Abstract #2926

Design of Novel RF Pulse for Fetal MRI Refocusing Trains using Rank Factorization (SLfRank) to Reduce SAR and Improve Image Acquisition Efficiency

Sebastian Diaz¹, Yamin Arefeen², Borjan Gagoski^3,4, Ellen Grant^3,4, and Elfar Adalsteinsson^2,5,6

¹Department of Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ²Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ³Department of Radiology, Harvard Medical School, Boston, MA, United States, ⁴Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, ⁵Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁶Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States

Synopsis

Fetal MRI is inherently time-constrained due to unpredictable motion and comfort concerns. Single-shot spin-echo sequences address these concerns by rapidly acquiring images with desired tissue contrast. However, these sequences typically operate at specific absorption rate (SAR) limitations due to a train of refocusing pulses, which impose long TR times and reduce acquisition efficiency. This study leverages SLfRank, the use of ranked factorization to jointly solve for SLR bi-coupled spin parameters, to design refocusing profiles that reduce SAR while maintaining slice-profile performance. The proposed refocusing pulse reduced SAR by over 20% while producing similar image quality to the standard clinical sequence.

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