Possible artifacts in dynamic CEST MRI due to motion and field alterations

Purpose: Dynamic CEST studies such as dynamic glucose enhanced imaging, have gained a lot of attention recently. The expected CEST effects after injection are rather small in tissue especially at clinical field strengths (0.5-2%). Small movements during the dynamic CEST measurement together with a subtraction-based evaluation can lead to pseudo CEST effects of the same order of magnitude. These artifacts are studied herein. Methods: A brain tumor patient 3D-CEST baseline scan without glucose injection performed at 3 T is used to generate a virtual dynamic measurement introducing different kinds of simulated motion and B-0 shifts. Results: Minor motion (0.6 mm translations) and B-0 artifacts (7 Hz shift) can lead to pseudo effects in the order of 1% in dynamic CEST imaging. Especially around tissue interfaces such as CSF borders or tumor affected areas, the pseudo effect patterns are non-intuitive and can be mistaken as dynamic agent uptake. Conclusion: Correction or mitigation for small motions is crucial for dynamic CEST imaging, especially in subjects with lesions. Concomitant B-0 alterations can as well induce pseudo CEST effects at 3 T. (C) 2018 The Authors. Published by Elsevier Inc.