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Biomedical subjects

G Marchal

Publications and source records attributed to G Marchal.

At least 127 records · Page 7Linked to original sources
PubMed1997

Gastroepiploic artery coronary bypass graft: non-invasive patency evaluation using color and duplex Doppler ultrasonography.

OBJECTIVE: Color and duplex Doppler ultrasound and digital subtraction angiography were compared for the evaluation of graft patency of the gastroepiploic artery (GEA). METHODS: In 77 observations, ultrasound and digital subtraction angiography were compared. The coronary resistance index (cRI) was defined as the maximal systolic flow velocity minus the maximal diastolic flow velocity, divided by the maximal systolic flow velocity. On digital subtraction angiography, the graft was considered patent, occluded, or patent but non-functional. Grafts were defined as non-functional when they had a diameter of less than 5F with the absence of opacification of the native coronary artery. RESULTS: Of the 77 observations, 64 GEAs were patent angiographically, three were occluded and ten grafts were considered as patent but non-functional. Using color and duplex ultrasound, the GEA was identified in 65 out of 77 observations. There were no cases of false positive visualization of the GEA. All sonographically detected non-functional grafts (n = 7) had a cRI of greater than 0.60. When the non-visualized grafts are considered either non-functional or occluded, a cut-off value for a cRI of 0.60 results in a sensitivity and specificity of 100 and 75%, respectively. CONCLUSION: We propose ultrasound as a primary screening tool for evaluating graft patency. While color Doppler is a suitable technique for graft visualization, spectral analysis with the calculation of a cRI is required for functional evaluation.

Adult↗
PubMed1997

Localization and determination of infarct size by Gd-Mesoporphyrin enhanced MRI in dogs.

BACKGROUND: Accurate localization and sizing of a myocardial infarction are necessary for clinical decision making and even more in research. Gd-Mesoporphyrin enhanced magnetic resonance imaging (MRI) was recently shown to specifically delineate necrosis in liver tumors, renal and muscle necrosis and myocardial infarction in rats. In this study, we investigated this technique's potential to accurately delineate myocardial infarction in a larger animal species, the dog. METHODS: Myocardial infarction was induced in 8 dogs by ligation of the left anterior descending coronary artery, 4 of which were reperfused after 3 hr Gd-Mesoporphyrin (0.05 mmol/kg) was injected intravenously 210 min after the onset of ischemia (n = 6) or after 24 hr in 2 dogs with non-reperfused infarctions. MRI was performed 10 hr after administration of Gd-Mesoporphyrin. In vivo MRI consisted of EKG-triggered, respiratory gated T1-weighted spin echo and segmented turboFLASH long and short axis measurements. Post-mortem, a spin echo short axis measurement was repeated. Infarct size was determined planimetrically by TTC staining of left ventricular slices. RESULTS: In all instances, there was a very close qualitative agreement between the MRI and TTC defined myocardial infarction. Quantitatively, the linear regression from post-mortem MRI to TTC determined infarct size yielded a result very close to the line of identity (regression coefficient: 0.980 +/- 0.026, p < 0.000001, adjusted R2 = 0.964). CONCLUSION: We conclude that Gd-Mesoporphyrin enhanced MRI is a promising tool for the accurate delineation of myocardial infarction.

Animals↗
PubMed1997

Liver imaging. Clinical applications and future perspectives.

Primary hepatocellular carcinoma and liver metastases affect several million people each year. The main imaging modalities to detect and assist diagnosis of primary and secondary liver tumours include MR imaging, CT, and US. The value of these techniques is further increased by the use of contrast agents which increase the sensitivity, and sometimes also the specificity, of the investigations. The relative advantages and drawbacks of the different contrast agents and imaging modalities in the detection and characterisation of liver tumours are discussed. Currently there is no consensus amongst investigators as to which is superior, due to the technical complexities and number of combinations possible within each of the different modalities. There continues to be advances in the hardware and software of imaging equipment, as well as a trend to develop new contrast agents with more organ-specificity. These include those targeting the hepatocytes, such as mangafodipir trisodium (MnDPDP, Teslascan), and those with reticuloendothelial cell specificity, such as the superparamagnetic iron oxides. These developments have the potential for making significant contributions to the diagnostic value of imaging procedures and, by reducing the number of investigations necessary to reach a final diagnosis, having a significant and beneficial impact on the pharmaco-economics of patient health care.

