title: SAR prediction in adults and children by combining measured B1+ maps and simulations at 7.0 Tesla.
abstract: To predict local and global specific absorption rate (SAR) in individual subjects.
  
  
  
  SAR was simulated for a head volume coil for two imaging sequences: axial T1-weighted "zero" time-of-echo (ZTE) sequence, sagittal T2-weighted fluid attenuated inversion recovery (FLAIR). Two head models (one adult, one child) were simulated inside the coil. For 19 adults and 27 children, measured B1 (+) maps were acquired, and global (head) SAR estimated by the system was recorded. We performed t-test between the B1 (+) in models and human subjects. The B1 (+) maps of individual subjects were used to scale the SAR simulated on the models, to predict local and global (head) SAR. A phantom experiment was performed to validate SAR prediction, using a fiberoptic temperature probe to measure the temperature rise due to ZTE scanning.
  
  
  
  The normalized B1 (+) standard deviation in subjects was not significantly different from that of the models (P > 0.68 and P > 0.54). The rise in temperature generated in the phantom by ZTE was 0.3°C; from the heat equation it followed that the temperature-based measured SAR was 2.74 W/kg, while the predicted value was 3.1 W/kg.
  
  
  
  For ZTE and FLAIR, limits on maximum local and global SAR were met in all subjects, both adults and children. To enhance safety in adults and children with 7.0 Tesla MR systems, we suggest the possibility of using SAR prediction. J. MAGN. RESON. IMAGING 2016;44:1048-1055.
authors.affiliation: Imago7 Foundation, Pisa, Italy. g.tiberi@iet.unipi.it.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy. g.tiberi@iet.unipi.it.
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Tiberi
authors.affiliation: Imago7 Foundation, Pisa, Italy.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Costagli
authors.affiliation: Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Biagi
authors.affiliation: Meyer Children's Hospital, Firenze, Italy.
authors.forename: Alessio De
authors.initials: AD
authors.lastname: Ciantis
authors.affiliation: Department of Information Engineering, University of Pisa, Pisa, Italy.|National Institute of Nuclear Physics (INFN), Pisa, Italy.
authors.forename: Nunzia
authors.initials: N
authors.lastname: Fontana
authors.affiliation: National Institute of Nuclear Physics (INFN), Pisa, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Stara
authors.affiliation: General Electric ASL (EMEA), Pisa, Italy.
authors.forename: Mark Roger
authors.initials: MR
authors.lastname: Symms
authors.affiliation: Department of Translational Research and New Surgical and Medical Technologies, University of Pisa, Pisa, Italy.
authors.forename: Mirco
authors.initials: M
authors.lastname: Cosottini
authors.affiliation: Meyer Children's Hospital, Firenze, Italy.
authors.forename: Renzo
authors.initials: R
authors.lastname: Guerrini
authors.affiliation: Imago7 Foundation, Pisa, Italy.|Laboratory of Medical Physics and Biotechnologies for Magnetic Resonance, IRCCS Stella Maris Foundation, Pisa, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Tosetti
mesh_terms: D065638:Absorption, Radiation / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D002648:Child; D003198:Computer Simulation; D005260:Female; D006801:Humans; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000032:analysis* / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods; D011874:Radiometry / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: B1 mapping; RF full-wave simulations; SAR; safety; ultrahigh field magnetic resonance