Direct SAR mapping by thermoacoustic imaging: A feasibility study.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Physics

Background:

• Magnetic Resonance Imaging (MRI) utilizes radiofrequency (RF) pulses, which deposit energy in biological tissues.
• Accurate measurement of specific absorption rate (SAR) is crucial for ensuring patient safety during MRI procedures.
• Current SAR estimation methods often rely on simulations, lacking direct tissue measurement capabilities.

Purpose of the Study:

• To develop and validate a novel method for direct, in vivo measurement of SAR distribution in tissues.
• To establish a thermoacoustic-based approach for real-time SAR monitoring during MRI.
• To provide a tool for enhanced safety assessment in MRI applications.

Main Methods:

• Utilized short radiofrequency (RF) pulse excitation to induce thermoacoustic signals in tissue.
• Employed an array of ultrasound transducers to detect and measure the thermoacoustic waves.
• Developed a simulation framework and performed in vitro experiments to reconstruct 3D SAR distributions.

Main Results:

• Simulations demonstrated high accuracy in reconstructed SAR distributions, with errors below 8.4% in major planes.
• The method showed feasibility for direct experimental mapping of SAR distributions in vivo.
• In vitro experiments confirmed good agreement between the thermoacoustic method and theoretical predictions (r² = 0.52).

Conclusions:

• A novel thermoacoustic method for in vivo mapping of local SAR patterns in MRI has been successfully proposed.
• The method was validated through both simulation and phantom experiments, demonstrating its potential.
• This technique offers a promising approach for direct SAR measurement and safety monitoring in MRI.