Unraveling contributions to the saturated signal at 3.5 ppm in the Z-spectrum of human brain tumors

Increased cytosolic mobile protein content in gliomas causes amide proton transfer (APT) hyperintensity. However, most current APT imaging protocols acquire APT-weighted images that reflect multiple contributions, including residual direct water saturation (or relaxation), semisolid macromolecular magnetization transfer contrast (MTC) asymmetry, and nuclear Overhauser enhancement (NOE) effects, thus limiting the assessment of clean APT. Herein, we separated water, MTC, and APT signal components from RF saturated signals using an MR fingerprinting sequence and evaluated the contributions to the saturation signal at 3.5 ppm in the Z-spectrum of brain tumors.