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Biomedical subjects

G Marchal

Publications and source records attributed to G Marchal.

At least 19 recordsLinked to original sources
PubMed1992

[Cerebral and cardiovascular aging and brain energy metabolism. Studies with positron-emission tomography in man].

Positron emission tomography (PET) is the only method that measures concomitantly in the same cerebral region the main haemodynamic (blood flow, blood volume) and metabolic (oxygen and glucose consumption) parameters, thereby providing essential data concerning the supply of substrates by circulation and their principally neuronal/synaptic use by the cells. In "healthy" (i.e. normal) ageing, there is a progressive decrease of oxygen and glucose consumption--with subsequent reduction of cerebral blood flow (CBF)--which predominates in the neocortex and suggests a dysfunction of neuronal circuits perhaps responsible for some age-related changes in cognitive functions. The metabolic depression in the neocortex seems to be accentuated during the more "common" ageing which may include cerebrovascular risk factors, lesions of the white matter in varying numbers and/or degradation of cognitive functions. Strategically located brain lesions of vascular origin (e.g. damaging of the thalamic nuclei), may produce a thalamo-cortical disconnection which induces a diffuse cortical hypometabolism associated with severe cognitive disorders. In degenerative dementias (particularly Alzheimer's disease), which include cortical and subcortical neuronal lesions (e.g. those involving the cholinergic system), there is a hypometabolism preferentially affecting the associative cortex. The cumulative effects on cortical functioning of multiple vascular lesions, superimposed on degenerative neuron loss, might account for age-related cognitive disorders in "normal" ageing as well as in the so-called "vascular" or "mixed" dementias.

Adult↗
PubMed1992

Regional cerebral oxygen consumption, blood flow, and blood volume in healthy human aging.

Using high-resolution positron emission tomography and the oxygen 15 continuous inhalation method, we examined the changes in cerebral metabolic rate of oxygen, blood flow, blood volume, and oxygen extraction fraction as a function of age in 25 optimally healthy, unmedicated volunteers who ranged in age from 20 to 68 years. Subjects were strictly selected for absence of cerebrovascular risk factors, dementia, or mental disorders; they had neither biological nor clinical abnormalities, and no focal anomaly on computed tomographic scan. Regions of interest were determined according to the anatomical structures defined on corresponding computed tomographic scan cuts obtained using a stereotaxic head-positioning method. This same method was also used for positron emission tomographic imaging. There was no significant effect of aging on PaCO2 values, hematocrit, arterial blood pressure, cholesterol and triglyceride levels, and blood glucose levels. In most cerebral cortex gyri, the cerebral metabolic rate of oxygen significantly decreased with age according to a linear pattern, with the same magnitude (about -6% per decade) in all four lobes and on both sides. This effect of age on cortical cerebral metabolic rate of oxygen persisted when the possible influence of cortical atrophy, gender, and head size were partialled out. In contrast, the white matter, deep gray nuclei, thalamus, and cerebellum were not significantly affected. The cerebral blood volume declined with a similar pattern to cerebral metabolic rate of oxygen, while changes in cerebral blood flow were less significant, presumably because of larger variance of data across subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Isodense subdural haematomas on CT:MRI findings.

MRI findings are described in two patients with subdural haematomas isodense on CT. In one patient, admitted 6 weeks after trauma, a chronic subdural haematoma showed extreme hypointensity on T2-weighted images, suggesting acute trauma, and therefore acute rebleeding. In the second patient with severe anaemia, an acute subdural haematoma was hyperintense on T2-weighted images, suggesting chronic trauma; this may be explained by the low haematocrit and a possible mixture of blood with cerebrospinal fluid. The MRI features of subdural haematomas and hygromas have to be kept in mind, in order not to misjudge the age of the haematoma.

Female↗
PubMed1992

The influence of blood transfusion on brain blood flow autoregulation among stable preterm infants.

