ON T1 CANCELLATION SCHEMES IN GOLDMAN-SHEN-TYPE EXPERIMENTS

Modifications to Goldman-Shen-type spin-diffusion pulse sequences, designed to cancel spin-lattice relaxation effects by alternation of the magnetisation orientation during the spin-diffusion evolution period, are critically evaluated. In particular, the spin-diffusion-coupled relaxation behaviour of a three-region model, evaluated numerically, is used to show that such "T1 cancellation" schemes cannot, in general, separate T1 and spin-diffusion effects. A further simple calculation shows that, even for a two-region system with uniform T1 and no spin diffusion, a spatial magnetisation gradient is attenuated under such inversions giving the appearance of a spin-diffusion phenomenon. It is concluded that, in general, solutions of the full spin-diffusion-coupled relaxation behaviour must be undertaken if accurate morphological information is the aim of such experiments. © 1990.