APTw/CEST-MRI for body oncology with SPIR fat suppression using improved Z-spectral modeling for olefinic fat components

Motivation: Fat-artifacts are challenging in CEST-MRI for body applications as they overlap spectrally with clinically relevant signals like amide or hydroxyl. Goal(s): Improve the quality of in vivo fat correction based on previously explored Z-spectral fitting of data obtained with SPIR fat suppression. Approach: Olefinic fat is modeled separately while scaling and inverting aliphatic components. Fitting was tested on Z-spectral data from breast ROIs with variable fat content. Results: The new model is accurate for a large range of fat fractions. The opposite phase of aliphatic and olefinic fat components provides a better explanation for the observed Z-spectra in vivo. Impact: Understanding and accurate modeling of fat signals in fat-suppressed APT/CEST-MRI will allow unbiased assessment of CEST effects in body-oncology (breast, kidney cancer).