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Abstract #1359

Flip Angle Inhomogeneity Constrained pTx Pulse Design for Minimum Peak Local SAR

Mihir Pendse 1 , Simone Winkler 2 , and Brian Rutt 2

1 Department of Electrical Engineering, Stanford University, Stanford, CA, United States, 2 Department of Radiology, Stanford University, CA, United States

This work introduces a new minimum SAR spokes-based pTx pulse design algorithm using a spokes trajectory that achieves a desired flip angle inhomogeneity (FAI) threshold while minimizing peak local SAR. Several realistic scan situations are modeled including the use of slightly inaccurate E-field maps for SAR matrix computation to represent patient/body model mismatch and enforcing a constraint on computation time for the optimization. Simulated L-curves show that for four different cases our proposed method achieves equal or lower SAR at low values of FAI compared to prior approaches for SAR-constrained pTx pulse design.

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Keywords

pulsematricesoptimizationconstraintlocalmatrixcomputationcomputediterationmapsspokespokestargetcompresseddesigngridminuteoverestimationpeakaccurateactualalthoughbestbodycurvecurvesdurationelementfieldfixedpatientpulsestableupdatedabsoluteachievesbenefitcoilcompcomplexcompressionconstraineddegreeserrorerrorsestimationexcitationfieldsfundamentalidenticalinhomogeneitylimitlimitedlocationlocationsmeetminimizationminimizingmodelnearlyoptimizationsparallelpositivepowerproblemproposedrealsincesituationsspecifiedstoppingsubjectsystemthresholdtruevirtualadjustedalwaysamplifiedamplitudeapproachesboundedchannelschosenconcernconditionsconservativeconstraintsconvexcycledatasetsdefinitedependentdesirabledeterminingdifferdirectlydonedrawbackdutyefficientengineeringequalexceedingfamilyfullimplementincorporateincorporatesinsensitiveintroducediterativelimitsmagnetizationmatchedmismatchmultichannelnontrivialobservingoperatingoptimizedoptimumoriginaloverlyradiologyreasonrecomputedreducesrelationshiprequiresriskrobustnesssafetysearchsetsseveralsignificantlysimulatedsituationsliceslowspecifyingstaticsteadysubsetsubstantiallysuperiorsurrogatestheorytypicallyworld