Carcinoma, Hepatocellular↗
PubMed1997

Comparison of manganese biodistribution and MR contrast enhancement in rats after intravenous injection of MnDPDP and MnCl2.

PURPOSE: To compare the time course of the MR enhancing properties and biodistribution of manganese (Mn) in rats given i.v. Mn dipyridoxyl diphosphate (MnDPDP) or Mn chloride (MnCl2). MATERIAL AND METHODS: Twenty-four adult rats were injected i.v. with 5 mumol/kg MnDPDP or MnCl2, or with 0.5 ml/kg saline. High resolution T1-weighted MR imaging was performed during early (10 min), mid (2 h) and late (24 h) phases after injection. Mn concentrations in major organs were measured by using an ICP-AES technique, and correlated with MR findings. RESULTS: Variable degrees of signal enhancement of major organs observed in MR images corresponded with the amount of Mn uptake after injection of MnDPDP or MnCl2. A prominently lower cardiac, pancreatic and hepatic uptake of Mn was seen at 10 min in rats injected with MnDPDP compared with those given MnCl2 and this was reflected in a difference in signal intensity (SI) in the MR images. At 2 h, the Mn content and SI in the major organs were similar with both MnDPDP and MnCl2. An overall Mn clearance was achieved at 24 h without any important organ retention, with kidney excretion of Mn seen only with MnDPDP. CONCLUSION: With both MnDPDP and MnCl2, the Mn uptake correlates with the SI enhancement in tissues. The reduced initial cardiac uptake of Mn after MnDPDP treatment compared to MnCl2 may account for the favourable cardiovascular safety of the contrast agent. These data contribute to an understanding of SI enhancement by MnDPDP, and are consistent with other studies showing that at a dose of 5 mumol/kg, MnDPDP can be safely used as a potent MR organ-specific contrast agent.

Animals↗
PubMed1997

Clinical implications of studies with MnDPDP in animal models of hepatic abnormalities.

Mangafodipir trisodium (manganese dipyridoxal diphosphate or MnDPDP) has been introduced as a hepatobiliary MR contrast agent (Teslascan). Its potential to assist in the characterisation of focal liver lesions, the diagnosis of local and global obstructive cholestasis and the evaluation of hepatic function in diffuse liver diseases has been explored in multiple pre-clinical experiments with appropriate animal models. The prompt negative contrast enhancement and delayed peritumoural rim-enhancement seen after i.v. injection of MnDPDP are 2 typical features of primary and secondary liver tumours with high malignancy, while the persistent positive enhancement is a sign of liver tumours of well preserved hepatocytic nature. Liver with local and total biliary obstruction can be visualized in MnDPDP-enhanced MR images as a region with prolonged signal enhancement. This agent could also be used to non-invasively evaluate diffuse liver diseases of different causes. In the present paper, we review the experimental data in the literature, provide some unpublished results and discuss the potential impact on the clinical use of MnDPDP in the liver. We conclude that MnDPDP is a promising MR liver contrast agent for the detection and characterisation of focal and diffuse liver diseases.

Animals↗
PubMed1997

Magnetic resonance imaging-histomorphologic correlation studies on paramagnetic metalloporphyrins in rat models of necrosis.

