This paper presents the first simultaneous 2 H single-and doublearea prompted quantitative investigations of water diffusion quantum (SQ and DQ, respectively) diffusion study of excised in biological tissues. Recently, the effect of compartments brain tissue. The apparent diffusion coefficients (ADCs) of the 2 H and membrane permeability on water diffusion have been SQ and DQ signals were measured at a fixed diffusion time (D 0 studied both theoretically and experimentally (13,14). Difd/3 Γ
21.3 ms) and as a function of the diffusion time to assess fusion anisotropy was also found to be important in the restricted diffusion [(D 0 d/3) was changed from 21.3 to 271.3 central nervous system (CNS) and was suggested as a potenms]. As expected, the ADC of the SQ signal was higher than that tial diagnostic tool for certain brain pathologies (15,16). of the DQ signal [0.53 { 0.03 1 10 05 (n Γ
3) and 0.30 { 0.03 1 Multiple-quantum-filtered (MQF) NMR spectroscopy which 10 05 cm 2 s 01 (n Γ
4), respectively]. When the ADCs of the SQ allows observing ''forbidden'' transitions (i.e., transitions and DQ signals were measured as a function of the diffusion time,
where Dm ΓΊ {1) can be observed in quadrupolar nuclei of two components, a fast and a slow component, were observed in each case. The ADCs for the SQ signal were 1.16 { 0.2 1 10 05 spin Β§ 3 2 whose magnetization decays biexponentially and 0.35 { 0.06 1 10 05 cm 2 s 01 (n Γ
3) for the fast and the slow (17,18). Such a quadrupolar nucleus has a biexponential components, respectively. The ADCs for the DQ signal were 0.31 transverse relaxation if it exhibits microscopic or macro-{ 0.05 1 10 05 and Γ0.03 { 0.03 1 10 05 cm 2 s 01 (n Γ
2) with scopic anisotropy, i.e., if it is bound to a site where v 0 t c is the slow component being relatively small. Interestingly, the slowclose to or greater than unity, or if the nucleus exchanges diffusion component of the SQ signal was found to have an ADC with at least one site which fulfills this condition. Lyon et similar to that of the fast component of the DQ signal. These al. (19) were the first to report the 23 Na and 39 K DQF NMR results suggest that brain water can be divided into at least three spectra of rat brain in situ, demonstrating the increased sensiwater populations and that the DQ signal originates from water tivity of DQF spectra toward the pathophysiological state of molecules which interact with slow-diffusing structural compothe tissue as compared to one-pulse spectra. Very recently, nents of the brain. The new insights that one can obtain using residual quadrupolar interactions have been measured in in simultaneous SQ and DQ diffusion measurement and the ability to distinguish among water populations in biological tissues using vivo human muscle and brain via MQF 23 Na NMR spectrosthe above approach are discussed. α§ 1996 Academic Press, Inc.
copy (20).
2 H DQF NMR spectra were obtained recently for D 2 O solutions of bovine nasal cartilage (21). These spectra were