title: Investigation of maximum local specific absorption rate in 7 T magnetic resonance with respect to load size by use of electromagnetic simulations.
abstract: Local specific absorption rate (SAR) evaluation in ultra high field (UHF) magnetic resonance (MR) systems is a major concern. In fact, at UHF, radiofrequency (RF) field inhomogeneity generates hot-spots that could cause localized tissue heating. Unfortunately, local SAR measurements are not available in present MR systems; thus, electromagnetic simulations must be performed for RF fields and SAR analysis. In this study, we used three-dimensional full-wave numerical electromagnetic simulations to investigate the dependence of local SAR at 7.0 T with respect to subject size in two different scenarios: surface coil loaded by adult and child calves and quadrature volume coil loaded by adult and child heads. In the surface coil scenario, maximum local SAR decreased with decreasing load size, provided that the RF magnetic fields for the different load sizes were scaled to achieve the same slice average value. On the contrary, in the volume coil scenario, maximum local SAR was up to 15% higher in children than in adults.
authors: Imago7 Foundation, Pisa, Italy.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors: Gianluigi
authors: G
authors: Tiberi
authors: Department of Information Engineering, University of Pisa, Pisa, Italy.|National Institute of Nuclear Physics (INFN), Pisa, Italy.
authors: Nunzia
authors: N
authors: Fontana
authors: Imago7 Foundation, Pisa, Italy.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors: Mauro
authors: M
authors: Costagli
authors: National Institute of Nuclear Physics (INFN), Pisa, Italy.|Physics Department, University of Pisa, Pisa, Italy.
authors: Riccardo
authors: R
authors: Stara
authors: Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors: Laura
authors: L
authors: Biagi
authors: General Electric ASL (EMEA), Pisa, Italy.
authors: Mark Roger
authors: MR
authors: Symms
authors: Department of Information Engineering, University of Pisa, Pisa, Italy.|National Institute of Nuclear Physics (INFN), Pisa, Italy.
authors: Agostino
authors: A
authors: Monorchio
authors: National Institute of Nuclear Physics (INFN), Pisa, Italy.
authors: Alessandra
authors: A
authors: Retico
authors: Department of Translational Research and New Surgical and Medical Technologies, University of Pisa, Pisa, Italy.
authors: Mirco
authors: M
authors: Cosottini
authors: Imago7 Foundation, Pisa, Italy.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors: Michela
authors: M
authors: Tosetti
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D004574:Electromagnetic Fields; D005260:Female; D006257:Head; D006801:Humans; D007866:Leg; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D008297:Male; D008954:Models, Biological
keywords: RF full-wave simulations; RF safety; SAR; anatomic human models; ultra high field Magnetic Resonance