EPI proton resonant frequency temperature mapping at 0.5T in the brain: Comparison to single-echo gradient recalled...

Area of Science:

• Medical Imaging
• Biophysics

Background:

• Accurate temperature monitoring is crucial for various medical applications, including thermal therapies and understanding physiological processes.
• Mid-field MRI systems present unique challenges for thermometry due to lower signal-to-noise ratios and longer echo times.

Purpose of the Study:

• To evaluate the efficacy of single-echo gradient recalled echo (SE-GRE) and echo planar imaging (EPI) techniques for generating temperature maps on a mid-field (0.5T) head-only MRI scanner.
• To compare the performance of these thermometry methods in both phantom (tissue-mimicking gel) and in vivo (brain) settings.

Main Methods:

• Three 2D MRI protocols were investigated: SE-GRE, single-shot EPI, and averaged single-shot EPI.
• EPI parameters were optimized for lower field strengths, and phantom experiments assessed temperature tracking during cooling against an optical fiber thermometer.
• In vivo studies on a 0.5T head-only scanner generated temperature stability maps to evaluate protocol precision.

Main Results:

• EPI protocols demonstrated enhanced temperature precision in a phantom and an 18% improvement in in vivo temperature measurement precision.
• Fast (<2s) update rate EPI thermometry achieved precision comparable to slower SE-GRE protocols.
• The study confirmed improved temperature tracking precision with EPI methods.

Conclusions:

• Echo planar imaging (EPI) methods provide superior temperature tracking precision and/or faster update rates for brain thermometry at mid-field MRI strengths.
• While SE-GRE PRF thermometry performs well, EPI offers advantages for dynamic temperature monitoring in neurological applications.