title: System and SAR characterization in parallel RF transmission.
abstract: The markedly increased degrees of freedom introduced by parallel radiofrequency transmission presents both opportunities and challenges for specific absorption rate (SAR) management. On one hand they enable E-field tailoring and SAR reduction while facilitating excitation profile control. On other hand they increase the complexity of SAR behavior and the risk of inadvertently exacerbating SAR by improper design or playout of radiofrequency pulses. The substantial subject-dependency of SAR in high field magnetic resonance can be a compounding factor. Building upon a linear system concept and a calibration scheme involving a finite number of in situ measurements, this work establishes a clinically applicable method for characterizing global SAR behavior as well as channel-by-channel power transmission. The method offers a unique capability of predicting, for any excitation, the SAR and power consequences that are specific to the subject to be scanned and the MRI hardware. The method was validated in simulation and experimental studies, showing promise as the foundation to a prospective paradigm where power and SAR are not only monitored but, through prediction-guided optimization, proactively managed.
authors.affiliation: Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York, New York 10016, USA. Yudong.Zhu@nyumc.org
authors.forename: Yudong
authors.initials: Y
authors.lastname: Zhu
authors.forename: Leeor
authors.initials: L
authors.lastname: Alon
authors.forename: Cem M
authors.initials: CM
authors.lastname: Deniz
authors.forename: Ryan
authors.initials: R
authors.lastname: Brown
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Sodickson
mesh_terms: D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011846:Radio Waves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity