Mitigation of T1 impact for unbiased tumor APT MRI using quasi-steady-state based apparent exchange-dependent relaxation analysis

Motivation: T1 confounds CEST measurements, leading to reduced specificity and misinterpretation of CEST MRI. Goal(s): The study aimed to investigate the feasibility of quasi-steady-state (QUASS)-based apparent exchange-dependent relaxation (AREX) analysis in correcting T1. Approach: CEST MRI experiments were conducted on a creatine phantom and brain tumor patients. Conventional CEST effect was quantified with the asymmetry analysis for the phantom or a multipool Lorentzian function for human brains from QUASS Z-spectra. The AREX metric with T1 correction was calculated from the inverse of QUASS Z-spectra. Results: Substantial T1 impact was shown on conventional CEST images, whereas the QUASS-based AREX measurements were less affected by T1. Impact: The QUASS-based AREX analysis can effectively correct the T1 confoundment in CEST measurements, facilitating unbiased tumor CEST MRI at 3 T.