Measuring local RF heating in MRI: Simulating perfusion in a perfusionless phantom.

Area of Science:

• Biomedical Engineering
• Medical Physics
• Radiology

Background:

• In vivo radiofrequency (RF) heating measurements during MRI are challenging due to reproducibility issues.
• Existing phantom methods have limitations, such as convection in fluid phantoms and lack of perfusion in gel phantoms.
• Accurate temperature rise prediction is crucial for safe MRI examinations, especially for patients with metallic implants.

Purpose of the Study:

• To propose a simple and reliable technique for predicting local RF heating in vivo using a gel phantom experiment.
• To overcome the limitations of current methods for measuring RF-induced temperature rise.
• To enable better control of scanner power for enhanced patient safety.

Main Methods:

• A gel phantom experiment was designed to measure local temperature rise.
• The measurement was taken at a specific timepoint where the phantom temperature equals the steady-state temperature of a perfused body.
• This timepoint accounts for the perfusion time constant, bridging the gap between phantom and in vivo conditions.

Main Results:

• The proposed method was validated through phantom and in vivo experiments.
• The technique demonstrated an average underestimation error of 30.8%.
• This error is comparable to the inherent variability observed in in vivo experiments (45%).

Conclusions:

• The developed method provides a reliable prediction of in vivo temperature rise.
• This prediction allows for precise control of MRI scanner power output.
• Enables safer MRI examinations for patients, particularly those with implanted medical devices.