From Complex B1 Mapping to Local SAR Estimation for Human Brain MR Imaging Using Multi-Channel Transceiver Coil at 7T

Xiaotong Zhang, Sebastian Schmitter, Pierre Francois Van De Moortele, Jiaen Liu, Bin He

Research output: Contribution to journalArticle

41 Scopus citations

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 languageEnglish (US)
Article number6477144
Pages (from-to)1058-1067
Number of pages10
JournalIEEE Transactions on Medical Imaging
Volume32
Issue number6
DOIs
StatePublished - 2013

Keywords

  • B-mapping
  • Electrical properties tomography (EPT)
  • magnetic resonance imaging (MRI)
  • parallel transmission
  • specific absorption rate (SAR)
  • ultra-high-field (UHF)

Fingerprint Dive into the research topics of 'From Complex B<sub>1</sub> Mapping to Local SAR Estimation for Human Brain MR Imaging Using Multi-Channel Transceiver Coil at 7T'. Together they form a unique fingerprint.

  • Cite this