Insight into the quantitative metrics of chemical exchange saturation transfer (CEST) imaging

Hye-Young Heo, Dong-Hoon Lee, Yi Zhang, Xuna Zhao, Shanshan Jiang, Min Chen, Jinyuan Zhou
2016 Magnetic Resonance in Medicine  
Purpose-To evaluate the reliability of four CEST imaging metrics for brain tumors, at varied saturation power levels and magnetic field strengths (3-9.4 T). Methods-A five-pool proton exchange model (free water, semi-solid, amide, amine, and NOErelated protons) was used for the simulations. For the in vivo study, eight glioma-bearing rats were scanned at 4.7 T. The CEST ratio (CESTR), CESTR normalized with the reference value (CESTR nr ), inverse Z-spectrum-based (MTR Rex ), and apparent
more » ... e-related relaxation (AREX) were compared. Results-The simulated CEST signal intensities using MTR Rex and AREX were substantially increased at relatively high RF saturation powers at 3 T and 4.7 T, while CESTR and CESTR nr metrics remained relatively stable. There were tremendously high MTR Rex and AREX signals around the water frequency at all field strengths due to the small denominators. In the rat tumor study at 4.7 T, both CESTR and CESTR nr showed clear contrasts in the tumor with respect to the normal tissue across all saturation power levels (0.5-3 µT), while the AREX showed negligible to negative insignificant contrasts. Conclusion-CEST metrics must be carefully selected based on the different experimental settings. CESTR and CESTR nr are more reliable at 3 T (a clinical field strength) and 4.7 T.
doi:10.1002/mrm.26264 pmid:27170222 pmcid:PMC5107181 fatcat:3tw2fmpwv5hajbnlbia3ruauiy