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EP-4393392-B1 - CATHETER WITH DISTAL TILT DETECTION

EP4393392B1EP 4393392 B1EP4393392 B1EP 4393392B1EP-4393392-B1

Inventors

  • GOVARI, ASSAF
  • ALTMANN, ANDRES CLAUDIO
  • FRIED, SHLOMO

Dates

Publication Date
20260513
Application Date
20231222

Claims (8)

  1. Medical apparatus (20), comprising: a probe (26) comprising a distal part (28) adapted for insertion into a body of a living subject (23) and comprising first and second magnetic transducers (68, 70, 72, 74) disposed at respective first and second locations in the distal part of the probe; wherein the distal part of the probe comprises a joint, which is configured to deform in response to a force exerted by the distal part of the probe against tissue, and wherein the first and second magnetic transducers are disposed on opposing sides of the joint; at least one magnetic field generator (38) disposed externally to the probe and adapted for placement in proximity to the body of the living subject; and control circuitry (50) configured to (a) drive the first magnetic transducer in the probe to generate a first AC magnetic field at a first frequency, (b) drive the at least one magnetic field generator external to the probe to generate a second AC magnetic field at a second frequency, (c) calculate a disposition of the distal part of the probe by processing a first signal output by the second magnetic transducer at the first frequency, and (d) calculate position coordinates of the distal part of the probe by processing a component of a second signal output by one of the first and second magnetic transducers at the second frequency while canceling from the second signal interference at the first frequency; characterised in that the control circuitry is configured to cancel the interference by measuring an amplitude of the interference in the second signal at the first frequency, generating a third signal having the measured amplitude at the first frequency, and subtracting the third signal from the second signal.
  2. The apparatus according to claim 1, wherein the first and second magnetic transducers respectively comprise first and second coils, and the control circuitry is configured to drive the first magnetic transducer by applying an AC electrical current at the first frequency to the first coil.
  3. The apparatus according to claim 1, wherein the control circuitry is configured to calculate a deformation of the joint responsively to the first signal output by the second magnetic transducer at the first frequency, and to measure the force exerted by the distal part of the probe against the tissue based on the calculated deformation.
  4. The apparatus according to claim 1, wherein the first magnetic transducer is disposed on a distal side of the joint, while the second magnetic transducer is disposed on a proximal side of the joint.
  5. The apparatus according to claim 1, wherein the probe comprises a third magnetic transducer in a third location, proximal to the first and second locations, and wherein the control circuitry is configured to calculate the position coordinates of the distal part of the probe by both processing the second signal and processing a third signal output by the third magnetic transducers at the second frequency.
  6. The apparatus according to claim 1, wherein the distal part of the probe comprises a basket assembly, comprising multiple spines and electrodes, which are disposed along the spines and configured to contact tissue within a cavity in the body.
  7. The apparatus according to claim 1, wherein the control circuitry is configured to measure the amplitude of the interference by digitizing the second signal and extracting the amplitude and a phase of an element of the digitized second signal at the first frequency, and to generate the third signal as a digital signal at the measured amplitude in antiphase to the element of the digitized second signal at the first frequency and convert the digital signal to an analog interference cancellation signal, and to subtract the third signal from the second signal by analog summation of the analog interference cancellation signal with the second signal.
  8. The apparatus according to claim 7, wherein the second signal is output by the first magnetic transducer while the first magnetic transducer is driven to generate the first AC magnetic field.

Description

FIELD The present disclosure relates to invasive medical devices, and specifically to methods and devices for sensing displacement of a distal part of a probe, such as a catheter, that is applied to the body of a patient. BACKGROUND In some diagnostic and therapeutic techniques, a catheter is inserted into a chamber of the heart and brought into contact with the inner heart wall. In such procedures, it is generally important that the distal tip of the catheter engages the endocardium with sufficient pressure to ensure good contact. Excessive pressure, however, may cause undesired damage to the heart tissue and even perforation of the heart wall. Catheters with integrated pressure sensors for sensing tissue contact have been described in the patent literature. As one example, U.S. Patent 8,535,308, describes a medical probe, which includes an insertion tube, having a longitudinal axis and having a distal end. A distal tip is disposed at the distal end of the insertion tube and is configured to be brought into contact with a body tissue. A joint couples the distal tip to the distal end of the insertion tube. A joint sensor, contained within the probe, senses a position of the distal tip relative to the distal end of the insertion tube. The joint sensor includes first and second subassemblies, which are disposed within the probe on opposite, respective sides of the joint and each include one or more magnetic transducers. US 2013/096551 A1 and US 2013/303886 A1 are other applications which describe flexible probes. The present disclosure will be more fully understood from the following detailed description of the examples thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is schematic pictorial illustration of a catheter-based electrophysiology mapping and ablation system, in accordance with an example of the disclosure;Fig. 2 is a schematic detail view showing a basket assembly at the distal end of a catheter, in accordance with an example of the present disclosure;Fig. 3 is a schematic sectional view showing details of the distal part of a catheter, in accordance with an example of the present disclosure;Fig. 4 is a block diagram that schematically illustrates sensing and signal processing circuits associated with a catheter, in accordance with an example of the disclosure; andFig. 5 is a flow chart that schematically illustrates a method for position sensing, in accordance with an example of the disclosure. DETAILED DESCRIPTION OVERVIEW Certain types of medical probes, such as catheters for insertion into chambers of the heart, contain magnetic position sensors, which are used in navigating the distal part of the probe within the patient's body. The magnetic position sensor comprises a magnetic transducer, i.e., a device that converts magnetic energy into an electrical signal, or vice versa. A magnetic field generator in proximity to the patient's body produces an alternating-current ("AC") or time-varying magnetic field within the body at a certain frequency, and the signals output by the magnetic transducer at this frequency are processed to calculate position coordinates of the distal part of the probe. Typically, the magnetic transducer comprises one or more coils; but alternatively, other types of transducers, such as Hall sensors, may be used for the present purposes. Some probes comprise a deflectable distal assembly. For example, some cardiac catheters comprise a basket assembly at their distal end, with electrodes distributed along the spines of the basket assembly for contacting tissue within the heart. The magnetic transducer used for position sensing in these sorts of catheters is commonly located near the distal end of the catheter insertion tube, while the basket assembly extends distally away from the distal end of the insertion tube. The basket assembly may deflect transversely, relative to the axis of the insertion tube, due to force exerted by the basket assembly against the tissue. When the deflection is substantial, for example more than a few degrees, the position coordinates given by the magnetic transducer will not give an accurate reading of the locations of the electrodes on the basket assembly. Some probes with deflectable distal assemblies include a force sensor for measuring the force exerted by the distal assembly against tissue in the body. For example, the sorts of cardiac catheters that were described above may comprise a joint between the distal end of the insertion tube and the basket assembly. The joint deforms in response to force exerted by the basket assembly against the tissue. To measure the deformation, and thus estimate the force, magnetic transducers are disposed in the catheter on opposing sides of the joint. One of the transducers, for example the transducer on the distal side of the joint, is driven to generate an AC magnetic field at a certain frequency, and the transducer (or transducers) on the other side of the joint