Prior to and 24 h following blood transfusion serial determinations of both cerebral artery flow velocity waveforms and mean arterial blood pressure have been used to reconstruct the autoregulatory curve and its upper blood pressure limit among five stable preterm infants. Prior to transfusion the autoregulatory range of cerebral blood flow (CBF) was narrow due to a relatively low-set upper blood pressure limit. At 24 h after transfusion each individual has been re-examined. Following correction of anemia both a significant reduction of CBF velocities as well as a concomitant rise of the Pulsatility Index (PI) occurred over the entire range of blood pressures indicating a reduction of CBF after transfusion. In addition a right-sided shift of the upper limit towards higher mean blood pressures occurred after transfusion and resulted in an extension of the autoregulatory plateau of CBF. These favourable effects of blood transfusion ameliorating autoregulation of brain blood flow particularly at higher blood pressures might well bear important therapeutic perspectives in our effort to prevent intracranial haemorrhage among sick preterm infants.

Blood Pressure↗
PubMed1992

Comparison of ultrasound and E.R.C.P. in the detection of the cause of obstructive biliary disease.

The value of ultrasound (US) in determining the cause and site of biliary obstruction was critically evaluated and compared to endoscopic retrograde cholangiography (ERCP), in a prospective study performed on 120 consecutive patients. The final diagnosis was based on surgery, endoscopic retrograde cholangiography or a combination of other examinations. Ultrasound successfully differentiated obstructive from non obstructive jaundice in 96% of the patients, comparing well with the results ERCP. US correctly defined the cause of obstruction in 71% of the patients with ductal stones, in 90% of the patients with tumoural bile duct obstruction, but only in 59% of the patients with chronic pancreatitis.

Adult↗
PubMed1992

Enhancement of the pancreas after single bolus injection combined with spiral scanning. A comparative study with conventional incremental scanning after biphasic contrast injection.

The combination of a rapid single bolus injection (72 ml of a 60% concentrated iodinated contrast medium) with spiral scanning versus dynamic sequential scanning with a conventional biphasic bolus injection (150 ml of 60% concentrated iodinated contrast medium) is compared. 60 patients with normal pancreatic morphology were included in this study. 30 patients were examined with dynamic sequential scanning (cycle times of 5 seconds) during a biphasic bolus injection, 30 patients were examined with spiral scanning (cycle times of 1 second) after a single uniphasic bolus injection. For both scanning techniques, mean attenuation values of the pancreas were measured before and at different time intervals after contrast injection. The difference in attenuation values of the pancreas before and after contrast injection reflects the level of contrast enhancement in both methods. The level of contrast enhancement of the pancreas after bolus injection was not statistically significantly different in spiral scanning versus in dynamic sequential scanning. In comparison with conventional scanning, spiral scanning allows to reduce the injected dose of contrast by 50% without compromising the contrast resolution.

Adult↗
PubMed1992

Transfer of both protection and delayed-type hypersensitivity against live Listeria is mediated by the CD8+ T cell subset: a study with Listeria-specific T lymphocytes recovered from murine infected liver.

The recruitment of specific T lymphocytes in murine liver is thought to be a key event in the ultimate control of Listeria monocytogenes growth during primary infection. However, there has been little functional characterization of the cell populations recruited in this non-lymphoid organ. Therefore in this study, the recruited lymphomyeloid cells were isolated from the liver of C57BL/6 mice at the peak of the immune response (day 7) triggered by a non-lethal L.monocytogenes infection. The anti-Listeria T lymphocytes were detected in vivo by their ability to transfer protection and delayed-type hypersensitivity (DTH) to live L.monocytogenes in naive recipients: protection was measured not only by the effect on reduction of the bacterial load in liver and spleen, but also on survival after the lethal challenge, and DTH was detected using as eliciting antigen, either live L.monocytogenes or heat-killed L.monocytogenes. When live pathogens were used, both functions were found to be mediated by T lymphocytes belonging to the CD8+ subset. However, when heat-killed L.monocytogenes were used as eliciting antigen in the DTH assay, Listeria-specific CD8+ T lymphocytes could not be restimulated in immune lymphoid cell populations recovered either from liver or spleen of Listeria-infected mice. Both populations were thus found to share the same qualitative properties in the DTH assay. The importance of the use of live pathogens versus heat-killed pathogens for detection of DTH and protection functions is discussed in the light of current concepts on processing and presentation pathways of Listeria-derived peptides.

