Fig. 2

Detail of T2-TSE and T2-GraSE mapping sequences. General scheme of Turbo Spin Echo (TSE) and Gradient Spin Echo (GraSE) mapping sequences. For the TSE a single k-space line is acquired for every excitation requiring as many excitations as k-space lines in the image (a). Conversely, for the GraSE sequence an echo planar imaging (EPI) readout is interleaved between each refocusing pulse, so that as many k-space lines are acquired as there are EPI factors, thus allowing shorter scan times (b). RF: radiofrequency pulse. MR: magnetic resonance signal. Meas.: measurement encoding