An analysis of the intracerebral ability to eliminate a nitroxide radical in the rat after administration of idebenone by anin vivo rapid scan electron spin resonance spectrometer

Electron spin resonance (ESR) measurements after intracerebroventricular injection of a nitroxide radical were carried out in rats (n=6) that received oral idebenone for 2 weeks and in control rats (n=5), using anin vivo rapid scan ESR spectrometer. The half-life of nitroxide, which was estimated from the change in the peak height (M=+1) of the ESR signals from the head, was used as a marker for the elimination of the nitroxide radical. The half-life in the rats treated with idebenone was significantly shorter than it was in the controls (p<0.05). This finding indicates that the treatment with idebenone can enhance the intracerebral-eliminating ability of the nitroxide radical.     

In vivo localized1 H spectroscopy of the rat eye at 7 T: preliminary studies

Preliminaryin vivo proton spectroscopic studies of the posterior chamber of the rat eye have been undertaken at 7 T. The Spatial and Chemical shift encoded Excitation (SPACE) localization sequence was used to acquire signals from 10-µl voxels and demonstrate the presence of metabolites associated with the vitreous humor, lens, retina, and the optic nerve. LocalizedT ₂ andT ₁ measurements of water in the vitreous humor indicate a relatively fluid environment. Susceptibility maps are used to demonstrate the difficulties ofin vivo spectroscopic investigations in the anterior regions of the eye. Comments are made concerning the implications for spectral resolution in these regions.     

In vivo 13C chemical shift imaging of the human liver

Chemical shift imaging (CSI) was applied to measure natural abundance proton-decoupled¹³C-NMR spectra of the human liver. Large surface coils were designed for¹³C spectra acquisition (16-cm-diameter circular coil) as well as for proton imaging and decoupling (21×20-cm butterfly coil). Such sizes allowed deep observations of the abdomen. A space matrix of 8×4 voxels (4×8 cm each) was defined using 32 phase-encoding steps. Magnetic field gradients were adjusted on multicompartment phantoms to limit contamination between voxels. Spectral maps containing {¹H}-¹³C spectra of liver from healthy volunteers with an acceptable signal-to-noise ratio were recorded within 20 min. Liver spectra exhibited well-defined resonances corresponding to fatty acyl chains, carbonyl groups, and sugars. The (C-l)-glycogen resonance was also detected under such conditions. Such a technique would be of interest in the development of metabolic investigations on the human liverin vivo.     

In vivo1H MR spectra analysis by means of second derivative method

Short echo time (TE) in vivo PRESS¹H MR spectra (2 T. TE = 35 ms) of normal brain were fitted in the frequency domain using the second derivative method. In this approach, local maxima and hidden peaks are found as local minima of spectrum second derivative. The Lorentzian robust minimisation procedure (referred to as maximum likelihood or m-estimate fitting) using Levenburg -Marquardt non-linear fitting engine was applied. Spectral lines were approximated under the assumption of the mixed Lorentzian/Gaussian lineshapes. The same procedure was applied to 18 proton spectra. The number of peaks found within the range of 0.74/4.2 parts per million (ppm) was 52 ± 3 and their positions were almost the same. The fitted lines were assigned on the basis of the J-pattern recalculated for the field strength of 2 T and by comparing the chemical shifts with the shifts in the single compound spectra. The ratios of main metabolites, such as NAA/Cr, Cho/Cr, Cho/NAA and ml/Cr, are in accord with those obtained earlier using the software supplied with the MR imager and the absolute concentrations ofN-acetylaspartate (NAA). choline containing compounds (Cho),myo Inositol (ml), glucose (Gle) and glutamate (Glu) obtained from the fit agree with those reported in literature, which confirms the usefulness of the second derivative method in routine analyses of¹H MR brain spectra.