Multiparametric exchange protons using Z-Spectrum Analysis Proton (ZAP) and CEST on phantoms and human abdomen.

Motivation: Together with specific CEST protons, Z-Spectrum Analysis Protons (ZAP) with an entire spectrum of broaden frequencies captures a wider range of exchange protons. Goal(s): This study aims to develop a combined ZAP and CEST method to improve sensitivity to proton exchange variations for detecting pathological conditions. Approach: Iopamidol and iohexol solutions with varying pH levels and human abdominal images at 3T were analyzed using a two-compartment model, while specific CEST protons were evaluated by MTRAsym. Results: ZAP metrics demonstrated sensitivity to pH, effectively differentiating abdominal organs and detecting bile fluid alterations associated with gallstones, while MTRAsym successfully identified CEST exchange peaks. Impact: Combining ZAP and CEST detects not only CEST protons but a wide spectrum of exchange protons. ZAP metrics demonstrate two proton exchange environments with good sensitivity. The combined CEST and ZAP outcomes indicates a possibility of biomarkers.