External continuous field tomography
Methods for evaluating tissue motion of a tissue location, e.g., a cardiac location, via external continuous field tomography are provided. Aspects of the methods include generating at least one substantially linear continuous field gradient across the tissue location of interest, and using a resultant signal from a sensing element stably associated with the tissue location to evaluate motion of the tissue location. Also provided are systems, devices and related compositions for practicing the subject methods. The subject methods and devices find use in a variety of different applications, including cardiac resynchronization therapy.
1. A method of evaluating a tissue location in a subject, the method comprising:
(a) generating a substantially linear field gradient in the subject across the tissue location by broadcasting from a plurality of broadcasting electrodes coupled to a signal generator a respective number of multi-frequency signals, wherein each one of the multi-frequency signals is a summation of signals with different frequencies and wherein the signals with the different frequencies in the each one of the multi-frequency signals are assigned with corresponding amplitudes to form the substantially linear field gradient;
(b) obtaining a linear field gradient dependent reading from a sensing element, wherein the sensing element is configured to physically attach to the tissue location with an attachment element such that movement of the sensing element coincides with movement of the tissue location and wherein the linear field gradient dependent reading is associated with a location of the sensing element in the substantially linear field gradient; and
(c) evaluating the tissue location based on the linear field gradient dependent reading.
2. The method according to claim 1 , wherein the substantially linear field gradient is a substantially linear electric field gradient.
3. The method according to claim 2 , wherein the plurality of broadcasting electrodes is adapted to contact the subject externally.
4. The method according to claim 3 , wherein each pair of the plurality of broadcasting electrodes comprises two electrodes.
5. The method according to claim 3 , wherein at least two pairs of the plurality of broadcasting electrodes share a common electrode.
6. The method according to claim 3 , wherein the plurality of broadcasting electrodes comprises three or more electrode pairs.
7. The method according to claim 3 , wherein the plurality of broadcasting electrodes comprises electrode pairs arranged circumferentially around a portion of the subject.
8. The method according to claim 2 , wherein the linear field gradient dependent reading comprises a voltage.
9. The method according to claim 8 , wherein the voltage is an AC voltage.
10. The method according to claim 2 , wherein the generating the substantially linear field gradient comprises generating two or more distinguishable substantially linear electric field gradients.
11. The method according to claim 10 , wherein the two or more distinguishable substantially linear electric field gradients differ from each other by frequency.
12. The method according to claim 1 , wherein the evaluating comprises determining location of the sensing element based on the linear field gradient dependent reading.
13. The method according to claim 1 , wherein the evaluating comprises determining velocity of the sensing element based on the linear field gradient dependent reading.
14. The method according to claim 1 , wherein the evaluating comprises determining acceleration of the sensing element based on the linear field gradient dependent reading.
15. The method according to claim 1 , wherein the tissue location is a cardiac location.
16. The method according to claim 15 , wherein the cardiac location is a heart wall location.
17. The method according to claim 1 , wherein the sensing element is a receive electrode.
18. The method according to claim 17 , wherein the receive electrode is present on a lead.
19. The method according to claim 1 , wherein the obtaining the linear field gradient dependent reading is performed at least twice over a duration of time.
20. The method according to claim 1 , wherein the evaluating the tissue location comprises determining timing of cardiac wall motion of the subject.
21. The method according to claim 1 , wherein the evaluating the tissue location comprises determining cardiac wall motion of a first cardiac wall relative to a second cardiac wall.
22. The method according to claim 1 , wherein the evaluating the tissue location comprises determining timing of cardiac wall motion of a first cardiac wall relative to a second cardiac wall.
23. The method according to claim 1 , wherein the evaluating the tissue location comprises detecting ventricular mechanical dyssynchrony.
24. The method according to claim 23 , wherein the evaluating the tissue location further comprises performing cardiac resynchronization therapy upon the detecting the ventricular mechanical dyssynchrony.
25. A system of evaluating a tissue location in a subject, the system comprising:
(a) a plurality of broadcasting electrodes coupled to a signal generator and configured to generate a substantially linear field gradient in the subject across the tissue location by broadcasting a respective number of multi-frequency signals, wherein each one of the multi-frequency signals is a summation of signals with different frequencies and wherein the signals with the different frequencies in the each one of the multi-frequency signals are assigned with corresponding amplitudes to form the substantially linear field gradient;
(b) a sensing element configured to obtain a linear field gradient dependent reading, wherein the sensing element is configured to physically attach to the tissue location with an attachment element such that movement of the sensing element coincides with movement of the tissue location and wherein the linear field gradient dependent reading is associated with a location of the sensing element in the substantially linear field gradient;
(c) a signal processing element configured to evaluate the linear field gradient dependent reading to determine the tissue location.