extent that the methods described herein are embodied in software, the resulting software can be stored in an associated memory and can also constitute the means for performing such methods. Implementation of certain embodiments, where done so in software, would require no more than routine application of programming skills by one of ordinary skill in the art, in view of the foregoing enabling description. Such an electronic control unit or ECU can further be of the type having both ROM, RAM, a combination of non-volatile and volatile (modifiable) memory so that the software can be stored and yet allow storage and processing of dynamically produced data and/or signals.
It should be further understood that an article of manufacture in accordance with this disclosure includes a computer-readable storage medium having a computer program encoded thereon for implementing the proximity/contact sensor interface described herein. The computer program includes code to perform one or more of the methods disclosed herein.
Although a number of embodiments of this disclosure have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and can include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure can be made without departing from the disclosure as defined in the appended claims.
