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Biomedical subjects

G Marchal

Publications and source records attributed to G Marchal.

At least 199 records · Page 11Linked to original sources
PubMed1995

[Three-dimensional imaging of acetabular fractures using spiral CT].

Seven adult patients with acetabular fractures were investigated with conventional X-rays, axial spiral computed tomographic (CT) images and three-dimensional (3D) surface rendered reconstructions. Spiral CT has the advantage that it acquires the data much faster than incremental CT, resulting in less motion artefacts. A semi-automatic three-dimensional environment for segmentation has been developed in our institution. It created significant reduction of user interaction and improved visualization of acetabular and femoral joint surfaces. The main advantages of three-dimensional visualization of acetabular fractures included: creation of unlimited and unique views by which fracture location, fracture extension, fragment shape and fragment position became more clear, better visualization of acetabular dome and quadrilateral plate and more simple and easier interpretation of these complex fracture patterns. On the other hand, 3D surface reconstructions do not accurately demonstrate undisplaced fractures, intra-articular fragments may be obscured, congruence assessment is uneasy, and soft tissue injuries are not shown. Therefore, we consider 3D images of acetabular fractures as being complementary to and not a substitute to plain radiographs and axial CT scans.

Acetabulum↗
PubMed1994

Potential role of bile duct collaterals in the recovery of the biliary obstruction: experimental study in rats using microcholangiography, histology, serology and magnetic resonance imaging.

Obstructive cholestasis induced in animals at the level of the lobar and common bile ducts is known to be reversible with time. This study was conducted not only to test the hypothesis that formation of bile duct collaterals is responsible for the recovery of biliary obstruction but also to assess the potential of hepatobiliary agent-enhanced magnetic resonance imaging for visualizing cholestasis. A total of 52 rats were divided into three groups with selective biliary obstruction, total biliary obstruction and sham surgery. We studied the evolution of cholestasis by correlating microcholangiographic, histological findings with the results of liver tests and hepatobiliary agent-enhanced magnetic resonance imaging. Lobar cholestasis undetected by liver tests but seen on magnetic resonance imaging as a difference between ligated and unligated lobes, occurred in 15 out of 20 rats subjected to selective biliary obstruction within 48 hr after ligation, and recovered later on as a result of the development of bile duct collaterals. Five rats failed to show local cholestasis as a result of the existence of interlobar accessory bile channels. All 18 total biliary obstruction-treated rats were cholestatic soon after ligation, as confirmed by high serum bilirubin and alkaline phosphatase levels and as documented by poor liver enhancement on magnetic resonance imaging. Cholestasis recovered within 4 wk with normalization of liver enhancement on magnetic resonance imaging as a result of the formation of bile duct collaterals (as demonstrated by microcholangiographic and histological study). Bile duct collateral formation is responsible for the recovery from obstructive cholestasis in rats. A similar mechanism might be present in conditions of bile duct obstruction without cholestasis. Hepatobiliary agent-enhanced magnetic resonance imaging is more sensitive than blood tests in detecting local cholestasis and can be used to monitor noninvasively the evolution of biliary obstruction.

Alanine Transaminase↗
PubMed1994

Localized brain proton NMR spectroscopy in young adult phenylketonuria patients.

Localized proton magnetic resonance spectroscopy with short echo time (TE = 20 ms) was used to investigate biochemical changes in the cerebral white matter of 20 young adult patients (median 19 years) with phenylketonuria (PKU). Results were compared with those of a group of 12 age-matched healthy volunteers (median 25 years). Concentrations of N-acetyl-aspartate (NAA) and choline (Cho) relative to creatine (Cr) were unchanged. However, concentrations of inositol (Ins) relative to creatine were found to be significantly lower (P < 0.001) in the PKU patients (0.30 +/- 0.09 versus 0.57 +/- 0.17). Individual inositol concentrations did not correlate with age, diet, serum phenylalanine (Phe) levels or extent of pathological regions in the T2-weighted images. The lack of correlation with individual data suggests that the decreased inositol concentration could be related to a metabolic deficiency during fetal development. No signal from the phenyl ring protons of phenylalanine was detected in the PKU patients (phenylalanine serum concentration < or = 1.27 mM), which suggests that concentration of phenylalanine may be lower in brain than in serum.

Adolescent↗
PubMed1994

Gadodiamide injection at 0.1 and 0.3 mmol/kg body weight: a phase III double-blind, parallel, randomised clinical investigation of known or suspected central nervous system lesions at 1.5 T.

