Abstract #0740

Improved acquisition efficiency in T2-weighted fetal MRI with optimized variable flip angles and prospective wave-encoding

Yamin Arefeen¹, Borjan Gagoski^2,3, Berkin Bilgic^4,5, Ellen Grant^2,3, and Elfar Adalsteinsson^1,6,7

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

Synopsis

Fetal MRI utilizes Half-Fourier-acquisition-single-shot-turbo-spin-echo (HASTE) for motion robust imaging. However, specific-absorption-rate (SAR) constraints from the refocusing pulse train lengthens scan time and increases vulnerability to motion-induced artifacts. Variable refocusing flip angle (VFA) acquisitions improve efficiency, but may suffer from poor contrast-to-noise-ratios (CNR). We propose an optimization technique for VFA that retains ~90% CNR with 2.5x SAR reduction. Furthermore, we demonstrate the first application of wave-encoding in fetal MRI at R_in-plane = 3-fold prospectively under-sampled acquisitions. Combining HASTE, VFA, and wave-encoding improves acquisition time with reduced repetition times and shorter echo-trains and could enable simultaneous-multislice acquisitions for further acceleration.

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