EP-4736796-A2 - CATHETER FRAME PIECES USED AS LARGE SINGLE AXIS SENSORS

EP4736796A2EP 4736796 A2EP4736796 A2EP 4736796A2EP-4736796-A2

Abstract

Catheterization of the heart is carried out using a framework formed by a plurality of electrically conducting wire loops. The wire loops are modeled as polygons, each subdivided into a plurality of triangles,. The wire loops are exposed to magnetic fluxes at respective frequencies, and signals read from the loops. Theoretical magnetic fluxes in the polygons are computed as sums of theoretical magnetic fluxes in the triangles thereof, The location and orientation of the framework in the heart is determined by relating the computed theoretical magnetic fluxes to the signals.

Inventors

MONTAG, AVRAM DAN
BAR-TAL, MEIR

Assignees

Biosense Webster (Israel) Ltd.

Dates

Publication Date: 20260506
Application Date: 20161222

Claims (15)

An apparatus, comprising: a probe (14, 37) adapted for insertion into a heart of a living subject, the probe having a distal end; a framework (39) disposed on the distal end, the framework comprising a plurality of electrically conducting wire loops (43), the loops independently connectable to a receiver, wherein each of the wire loops (43) is configured to function independently as a single-axis magnetic location sensor when subjected to a magnetic field produced by field generating coils (28).
A system comprising the apparatus of claim 1 and a positioning subsystem comprising a magnetic position tracking arrangement that is configured to determine the position and orientation of the probe (14, 37) by generating magnetic fields in a predefined working volume using the field generating coils (28) and sensing these fields using the wire loops.
The system according to claim 2, wherein the positioning subsystem comprises a processor (22), the processor configured to: model the wire loops as respective polygons; subdivide the polygons into a plurality of triangles; exposing the wire loops to magnetic fields at respective frequencies; reading signals from the wire loops responsively to the magnetic fields at the respective frequencies; compute the theoretical magnetic fluxes in the polygons as respective sums of theoretical magnetic fluxes in the triangles thereof; and determine a location and orientation of the framework by relating the computed theoretical magnetic fluxes to the signals.
The system according to claim 3, wherein the polygons are hexagons.
The system according to claim 3, wherein the processor is configured to subdivide the polygons into a plurality of triangles by: identify local coordinates of the triangles in a local coordinate system; and transform the local coordinates of the triangles to coordinates of a magnetic position tracking system.
The system according to claim 5, wherein the processor is configured to transform the local coordinates by optimizing a cost function.
The system according to claim 3, wherein the processor is configured to compute the theoretical magnetic fluxes based on areas and centroids of the triangles.
The system according to claim 3, wherein the processor is configured to model the wire loops by applying a first constraint, wherein segments of the triangles of adjacent polygons are required to intersect.
The system according to claim 3, wherein the processor is configured to model the wire loops by applying a second constraint, wherein a vertex of each triangle of one polygon coincides with a vertex of an adjacent triangle of the one polygon.
The system according to claim 3, wherein the processor is configured to model the wire loops by applying a third constraint, wherein adjacent polygons contact one another at exactly two points.
The system according to any one of claims 1 to 3, wherein the wire loops comprise three to eight loops.
The system according to any one of claims 1 to 3, wherein the wire loops comprise six to seven loops.
The system according to any one of claims 1 to 3, wherein the wire loops form spirals about an axis.
The system according to any one of claims 1 to 3, wherein the wire loops are deformable, further comprising deploying the framework through a lumen of the probe.
The system according to any one of claims 1 to 3, wherein one of the wire loops contacts at least another one of the wire loops.

Description

COPYRIGHT NOTICE A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. BACKGROUND OF THE INVENTION 1. Field of the Invention. This invention relates to apparatus and processes for diagnostic and surgical purposes. More particularly, this invention relates to an intra-body probe having a sensor of electromagnetic fields. 2. Description of the Related Art. Electrophysiology catheters are commonly-used for mapping electrical activity in the heart. Various electrode designs are known for different purposes. In particular, catheters having basket-shaped electrode arrays are known and described, for example, in U.S. Pat. No. 5,772,590, the disclosure of which is incorporated herein by reference. Such catheters are typically introduced into a patient through a guiding sheath with the electrode array in a folded position within the sheath so that the electrode array does not damage the patient during introduction. Within the heart, the guiding sheath is removed and the electrode array is permitted to expand to be generally basket-shaped. Some basket catheters include an additional mechanism in the form of a wire or the like connected to an appropriate control hand to assist in the expansion and contraction of the electrode array. Such catheters may incorporate magnetic location sensors as described, for example, in U.S. Patent Nos. 5,558,091, 5,443,489, 5,480,422, 5,546,951, and 5,568,809, and International Publication Nos. WO 95/02995, WO 97/24983, and WO 98/29033, the disclosures of which are incorporated herein by reference. Such electromagnetic mapping sensors typically have a length of from about 3 mm to about 7 mm. SUMMARY OF THE INVENTION It is common for multi-electrode catheters to have a wire frame on which electrodes are mounted. Embodiments of the invention provide a framework comprising several loops of wire forming a cage-like structure. When the frame is subjected to an electromagnetic field, each of the loops functions as a single axis magnetic sensor. Moreover, by partitioning the loops into triangles bends in the structure can be reconstructed. A solution, accurate to about a millimeter, can be obtained for each loop's location. An overall solution for the position of the catheter can be derived from data obtained from the loops. There is provided according to embodiments of the invention a probe adapted for insertion into a heart of a living subject. A framework disposed on the distal end is formed by a plurality of electrically conducting wire loops defining a chamber. The loops are independently connectable to a receiver. There may be six to seven wire loops. According to an aspect of the apparatus, the wire loops form spirals about an axis. According to one aspect of the apparatus, the wire loops are deformable for deployment through a catheter lumen. According to a further aspect of the apparatus, one of the wire loops contacts at least another of the wire loops. There is further provided according to embodiments of the invention a method which is carried out by inserting a probe into a heart of a living subject. A framework disposed on the distal end is formed by a plurality of electrically conducting wire loops defining a chamber. The loops are independently connectable to a receiver. The method is further carried out by modeling the wire loops as respective polygons, subdividing the polygons into a plurality of triangles, exposing the wire loops to magnetic fluxes at respective frequencies, reading signals from the wire loops responsively to the magnetic fluxes at the respective frequencies, computing the theoretical magnetic fluxes in the polygons as respective sums of theoretical magnetic fluxes in the triangles thereof, and determining a location and orientation of the framework by relating the computed theoretical magnetic fluxes to the signals. According to an aspect of the method, the polygons are hexagons. In one aspect of the method subdividing the polygons into a plurality of triangles includes identifying local coordinates of the triangles in a local coordinate system, and transforming the local coordinates of the triangles to coordinates of a magnetic position tracking system. According to another aspect of the method, transforming the local coordinates is performed by optimizing a cost function. According to a further aspect of the method, computing the theoretical magnetic fluxes is based on areas and centroids of the triangles. According to yet another aspect of the method, modeling the wire loops also includes applying a first constraint, wherein segments of the triangles of adjacent polygons are required to intersect. According to still another aspect of the method, m