Mei-Lan Chu1, Tzu-Cheng Chao2, Nan-kuei Chen3, and Hsiao-Wen Chung1
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Mayo Clinic, Rochester, MN, United States, 3University of Arizona, Tucson, AZ, United States
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Mayo Clinic, Rochester, MN, United States, 3University of Arizona, Tucson, AZ, United States
Our novel single-shot T2 mapping framework removes signal contamination of high-order echoes and reliably generate accurate T2 relaxation times.
The single-shot ES-GRASE sequence. The areas and polarities of prewinding and rewinding gradients (i.e. the green gradient) of the readout gradient are designed to remove high-order echo pathways. The alternating direction of the refocusing RF pules (i.e. 180x-180y-180x-180y) can generate 90° phase difference between the primary and residual high-order echo pathways. The phase difference is 90+2𝜃° when the background phase is involved.
Data preprcessing frameowrk: First, images of four echoes were reconstructed using parallel imaging techniques, and the N/2 ghost was removed using phase cycling method. Second, the background phase was estimated from the first-echo image (see the upper panel). Third, rotating the signal from the third and fourth echo with the estimated background phase . The real part of the rotated signal is only from the signal of the primary echo pathway, with which the primary echo signal can be calculated by basic Trigonometry (see the lower panel in which only the third echo is shown as an example).