In the case of tissues, the dominant lipid resonances sometimes make it prohibitively difficult to observe small metabolite signals [7].
To overcome the above problems and improve the detection, a number of NMR spectral editing methods can be employed utilizing the variation of diffusion properties [8] and spin relaxation [2–5]. Generally, molecules with greater molecular weight diffuse slowly but have relatively short spin-relaxation times, whereas small molecules diffuse quickly but have relatively long spin-relaxation times (unless they are bound to macro- molecules). Therefore, the complex NMR spectra of biofluids can be edited by taking advantage of the dif- ferences in diffusivity and spin-relaxation times.