TECHNIQUES FOR TEMPERATURE MEASUREMENT AND CORRECTIONS IN LONG-TERM MAGNETIC RESONANCE THERMOMETRY

• US 20110046472A1
• Filed: 08/19/2009
• Published: 02/24/2011
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: InSightec Ltd.
• Original Assignee: InSightec Ltd.
• Inventors: Dogadkin, Osnat, Freundlich, David, Levy, Yoav, Schmidt, Rita, Ziso, Hadas, Assif, Benny, Vitek, Shuki
• Granted Patent: US 9,289,154 B2
• Time in Patent Office: Days
• US Class Current: 600/411
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61N 2007/0004 Applications of ultrasound therapy
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G01R 33/56563 caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 G01R33/56509, G01R33/56518, G01R33/56536 take precedence

Abstract

Techniques for temperature measurement and correction in long-term MR thermometry utilize a known temperature distribution in an MR imaging area as a baseline for absolute temperature measurement. Phase shifts that arise from magnetic field drifts are detected in one or more portions of the MR imaging area, facilitating correction of temperature measurements in an area of interest.

Claims

1. A method of performing proton resonance frequency (PRF) based magnetic resonance (MR) temperature measurement, the method comprising the steps of:

acquiring a first phase image of an MR imaging area having a known temperature distribution, the MR imaging area comprising an area of interest;

acquiring a second phase image of the MR imaging area subsequent to the acquisition of the first phase image;

determining, from the second phase image, one or more first corrections in one or more portions of the MR imaging area that have experienced a known or clinically insignificant change in temperature since the acquisition of the first phase image;

determining one or more second corrections in at least the area of interest by extrapolating the one or more first corrections; and

assigning a first set of one or more absolute temperatures to the area of interest based at least in part on (i) the known temperature distribution and (ii) the one or more second corrections.

2. The method of claim 1, further comprising:

establishing the known temperature distribution in the MR imaging area.

3. The method of claim 2, further comprising:

establishing a uniform temperature in the MR imaging area.

4. The method of claim 1, wherein the MR imaging area is centered on the area of interest.

5. The method of claim 1, wherein (i) the area of interest comprises a treatment area of a patient undergoing an MR-guided focused ultrasound treatment, and (ii) the MR imaging area comprises at least a portion of the patient'"'"'s body.

6. The method of claim 5, wherein the treatment area comprises the patient'"'"'s prostate area.

7. The method of claim 6, further comprising:

establishing a uniform temperature in the MR imaging area by circulating heated water in a balloon pressed against the patient'"'"'s rectal wall.

8. The method of claim 7, wherein the uniform temperature is substantially the same as the patient'"'"'s body temperature.

9. The method of claim 1, further comprising:

determining the second correction(s) with a two-dimensional (2-D) polynomial fit based on the first correction(s).

10. The method of claim 9, wherein the two-dimensional (2-D) polynomial fit is a linear fit.

11. The method of claim 1, further comprising:

recording MR operating parameters used in the acquisition of the first phase image; and

overriding MRI automatic adjustments in the acquisition of the second phase image with the recorded MR operating parameters.

12. The method of claim 1, further comprising:

detecting a movement and/or deformation of the area of interest;

determining a new temperature distribution of at least the area of interest by registering the known temperature distribution to the new temperature distribution based at least in part on the detected movement and/or deformation;

acquiring a third phase image of the MR imaging area subsequent to the detected movement and/or deformation;

acquiring a fourth phase image of the MR imaging area subsequent to the acquisition of the third phase image; and

assigning a second set of one or more absolute temperatures to the area of interest based at least in part on (i) the new temperature distribution and (ii) a difference between the fourth phase image and the third phase image.

13. A system for performing proton resonance frequency (PRF) based magnetic resonance (MR) temperature measurement, the system comprising:

an MRI unit;

a control module in communication with the MRI unit, and configured to cause the MRI unit to;

acquire a first phase image of an MR imaging area having a known temperature distribution, the MR imaging area comprising an area of interest, and

acquire a second phase image of the MR imaging area subsequent to the acquisition of the first phase image; and

a processor module having access to image data acquired by the MRI unit, and configured to;

determine, from the second phase image, one or more first corrections in one or more portions of the MR imaging area that have experienced a known or clinically insignificant change in temperature since the acquisition of the first phase image,

determine one or more second corrections in at least the area of interest by extrapolating the one or more first corrections, and

assigning a first set of one or more absolute temperatures to the area of interest based at least in part on (i) the known temperature distribution and (ii) the one or more second corrections.

14. The system of claim 13, further comprising:

a temperature regulating module adapted to establish the known temperature distribution in the MR imaging area.

