Magnetic resonance thermometry during ablation

Patent metadata

Field	Value
Publication number	US-10555776-B2
Application number	US-201715425166-A
Country	US
Kind code	B2
Filing date	Feb 6, 2017
Priority date	Mar 8, 2016
Publication date	Feb 11, 2020
Grant date	Feb 11, 2020

Abstract

Thermography of an ablation site is carried out by navigating a probe into contact with target tissue in the heart, obtaining a first position of a position sensor in the probe and acquiring a first magnetic resonance thermometry image of the target tissue. The method is further carried out during ablation by iteratively reading the position sensor to obtain second positions, and acquiring a new magnetic resonance thermometry image of the target tissue when the distance between the first position and one of the second positions is less than a predetermined distance. The images are analyzed to determine the temperature of the target tissue.

First claim

The invention claimed is:

1. A method, comprising the steps of:
inserting a probe into a heart of a living subject, the probe having a distal portion, a position sensor and an ablation electrode being disposed on the distal portion;
navigating the probe into a contacting relationship with a target tissue of the heart and activating the ablation electrode;
obtaining a first reading of the position sensor to obtain a first position of the probe in the heart;
acquiring a first magnetic resonance thermometry image of the target tissue at the first position; and
thereafter during ablation iteratively performing the steps of:
taking new readings of the position sensor to obtain second positions of the probe in the heart;
acquiring a new magnetic resonance thermometry image of the target tissue only when a distance between the first position and one of the second positions is less than a predetermined distance; and
analyzing the first magnetic resonance thermometry image and the new magnetic resonance thermometry image to determine a temperature of the target tissue.

2. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprises determining a phase change therebetween of a proton resonant frequency and calculating the temperature of the target tissue from the phase change.

3. The method according to claim 1 , wherein the position sensor is a magnetic location sensor and the new readings are taken at 10 ms intervals.

4. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a proton resonance frequency phase shift and correlating the phase shift with temperature.

5. The method according to claim 4 , wherein the first magnetic resonance thermometry image and the new magnetic resonance thermometry image are obtained from pulse sequences.

6. The method according to claim 5 , wherein the pulse sequences are gradient-recalled echo pulse sequences.

7. The method according to claim 4 , wherein measuring a proton resonance frequency phase shift is performed spectroscopically.

8. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a proton density spin lattice relaxation time.

9. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a spin-spin relaxation time.

10. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a diffusion coefficient.

11. The method according to claim 1 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a magnetization transfer.

12. The method according to claim 1 , wherein when the distance between the first position and one of the second positions is greater than the predetermined distance then acquiring a new magnetic resonance thermometry image of the target tissue.

13. An apparatus comprising:
a flexible probe having a proximal portion and a distal portion adapted for insertion into a heart of a patient;
a position sensor and an ablation electrode in the distal portion;
a processor linked to the position sensor and configured for sending control signals to a magnetic resonance imager, the processor cooperative with the magnetic resonance imager for:
obtaining a first reading of the position sensor to obtain a first position during ablation of a target tissue of the heart;
acquiring a first magnetic resonance thermometry image of the heart at the first position; and
thereafter during ablation with the ablation electrode iteratively performing the steps of:
taking new readings of the position sensor to obtain second positions of the probe in the heart;
acquiring a new magnetic resonance thermometry image of the target tissue only when a distance between the first position and one of the second positions is less than a predetermined distance; and
analyzing the first magnetic resonance thermometry image and the new magnetic resonance thermometry image to determine a temperature of the target tissue.

14. The apparatus according to claim 13 , wherein the first magnetic resonance thermometry image and the new magnetic resonance thermometry image are proton resonance frequency phase images.

15. The apparatus according to claim 13 , wherein the first magnetic resonance thermometry image and the new magnetic resonance thermometry image are obtained from pulse sequences.

16. The apparatus according to claim 15 , wherein the pulse sequences are gradient-recalled echo pulse sequences.

17. The apparatus according to claim 13 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a proton density spin lattice relaxation time.

18. The apparatus according to claim 13 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a spin-spin relaxation time.

19. The apparatus according to claim 13 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a diffusion coefficient.

20. The apparatus according to claim 13 , wherein acquiring the first magnetic resonance thermometry image and the new magnetic resonance thermometry image comprise measuring a magnetization transfer.

21. The apparatus according to claim 13 , wherein when the distance between the first position and one of the second positions is greater than the predetermined distance then acquiring a new magnetic resonance thermometry image of the target tissue.

Assignees

• Biosense Webster Israel Ltd

Inventors

• Govari Assaf
• Altmann Andres Claudio
• Ephrath Yaron
• Gliner Vadim
• Dror Eyal

Classifications

• G01R33/287

  involving active visualization of interventional instruments, e.g. using active tracking RF coils or coils for intentionally creating magnetic field inhomogeneities · CPC title

• A61B2090/3954

  magnetic, e.g. NMR or MRI · CPC title

• A61B18/1492

  having a flexible, catheter-like structure, e.g. for heart ablation (A61B18/1477 takes precedence) · CPC title

• A61B2018/00577

  Ablation · CPC title

• A61B2018/00351

  Heart · CPC title