RATIONALE AND OBJECTIVES: The authors intended to confirm previous findings that paramagnetic porphyrins are avid only for intratumoral nonviable tissues, but not for viable tumor cells, and to test the hypothesis that necrosis, regardless of location and origin, can be visualized by metalloporphyrin enhanced magnetic resonance imaging (MRI). METHODS: Intravenous administrations of gadolinium mesoporphyrin (Gd-MP), manganese tetraphenylporphyrin (Mn-TPP), manganese methylpyrroporphyrin-gadopentetate dimeglumine complex (Mn-MPP-Gd) and manganese tetra(4-sulfonatophenyl)porphyrin (MnTPPS4) at 0.05 mmol/kg were compared with those of gadopentetate dimeglumine (Gd-DTPA) at 0.1 mmol/kg in 38 rats with cholestatic liver necrosis, alcohol- and laser-induced coagulation necrosis in liver, and skeletal muscle, reperfused hepatic infarction, and segmental renal infarction. T1-weighted spin echo MRI (TR/TE = 300/15 mseconds) was acquired before and as long as 48 hours after injection, matched with histologic findings, and correlated with Gd/ Mn tissue content measurements. RESULTS: Both Gd-DTPA and the four metalloporphyrins initially caused a similar nonspecific negative contrast enhancement in the necrosis. However, a strong and persisting positive enhancement (necrosis-to-normal contrast ratio ranging from 1.5 to 2.0) developed only with metalloporphyrins in all types of necrosis. In liver and kidney, Gd and Mn concentrations at 24 hours were comparable in necrotic and normal tissues. In muscle, the concentrations were more than eight times higher in necrotic than in normal tissue. CONCLUSIONS: The implied affinity of metalloporphyrins for necrosis with presumably increased relaxivity suggests a possible mode of targetability for MRI contrast media that may elicit novel applications.

Animals↗
PubMed1997

Multimodality image registration by maximization of mutual information.

A new approach to the problem of multimodality medical image registration is proposed, using a basic concept from information theory, mutual information (MI), or relative entropy, as a new matching criterion. The method presented in this paper applies MI to measure the statistical dependence or information redundancy between the image intensities of corresponding voxels in both images, which is assumed to be maximal if the images are geometrically aligned. Maximization of MI is a very general and powerful criterion, because no assumptions are made regarding the nature of this dependence and no limiting constraints are imposed on the image content of the modalities involved. The accuracy of the MI criterion is validated for rigid body registration of computed tomography (CT), magnetic resonance (MR), and photon emission tomography (PET) images by comparison with the stereotactic registration solution, while robustness is evaluated with respect to implementation issues, such as interpolation and optimization, and image content, including partial overlap and image degradation. Our results demonstrate that subvoxel accuracy with respect to the stereotactic reference solution can be achieved completely automatically and without any prior segmentation, feature extraction, or other preprocessing steps which makes this method very well suited for clinical applications.

Algorithms↗
PubMed1997

Immunoblot analysis for serodiagnosis of tuberculosis using a 45/47-kilodalton antigen complex of Mycobacterium tuberculosis.

We evaluated the immunoglobulin G (IgG) antibody response to the 45/47-kDa secreted protein of Mycobacterium tuberculosis by immunoblot assay, to assess its potential value for serological diagnosis. Control subjects consisted of healthy volunteers with negative or positive tuberculin skin tests. Most (>98%) scored negative in an immunoblot test when the sera were analyzed at a 1:400 dilution. Approximately 40% of sera (diluted 1 in 400) from tuberculous patients (positive smears) recognized the antigen complex. The sensitivity of the test for patients suffering from extrapulmonary tuberculosis was similar to that for patients suffering from pulmonary tuberculosis but who had negative smears. The frequency of positive reactions among the patients suffering from other pulmonary diseases was similar to that among the control subjects. In tuberculous patients infected with human immunodeficiency virus, the sensitivity of the immunoblot test was significantly lower. Thus, this test based on an antigen complex used in an immunoblot assay to detect the presence of IgG antibody has a specificity of 98% and a sensitivity of 40%. The simultaneous use of different purified antigens, selected at the same high specificity level, may improve the sensitivity of such an assay.

AIDS-Related Opportunistic Infections↗
PubMed1997

Transient global amnesia: implicit/explicit memory dissociation and PET assessment of brain perfusion and oxygen metabolism in the acute stage.

