Tracking system using field mapping
In some aspects, a method includes (i) securing multiple sets of current injecting electrodes to an organ in a patient's body, (ii) causing current to flow among the multiple sets of current injecting electrodes to generate a field in the organ, (iii) in response to current flow caused by the multiple sets of current injecting electrodes, measuring the field at each of one or more additional electrodes, (iv) determining expected signal measurements of the field inside the organ using a pre-determined model of the field, and (v) determining a position of each of the one or more additional electrodes in the organ based on the measurements made by the additional electrodes and the determined expected signal measurements of the field.
1. A method comprising:
determining expected signal measurements of a field inside an organ of a body using a noninterpolation based calculation, the expected signal measurements being based on signals generated by current injecting electrodes that are mounted on a first catheter placed inside the body or body surface electrodes and measured by electrodes on a second catheter; and
determining a position of each of one or more additional electrodes on a third catheter in the organ based on measurements made by the additional electrodes and the determined expected signal measurements of the field;
the method further comprising:
causing current to flow among multiple sets of current injecting electrodes to generate a field in the organ in the body, the multiple sets of current injecting electrodes being secured to one or more stable locations relative to the organ in the body;
obtaining positions within the organ of one or more measuring electrodes used for measuring the field generated by the multiple sets of current injecting electrodes;
in response to the current flow, measuring the field at multiple locations in the organ using the one or more measuring electrodes;
modeling the field using the measurements of the field from the one or more measuring electrodes and the positions within the organ of the one or more measuring electrodes; and
determining the expected signal measurements of the field at additional locations within the organ using the model of the field.
2. The method of claim 1 , wherein modeling the field comprises modeling the field based on physical characteristics using Laplace's equation.
3. The method of claim 1 , wherein modeling the field comprises modeling the field based on physical characteristics using Poisson's equation.
4. The method of claim 1 , wherein modeling of the field further comprises using a function that correlates field measurements with position coordinates.
5. The method of claim 4 , wherein the function is a differentiable function.
6. The method of claim 1 , wherein the multiple sets of current injecting electrodes are mounted on one or more catheters that are placed inside the body.
7. The method of claim 1 , wherein the multiple sets of current injecting electrodes comprise one or more body-surface electrodes.
8. The method of claim 1 , wherein the multiple sets of current injecting electrodes comprise both electrodes mounted on one or more catheters that are placed inside the body and body surface electrodes.
9. The method of claim 8 , wherein the electrodes mounted on one or more catheters comprise one or more electrodes secured to the organ.
10. The method of claim 8 , wherein the electrodes mounted on the one or more catheters comprise one or more electrodes that can be moved and positioned at multiple locations in an organ.
11. The method of claim 1 , wherein obtaining the position of the one or more measuring electrodes comprises using a tracking system to track the position of the one or more measuring electrodes.