Animals↗
PubMed1992

Magnetic resonance imaging, microangiography, and histology in a rat model of primary liver cancer.

RATIONALE AND OBJECTIVES: N-nitrosodiethylamine is able to induce various benign and malignant liver lesions in rats with a high success rate and a low mortality rate. It provides a more appropriate model that better simulates the various lesions occurring in patients than the usual model of tumor implantations. METHODS: Hepatic carcinogenesis was induced in 58 Wistar rats using oral N-nitrosodiethylamine. The rats subsequently were studied by liver magnetic resonance imaging (MRI), postmortem microangiography, and histologic examination. RESULTS: Hepatic tumors developed in 57 rats. A wide variety of the tumors in the degree of vascularization, the type of vessels, the areas of intratumoral secretion and necrosis, and the tumor cell differentiation resulted from the tumor model. The authors were able to assess the contribution of the vascular, extravascular, and cellular components in the final pattern of contrast enhancement in MRI. CONCLUSIONS: The N-nitrosoethylamine model for hepatic tumor induction is simple, and provides a more representative range of tumors for experimental evaluation.

Animals↗
PubMed1992

Evaluation of section sensitivity profiles and image noise in spiral CT.

Spiral computed tomography (CT) offers continuous volume scanning of complete organs or body sections within a single breath hold. Almost all image quality characteristics of spiral CT are identical to those of conventional section-by-section CT; however, there is a change in pixel noise values and degradation in the shape of the section sensitivity profiles (SSPs). Computer simulations, phantom measurements, and clinical studies were used in evaluating the SSP and noise characteristics of two new section-interpolation algorithms. The results were compared with standard CT and spiral CT data processed with the commonly employed linear section-interpolation algorithm. Degradation of SSP quality was insignificant for a table feed distance per 360 degrees revolution equal to the section thickness when the new algorithms were applied; noise values, however, increased. SSP width increased for table feed distances greater than the section width, the effect being less pronounced with the new algorithms. The value of these algorithms is primarily seen in the improved quality of multiplanar reformations and cine and three-dimensional displays.

Algorithms↗
PubMed1992

Chronic focal fibrosing pancreatitis: detection by MRI.

The study of a 70-year-old woman with fibrosing pancreatitis, an uncommon variety of chronic pancreatitis, presenting as a discrete solid mass in the head of the pancreas, is reported. CT and US were non-diagnostic while ERCP and MR detected a focal anomaly. This case report stresses the sensitivity of MR in some pancreatic pathologies.

Aged↗
PubMed1992

Congenital intrahepatic porto-systemic shunt.

An asymptomatic case of intrahepatic shunt between a portal and hepatic vein is presented. Ultrasound examination combined with Doppler sonography showed a communication between a dilated portal vein and a hepatic vein. Computed tomography and angiography confirmed the findings. Porto-hepatic venous shunting is very rare and has previously been reported in association with cirrhosis. The vascular malformation we present is believed to be a congenital anomaly, as no signs of cirrhosis or trauma were found.

Angiography↗
PubMed1992

Dynamic CT of the liver.

The most commonly used CT technique for contrast enhancement CE of the liver are dynamic CT scanning after either IV, direct hepatic arterial or indirect portal contrast injection. The need for these different approaches is because compromises have to be made which take into account the scanner performance, the pharmacodynamics of the available urographic contrast agent and the complex vascularisation of the liver and the tumors. Spiral scanning is a novel technique which allows to scan the entire liver in a single breathhold period of about 10 to 20 seconds with the a posteriori calculation of perfectly contiguous or even overlapping slices. These two new specifications offer entirely new perspectives in terms of liver enhancement. It becomes theoretically possible to scan the entire liver twice, during both the early arterial phase and the subsequent venous phase after one single short IV bolus injection. Hence the total amount of contrast media to be administered can be reduced while the diagnostic potential of the contrast agent is significantly increased.

Carcinoma, Hepatocellular↗
PubMed1992

MR imaging of intracranial aspergilloma extending from the sphenoid sinus in an immunocompromised patient with multiple myeloma.

