Sebastian (Sebo) Diaz

MIT Department: Electrical Engineering and Computer Science
Faculty Mentor: Prof. Elfar Adalsteinsson
Undergraduate Institution: University of Arizona
Website: LinkedIn, Github
Research Poster
Lightning Talk


Hello, my name is Sebastian (Sebo) Diaz. I am a rising junior at the University of Arizona majoring in Biomedical Engineering and minoring in Mathematics. My research interests include biomedical imaging and optics. I have been a member Dr. Jennifer K. Barton’s Tissue Optics Laboratory for the past year and have participated in various imaging projects under Dr. Arthur F. Gmitro. In the future, I intend to pursue an MD/PhD dual-degree program and serve as a mentor for underrepresented minorities in STEM as a physician-scientist.

2021 Abstract

Design of Novel RF Pulses for Fetal MRI using Rank Factorization (SLfRANK) to Reduce Heating and Improve Imaging Speed

Sebastian Diaz1, Yamin Arefeen2, Elfar Adalsteinsson3
1Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA
2,3Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
3Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
3Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA

Imaging in pregnancy proves to be a complex and challenging scenario in MR due to unpredictable fetal motion. Single-shot T2 weighted sequences, the gold standard for fetal imaging, use fast pulses with large flip-angle pulses to freeze fetal motion, maximize signal-to-noise, and provide adequate tissue contrast. However, the radiofrequency (RF) pulses deposit a significant amount of energy into the subject, denoted by signal absorption rate (SAR), reducing patient comfort and acquisition efficiency. Currently, these fetal imaging pulse trains hit the FDA limitations regarding patient safety. Embedded in the sequences are clinically designed excitation and refocusing envelopes intended to reduce SAR and limit dephasing. Nonetheless, these pulses still encounter SAR-related complications. Our group’s novel excitation and refocusing pulses replicate slice profiles while simultaneously reducing energy output and producing a more linear phase. We leverage SLfRank, a recently proposed algorithm that combines convex optimization and the Shinnar-Le Roux Algorithm to jointly solve for traditionally bi-coupled spin parameters. Our proposed excitation and refocusing pulse design reduces the energy output of the RF envelope by 9.75% and 22.55%, respectively, and maintains comparable excitation performance compared to clinically-designed pulses.