Functional Imaging Using NMR

The signal intensity and contrast of NMR images depend both on measurement parameters and on tissue parameters. The most essential measurement parameters are the repetition time TR and the spin echo time TE. The effect of the echo time on the image contrast is demonstrated by the multi echo images shown in Fig. 3.1. The significant change in image contrast with increasing echo time is clearly demonstrated. The tissue specific parameters are the relaxation times T1 and T2, the proton density P and the diffusion coefficient D. Furthermore, the signal intensity in vessels is also fundamentally influenced by the flow velocity of the blood (see below). By applying chemical shift imaging methods, it is also possible to generate separate images of fat, water and magnetic susceptibility.