Biomedical subjects
Publications and source records attributed to M Decorps.
The efficiency of selective refocusing pulses to suppress J modulation of spin echoes when using the surface-coil technique has been investigated. 31P T2 values obtained for ATP by the HAHN spin-echo method remain in good agreement when the standard refocusing pulse is replaced by selective pulses based on the DANTE excitation method.
Chronic implantation of surface coils on the skull has been developed to record 31P NMR spectra of the brain in unanesthetized rats. Intraperitoneal sublethal potassium cyanide doses induce strong and reversible changes in high-energy phosphate compounds in the brain, similar in part to those induced by ischemia. These effects are dose-dependent as far as phosphocreatine, inorganic orthophosphates and pH are concerned; ATP does not seem to be altered by KCN doses ranging from 3 to 5 mg/kg but starts decreasing at a dose of 6 mg/kg. The fraction of Mg2+ complexed ATP which could be estimated as about 90% was not affected by KCN intoxication. For high doses (6 mg/kg) a new peak, appearing on the upfield side of the inorganic phosphate peak, may correspond to an acidic compartment, the significance of which is discussed.
Tissue samples were obtained by serial stereotactic biopsies in 32 patients with glial brain tumors localized by CT. On each sample, several tissue parameters, such as water content, specific gravity of the dry and wet tissue, electrical impedance, histopathological and cytological examinations, as well as nuclear magnetic resonance (NMR) relaxation times T1 and T2 were measured and correlated. Comparisons were made between both normal and tumorous tissues and between the various types of neoplasms. Differences of the measured parameters between tumors and normal brain tissue and their intercorrelations are analyzed and discussed. Comparison of the NMR results with the corresponding densitometric data from CT images suggests that NMR may add useful information in brain tumor imaging. The authors propose an index of malignancy for gliomas dependent on relaxation time T1 and proton density measured by NMR imaging.
Two-dimensional 1H spectroscopic imaging and magnetic resonance imaging were used to study focal ischemia induced by middle cerebral artery occlusion in rats. A water suppressing spin-echo sequence was used at 4.7 T. Phase encoding during the spin-echo delay (TE = 272 ms) yielded an 8 x 8 array of 35 microL voxels. The injured area of the brain had a higher lactate level and markedly lower N-acetyl aspartate, creatine and choline levels than did the non-ischemic regions. The spectroscopic imaging data clearly showed the localization of the infarct, which agreed well with both magnetic resonance imaging and the histological data obtained post-mortem. This study demonstrates the potential usefulness of combining magnetic resonance imaging and 1H spectroscopic imaging for studying animal models of stroke, and indicates the suitability of the technique for further pharmacological approaches.