Chemical exchange saturation transfer is a noncontrast MRI technique that indirectly detects exchangeable protons in the water pool by presaturation at different frequency offsets. [1][2][3] Chemical exchange saturation transfer MRI provides a novel contrast mechanism to image important physiological information, such as pH and metabolite concentration. 4,5 It can be applied to detect and diagnose various pathologies, such as cancer, 6 ischemia, 2,7 and lymphedema. 8

Purpose To develop a novel 3D abdominal CEST MRI technique at 3 T using MR multitasking, which enables entire‐liver coverage with free‐breathing acquisition. Methods k‐Space data were continuously acquired with repetitive steady‐state CEST (ss‐CEST) modules. The stack‐of‐stars acquisition pattern was used for k‐space sampling. MR multitasking was used to reconstruct motion‐resolved 3D CEST images of 53 frequency offsets with entire‐liver coverage and 2.0 × 2.0 × 6.0 mm3 spatial resolution. The total scan time was 9 min. The sensitivity of amide proton transfer (APT)‐CEST (magnetization transfer asymmetry [MTRasym] at 3.5 ppm) and glycogen CEST (glycoCEST) (mean MTRasym around 1.0 ppm) signals generated with the proposed method were tested with fasting experiments. Results Both APT‐CEST and glycoCEST signals showed high sensitivity between post‐fasting and post‐meal acquisitions. APT‐CEST and glycoCEST MTRasym signals from post‐mean scans were significantly increased (APT‐CEST: −0.019 ± 0.017 in post‐fasting scans, 0.014 ± 0.021 in post‐meal scans, p < 0.01; glycoCEST: 0.003 ± 0.009 in post‐fasting scans, 0.027 ± 0.021 in post‐meal scans, p < 0.01). Conclusion The proposed 3D abdominal steady‐state CEST method using MR multitasking can generate CEST images of the entire liver during free breathing.

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