Enhanced quantitative susceptibility mapping (QSM) using real-time field control.

PurposeTo assess the potential of a real-time field-control (FC) system for mitigating effects of spatiotemporal field fluctuations in quantitative susceptibility mapping (QSM) at 7T. MethodsMagnitude, phase, and QSM images of phantoms and healthy volunteers were acquired under standard conditions and under induced field perturbation (FP) (phantoms: periodic water-bottle displacement; volunteers: deep breathing and forearm movement) with and without FC, which continuously detects and minimizes magnetic-field variations. ResultsField control successfully eliminated FP-induced impairment of phantom image quality and deviations from a linear susceptibility increase for increasing gadolinium concentration in a Gd dilution series (y=320x - 0.60, R-2=0.93 for the scan with FP and FC versus y=259x - 0.54, R-2=0.78 for the scan with FP and no FC (slope literature value: 326ppm L/mol)). Similarly, in volunteers, FC allowed a recovery of a FP-induced loss of identifiable brain structures and reduced the relative change of mean susceptibilities and standard deviations (9353% to 34 +/- 46%) in all regions of interests with respect to the reference scan. ConclusionsReal-time FC improved the delineation of brain structures and the match of susceptibility values with reference values obtained without FP. Magn Reson Med 79:770-778, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.