Global Deep Learning Optimization of CEST MR Fingerprinting (CEST-MRF) Acquisition Schedule.

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Abstract

Chemical exchange saturation transfer (CEST) MRI is a promising molecular imaging technique but suffers from long scan times and complicated processing. CEST was recently combined with MR fingerprinting (MRF) to address these shortcomings. However, the CEST-MRF signal depends on multiple acquisition and tissue parameters, and thus the of an optimal acquisition schedule is challenging. In this work, we propose a novel dual-network deep learning framework is proposed for optimizing the CEST-MRF acquisition schedule. The quality of the optimized schedule was assessed in a digital brain phantom and compared to alternative deep learning optimization approaches. The effect of schedule length on the reconstruction error was also investigated. A healthy subject was scanned with optimized and random schedules and with a conventional CEST sequence for comparison. The optimized schedule was also tested in a subject with metastatic renal cell carcinoma. Reproducibility was assessed via test-retest experiments and the concordance correlation coefficient (CCC) calculated for white matter (WM) and gray matter (GM). The optimized schedule was 12% shorter but yielded equal or lower normalized root-mean-square error for all parameters. The proposed optimization also provided a lower error compared to alternative methodologies. Longer schedules generally yielded lower error. In vivo maps obtained with the optimized schedule showed reduced noise and improved delineation of GM and WM. CEST curves synthesized from the optimized parameters were highly correlated (r=0.99) with measured conventional CEST. The mean concordance correlation coefficient in WM/GM for all tissue parameters was 0.990/0.978 for the optimized schedule but only 0.979/0.975 for the random schedule. The proposed schedule optimization is widely applicable to MRF pulse sequences and provides accurate and reproducible tissue maps with reduced noise at a shorter scan time than a randomly generated schedule.This article is protected by copyright. All rights reserved.