Abstract
Elevated specific absorption rate (SAR) associated with increased main magnetic field strength remains a major safety concern in ultra-high-field (UHF) magnetic resonance imaging (MRI) applications. The calculation of local SAR requires the knowledge of the electric field induced by radio-frequency (RF) excitation, and the local electrical properties of tissues. Since electric field distribution cannot be directly mapped in conventional MR measurements, SAR estimation is usually performed using numerical model-based electromagnetic simulations which, however, are highly time consuming and cannot account for the specific anatomy and tissue properties of the subject undergoing a scan. In the present study, starting from the measurable RF magnetic fields B1 in MRI, we conducted a series of mathematical deduction to estimate the local, voxel-wise and subject-specific SAR for each single coil element using a multi-channel transceiver array coil. We first evaluated the feasibility of this approach in numerical simulations including two different human head models. We further conducted experimental study in a physical phantom and in two human subjects at 7T using a multi-channel transceiver head coil. Accuracy of the results is discussed in the context of predicting local SAR in the human brain at UHF MRI using multi-channel RF transmission.
Original language | English (US) |
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Article number | 6477144 |
Pages (from-to) | 1058-1067 |
Number of pages | 10 |
Journal | IEEE Transactions on Medical Imaging |
Volume | 32 |
Issue number | 6 |
DOIs | |
State | Published - 2013 |
Externally published | Yes |
Keywords
- B-mapping
- Electrical properties tomography (EPT)
- magnetic resonance imaging (MRI)
- parallel transmission
- specific absorption rate (SAR)
- ultra-high-field (UHF)
ASJC Scopus subject areas
- Software
- Radiological and Ultrasound Technology
- Computer Science Applications
- Electrical and Electronic Engineering