15. The system of claim 14, wherein the temperature regulating module is further adapted to establish a uniform temperature in the MR imaging area.

16. The system of claim 14, further comprising:

a water circulation device adapted to circulate heated water in a balloon pressed against a patient'"'"'s rectal wall, thereby establishing the uniform temperature in the MR imaging area.

17. The system of claim 16, wherein the uniform temperature is substantially the same as the patient'"'"'s body temperature.

18. The system of claim 13, wherein the processor module is further configured to:

determine the one or more second corrections with a two-dimensional (2-D) polynomial fit based on the one or more first corrections.

19. The system of claim 18, wherein the two-dimensional (2-D) polynomial fit is a linear fit.

20. The system of claim 13, being further configured to:

record MR operating parameters used by the MRI unit in the acquisition of the first phase image; and

override automatic adjustments of the MRI unit with the recorded MR operating parameters during the acquisition of the second phase image.

21. The system of claim 13, being further configured to:

detect a movement and/or deformation of the area of interest;

determine a new temperature distribution of at least the area of interest by registering the known temperature distribution to the new temperature distribution based at least in part on the detected movement and/or deformation;

acquire a third phase image of the MR imaging area subsequent to the detected movement and/or deformation;

acquire a fourth phase image of the MR imaging area subsequent to the acquisition of the third phase image; and

assign a second set of one or more absolute temperatures to the area of interest based at least in part on (i) the new temperature distribution and (ii) a difference between the fourth phase image and the third phase image.

22. A computer-readable medium storing computer-executable codes for causing at least one processor to correct proton resonance frequency (PRF) based magnetic resonance (MR) temperature measurement, the computer-readable medium comprising:

computer-executable code adapted to acquire a first phase image of an MR imaging area having a known temperature distribution, the MR imaging area comprising an area of interest;

computer-executable code adapted to acquire a second phase image of the MR imaging area subsequent to the acquisition of the first phase image;

computer-executable code adapted to determine, from the second phase image, one or more first corrections in one or more portions of the MR imaging area that have experienced a known or clinically insignificant change in temperature since the acquisition of the first phase image;

computer-executable code adapted to determine one or more second corrections in at least the area of interest by extrapolating the one or more first corrections; and

computer-executable code adapted to assign a first set of one or more absolute temperatures to the area of interest based at least in part on (i) the known temperature distribution and (ii) the one or more second corrections.

23. The computer-readable medium of claim 22, further comprising:

computer-executable code adapted to determine the one or more second corrections with a two-dimensional (2-D) polynomial fit based on the one or more first corrections.

24. The computer-readable medium of claim 23, wherein the two-dimensional (2-D) polynomial fit is a linear fit.

25. The computer-readable medium of claim 22, further comprising:

computer-executable code adapted to record MR operating parameters used in the acquisition of the first phase image; and

computer-executable code adapted to override MRI automatic adjustments in the acquisition of the second phase image with the recorded MR operating parameters.

26. The computer-readable medium of claim 22, further comprising:

computer-executable code adapted to detect a movement and/or deformation of the area of interest;

computer-executable code adapted to determine a new temperature distribution of at least the area of interest by registering the known temperature distribution to the new temperature distribution based at least in part on the detected movement and/or deformation;

computer-executable code adapted to acquire a third phase image of the MR imaging area subsequent to the detected movement and/or deformation;

computer-executable code adapted to acquire a fourth phase image of the MR imaging area subsequent to the acquisition of the third phase image; and

computer-executable code adapted to assign a second set of one or more absolute temperatures to the area of interest based at least in part on (i) the new temperature distribution and (ii) a difference between the fourth phase image and the third phase image.

27. A method of performing proton resonance frequency (PRF) based magnetic resonance (MR) temperature measurement, the method comprising the steps of:

obtaining a temperature distribution in an area of interest;

detecting a movement and/or deformation of the area of interest;

transforming the temperature distribution into a new temperature distribution through image registration based on the detected movement and/or deformation;

acquiring a first phase image of the area of interest subsequent to the detected movement and/or deformation;

acquiring a second phase image of the area of interest subsequent to the acquisition of the first phase image; and

assigning one or more absolute temperatures of the area of interest based at least in part on (i) the new temperature distribution and (ii) a difference between the second phase image and the first phase image.

28. The method of claim 27, wherein the step of obtaining the temperature distribution further comprises:

acquiring a baseline phase image of the area of interest;

acquiring another phase image of the area of interest subsequent to the acquisition of said baseline phase image; and

determining the temperature distribution based at least in part on differences between said another phase image and said baseline phase image.