Inversion Recovery: Part 1

20 Inversion Recovery: Part 1

Adipose tissue has a very short T1 relaxation time (-260 msec at 1.5 T), a fact that is used in short tau inversion recovery (STIR; also known as short T1 inversion recovery) imaging to eliminate the signal from fat. As illustrated in Fig. 20.1, the sequence starts with an inversion pulse. The relatively short inversion time (called short tau), in this case 150 msec, is chosen such that the 90° pulse is applied at a time at which the longitudinal magnetization of adipose tissue is zero and therefore no transverse magnetization is generated. The graph presented in Fig. 20.1 shows the evolution of the longitudinal magnetization after the inversion pulse. The dashed lines in the graph illustrate the theoretical evolution of the longitudinal magnetization with time.