Rapid three-dimensional steady-state chemical exchange saturation transfer magnetic resonance imaging

Purpose To make clinically feasible whole-brain chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) by enhancing imaging efficiency. Methods A novel, whole-brain three-dimensional (3D) steady-state CEST MRI method was introduced by utilizing a time-efficient, fat-suppressed excitation followed by rapid, segmented 3D echo-planar-imaging with incoherent undersampling ink-omega space. Missing signals and CEST-specific spectral images were then jointly estimated directly from incomplete measurements using model-based reconstruction and robust spectral analysis. In vivo studies were performed at 3T both retrospectively (using a fully sampled reference) and prospectively to validate the effectiveness of the proposed method in patients with brain cancer. Results In retrospective studies, the proposed method exhibits superior accuracies to existing methods in estimating images, z-spectra, and APTw relative to the reference. In prospective patient studies, compared with existing methods, the proposed method is statistically significantly different in contrast-to-noise ratio of the APTw contrast between tumor and normal appearing white matter (NAWM) and amide proton transfer weighted contrast (p < 0.05) while not being significantly different in signal-to-noise ratio in an NAWM region. Conclusions We successfully demonstrated that it is feasible to perform whole-brain CEST MRI roughly within 4 minutes for patients with brain cancer. It is expected that the proposed method widens clinical utilities of CEST MRI.