A case of fatal intracranial aspergillosis, extending from the sphenoid sinus via the orbit into the subarachnoid space of the optochiasmatic cistern and the cistern of the middle cerebral artery is presented in an immunosuppressed patient with multiple myeloma. Adequate treatment was not instituted and the patient died because the condition was not recognised and interpreted as a soft tissue extension of an orbital localization of myeloma. MRI, especially after intravenous injection of Gadolinium, depicted very accurately the extension of the disease, as defined at autopsy.

Aspergillosis↗
PubMed1992

Temporomandibular joint imaging.

Pain and discomfort caused by internal derangement of the temporomandibular joint are frequent in our society. Patients can present with very divergent complaints, not always clearly related to the temporomandibular joint. Good imaging studies of the temporomandibular joint that can show the presence or absence of a problem and give an idea as to type of disease and its seriousness are, therefore, necessary. The choice of which imaging study to use largely depends on whether MR imaging is easily available. Ongoing investigations show that MR imaging of the temporomandibular joint not only depicts the soft tissue derangements very well, but also shows the associated bony changes. However, the exact significance of disk displacement is not always clear because anterior displacement is also seen in asymptomatic volunteers and after clinically successful treatment.

Diagnostic Imaging↗
PubMed1991

Human brain proton localized NMR spectroscopy in multiple sclerosis.

Localized proton spectroscopy of the brain was performed on MS patients (n = 18) and the results are compared with those of a control group (n = 17). The experiments were performed in a 1.5-T Siemens Magnetom using the stimulated echo method and selective water suppression. Acquisition parameters were TR/TE/TM = 3000/270/30 ms, NA = 256, and Acq = 13 min. Localized volumes ranged from 8 to about 80 cc. The patients (ages 25 to 66) were at various stages of the disease. Three of the eighteen patients did not show any plaques on the MR images. VOIs were chosen to contain as much plaque volume as possible in the cerebrum white matter. In the controls and in the patients with no plaques, the VOI were localized in similar white matter regions. All spectra were characterized by the presence of Cho (3.2 ppm), PCr + Cr (3.0 ppm), and NAA (2.0 ppm). The ratios NAA/Cho and NAA/(PCr + Cr) were calculated for both the MS and the control group. The results for the three MS patients with no detectable plaques did not differ significantly from the results of the control group. The former group is, however, too limited to draw any conclusion for the moment. For the MRI positive patients, the following values were found (means +/- 1 SD); NAA/Cho = 1.98 +/- 0.33 and NAA/(PCr + Cr) = 2.16 +/- 0.14. In the normals, these values were NAA/Cho = 2.54 +/- 0.39 and NAA/(PCr + Cr) = 2.76 +/- 0.25. The results quoted are TR and TE dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Shortcomings and pitfalls of ocular MRI.

MRI was performed in 41 patients with ocular lesions: 27 cases of malignant melanoma, 5 of haemorrhage, 3 of choroidal metastasis, 3 of senile disciform macular degeneration, 2 retinoblastomas and 1 hamartoma. On MRI 5 small lesions (less than 2 mm thick): 1 melanoma, the 3 metastases and the hamartoma, were not seen. All the malignant melanomas visualised were hyperintense compared to the vitreous on T1-weighted images. On T2-weighted images 24 of 26 lesions were hypointense compared to the vitreous. The remaining two lesions were almost isointense, corresponding to amelanotic lesions. These MRI features did not differ significantly from those of retinoblastomas, senile disciform macular degeneration or subacute choroidal haemorrhage. Major shortcomings of MRI in lesions of the globe lie in a lack of spatial resolution and poor specificity of the findings.

Adult↗
PubMed1991

The solitary hyperdynamic pulsating superior mesenteric artery: an additional dynamic sonographic feature of midgut volvulus.

Midgut malrotation complicated by volvulus is a surgical emergency. The diagnosis is often suspected clinically and usually confirmed by barium meal. In this case the diagnosis of malrotation with midgut volvulus is made by ultrasound. We describe the solitary hyperdynamic pulsating superior mesenteric artery as an additional dynamic sonographic feature of midgut volvulus.

Humans↗