Real time in vivo measurement of temperature changes with NMR imaging

• US 5,711,300 A
• Filed: 08/16/1995
• Issued: 01/27/1998
• Est. Priority Date: 08/16/1995
• Status: Expired due to Term

• Current Assignee: InSightec Ltd.
• Original Assignee: General Electric Company
• Inventors: Watkins, Ronald Dean, Washburn, Sheila Srinivasan, Hardy, Christopher Judson, Cline, Harvey Ellis, Schneider, Erika
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): FIELDS, DERRICK LAMAR
• Application Number:
  US08/515,876
• Time in Patent Office: 895 Days
• Field of Search: 128/653.2, 128/653.4, 128/653.5
• US Class Current: 600/412
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH

Abstract

NMR images indicative of thermal changes in tissues undergoing therapy are produced using a gradient-recalled double-echo pulse sequence. A reference phase image is produced using a short echo time (TE₁) and a measurement phase image is produced with a longer echo time (TE₂). Temperature maps are produced during therapy using the phase difference information at corresponding pixels of the two phase images.

Claims

1. A method for producing an image indicative of temperature changes in a subject positioned in an NMR system, the steps comprising a) performing a scan by executing an NMR pulse sequence having an echo time (TE₁) to acquire reference NMR data from tissues in the subject;

b) reconstructing a reference phase image from the acquired NMR data

c) performing a scan by executing an NMR pulse sequence having an echo time (TE₂) to acquire measurement NMR data from said tissues;

d) reconstructing a measurement phase image from the acquired measurement NMR data; and

e) producing a temperature map based on the difference between the measurement phase image and the reference phase image.

2. The method as recited in claim 1 in which the echo times TE₁ and TE₂ are chosen to correspond with moments when the NMR signals produced by fat spins and water spins are in-phase and out-of-phase respectively.

3. The method as recited in claim 1 in which the echo times TE₁ and TE₂ are chosen to correspond with moments when the NMR signals produced by fat spins and water spins are out-of-phase and in-phase respectively.

4. The method as recited in claim 1 in which the steps c), d) and e) are repeated a plurality of times to produce a corresponding plurality of additional temperature maps.

5. The method as recited in claim 1 in which the NMR pulse sequences are gradient echo pulse sequences.

6. The method as recited in claim 1 in which the temperature map is produced by calculating the complex difference between corresponding values in the measurement phase image and the reference phase image.

7. A method for producing an image indicative of temperature changes in a subject positioned in an NMR system, the steps comprising:

a) performing a scan by executing an NMR pulse sequence that produces a first NMR echo signal at a first echo time (TE₁) and a second NMR echo signal at a second echo time (TE₂) from tissues in the subject;

b) separately acquiring NMR data produced by the first and second NMR echo signals during the scan to form respective reference and measurement data sets;

c) reconstructing a reference phase image from the reference data set;

d) reconstructing a measurement phase image from the measurement data set;

e) producing a temperature map based on the difference between the measurement phase image and the reference phase image.

8. The method as recited in claim 7 in which the echo times TE₁ and TE₂ are chosen to correspond with moments when the NMR signals produced by fat spins and water spins are in-phase and out-of-phase respectively.

9. The method as recited in claim 7 in which the echo times TE₁ and TE₂ are chosen to correspond with moments when the NMR signals produced by fat spins and water spins are out-of-phase and in-phase respectively.

10. The method as recited in claim 7 in which the NMR pulse sequence is a gradient echo pulse sequence.

11. The method as recited in claim 7 in which the temperature map is produced by calculating the complex difference between corresponding values in the measurement phase image and the reference phase image.

12. The method in claim 7 in which variable bandwidth readouts are used.