The previously observed improvement in spectral resolution of tissue proton NMR with high-resolution magic angle spinning (HRMAS) was speculated to be due largely to freeze-thawing artifacts resulting from tissue storage. In this study, 12 human prostate samples were analyzed on a 14.1T spectrometer at 3°C, with HRMAS rates of 600 and 700 Hz. These samples were measured fresh and after they were frozen for 12-16 hr prior to thawing. The spectral linewidths measured from fresh and previously frozen samples were identical for all metabolites except citrate and acetate. The metabolite intensities of fresh and freeze-thawed samples depend on the quantification procedures used; however, in this experiment the differences of means were <30%. As expected, it was found that tissue storage impacts tissue quality for pathological analysis, and HRMAS conditions alone are not sufficiently destructive to impair pathological evaluation. Furthermore, although storage conditions affect absolute metabolite concentrations in NMR analysis, relative metabolite concentrations are less affected.

High-resolution magic angle spinning (HRMAS) NMR spectroscopy has proven useful for analyzing intact tissue and permitting correlations to be made between tissue metabolites and disease pathologies. Extending these studies to slow-spinning methodologies helps protect tissue pathological structures from HRMAS centrifuging damage and may permit the study of larger objects. Spinning sidebands (SSBs), which are produced by slow spinning, must be suppressed to prevent the complication of metabolic spectral regions. In this study human prostate tissues, as well as gel samples of a metabolite mixture solution, were measured with continuous-wave (CW) water presaturation on a 14.1T spectrometer, with HRMAS spinning rates of 250, 300, 350, 600, and 700 Hz, and 3.0 kHz. Editing the spectra by means of a simple minimum function (Min(A, B, . . ., N) for N spectra acquired at different but close spinning rates) produced SSB-free spectra. Statistically significant linear correlations were observed for metabolite concentrations quantified from the Min(A, B, . . ., N)-edited spectra generated at low spinning rates, with concentrations measured from the 3 kHz spectra, and also with quantitative pathology. These results indicate the empirical utility of this scheme for analyzing intact tissue, which also may be used as an adjunct tool in pathology for diagnosing disease. The utility of high-resolution magic angle spinning (HR-MAS) proton NMR spectroscopy for the analyzing intact biological tissues is being demonstrated increasingly by spectroscopic laboratories in the field of medical MR (1-11). Correlations between tissue metabolites measured with this spectroscopic method and tissue pathologies have been identified, demonstrating the potential of this method for supplementing histopathological evaluations. The most significant asset of this method is that it does not jeopardize the structural integrity of the tissue, and therefore makes it possible to evaluate tissue samples histopathologically after they have been studied spectroscopically (12). Therefore, the use of slow-spinning measurements for optimally protecting histopathological tissue structures from possible damage resulting from high-rate spinning has become the subject of research. Studies in this area have also evaluated the possibility of conducting HRMAS measurements on objects larger than surgical specimens (13-15).MAS, a line-narrowing technique, has the potential to reduce line-broadenings due to both homogeneous and inhomogeneous interactions. Homogeneous line-broadenings, which result from fast spin diffusions (e.g., dipolar couplings) and exchanges, generate the final isotropic lineshape, and obscure the identification of contributions from individual spins. In theory, inhomogeneous line-broadenings can be traced to individual spins that are either oriented differently to the magnetic field (e.g., chemical shift anisotropy), or are experiencing a different field strength (e.g., magnetic susceptibility). With MAS on protons, homogeneous line-broadenings (part...

Choline and the related compounds phosphocholine (PC) and glycerophosphocholine (GPC) are considered to be important metabolites in oncology. Past studies have demonstrated correlations linking the relative ratios and concentrations of these metabolites with the development and progression of cancer. Currently, in vivo and tissue ex vivo magnetic resonance spectroscopy methods have mostly centered on measuring the total concentration of these metabolites and have difficulty in differentiating between them. Here, a new scheme that uses (31)P edited (1)H spectroscopy to quantify the concentrations of choline, PC and GPC in biological samples is reported and its applicability is demonstrated using samples of human brain tumor extracts. This method is particularly well-suited for analytical situations where the PC and GPC resonances are not sufficiently resolved and/or are obscured by other metabolites. Consequently, this scheme has the potential to be used for the analysis of choline compounds in ex vivo tissue samples.