Compensating for magnetic field inhomogeneity in multigradient-echo-based MR thermometry

Area of Science:

• Medical Imaging
• Biophysics
• Radiofrequency Engineering

Background:

• Magnetic Resonance Thermometry (MRT) is a noninvasive temperature measurement technique.
• Accurate absolute temperature measurement is crucial for radio frequency (RF) safety monitoring.
• Multigradient-echo (mGE) MRT sequences are susceptible to background gradient errors.

Purpose of the Study:

• To present a novel method for minimizing background gradient effects in mGE MRT.
• To improve the accuracy of absolute temperature measurements using MRI.
• To enhance the utility of MRT for RF safety assessment.

Main Methods:

• Utilized a 3T MRI system with ethylene glycol phantoms.
• Varied background gradients and applied uniform heating to phantoms.
• Implemented two compensation approaches: B0 mapping and opposing readout directions.
• Validated temperature measurements against independent optical probes.

Main Results:

• Experimental errors in temperature measurements strongly correlated with background gradients.
• Applied corrections significantly reduced temperature distribution standard deviation (0.21°C vs. 0.45°C).
• Corrected temperature maps showed excellent correlation with optical probe measurements.

Conclusions:

• The developed correction method enhances the precision of RF heating measurements in phantoms.
• This advancement positions mGE MRT as a valuable tool for RF safety assessment.
• Improved accuracy facilitates reliable noninvasive temperature monitoring.