Figure 5
(according to Dwyer et al., Radiology 1988; adjusted to application in myocardial imaging at 1.5 T with TI 180 ms, TE 100 ms, assuming long TR allowing full relaxation). STIR pulse sequence scheme (top) and its effect on net magnetization vectors for 5 categories of tissues with increasing T1 and T2. The first part (left of the vertical dashed line) shows the recovery of the longitudinal components (Mz) in the interval between the initial STIR 180° and the TSE 90° pulses, the second part (right of the dotted line) shows the decay of the transversal components (Mxy) after the 90° pulse. Mz of tissues A and B with short T1 times (T1/T2 100/20 and 150/30 ms) reach positive values during the TI interval, with the shorter T1 yielding higher Mz (T1 weighting). Following the 90° pulse, the difference (= contrast) between signal intensities is diminished during the long TE interval (T2 weighting). The signal of tissue C (250/80 ms, e.g. fat) is cancelled due to zero-crossing at the time of the 90° pulse. Mz of tissues D and E with long T1 (1000/50 and 1300/80 ms; e.g. remote myocardium and edematous myocardium at 1.5 T, respectively [20, 33]) are still negative by the time of the 90° pulse. The following T2 decay further adds to their contrast (additive effect of STIR in edema imaging).