SPIN-LATTICE RELAXATION IN MULTIPLE-PULSE EXPERIMENTS AS CONTRAST PARAMETER IN NMR IMAGING OF SOLIDS

The molecular motion contrast parameter for NMR imaging of solids and quasi-solids based on the spin-lattice relaxation (T-leff) in multiple -pulse experiments is discussed. For Ostroff-Waugh multiple-pulse sequ ence the T-leff contrast parameter is evaluated in slow and fast molec ular motion regime and compared with spin-lattice relaxation in the ro tating frame contrast parameter. It is shown that T-leff is offering a good molecular motion contrast in NMR imaging of polymer systems. The radio-frequency pulse scheme for T-leff-imaging using magic-echo phas e-encoding procedure for recording spatial distribution in solids is i ntroduced. A method for T-leff-weighted imaging using gradient spin-ec ho valid for weak dipolar solids is also discussed. The one-dimensiona l proton T-leff image using Ostroff-Waugh pulse sequence in combinatio n with frequency-encoding imaging procedure is presented for a phantom of poly(ethyleneoxide) and poly(methylmethacIylate). The distribution of mechanical stresses in a acrylate film on glass is investigated by proton T-leff-imaging. A proton spin-density image weighted by T-leff , for a mixture of two elastomers with different crosslink density is also shown.