Yamin Arefeen1, Tae Hyung Kim2, Justin Haldar3, Ellen Grant4,5, Borjan Gagoski6,7, Berkin Bilgic2,7, and Elfar Adalsteinsson1,8,9
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
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
Variable refocusing flip angles and rapid external reference scans could improve efficiency in fetal T2-weighted MRI with reduced specific-absorption rates, enabling simultaneous multi-slice with wave encoding and constrained reconstruction.
Figure 4: Prospectively acquired in-vivo data comparing (a) GRAPPA reconstructions of standard HASTE and the proposed VFA scheme. VFA reduces blurring and retains 83% SNR in comparison to standard HASTE. (b) HASTE reconstructed with GRAPPA and POCS partial Fourier, and the proposed VFA reconstructed with SENSE-LORAKS using the external calibration scan. The reference scan allows prospective calibration of SENSE-LORAKS, and the proposed VFA regime acquired the entire stack of slices 2.3x faster than the standard HASTE.
Figure 5: Comparison between slice-by-slice GRAPPA, retrospective GRAPPA SMS, wave-encoded SMS and wave-LORAKS SMS. While slice-GRAPPA incurs some noise amplification, wave-LORAKS SMS produces cleaner images. Accounting for SAR associated with multi-band pulses in a prospective implementation, combining the proposed VFA technique with SMS could yield between 3-5x reduction in total scan time.