Rapid and quantitative chemical exchange saturation transfer (CEST) imaging with magnetic resonance fingerprinting (MRF)

Purpose To develop a fast magnetic resonance fingerprinting (MRF) method for quantitative chemical exchange saturation transfer (CEST) imaging. Methods We implemented a CEST‐MRF method to quantify the chemical exchange rate and volume fraction of the Nα‐amine protons of L‐arginine (L‐Arg) phantoms and the amide and semi‐solid exchangeable protons of in vivo rat brain tissue. L‐Arg phantoms were made with different concentrations (25–100 mM) and pH (pH 4–6). The MRF acquisition schedule varied the saturation power randomly for 30 iterations (phantom: 0–6 μT; in vivo: 0–4 μT) with a total acquisition time of ≤2 min. The signal trajectories were pattern‐matched to a large dictionary of signal trajectories simulated using the Bloch‐McConnell equations for different combinations of exchange rate, exchangeable proton volume fraction, and water T1 and T2 relaxation times. Results The chemical exchange rates of the Nα‐amine protons of L‐Arg were significantly (P