Individualized and accurate SAR characterization method based on equivalent circuit model for MRI system

Area of Science:

• Medical Imaging Physics
• Biomedical Engineering
• Electromagnetics

Background:

• Radiofrequency (RF) heating during Magnetic Resonance Imaging (MRI) poses a safety risk to patients.
• Accurate characterization of whole-body specific absorption rate (SAR) is crucial for patient safety.
• Existing methods, like the standard pulse energy method, can be complex to implement.

Purpose of the Study:

• To develop an accurate and patient-specific whole-body SAR characterization method for MRI.
• To propose an equivalent circuit model approach that simplifies SAR assessment.
• To offer a method easily implementable in clinical MRI scanners.

Main Methods:

• An equivalent parallel circuit model was used to represent power distribution between the transmit coil and the subject.
• Coil and subject resistances were determined using frequency response functions of the reflection coefficient.
• Subject absorbed power was measured in phantoms and volunteers and compared to the standard flux loop method.

Main Results:

• The equivalent circuit model accurately fitted transmit coil parameters under various conditions.
• Whole-body SAR was measured in volunteers, showing good agreement with the flux loop method.
• The proposed method achieved high accuracy with low RMS (3.77%) and maximum (9.47%) errors.

Conclusions:

• The equivalent circuit model provides an individualized and accurate method for SAR characterization.
• This approach simplifies SAR assessment for both clinical applications and research.
• The method offers a practical solution with moderate implementation complexity for MRI safety.