We studied 78 patients with clinically suspected central nervous system abnormalities (66 intracranial, 12 spinal) by MRI before and after administration of the nonionic contrast medium gadodiamide injection. A parallel, double-blind, randomised design was followed. Two dosages were used: 38 patients underwent studies with 0.1 mmol/kg body weight (b.w.) and 40 with 0.3 mmol/kg b.w. MRI showed abnormalities in 36 of the 38 patients receiving the lower dose and 39 of the 40 patients receiving the higher dose. In 3 patients from each group more lesions were seen following injection than before. The contrast medium improved the delineation of abnormal structures and assessment of tumour size and increased their signal intensity indices in both groups, but especially at the higher dose. Administration of gadodiamide injection provided more diagnostic information in about 75% of the patients, independently of the dose. There were no reports of discomfort, but 7 patients reported adverse events considered unrelated to the gadodiamide injection. The two doses were found to be equally safe and efficient for diagnosis.

Central Nervous System Diseases↗
PubMed1994

Combining fast response and low cost in an intensive care unit viewing station.

This paper describes a prototype viewing station for the Intensive Care Unit (ICU) that combines a low cost with a fast response for the primary viewing tasks. A single monitor is used together with the possibility to switch to another image on the same screen instantaneously. To reduce the time for image retrieval and display, the viewing station anticipates the need for particular images, and preloads these from the disk into the internal memory whenever the computer has some idle time. Preliminary experience suggests that the use of a single monitor is no fundamental limitation for this application. Most of the time, the system can anticipate which images will be required shortly. This has an important impact on the user efficiency.

Data Display↗
PubMed1994

On the problem of geometric distortion in magnetic resonance images for stereotactic neurosurgery.

In this paper, we discuss the issue of geometric distortion in magnetic resonance (MR) images used to plan stereotactic neurosurgical interventions. We analyze the process for the case of Fourier transform imaging and demonstrate that spatial misregistrations are fundamentally due to two causes: deviations of the magnetic field from its ideal value and blood flow. This enables us to relate the causes of geometric distortion to the MR imaging system, the patient and the stereotactic localizer frame. Based on the general model, we propose model refinements and discuss methods for the quantification and correction of all causes. The results of our calculations and experiments indicate that, using the proposed corrections, MRI and MR angiography should be considered valuable and reliable acquisition modalities for the planning of stereotactic neurosurgical interventions.

Brain↗
PubMed1994

Transient inducible events in different tissues: in situ studies in the context of the development and expression of the immune responses to intracellular pathogens.

Intracellular pathogens whether facultative like Mycobacterium sp., e.g. Bacillus Calmette Guérin, Listeria monocytogenes or strictly intracellular like Leishmania sp. initiate either asymptomatic infectious processes or disease depending both on factors of the host (genetic as well as environmental ones) and the infectious/pathogenic agents. In this contribution, we first summarized informations which justify to develop in situ analysis to decipher the sequential events that result in different modes/classes of immune responses. How the mode of the immune response is determined remains a main question to address. Although it has recently become clear, in vitro, that immunocompetent cells and their cytokines are critical to set on a stable mode of immune response, acting on naive T cells, this area deserves more in vivo studies. Indeed, peripheral T cells, at different stages of differentiation, may exist in vivo (a) naive/virgin, (b) experienced, (c) effector T cells, depending on the level of stimulation of the immune system by either endogenous or exogenous (e.g. gut flora) signals. The three chosen examples illustrate our contributions in this field focusing on three different non-lymphoid tissues which may become infected: bone marrow (Bacille de Calmette Guérin), liver (Listeria monocytogenes), skin (Leishmania major). These three illustrations also allow to attract attention on the interest of using mice of genetically different strains the immune response of which is set up under different modes.

Animals↗
PubMed1994

Three cases of non-tumoural tight stenosis of the bifurcation of the hilar bile ducts.

Stenosis of the bifurcation of the hepatic bile duct is usually caused by malignant lesion. We report on three different causes of benign stenosis of the hepatic confluence with a similar radiological pattern on direct cholangiography. The first case is considered a spontaneous neuroma, the second a periductal abscess, and the third case a postoperative stricture Bismuth type 4.

Adult↗
PubMed1994

Right frontal cortex hypometabolism in transient global amnesia. A PET study.

A 60-year-old lady with previous hypertension was studied with PET in the acute (early recovery) phase of an otherwise typical episode of transient global amnesia (TGA). Follow-up over > 1 year was uneventful, and delayed CT scans and MRI showed no brain damage. No medical cause was disclosed despite extensive work-up. The PET study revealed a matched reduction in cerebral blood flow and oxygen consumption over the entire lateral frontal cortex on the right side, with an associated, less significant reduction in ipsilateral thalamic and lentiform nucleus metabolism, but sparing the hippocampal area. These changes, which had resolved at a repeat PET study 3 months later, suggest right prefrontal metabolic depression, possibly secondary to thalamic dysfunction, as the underlying mechanism for TGA in this case, consistent with the emerging involvement of the prefrontal cortex in strategies or control of memory traces retrieval. Thus, in analogy with permanent amnesia, TGA may be a core syndrome with several possible foci of dysfunction along the neuronal networks that subserve explicit memory. In the future, combined PET neuropsychological assessment in the acute stage of TGA may prove useful in defining distinct neuropsychological-topographical subtypes of this intriguing clinical entity.

