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M Dujardin

Publications and source records attributed to M Dujardin.

16 recordsLinked to original sources
PubMed2006

Pixel-by-pixel deconvolution of bolus-tracking data: optimization and implementation.

Quantification of haemodynamic parameters with a deconvolution analysis of bolus-tracking data is an ill-posed problem which requires regularization. In a previous study, simulated data without structural errors were used to validate two methods for a pixel-by-pixel analysis: standard-form Tikhonov regularization with either the L-curve criterion (LCC) or generalized cross validation (GCV) for selecting the regularization parameter. However, problems of image artefacts were reported when the methods were applied to patient data. The aim of this study was to investigate the nature of these problems in more detail and evaluate strategies of optimization for routine application in the clinic. In addition we investigated to which extent the calculation time of the algorithm can be minimized. In order to ensure that the conclusions are relevant for a larger range of clinical applications, we relied on patient data for evaluation of the algorithms. Simulated data were used to validate the conclusions in a more quantitative manner. We conclude that the reported problems with image quality can be removed by appropriate optimization of either LCC or GCV. In all examples this could be achieved with LCC without significant perturbation of the values in pixels where the regularization parameter was originally selected accurately. GCV could not be optimized for the renal data, and in the CT data only at the cost of image resolution. Using the implementations given, calculation times were sufficiently short for routine application in the clinic.

Algorithms↗
PubMed2005

Quantification of renal perfusion and function on a voxel-by-voxel basis: a feasibility study.

The feasibility of a voxel-by-voxel deconvolution analysis of T(1)-weighted DCE data in the human kidney and its potential for obtaining quantification of perfusion and filtration was investigated. Measurements were performed on 14 normal humans and 1 transplant at 1.5 T using a Turboflash sequence. Signal time-courses were converted to tracer concentrations and deconvolved with an aorta AIF. Parametric maps of relative renal blood flow (rRBF), relative renal volume of distribution (rRVD), relative mean transit time (rMTT), and whole cortex extraction fraction (E) were obtained from the impulse response functions. For the normals average cortical rRBF, rRVD, rMTT, and E were 1.6 mL/min/mL (SD 0.8), 0.4 mL/mL (SD 0.1), 17s (SD 7), and 22.6% (SD 6.1), respectively. A gradual voxelwise rRBF increase is found from the center of two infarction zones toward the edges. Voxel IRFs showed more detail on the nefron substructure than ROI IRFs. In conclusion, quantitative voxelwise perfusion mapping based on deconvolved T(1)-DCE renal data is feasible, but absolute quantification requires inflow correction. rRBF maps and quantitative values are sufficiently sensitive to detect perfusion abnormality in pathologic areas, but further research is necessary to separate perfusion from extraction and to characterize the different compartments of the nephron on the (sub)voxel level.

Algorithms↗
PubMed2004

Choice of the regularization parameter for perfusion quantification with MRI.

Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast enhanced (DCE) MRI. Two robust methods for the selection of the truncation threshold on a pixel-by-pixel basis--generalized cross validation (GCV) and the L-curve criterion (LCC)--were optimized and compared to paradigms in the literature. GCV and LCC were found to perform optimally when applied with a smooth version of TSVD, known as standard form Tikhonov regularization (SFTR). The methods lead to improvements in the estimate of the residue function and of its maximum, and converge properly with SNR. The oscillations typically observed in the solution vanish entirely, and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1-2 min in calculation time and hyperintense clusters in the image. Preliminary experience with clinical data suggests that the latter problem can be resolved using spatial continuity and/or hybrid thresholding methods. In the simulations GCV and LCC are equivalent in terms of performance, but GCV thresholding is faster.

Arteries↗
PubMed2003

[Structural adjustment, cultural adjustment?].

