Electromagnetic tracking surgical system and method of controlling the same

1. An instrument tracking system comprising:

a first set of one or more electromagnetic (EM) field generators associated with a first structure and configured to generate a first EM field volume;

a second set of one or more EM field generators associated with a second structure and configured to generate a second EM field volume, the second EM field volume overlapping the first EM field volume in an overlapping EM field volume; and

controller circuitry configured to:

determine a first spatial relationship between the first EM field volume and the second EM field volume relative to a global coordinate system;

after movement of the first structure relative to the second structure, determine a modified spatial relationship between the first EM field volume and the second EM field volume relative to the global coordinate system;

detect a position sensor within the first EM field volume, the position sensor being associated with an instrument; and

in response to said detecting the position sensor within the first EM field volume, activate the first set of one or more EM field generators.

2. The system of claim 1 , wherein:

the first EM field volume is associated with a first local coordinate system defined above a center portion of the first structure;

the second EM field volume is associated with a second local coordinate system defined above a center portion of the second structure; and

the modified spatial relationship between the first EM field volume and the second EM field volume is based on at least one of:

a first vector between the first local coordinate system and the global coordinate system; or

a second vector between the second local coordinate system and the global coordinate system.

3. The system of claim 2 , wherein the global coordinate system lies above a hinge between the first structure and the second structure.

4. The system of claim 2 , wherein the first local coordinate system and the second local coordinate system have origin points in space that are lower than an origin point of the global coordinate system.

5. The system of claim 1 , wherein the controller circuitry is further configured to determine vectors between local coordinate systems of the first and second EM field volumes, respectively, and the global coordinate system.

6. The system of claim 1 , wherein:

said movement of the first structure is a rotational movement relative to the second structure; and

the modified spatial relationship between the first EM field volume and the second EM field volume indicates an offset angle between the first EM field volume and the second EM field volume.

7. The system of claim 1 , wherein:

prior to said movement of the first structure relative to the second structure, the overlapping EM field volume has a rectangular side profile shape; and

after said movement of the first structure relative to the second structure, the overlapping EM field volume has a non-rectangular side profile shape.

8. The system of claim 7 , wherein the non-rectangular side profile shape is a trapezoidal shape.

9. An instrument tracking system comprising:

a first set of one or more electromagnetic (EM) field generators associated with a first surgical bed portion of a surgical bed and configured to generate a first EM field volume;

a second set of one or more EM field generators associated with a second surgical bed portion of the surgical bed and configured to generate a second EM field volume, the second EM field volume overlapping the first EM field volume in an overlapping EM field volume; and

controller circuitry configured to:

determine a first vector between a first local coordinate system associated with the first EM field volume and a global coordinate system;

determine a second vector between a second local coordinate system associated with the second EM field volume and the global coordinate system; and

after relative movement between the first surgical bed portion and the second surgical bed portion, determine a modified first vector between the first local coordinate system and the global coordinate system.

10. The system of claim 9 , wherein:

prior to said relative movement between the first surgical bed portion and the second surgical bed portion, a center of the overlapping EM field volume is located at an origin of the global coordinate system; and

after said relative movement between the first surgical bed portion and the second surgical bed portion, the center of the overlapping EM field volume is offset from the origin of the global coordinate system.

11. The system of claim 10 , wherein the controller circuitry is further configured to determine a third vector representing an offset between the center of the overlapping EM field volume and the origin of the global coordinate system.

12. The system of claim 11 , wherein the global coordinate system is defined above a center portion of the surgical bed.

13. The system of claim 9 , wherein the controller circuitry is further configured to define a position of a patient relative to an origin of the global coordinate system.

14. The system of claim 9 , wherein:

the first local coordinate system is defined above a center portion of the first surgical bed portion; and

the second local coordinate system is defined above a center portion of the second surgical bed portion.

15. A method of tracking an instrument, the method comprising:

determining, relative to a global coordinate system, a first spatial relationship between a first electromagnetic (EM) field volume associated with a first structure and a second EM filed volume associated with a second structure;

after movement of the first structure relative to the second structure, determining a modified spatial relationship between the first EM field volume and the second EM field volume relative to the global coordinate system;

detecting a first position sensor of a set of one or more position sensors within a first electromagnetic (EM) field volume associated with a first set of EM field generators, the first position sensor being associated with an instrument;

in response to said detecting the first position sensor within the first EM field volume, activating the first set of EM field generators;

detecting the first position sensor in an overlapping EM field volume where the first EM field volume overlaps with a second EM field volume associated with a second set of EM field generators; and

in response to said detecting the first position sensor in the overlapping EM field volume, activating the second set of EM field generators.

16. The method of claim 15 , wherein, when the second set of EM field generators is activated, the first set of EM field generators remains activated while the first position sensor is disposed within the overlapping EM field volume.

17. The method of claim 16 , further comprising:

after said activating the second set of EM field generators:

detecting the first position sensor within the second EM field volume outside of the overlapping EM field volume; and

determining that none of the set of one or more position sensors is disposed in the first EM field volume; and

in response to said detecting the first position sensor within the second EM field volume outside of the overlapping EM field volume and said determining that none of the set of one or more position sensors is disposed in the first EM field volume, deactivating the first set of EM field generators.

18. The method of claim 15 , wherein the modified spatial relationship between the first EM field volume and the second EM field volume is based on a first vector between the first EM field volume and the global coordinate system and a second vector between the second EM field volume and the global coordinate system.

19. The method of claim 15 , wherein:

prior to said movement of the first structure relative to the second structure, the overlapping EM field volume has a regular shape; and

after said movement of the first structure relative to the second structure, the overlapping EM field volume has an irregular shape.

20. The method of claim 19 , wherein the regular shape is an elliptical, cylindrical, or cubic shape.