Abstract #0347

Rapid fetal HASTE imaging using variable flip angles and simultaneous multislice wave-LORAKS

Yamin Arefeen¹, Tae Hyung Kim², Justin Haldar³, Ellen Grant^4,5, Borjan Gagoski^6,7, Berkin Bilgic^2,7, and Elfar Adalsteinsson^1,8,9

¹Massachusetts Institute of Technology, Cambridge, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ³Department of Electrical Engineering, University of Southern California, Los Angeles, CA, United States, ⁴Boston Children’s Hospital, Boston, MA, United States, ⁵Harvard Medical School, Boston, MA, United States, ⁶Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children’s Hospital, Boston, MA, United States, ⁷Department of Radiology, Harvard Medical School, Cambridge, MA, United States, ⁸Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States, ⁹Institute for Medical Engineering and Science, Cambridge, MA, United States

Fetal MRI utilizes Half-Fourier-acquisition-single-shot-turbo-spin-echo (HASTE) for rapid T₂-weighted imaging to mitigate motion. However, specific-absorption-rate (SAR) constraints from the refocusing pulse train reduce acquisition efficiency. Variable refocusing flip angle (VFA) acquisitions can improve efficiency, but may suffer from low signal-to-noise ratios (SNR). Here, we propose a VFA scheme and incorporate a rapid, low-SAR calibration scan. We simulate and prospectively evaluate the SNR and SAR properties of the VFA scheme and utilize the calibration scan for LORAKS parallel imaging and retrospective evaluation of wave-encoded simultaneous-multislice (SMS). VFA prospectively reduces acquisition time by ~2.3-2.5x and incorporating SMS could further improve efficiency.

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