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Specific absorption rate (SAR) simulations for low-field (< 0.1 T) MRI systems
Javad Parsa1,2, Andrew Webb3
1C.J. Gorter MRI Centre, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
Magma (New York, N.Y.)
|March 18, 2023
Summary
Simulations show radiofrequency (RF) coil performance for point-of-care neuroimaging. Specific absorption rate (SAR) efficiency is higher at lower fields but manageable, especially with longer RF pulses.
Area of Science:
- Magnetic Resonance Imaging
- Biomedical Engineering
- Electromagnetics
Background:
- Low-field Magnetic Resonance Imaging (MRI) systems are emerging for point-of-care (POC) neuroimaging.
- Understanding radiofrequency (RF) coil performance and specific absorption rate (SAR) is crucial for safe operation, especially with advanced pulse sequences.
Approach:
- Electromagnetic simulations were conducted for RF coil geometries at field strengths of 0.05–0.1 T.
- Transmit fields, efficiency, and SAR efficiency were analyzed, including the impact of shielding.
- SAR calculations were performed for various RF pulse lengths in turbo-spin echo (TSE) sequences.
Key Points:
- Simulated RF coil parameters closely matched experimental data.
- SAR efficiency was significantly higher at lower frequencies compared to clinical strengths.
- A tight-fitting coil concentrated SAR in non-critical areas like the nose and skull.
Conclusions:
- This study provides a comprehensive analysis of RF coil and SAR efficiencies for POC neuroimaging.
- While conventional sequences pose no SAR issue, RF-intensive sequences require careful SAR assessment.
- Short RF pulses necessitate thorough SAR calculations for safe POC MRI operation.
