TEMPERATURE MEASUREMENT NEAR AN ICE BALL USING A PROTON RESONANCE FREQUENCY METHOD AND RECALCULATION OF SUSCEPTIBILITY ARTIFACTS

• US 20120116208A1
• Filed: 11/10/2010
• Published: 05/10/2012
• Est. Priority Date: 11/10/2010
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Gross, Patrick, Roland, Joerg, Salomir, Rares, Kickhefel, Antje
• Granted Patent: US 8,706,190 B2
• Time in Patent Office: Days
• US Class Current: 600/411
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH
• CPC Class Codes: G01R 33/56536 due to magnetic susceptibility variations

Abstract

In a method or system for magnetic resonance imaging based temperature monitoring for real-time feedback to a physician for a cryoablation therapy of a lesion which creates an ice ball of the lesion to induce cell death, the magnetic resonance imaging system, using proton resonance frequency imaging, obtains a real-time temperature image of the ice ball of the lesion undergoing the cryoablation therapy and the adjacent surrounding tissue. By use of an algorithm, correcting temperature errors at a border of the ice ball are corrected in the real-time image, the temperature error correction correcting susceptibility contrast errors caused by a distortion of the local magnetic field at the border of the ice ball.

Claims

1. A method for magnetic resonance imaging based temperature monitoring for real-time feedback to a physician for a cryoablation therapy of a lesion which creates an ice ball of the lesion to induce cell death, comprising the steps of:

with a magnetic resonance imaging system, using proton resonance frequency (PRF) imaging, obtaining a real-time gradient echo sequence (GRE) phase temperature image of the ice ball of the lesion undergoing the cryoablation therapy and the surrounding tissue adjacent the lesion;

by use of an algorithm correcting temperature errors at a border of the ice ball in the real-time image, said temperature error correction correcting for susceptibility contrast errors caused by a distortion of a local magnetic field at the border of the ice ball caused by susceptibility contrast resulting from differences in susceptibility existing between frozen tissue and non-frozen tissue, said algorithm accounting for the susceptibility differences between the frozen and the non-frozen tissue by simulating susceptibility artifacts.

2. The method of claim 1 wherein to determine said susceptibility differences between the frozen and the non-frozen tissue, searching for a minimum of a cost function defined as a standard deviation at a corrected temperature series, it being assumed that the border of the ice ball has a watery physical state.

3. The method of claim 1 wherein said algorithm comprises the following:

4. The method of claim 1 wherein said algorithm comprises a convolution of a k-space and a perturbation field defined by the susceptibility differences.

5. The method of claim 1 wherein said algorithm is designed assuming that the border of the ice ball has a water physical state transition temperature and hence a uniform value so that the algorithm can then correct phase data for the gradient echo sequence for said susceptibility artifacts.

6. The method of claim 1 wherein said cryoablation therapy comprises non-invasive monitoring of near zero temperatures at tissues adjacent to the lesion.

7. The method of claim 1 wherein said lesion comprises a tumor.

8. The method of claim 1 wherein said temperature errors induced by said susceptibility contrast errors are proportionate to a volume of the ice ball.

9. The method of claim 1 wherein said ice ball creates a perturbation of the local magnetic field during said magnetic resonance imaging.

10. The method of claim 1 wherein said algorithm comprises a convolution in k-space that has a susceptibility contrast matrix.

11. A method for magnetic resonance imaging based temperature monitoring for real-time feedback to a physician for a cryoablation therapy of a lesion which creates an ice ball of the lesion to induce cell death, comprising the steps of:

with a magnetic resonance imaging system, using proton resonance frequency (PRF) imaging, obtaining a real-time temperature image of the ice ball of the lesion undergoing the cryoablation therapy and the adjacent surrounding tissue;

by use of an algorithm correcting temperature errors at a border of the ice ball in the real-time image, said temperature error correction correcting for susceptibility contrast errors caused by a distortion of a local magnetic field at the border of the ice ball.

12. A system for magnetic resonance imaging based temperature monitoring for real-time feedback to a physician for a cyroablation therapy of a lesion which creates an ice ball of the lesion to induce cell death, comprising:

a magnetic resonance imaging system using proton resonance frequency imaging and which obtains a real-time temperature image of the ice ball of the lesion undergoing the cryoablation therapy and adjacent surrounding tissue;

a magnetic resonance imaging system which, by use of an algorithm, corrects temperature errors at a border of the ice ball in the real-time image, said temperature error correction correcting for susceptibility contrast errors caused by a distortion of a local magnetic field at a border of the ice ball caused by susceptibility contrast resulting from differences in susceptibility existing between frozen tissue and non-frozen tissue, said algorithm accounting for the susceptibility differences between the frozen and the non-frozen tissue by simulating susceptibility artifacts.