Investigation of multiparametric exchange protons using CEST and Z-spectrum analysis proton (ZAP) in human brain

Motivation: To investigate a combination of CEST and ZAP as multiparametric biomarkers of age-associated changes in the human brain. Goal(s): To investigate and find biomarkers using CEST/ZAP in the brain. Approach: Multiparametric macromolecular exchange proton CEST/ZAP measurements are investigated at clinical 3T. 2D SSFSE sequence is acquired using an MT pulse train with a B1,rms of 2 uT to cover ± 6 ppm for CEST and ± 100 ppm for ZAP. Results: CEST yields presence of hydroxyl-, amino-, and amide protons, while ZAP offers restricted and free exchange protons and their fractions. CEST and ZAP demonstrate distinguished metrics in different parts of the brain. Impact: Observing macromolecular exchange protons by CEST and ZAP may provide the presence of characteristic irregular tissues that are not possible to observe in regular MRI. This suggests a potential biomarker related to age-associated changes in the brain.