title: Statistical simulation of SAR variability with geometric and tissue property changes by using the unscented transform.
abstract: OBJECTIVE
  The local specific absorption rate (SAR) is critical to the safety of radio frequency transmit coils. A statistical simulation approach is introduced to address the local SAR variability related to tissue property and geometric variations.
  
  
  METHODS
  The local SAR is modeled as the output of a nonlinear transformation with factors that may affect its value being treated as random input variables. Instead of using the Monte Carlo method with a large number of sample points, the unscented transform is applied with a small set of deterministic sample points. A sensitivity analysis is further performed to determine the significance of each input variable. Electromagnetic simulations are carried out by the finite-difference time-domain method implemented on graphic processing unit.
  
  
  RESULTS
  The local SAR variability of a 7 Tesla square loop coil for spine imaging and a 16-element brain imaging array as the result of tissue property and geometric changes were examined respectively. SAR limits were determined based on their means and standard deviations.
  
  
  CONCLUSIONS
  The proposed approach is efficient and general for the study of local SAR variability.
authors.affiliation: Department of Electrical and Computer Engineering, Auburn University, Alabama, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Department of Mathematics and Statistics, Auburn University, Auburn, Alabama, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Zeng
authors.affiliation: Department of Electrical and Computer Engineering, Auburn University, Alabama, USA.
authors.forename: Shumin
authors.initials: S
authors.lastname: Wang
mesh_terms: D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods
keywords: specific absorption rate; statistical study; validation