OBJECTIVES: To assess explicit memory and two components of implicit memory--that is, perceptual-verbal skill learning and lexical-semantic priming effects--as well as resting cerebral blood flow (CBF) and oxygen metabolism (CMRO2) during the acute phase of transient global amnesia. METHODS: In a 59 year old woman, whose amnestic episode fulfilled all current criteria for transient global amnesia, a neuropsychological protocol was administered, including word learning, story recall, categorical fluency, mirror reading, and word stem completion tasks. PET was performed using the (15)O steady state inhalation method, while the patient still exhibited severe anterograde amnesia and was interleaved with the cognitive tests. RESULTS: There was a clear cut dissociation between impaired long term episodic memory and preserved implicit memory for its two components. Categorical fluency was significantly altered, suggesting word retrieval strategy--rather than semantic memory--impairment. The PET study disclosed a reduced CMRO2 with relatively or fully preserved CBF in the left prefrontotemporal cortex and lentiform nucleus, and the reverse pattern over the left occipital cortex. CONCLUSIONS: The PET alterations with patchy CBF-CMRO2 uncoupling would be compatible with a migraine-like phenomenon and indicate that the isolated assessment of perfusion in transient global amnesia may be misleading. The pattern of metabolic depression, with sparing of the hippocampal area, is one among the distinct patterns of brain dysfunction that underlie the (apparently) uniform clinical presentation of transient global amnesia. The finding of a left prefrontal hypometabolism in the face of impaired episodic memory and altered verbal fluency would fit present day concepts from PET activation studies about the role of this area in episodic and semantic memory encoding/retrieval. Likewise, the changes affecting the lenticular nucleus but sparing the caudate would be consistent with the normal performance in perceptual-verbal skill learning. Finally, unaltered lexical-semantic priming effects, despite left temporal cortex hypometabolism, suggest that these processes are subserved by a more distributed neocortical network.

Acute Disease↗
PubMed1997

Size quantification of liver metastases in patients undergoing cancer treatment: reproducibility of one-, two-, and three-dimensional measurements determined with spiral CT.

PURPOSE: To assess the reproducibility of one-, two-, and three-dimensional measurements of the size of liver metastases. MATERIALS AND METHODS: The sizes of 10 liver metastases were determined 200 times: Ten observers measured each lesion by using images obtained at two different CT studies and with five different measurement techniques (maximum diameter, product of diameters, area, volume, and product of three diameters). They repeated each measurement in a separate session. The influence of measurement technique and lesion type (size and morphologic appearance) on measurement reproducibility was assessed. RESULTS: Three-dimensional measurements proved to be as reproducible as one- and two-dimensional measurements. Measurement reproducibility was influenced mainly by the size (P < .0001) and morphologic appearance (P < .01) of the lesions. CONCLUSION: Three-dimensional size measurements obtained with spiral CT are reproducible and could therefore replace the two-dimensional measurements of tumor size currently obtained with follow-up CT studies.

Humans↗
PubMed1997

Multivariate genetic analysis of maximal isometric muscle force at different elbow angles.

The maximal isometric moment at five different elbow joint angles was measured in 25 monozygotic and 16 dizygotic male adult twin pairs (22.4 +/- 3.7 yr). Genetic model fitting was used to quantify the genetic and environmental contributions to individual differences in isometric strength. Additive genetic factors explained 66-78% of the variance in maximal torque at 170-140-110 and 80 degrees flexion (extension = 180 degrees). At 50 degrees flexion, common and subject-specific environmental factors contributed equally to the variation. The contribution of unique environmental factors concurs with the level of variability in muscle activation and (dis)-comfort of torque production in the specific angle. The relative contribution of lever arm and force-length relationship in torque varies according to the angle. Because these factors might be genetic, this variability is reflected in the genetic contribution at the extreme angles of 170 and 50 degrees. Multivariate analyses suggested a general set of genes that control muscle area and isometric strength, together with a more specific strength factor. Genetic correlations were high (0.82-0.99). Genes responsible for arm-segment lengths did not contribute to muscle area nor to isometric strength.

Adolescent↗
PubMed1997

Dual-phase helical CT of the liver: value of an early-phase acquisition in the differential diagnosis of noncystic focal lesions.

