Fig. 2.

Effect of sequence parameters on image contrast. Phantoms with different T2 values and diffusivities show different contrast in the two echoes and for different diffusion attenuations. The plots show signal ratios to account for differences in proton density. Each acquisition produces an image (Echo 1) with a shorter TE (TE₁) and an image (Echo 2) with a longer effective TE (TE₂). (In regions of high diffusivity (egg white, water), the signal loss from Echo 1 to Echo 2 increases as the diffusion attenuation increases. This change in signal ratios reflects the mixed contrast of the DESS sequence: the images have both T2 and diffusion weighting, so multiple acquisitions are necessary to separate out the effects of each.)