Biomedical subjects

J F Le Bas

Publications and source records attributed to J F Le Bas.

95 records · Page 6Linked to original sources

PubMed1984

NMR relaxation times from serial stereotactic biopsies in human brain tumors.

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.

Adult↗

PubMedDate not supplied

Subthalamic stimulation for Parkinson's disease.

Deep brain stimulation by high frequency (HFS) has been developed starting in the thalamic target (Vim) from pragmatic observations and subsequently followed by other targets, such as the subthalamic nucleus (STN) and pallidum as an application of current knowledge from basic preclinical research in neuroscience. The mechanism involved by this neurosurgical approach is not completely solved. For Vim we have formed the hypothesis that HFS induces a jamming of sensory-motor loops but for the STN, from our experimental research in rats we have shown that HFS induces functional inhibition of cell activity in the target nuclei. In our patients the implantation of the stimulation electrodes was carried out stereotactically, under local anesthesia, using ventriculography, MRI, microrecordings and clinical evaluation of the effects of stimulation on rigidity. When the stimulation is turned ON in the STN area a significant decrease in rigidity was determined by the neurologists. Stimulation or even penetration of the electrode may be responsible for transient dyskinesias. The average location of the clinically efficient contact of the chronic stimulating electrodes is statistically located at 5.02 +/- 0.71 1/12 degrees of AC-PC in the AP direction, at -1.5 +/- 0.66 1/8 degrees of the height of the thalamus in the ventricle direction, with laterality at 11.98 +/- 1.12 mm in the lateral direction. The beneficial effects of STN stimulation are significant providing that the electrodes are correctly placed into the target. There is strong improvement of the symptoms of the triad in which akinesia, rigidity, and tremor are reduced on average to 41. 6, 48.6, and 27%, respectively, when compared with the previous preoperative level. From our experience, HFS of the STN could be considered the surgical therapy of choice at advanced stages of Parkinson's disease.

Electric Stimulation Therapy↗

PubMedDate not supplied

Central processing of rectal pain: a functional MR imaging study.

BACKGROUND AND PURPOSE: Although the central processing of somatic pain has been dealt with in numerous brain imaging studies, the neural correlates of visceral pain have received much more limited attention. Our goal was to assess the feasibility of detecting brain activation patterns induced by rectal pain by means of functional MR imaging. We hypothesized that the cerebral processing of rectal pain would exhibit strong similarities with the central processing of somatic pain. METHODS: Functional MR imaging data were obtained from eight healthy subjects. A block paradigm was applied. Rectal pain was induced by inflating a latex balloon catheter that had been inserted into the rectum. Functional responses were established by means of cross-correlation analysis. RESULTS: Activation was detected within the anterior cingulate gyrus, the prefrontal cortex, the insular cortex, the sensory-motor cortex, the inferior parietal lobule, the posterior cingulate gyrus, and the visual cortex. CONCLUSION: Functional MR imaging of visceral pain is feasible in healthy subjects. The activation patterns observed in this study support the hypothesis that the cerebral processing of visceral pain involves multiple components, similar to the central processing of somatic pain. Our results constitute a first step toward the identification of possible aberrations in the activation patterns of patients suffering from visceral hypersensitivity.

Adult↗

PubMedDate not supplied

Quantification and distribution of neovascularization following microinjection of C6 glioma cells in rat brain.

BACKGROUND: It has been suggested that the switch to an angiogenic phenotype can separate the development of a tumor into two stages: the prevascular phase and the vascular phase. The purpose of the present work is to demonstrate the existence of an angiogenic switch in a longitudinal study of a brain tumor model during tumor growth by means of microvessel density measurements. MATERIALS AND METHODS: The study was performed on 32 rats bearing C6 glioma. At different stages of tumor growth, the histological aspects were described and sections were immunostained for factor VIII-related antigen in order to highlight microvessel endothelial cells. Microvessels were counted at 400 magnification for different areas (central non necrotic area, peripheral area, contralateral grey and white matter area), using image analysis software. RESULTS: Vessel density was significantly higher at the tumor-brain interface than in the center of the tumor or in the contralateral cortex. The vessel density remains stable in the tumor during the first 3 weeks after cell implantation, after which a clear increase of vessel density can be observed. CONCLUSION: The present study demonstrates the presence of an angiogenic switch which is concomitant with the development of necrosis and pseudopalisading pattern.

Animals↗

PubMedDate not supplied

[Magnetic resonance imaging with cardiac synchronization in chronic thrombosis of the main pulmonary arteries. Apropos of a case with computed x-ray tomographic correlation].

Results of nuclear magnetic resonance exploration in a patient with chronic thrombosis of main pulmonary arteries are used to outline an elementary semiology in agreement with current documented data. Signs observed relate to the thrombosis and showing of flow due to associated pulmonary artery hypertension. Cardiac synchronization is essential: obtaining 2 echos by the spin-echo technique allows differentiation of circulatory slowing phenomena, which provoke increased strength of 2nd echo, from the thrombus itself. Correlations established with V/Q scintigraphy, angiography and CT scan findings in this case provided preliminary evaluation of use of this imaging technique in this affection.

Angiography↗