Chemical Exchange Saturation Transfer (CEST) MR Technique for Liver Imaging at 3.0 Tesla: an Evaluation of Different Offset Number and an After-Meal and Over-Night-Fast Comparison

Purpose: This study seeks to explore whether chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) can detect liver composition changes between after-meal and over-night-fast statuses. Procedures: Fifteen healthy volunteers were scanned on a 3.0-T human MRI scanner in the evening 1.5–2 h after dinner and in the morning after over-night (12-h) fasting. Among them, seven volunteers were scanned twice to assess the scan–rescan reproducibility. Images were acquired at offsets (n = 41, increment = 0.25 ppm) from −5 to 5 ppm using a turbo spin echo (TSE) sequence with a continuous rectangular saturation pulse. Amide proton transfer-weighted (APTw) and GlycoCEST signals were quantified with the asymmetric magnetization transfer ratio (MTR_asym) at 3.5 ppm and the total MTR_asym integrated from 0.5 to 1.5 ppm from the corrected Z-spectrum, respectively. To explore scan time reduction, CEST images were reconstructed using 31 offsets (with 20 % time reduction) and 21 offsets (with 40 % time reduction), respectively. Results: For reproducibility, GlycoCEST measurements in 41 offsets showed the smallest scan-rescan mean measurements variability, indicated by the lowest mean difference of −0.049 % (95 % limits of agreement, −0.209 to 0.111 %); for APTw, the smallest mean difference was found to be 0.112 % (95 % limits of agreement, −0.698 to 0.921 %) in 41 offsets. Compared with after-meal, both GlycoCEST measurement and APTw measurement under different offset number decreased after 12-h fasting. However, as the offsets number decreased (41 offsets vs. 31 offsets vs. 21 offsets), GlycoCEST map and APTw map became more heterogeneous and noisier. Conclusion: Our results show that CEST liver imaging at 3.0 T has high sensitivity for fasting.