Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 69, Issue 5, Pages 1261-1267Publisher
WILEY
DOI: 10.1002/mrm.24719
Keywords
parallel imaging; multiband; simultaneous multislice; diffusion; fMRI
Funding
- NIH Biotechnology Research Center (BTRC) program [P41 RR008079]
- NCRR from NIBIB [P41 EB015894]
- 16 National Institutes of Health Institutes and Centers [1U54MH091657]
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Purpose: To evaluate an alternative method for generating multibanded radiofrequency (RF) pulses for use in multiband slice-accelerated imaging with slice-GRAPPA unaliasing, substantially reducing the required peak power without bandwidth compromises. This allows much higher accelerations for spin-echo methods such as SE-fMRI and diffusion-weighted MRI where multibanded slice acceleration has been limited by available peak power. Theory and Methods: Multibanded time-shifted RF pulses were generated by inserting temporal shifts between the applications of RF energy for individual bands, avoiding worst-case constructive interferences. Slice profiles and images in phantoms and human subjects were acquired at 3 T. Results: For typical sinc pulses, time-shifted multibanded RF pulses were generated with little increase in required peak power compared to single-banded pulses. Slice profile quality was improved by allowing for higher pulse bandwidths, and image quality was improved by allowing for optimum flip angles to be achieved. Conclusion: A simple approach has been demonstrated that significantly alleviates the restrictions imposed on achievable slice acceleration factors in multiband spin-echo imaging due to the power requirements of multibanded RF pulses. This solution will allow for increased accelerations in diffusion-weighted MRI applications where data acquisition times are normally very long and the ability to accelerate is extremely valuable. Magn Reson Med 69:12611267, 2013 Wiley Periodicals, Inc.
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