A robust phase-retrieval method with stable convergence and back-propagation properties for quick experimental whole body specific absorption rate (SAR) assessments is presented. A combination of a fast and coarse method and a more accurate gradient-based method is used to optimize the overall performance. To prevent the solution being trapped in a local minimum, several initial phase distributions are used. An accurate measurement procedure has been developed which reduces measurement time by roughly a factor of 2.5-4 at common mobile communication frequencies compared with a volume scan based procedure.
Jonas Fridén, H. Isaksson, Björn Hansson, Björn Thors