Heat equation inversion framework for average SAR calculation from magnetic resonance thermal imaging

Area of Science:

• Bioelectromagnetics
• Medical Physics
• Electromagnetic Field Theory

Background:

• Radiofrequency (RF) energy deposition is typically measured by electric fields or temperature changes.
• Magnetic Resonance Imaging (MRI) can detect small temperature variations from RF exposure.
• Calculating Specific Absorption Rate (SAR) from temperature changes is complex due to heat diffusion and conduction over longer exposure durations.

Purpose of the Study:

• To develop and validate a novel method for accurate SAR calculation.
• To incorporate heat diffusion and conduction effects into SAR determination.
• To utilize high-resolution 3D MRI thermometry for improved SAR assessment.

Main Methods:

• Developed a method for SAR calculation via inversion of the heat equation.
• Included heat-diffusion and conduction effects in the heat equation inversion.
• Employed high-resolution 3D MRI temperature images and measured phantom thermal properties.

Main Results:

• Successfully demonstrated a method for accurate SAR calculation.
• The method accounts for heat diffusion and conduction effects.
• Accuracy was analyzed concerning operating frequency and heat equation inversion parameters.

Conclusions:

• The proposed method provides accurate SAR calculation, even with significant heat diffusion and conduction.
• This approach enhances the understanding of RF energy absorption in biological tissues.
• High-resolution MRI thermometry is a valuable tool for SAR assessment.