期刊
MAGNETIC RESONANCE IN MEDICINE
卷 84, 期 6, 页码 3485-3493出版社
WILEY
DOI: 10.1002/mrm.28382
关键词
10; 5 Tesla; bumped transmitter; MRI; radiofrequency safety; ultra-high field
资金
- National Institutes of Health [U01 EB025144]
- National Institute of Biomedical Imaging and Bioengineering [P41 EB027061]
Purpose In this study, we investigate a strategy to reduce the local specific absorption rate (SAR) while keepingB1+constant inside the region of interest (ROI) at the ultra-high field (B-0 >= 7T) MRI. Methods Locally raising the resonance structure under the discontinuity (i.e., creating a bump) increases the distance between the accumulated charges and the tissue. As a result, it reduces the electric field and local SAR generated by these charges inside the tissue. TheB1+at a point that is sufficiently far from the coil, however, is not affected by this modification. In this study, three different resonant elements (i.e., loop coil, snake antenna, and fractionated dipole [FD]) are investigated. For experimental validation, a bumped FD is further investigated at 10.5T. After the validation, the transmit performances of eight-channel arrays of each element are compared through electromagnetic (EM) simulations. Results Introducing a bump reduced the peak 10g-averaged SAR by 21, 26, 23% for the loop and snake antenna at 7T, and FD at 10.5T, respectively. In addition, eight-channel bumped FD array at 10.5T had a 27% lower peak 10g-averaged SAR in a realistic human body simulation (i.e., prostate imaging) compared to an eight-channel FD array. Conclusion In this study, we investigated a simple design strategy based on adding bumps to a resonant element to reduce the local SAR while maintainingB1+inside an ROI. As an example, we modified an FD and performed EM simulations and phantom experiments with a 10.5T scanner. Results show that the peak 10g-averaged SAR can be reduced more than 25%.
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