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Abstract #3848

Threshold Criteria for Real Time RF Monitoring in 7T Parallel Transmit System

Borjan Gagoski1, Himanshu Bhat2, Philipp Hoecht2, Khaldoun Makhoul3,4, Ulrich Fontius5, Josef Pfeuffer5, Franz Schmitt5, Michael Hamm2, Joonsung Lee1, Kawin Setsompop3,4, Lawrence L. Wald3,6, Elfar Adalsteinsson1,6

1Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States; 2Siemens Healthcare, Charlestown, MA, United States; 3A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States; 4Harvard Medical School, Boston, MA, United States; 5Siemens Healthcare, Erlangen, Germany; 6Harvard-MIT Division of Health Sciences & Technology, MIT, Cambridge, MA, United States

To guard against run-time deviations in parallel transmission RF waveforms that may result in violation of SAR limits, real-time RF waveform monitoring serves an important role. In this work we investigated subject-to-subject variation in excitation coil array monitoring parameters and use these findings to propose threshold criteria to detect a mismatch between ideal and observed RF signals. Calibration of the cut-off values needed in the threshold algorithm was done empirically by monitoring the RF signals in 15 in-vivo acqisitions. The performance of the proposed algorithm was then tested for different types of RF pulses in undisturbed and purposely disturbed acquisitions.