Over the last two decades, multiple studies have been conducted and many articles published about Structural Adjustment Programmes (SAPs). These studies mainly describe the characteristics of SAPs and analyse their economic consequences as well as their effects upon a variety of sectors: health, education, agriculture and environment. However, very few focus on the sociological and cultural effects of SAPs. Following a summary of SAP's content and characteristics, the paper briefly discusses the historical course of SAPs and the different critiques which have been made. The cultural consequences of SAPs are introduced and are described on four different levels: political, community, familial, and individual. These levels are analysed through examples from the literature and individual testimonies from people in the Southern Hemisphere. The paper concludes that SAPs, alongside economic globalisation processes, are responsible for an acute breakdown of social and cultural structures in societies in the South. It should be a priority, not only to better understand the situation and its determining factors, but also to intervene and act with strategies that support and reinvest in the social and cultural sectors, which is vital in order to allow for individuals and communities in the South to strengthen their autonomy and identify.

Cultural Characteristics↗
PubMed2002

[Radiological differential diagnosis of focal liver lesions with anatomo-pathological correlations].

Starting from the macroscopic, microscopic and circulatory characteristics of focal liver lesions, we aimed at assessing the possibilities and the limits of their radiological differential diagnosis. We compared the normal hepatic parenchyma (in terms of: general morphology, cellularity, necrosis, macro- and micro-circulation) and the lesions, assessed following the radiological features of echoreflectivity, RX density, contrast dynamics and specific contrast uptake. The association of morphologic and dynamic features can sometimes lead to an excellent diagnostic specificity (by example: angioma); in other fields, interesting results are noted, but the limits of every modality require further evaluation. This study applies to the following focal lesions: angioma, focal hyperplasia, adenoma, regeneration nodule, hepatocarcinoma, metastasis.

Aged↗
PubMed2000

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery.

BACKGROUND: Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products. METHODS: One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded. RESULTS: The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 +/- 9 x 10(3)/mm3 vs 137 +/- 8 x 10(3)/mm3; p < 0.01). This was paralleled by a reduction in beta-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed. CONCLUSIONS: The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.

Adult↗
PubMed1999

Benign liver lesions: differentiation by magnetic resonance.

Optimal hepatic imaging involves both detection and characterization of focal lesions. Detection involves both determination of the presence of lesions and of their segmental extent of liver involvement. In the evaluation of hypervascular lesions, magnetic resonance imaging (MRI) has a greater impact on patient management than ultrasound (US) and computed tomography (CT). Most benign tumors are incidental findings and do not produce clinical symptoms. They must be accurately diagnosed without using aggressive procedures. Knowledge of their imaging features is essential to avoid unnecessary work-up and to minimize patient anxiety. In this article, the MR appearance, vascular and functional behavior of the most common benign liver tumors will be discussed.

Humans↗
PubMed1999

Cost of illness and disease severity in a cohort of French patients with Parkinson's disease.

OBJECTIVE: To assess the relationship between severity and progression of illness in Parkinson's disease and the use of healthcare resources. DESIGN AND SETTING: This was a prospective cost-of-illness study conducted in France based on clinical observation over a 6-month period of patients with Parkinson's disease treated in the hospital or community setting. Regression analyses were performed to construct the model that offered the best explanation for health expenditures using clinical and sociodemographic indicators. PATIENTS AND PARTICIPANTS: All patients included in the study had well-defined idiopathic Parkinson's disease, were aged > 35 years, were receiving treatment with levodopa or other antiparkinsonian agents, and were capable of completing questionnaires, alone or with the help of a household member. The final study population consisted of 294 patients, of whom 54 were enrolled by general practitioners and 240 by neurologists. INTERVENTIONS: Investigators completed a clinical questionnaire at the beginning and end of the 6-month observation period. Patients completed a questionnaire on their daily living conditions at the beginning and end of the study, and also completed monthly reports of healthcare use and loss of productivity. Patients with motor fluctuations also filled in fluctuation diaries on 4 consecutive days at the beginning and end of the 6-month period. Resource data collected included hospital stays, ancillary care, drug therapy, medical visits and transportation. Social costs were evaluated in nonmonetary terms, with the exception of costs of adapting the home environment. Transfer payments were analysed using reports from patients. MAIN OUTCOME MEASURES AND RESULTS: Hospital stays were the most expensive component of care (39% of costs), followed by ancillary care (30%) and drug therapy (22%). The mean medical cost was 308 euros (EUR) [$US357] for patients followed by a general practitioner and EUR2580 ($US2993) for patients followed by a neurologist. Costs also varied with age and motor fluctuations. Medical costs were strongly correlated with most clinical indicators and the cost generally progressed in line with the severity of the disease. The strongest correlation was between clinical indicators and ancillary care costs. CONCLUSIONS: These results confirm the importance of the social burden of Parkinson's disease. The regression results could be used to evaluate the benefit of novel treatments that reduce the intensity of motor fluctuations.

