TI-CORRECTED PROTON RESONANCE FREQUENCY SHIFT THERMOMETRY

• US 20090275821A1
• Filed: 05/05/2008
• Published: 11/05/2009
• Est. Priority Date: 05/05/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Dumoulin, Charles Lucian, Mallozzi, Richard Philip
• Granted Patent: US 8,024,025 B2
• Time in Patent Office: Days
• US Class Current: 600/412
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH
• CPC Class Codes: G01R 33/4808 Multimodal MR, e.g. MR combined with positron emission tomography [PET], MR combined with ultrasound or MR combined with computed tomography [CT]
• CPC Class Codes: G01R 33/5602 by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse
• CPC Class Codes: G01R 33/565 Correction of image distortions, e.g. due to magnetic field inhomogeneities
• 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

An apparatus and method for correcting magnetic resonance temperature measurements is disclosed. In one aspect, the method identifies monitoring regions of interest outside a therapeutic region of interest. Next, a pulse sequence sensitive to changes in T1 and proton density is used to measure the temperature changes in these regions. Next, the PRFS is measured in these same regions. The PRFS in these regions will be caused both by the desired shift from temperature change, and the undesired shift from background magnetic field changes. Using the measured temperature changes from the T1-method, the component of the PRFS due to actual temperature changes is subtracted from the PRFS method, leaving only the component caused by the unwanted magnetic field changes. This analysis is performed separately for each region. At the end of this step, one has measured the change in background magnetic field within each region.

Claims

1. A method of correcting magnetic resonance temperature measurements, comprising the steps of:

determining a proton resonance frequency (PRF) reference phase map of a therapeutic region of interest and at least one PRF monitoring region of interest;

determining a spin-lattice relaxation time T1 reference map of at least one T1 monitoring region of interest;

repeatedly acquiring a phase map of the therapeutic region of interest and the at least one PRF monitoring region of interest;

determining an apparent change of temperature of the therapeutic region of interest and the at least one PRF monitoring region of interest based on the proton resonance frequency (PRF) reference phase map;

intermittently acquiring an updated T1 reference map of the at least one T1 monitoring region of interest;

determining an apparent change of temperature of the at least one T1 monitoring region of interest based on the updated T1 reference map;

computing a phase correction map from the apparent change of temperature of the at least one T1 monitoring region of interest based on the updated T1 reference map;

updating the PRF reference phase map by incorporating the computed phase correction map; and

applying the updated PRF reference phase map to correct the magnetic resonance temperature measurement of the apparent change in temperature of the therapeutic region of interest.

2. The method of claim 1, wherein the at least one PRF monitoring region of interest is the same as the at least one T1 monitoring region of interest.

3. A method of correcting magnetic resonance temperature measurements, comprising the steps of:

determining a proton resonance frequency (PRF) reference phase map of a therapeutic region of interest and at least one PRF monitoring region of interest;

determining a spin-lattice relaxation time T1 reference map of at least one T1 monitoring region of interest;

repeatedly acquiring a T1-based temperature map of the therapeutic region of interest and the at least one T1 monitoring region of interest;

determining an apparent change of temperature of the therapeutic region of interest and the at least one T1 monitoring region of interest based on the spin-lattice relaxation time T1 reference map;

intermittently acquiring an updated PRF reference map of the at least one PRF monitoring region of interest;

determining an apparent change of temperature of the at least one PRF monitoring region of interest based on the updated PRF reference map;

computing a T1 correction map from the apparent change of temperature of the at least one PRF monitoring region of interest based on the updated PRF reference map;

updating the T1-based temperature map by incorporating the computed T1 correction map; and

applying the updated T1-based temperature map to correct the magnetic resonance temperature measurement of the apparent change in temperature of the therapeutic region of interest.

4. The method of claim 3, wherein the at least one T1 monitoring region of interest is the same as the at least one PRF monitoring region of interest.