Myelin water fraction estimation using small‐tip fast recovery MRI

Autor: Jeffrey A. Fessler, Gopal Nataraj, Jon-Fredrik Nielsen, Steven T. Whitaker
Rok vydání: 2020
Předmět:
Zdroj: Magn Reson Med
ISSN: 1522-2594
0740-3194
DOI: 10.1002/mrm.28259
Popis: PURPOSE: To demonstrate the feasibility of an optimized set of small-tip fast recovery (STFR) MRI scans for rapidly estimating myelin water fraction (MWF) in the brain. METHODS: We optimized a set of STFR scans to minimize the Cramér-Rao Lower Bound (CRLB) of estimates of MWF. We evaluated the RMSE of MWF estimates from the optimized scans in simulation. We compared STFR-based MWF estimates (both modeling exchange and not modeling exchange) to multi-echo spin echo (MESE)-based estimates. We used the optimized scans to acquire in vivo data from which a MWF map was estimated. We computed the STFR-based MWF estimates using PERK, a recently developed kernel regression technique, and the MESE-based MWF estimates using both regularized non-negative least squares (NNLS) and PERK. RESULTS: In simulation, the optimized STFR scans led to estimates of MWF with low RMSE across a range of tissue parameters and across white matter and gray matter. The STFR-based MWF estimates that modeled exchange compared well to MESE-based MWF estimates in simulation. When the optimized scans were tested in vivo, the MWF map that was estimated using a three-compartment model with exchange was closer to the MESE-based MWF map. CONCLUSION: The optimized STFR scans appear to be well-suited for estimating MWF in simulation and in vivo when we model exchange in training. In this case, the STFR-based MWF estimates are close to the MESE-based estimates.
Databáze: OpenAIRE
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