Periodically Rotated Spiral Sampling (PRSS) and Multi-offset Transformer Reconstruction (MoTR) for CEST MRI

Motivation: CEST MRI is often limited in its application due to its time-consuming nature. Also, multiple saturation frequency offsets are required to accurately measure CEST effects. Goal(s): Accelerate CEST imaging by undersampling k-space of each frequency offset below Nyquist rate. Approach: Periodically rotated spiral sampling (PRSS) is proposed to make adjacent offsets capture different k-space subregions. Besides, a multi-offset transformer reconstruction (MoTR) network is further presented to fuse complementary information from multiple offsets. Results: Compared to fully-sampled images, reconstructed images using our method can achieve an average SSIM/MAE of 0.9899/0.0032, resulting a coefficient R value of 0.93/0.95 in terms of CEST signals at -3.5ppm/+3.5ppm. Impact: Our method can realize 4× acceleration of CEST imaging without sacrificing down-stream CEST analysis performance. Besides, our method has the potential to work on MRI scanner for CEST acceleration, which can further expand the application of CEST MRI.