Amnesia↗
PubMed1994

Contralateral cerebellar hypometabolism: a predictor for stroke outcome?

Contralateral cerebellar hypometabolism (CCH) is a well established remote functional effect of cerebral damage. Because CCH has been reported to be reversible in acute stroke in at least some patients, the value of cerebellar metabolic asymmetry (CbMA; a reflection of the degree of CCH) as a predictor of stroke outcome has been assessed. Measurements of cerebellar oxygen consumption were performed by positron emission tomography (PET) in 16 patients within 5-30 hours of onset of their first ever middle cerebral artery territory stroke, and again 13-56 days later in 12 survivors. The neurological state was quantified at the time of each PET study and at day 60, with both the Mathew and Orgogozo scales. In the early PET study, the CbMAs ranged from around 0% to nearly 50% (individually significant at p < 0.05 in 9/16 patients) but were neither strongly nor consistently correlated with neurological outcome or recovery at day 60. Similarly, the changes in CbMAs from the early to the late PET study were not correlated with the concomitant neurological evolution. At the late PET study, however, there were excellent positive correlations between CbMAs and both neurological status and size of infarction (assessed by CT in the chronic stage). The correlation with neurological status was explained by the correlation with size of infarction. The poor predictive value of CbMAs in the early PET study may be partly because the cerebral metabolic disturbance might still be evolving at this early stage in some cases. Despite this lack of a strong quantitative link between CbMAs at the early PET study and outcome, the outcome was good in all the patients who did not exhibit significant CCH, suggesting that lack of CCH may predict good outcome in acute middle cerebral artery stroke.

Aged↗
PubMed1994

MR imaging evaluation of liver enhancement by Gd-EOB-DTPA in selective and total bile duct obstruction in rats: correlation with serologic, microcholangiographic, and histologic findings.

PURPOSE: To investigate the behavior and potential application of the hepatobiliary magnetic resonance (MR) imaging contrast agent gadolinium-ethoxybenzyl (EOB)-diethylene-triamine-pentaacetic acid (DTPA) in cholestasis. MATERIALS AND METHODS: Rat models of selective biliary obstruction (SBO) (n = 20) and total biliary obstruction (TBO) (n = 14) were used. Serial Gd-EOB-DTPA-enhanced MR images were obtained, and the findings were correlated with serologic, microcholangiographic, and histologic findings. RESULTS: In SBO rats, statistically significantly prolonged enhancement of ligated lobes occurred during the acute phase (P < .01) but was absent during the chronic phase owing to bile collateral vessels. In TBO rats, statistically significantly lower liver enhancement (P < .01) was observed as long as the obstruction persisted, until collateral bile ducts developed. CONCLUSION: The distinction between obstructed and unobstructed liver on Gd-EOB-DTPA-enhanced MR images suggests a novel application for visualizing cholestasis.

Animals↗
PubMed1994

How does the stereotactic workstation help the neurosurgeon?

At the KUL University of Leuven a workstation for the planning of neurosurgical stereotactic procedures has been developed. Its benefits are illustrated in three exemplary cases. The CT and/or MR images, acquired under stereotactic conditions, are transmitted via a PACS network (picture archiving and communication systems) directly to the stereotactic workstation in the operating theater. Target and entry point can be accurately defined on zoomed images. The trajectory can be checked and modified on all registered data sets and on resliced images along any plane. Maximum intensity projection of magnetic resonance angiography data sets along any arbitrary direction show the relative position of the blood vessels and the trajectory. During the preceding 32 months 29 patients were operated on using the stereotactic workstation. Postoperatively no new neurological deficit was observed in any of these patients. The workstation improves patient safety and increases the accuracy of neurosurgical stereotactic operations, because it helps the neurosurgeon to avoid blood vessels and/or important functional areas.

Adult↗
PubMed1994

Imaging of polypoid endoluminal growing bile duct tumors.

We reviewed the radiological documents and protocols of 196 cases of bile duct tumors examined over a period of 12 years: 20 of them (10.2%) presented with a polypoid endoluminal growth. The aim of this study was to provide a better knowledge about the radiological features of this less frequent kind of tumor. In these 20 cases, the correct diagnosis of bile duct lesion was provided in 100% by E.R.C.P., P.T.C., U.S. as well as C.T., and in 42% by arteriography. The correct diagnosis of tumor was made by E.R.C.P. in 86%, by P.T.C. in 88%, by U.S. in 61%, by C.T. in 63%, and by arteriography in 25%. A correct diagnosis of tumor could be reached in all cases by combination of several examination techniques. The anatomopathological diagnosis was: bile duct adenocarcinoma (7 cases), adenocarcinoma of the ampulla of Vater (4), villous adenoma of Vater's ampulla (2), cystadenoma (1), cystadenocarcinoma (1), hepatocellular carcinoma (1), apudoma (1), and metastases (3).

Adenocarcinoma↗