Fast Chemical Exchange Saturation Transfer (CEST) MRI With Dual-channel Segmented RF Irradiation

The aim of this study was to develop a technique for rapid acquisition of chemical saturation exchange transfer (CEST) images with dual-channel segmented RF irradiation to reduce scan time and enhance contrast. Conventional CEST MRI is implemented with a long radiofrequency (RF) irradiation module, followed by fast image acquisition to obtain the steady state CEST contrast. However, the saturation preparation time of the conventional CEST MRI method may too long and contrast too small. Our study proposed a dual-channel segmented RF irradiation labeling scheme that includes a long dual-channel RF irradiation module which reduces the preparation time to generate the steady state CEST contrast and repetitive short dual-channel segmented RF irradiation modules during the image acquisition so as to maintain the steady state CEST contrast and enhance the contrast-to-noise ratio (CNR). Theoretical analysis and simulations based on the modified two-pool Bloch equation demonstrated the proposed method was able to increase CEST contrast. CEST experiments with model solutions, e.g., creatine dissolved in water, showed that the saturation preparation time reduced by above 60%, and the CEST contrast increase above 5%. In conclusion, the proposed CEST MRI sequence speeds up CEST imaging and increase CNR effectively.