TECHNIQUES FOR CORRECTING MEASUREMENT ARTIFACTS IN MAGNETIC RESONANCE THERMOMETRY

• US 20110109309A1
• Filed: 11/10/2009
• Published: 05/12/2011
• Est. Priority Date: 11/10/2009
• Status: Active Grant

• Current Assignee: InSightec Ltd.
• Original Assignee: InSightec Ltd.
• Inventors: Hananel, Arik, Halevy, Gilad, Assif, Benny, Freundlich, David, Levy, Yoav, Ziso, Hadas
• Granted Patent: US 8,368,401 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH
• CPC Class Codes: G01R 33/4814 MR combined with ultrasound
• 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 33/56536 due to magnetic susceptibility variations

Abstract

Techniques for correcting measurement artifacts in MR thermometry predict or anticipate movements of objects in or near an MR imaging region that may potentially affect a phase background and then acquire a library of reference phase images corresponding to different phase backgrounds that result from the predicted movements. For each phase image subsequently acquired, one reference phase image is selected from the library of reference phase images to serve as the baseline image for temperature measurement purposes. To avoid measurement artifacts that arise from phase wrapping, the phase shift associated with each phase image is calculated incrementally, that is, by accumulating phase increments from each pair of consecutively scanned phase images.

Claims

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

acquiring a plurality of reference phase images of an MR imaging region, each of the reference images corresponding to a phase background resulting from a different arrangement of one or more devices in or near the MR imaging region;

acquiring a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images;

selecting, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image;

calculating a first phase shift based at least in part on a difference between the first phase image and the first reference phase image;

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

selecting, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image;

calculating a second phase shift by summing (i) the first phase shift and (ii) an incremental phase shift of the second phase image as compared to the first phase image; and

determining at least one temperature change based on at least one of the first phase shift and the second phase shift.

2. The method of claim 1, wherein the plurality of reference phase images correspond to predicted positionings of at least one treatment device.

3. The method of claim 2, wherein the treatment device comprises an MR guided focused ultrasound (MRgFUS) transducer.

4. The method of claim 1, further comprising:

generating a temperature map of the MR imaging region based at least in part on the first phase image and on the differences.

5. The method of claim 1, further comprising:

calculating a movement compensation map based on differences between the first reference phase image and the second reference phase image.

6. The method of claim 1, wherein the incremental phase shift is calculated at least by subtracting (i) a first difference between the first phase image and the first reference phase image from (ii) a second difference between the second phase image and the second reference phase image.

7. The method of claim 1, further comprising:

comparing the first phase image with the plurality of reference phase images to find matching physical features.

8. The method of claim 1, further comprising:

acquiring a third phase image of the MR imaging region subsequent to the acquisition of the second phase image;

selecting, from the plurality of reference phase images, a third reference phase image most closely corresponding to the second phase image; and

calculating a third phase shift by summing (i) the second phase shift and (ii) an incremental phase shift of the third phase image as compared to the second phase image.

9. 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 plurality of reference phase images of an MR imaging region, each of the reference images corresponding to a phase background resulting from a different arrangement of one or more devices in or near the MR imaging region,

acquire a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images, and

acquire a second phase image of the MR imaging region 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;

select, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image,

calculate a first phase shift based at least in part on a difference between the first phase image and the first reference phase image,

select, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image,

calculate a second phase shift based at least in part on a difference between the second phase image and the second reference phase image, and

determine at least one temperature change based on at least one of the first phase shift and the second phase shift.

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

computer-executable code for causing acquisition of a plurality of reference phase images of an MR imaging region, each of the reference images corresponding to a phase background resulting from a different arrangement of one or more devices in or near the MR imaging region;

computer-executable code for causing acquisition of a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images;

computer-executable code for causing selection, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image;

computer-executable code for causing calculation of a first phase shift based at least in part on a difference between the first phase image and the first reference phase image;

computer-executable code for causing acquisition of a second phase image of the MR imaging region subsequent to the acquisition of the first phase image;

computer-executable code for causing selection, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image;

computer-executable code for causing calculation of a second phase shift by summing (i) the first phase shift and (ii) an incremental phase shift of the second phase image as compared to the first phase image; and

computer-executable code for causing determination of at least one temperature change based on at least one of the first phase shift and the second phase shift.

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

acquiring a plurality of reference phase images of an MR imaging region, each of the reference phase images corresponding to a phase background resulting from one or more predicted anatomical movements of at least a part of a patient'"'"'s body;

acquiring a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images;

selecting, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image;

calculating a first phase shift based at least in part on a difference between the first phase image and the first reference phase image;

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

selecting, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image;

calculating a second phase shift by summing (i) the first phase shift and (ii) an incremental phase shift of the second phase image as compared to the first phase image; and

determining at least one temperature change based on at least one of the first phase shift and the second phase shift.

12. The method of claim 11, further comprising:

predicting a trajectory for the one or more predicted anatomical movements.

13. The method of claim 12, wherein the predicted trajectory is associated with the patient'"'"'s respiratory cycles.

14. The method of claim 11, further comprising:

acquiring a third phase image of the MR imaging region subsequent to the acquisition of the second phase image;

selecting, from the plurality of reference phase images, a third reference phase image most closely corresponding to the second phase image; and

calculating a third phase shift by summing (i) the second phase shift and (ii) an incremental phase shift of the third phase image as compared to the second phase image.

15. 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 plurality of reference phase images of an MR imaging region, each of the reference images corresponding to a phase background resulting from one or more predicted anatomical movements of at least a part of a patient'"'"'s body,

acquire a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images, and

acquire a second phase image of the MR imaging region 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;

select, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image,

calculate a first phase shift based at least in part on a difference between the first phase image and the first reference phase image,

select, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image,

calculate a second phase shift by summing (i) the first phase shift and (ii) an incremental phase shift of the second phase image as compared to the first phase image, and

determine at least one temperature change based on at least one of the first phase shift and the second phase shift.

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

computer-executable code for causing acquisition of a plurality of reference phase images of an MR imaging region, each of the reference images corresponding to a phase background resulting from one or more predicted anatomical movements of at least a part of a patient'"'"'s body;

computer-executable code for causing acquisition of a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images;

computer-executable code for causing selection, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image;

computer-executable code for causing calculation of a first phase shift based at least in part on a difference between the first phase image and the first reference phase image;

computer-executable code for causing acquisition of a second phase image of the MR imaging region subsequent to the acquisition of the first phase image;

computer-executable code for causing selection, from the plurality of reference phase images, a second reference phase image most closely corresponding to the second phase image;

computer-executable code for causing a calculation of a second phase shift by summing (i) the first phase shift and (ii) an incremental phase shift of the second phase image as compared to the first phase image; and

computer-executable code for causing determination of at least one temperature change based on at least one of the first phase shift and the second phase shift.

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

acquiring a plurality of reference phase images of an MR imaging region associated with a patient, each of the reference images corresponding to a phase background resulting from a different arrangement of one or more devices in or near the MR imaging region in combination with one or more predicted movements of the patient;

acquiring a first phase image of the MR imaging region subsequent to the acquisition of the plurality of reference phase images;

selecting, from the plurality of reference phase images, a first reference phase image most closely corresponding to the first phase image; and

determining at least one temperature change based at least in part on a difference between the first phase image and the first reference phase image.