Adult↗
PubMed1985

IgG (Gm) allotypes and multiple sclerosis in a French population: phenotype distribution and quantitative abnormalities in CSF with respect to sex, disease severity, and presence of intrathecal antibodies.

The association of a given Gm allotype or phenotype with MS susceptibility, as previously described in some Caucasian populations, was not observed in a large French MS group, whether or not considering the possible influence of sex or disease severity. This result could be related to variations in geographical distribution of Gm alleles and MS susceptibility gene(s) or suggests the simultaneous involvement of Gm and other genetic system(s). In contrast, the corresponding CSFs exhibited already known MS-associated abnormalities of IgG1 (G1m) allotype contents, which therefore did not merely result from a Gm-associated MS susceptibility. These quantitative abnormalities were not sex dependent, but may fluctuate with MS severity. The G1m allotype levels in each CSF were not correlated with titers of various intrathecal antibodies but with the number of antibody specificities detected, a picture arguing for a polyclonal, non-antigen-specific activation of G1m allotype-producing B cells present in MS brain.

Antibodies↗
PubMed1984

[Hematoma of the pyramidal muscle. A complication of anticoagulant treatment].

A patient developed a hematoma of the pyramidal muscle as a complication of anticoagulant treatment. The lesion provoked an entrapment neuropathy due to the compression between the muscle and the iliac spine of the great sciatic, inferior gluteal and pudendal nerves. Hyperalgic paralysis of the leg and buttock was associated with bladder sphincter disorders and impotence, a remarkable finding in view of the unilateral disturbance in nervous control. Pain, and urinary and sexual disorders were reversed dramatically by an early neurolysis. A CT scan enables the identification of the lesion.

Abdominal Muscles↗
PubMed1984

[Dura mater arteriovenous fistula and lateral sinus occlusion].

It is rare to find an arteriovenous fistula of the dura mater associated with a venous sinus occlusion, but this may provide evidence of an etiology. In the case reported, the malformation was probably of congenital origin, the sinus thrombosis having occurred secondarily to the venous stasis adjacent to the fistula.

Aged↗
PubMed1977

Ferastral, an iron-poly (sorbitol-gluconic acid) complex, in the treatment of severe iron-deficiency anaemia in pregnancy.

Thirteen pregnant women with iron-deficiency anaemia have been treated with Ferastral. In a further seven women, Ferastral was given 24 hours before delivery, when induction of labour was indicated, to investigation of iron concentration in maternal serum, cord blood and amniotic fluid simultaneously. The efficacy of Ferastral was demonstrated by a significant increase in haemoglobin and haematocrit. No serious reactions occurred and no evidence was found of disturbance of liver or renal function. It was shown that Ferastral does not pass the placental barrier and that no direct transport takes place through the uterine wall or amnion. No effects on the newborn were demonstrated.

Adolescent↗
PubMedDate not supplied

Inverted Meckel's diverticulum as a leading point for ileoileal intussusception in an adult: case report.

Intussusception due to an inverted Meckel's diverticulum is considered a rare occurrence. We present a case of a 37-year-old male with anemia and melena due to an inverted Meckel's diverticulum at the base of an ileoileal intussusception. To our knowledge, this is the first case in which small bowel enema, computed tomography, and magnetic resonance imaging showed the pathology.

Adult↗