Chemical exchange saturation transfer (CEST) MR technique for in-vivo liver imaging at 3.0 tesla

Purpose: To evaluate Chemical Exchange Saturation Transfer (CEST) MRI for liver imaging at 3.0-T. Materials and methods: Images were acquired at offsets (n = 41, increment = 0.25 ppm) from −5 to 5 ppm using a TSE sequence with a continuous rectangular saturation pulse. Amide proton transfer-weighted (APTw) and GlycoCEST signals were quantified as the asymmetric magnetization transfer ratio (MTR_asym) at 3.5 ppm and the total MTR_asym integrated from 0.5 to 1.5 ppm, respectively, from the corrected Z-spectrum. Reproducibility was assessed for rats and humans. Eight rats were devoid of chow for 24 hours and scanned before and after fasting. Eleven rats were scanned before and after one-time CCl4 intoxication. Results: For reproducibility, rat liver APTw and GlycoCEST measurements had 95 % limits of agreement of −1.49 % to 1.28 % and −0.317 % to 0.345 %. Human liver APTw and GlycoCEST measurements had 95 % limits of agreement of −0.842 % to 0.899 % and −0.344 % to 0.164 %. After 24 hours, fasting rat liver APTw and GlycoCEST signals decreased from 2.38 ± 0.86 % to 0.67 ± 1.12 % and from 0.34 ± 0.26 % to −0.18 ± 0.37 % respectively (p < 0.05). After CCl4 intoxication rat liver APTw and GlycoCEST signals decreased from 2.46 ± 0.48 % to 1.10 ± 0.77 %, and from 0.34 ± 0.23 % to −0.16 ± 0.51 % respectively (p < 0.05). Conclusion: CEST liver imaging at 3.0-T showed high sensitivity for fasting as well as CCl4 intoxication. Key Points: • CEST MRI of in-vivo liver was demonstrated at clinical 3 T field strength. • After 24-hour fasting, rat liver APTw and GlycoCEST signals decreased significantly. • After CCl4 intoxication both rat liver APTw and GlycoCEST signals decreased significantly. • Good scan–rescan reproducibility of liver CEST MRI was shown in healthy volunteers.