OBJECTIVE: Contrast-enhanced helical CT images of the liver are usually obtained during the portal vein phase (PVP), during which the parenchyma achieves peak enhancement. The purpose of this study was to determine whether the addition of arterial-phase (AP) scans would lead to improved characterization of focal lesions. MATERIALS AND METHODS: We reviewed the CT appearance of 102 focal lesions with a proven diagnosis. In the first part of the study, we assessed whether the addition of AP scans influenced the diagnostic performance of the three observers. In the second part of the study, we analyzed the morphologic appearance revealed on CT scans of the different types of lesions in the AP and PVP. RESULTS: The addition of AP scans led to a significant increase in the number of correct diagnoses: 71 lesions (70%) were correctly diagnosed with CT scans in both the AP and the PVP, compared with 54 lesions (53%) correctly diagnosed with CT scans in the PVP alone (p < .01). The largest difference was observed in the diagnosis of focal nodular hyperplasia (FNH) and adenoma (16/24 correct diagnoses instead of 6/24) (p < .005). Conversely, AP images did not significantly contribute to the diagnosis of hemangiomas and metastases. The following morphologic features were seen much more often on AP scans than on PVP scans and had a high positive predictive value (PPV): spoke-wheel pattern (FNH; PPV, 100%), central feeding vessel (FNH; PPV, 100%), and heterogeneous appearance with hyperdense components (hepatocellular carcinoma; PPV, 75%). CONCLUSION: Our data show that the radiologists' evaluation of CT scans in both the AP and the PVP improves the differentiation of hepatocellular carcinoma and FNH from other types of hepatic neoplasms.

Adenoma, Liver Cell↗
PubMed1997

Imaging of gallbladder and biliary tract before laparoscopic cholecystectomy: comparison of intravenous cholangiography and the combined use of HASTE and single-shot RARE MR imaging.

To compare intravenous cholangiography (i.v.c.) and magnetic resonance imaging (MRI) as preoperative imaging techniques in patients scheduled for laparoscopic cholecystectomy. Twenty patients underwent i.v.c. and MRI, 40 axial 'localizer' images were first obtained with a half-Fourier single-shot turbo spin echo (HASTE) sequence. Next, an extremely high T2-weighted rapid acquisition relaxation enhancement (RARE) acquisition (TE = 1100 msec) was used for MR cholangiography. All images obtained with i.v.c. and MRI were independently analyzed by two observers. The relative visibility of the (normal or abnormal) gallbladder (GB), cystic duct (CD), and bile ducts (BD) on both types of images was scored as follows: 1 = MRI better than i.v.c.; 2 = no difference; 3 = i.v.c. better than MRI. We observed 3 anatomic variants: 1 of the cystic duct and 2 of the intrahepatic bile ducts; 15 patients had gallstones; one had cholecystitis. Magnetic resonance images were considered more informative than i.v.c.-images for visualization of GB in 11 patients (55%), for CD in 9 patients (45%), and in 8 patients (40%) for visualization of the CBD. Intravenous cholangiography outperformed MRI in the evaluation of the CBD and CD in one patient (5%). The combined use of half-Fourier single-shot RARE and high T2-weighted RARE MR imaging is a valuable alternative to i.v.c. in the preoperative evaluation of gallbladder and biliary tract.

Adult↗
PubMed1997

[Pathophysiology and immunology of tuberculosis].

Only isolated bacilli are capable of reaching the pulmonary alveoli. Draining towards the lymphatic glanglia which corresponds to the infected pulmonary segment or transported by alveolar macrophages after being phagocytosed, these bacteria liberate molecules (antigens) presented to T lymphocytes. After clonal expansion, specific lymphocytes migrate out of the lymph nodes. From the initial area, other areas are infected and these specific lymphocytes lead to a local inflammatory reaction which is very rich in cells, in particular in activated monocytes and macrophages. The inflammatory granuloma or "tubercle" leads to control of the infection in the majority of cases. The inverse of this is that in five or ten per cent of cases a part of this granuloma is necrosed and caseus and leads to (or accompanies) an intense bacterial multiplication. At this stage with the formation of the cavity numerous bacilli may seed other regions of the lung or infect other people. The immune response in which T lymphocytes play a fundamental role thus permit at the same time the control of infection and the establishment of a lesion assuring the perpetuation of the species of Mycobacterium tuberculosis by contaminating new subjects. The respective roles of the different types of T lymphocyte and of liberated lymphokines remains to be determined. Also the principle antigens of the bacillus need to be characterised. The "dominant" antigens are probably liberated by bacteria during their growth phase.

Antigen-Presenting Cells↗