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Abstract #4629

Sensing low-frequency, low-amplitude AC magnetic fields at ultra-low field with steady-state SIRS

Bragi Sveinsson1,2,3, Neha Koonjoo1,2,3, Thomas Witzel1,2, and Matthew Rosen1,2,3

1Martinos Center, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Physics, Harvard University, Cambridge, MA, United States

In this work, we demonstrate a method to detect low-frequency, low-amplitude AC magnetic fields in an ultra-low-field (ULF) MRI system using a steady-state implementation of the Stimulus-Induced Rotary Saturation (SIRS) method. The method optimizes SNR efficiency by applying the SIRS mechanism in a bSSFP scan. This approach takes advantage of the low SAR and small absolute B0 deviations of the ULF system. We describe simulation results, show a clear signal response in phantoms, and describe an in vivo protocol for using the method to detect response from an auditory stimulus.

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