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Biomedical subjects

P Dupont

Publications and source records attributed to P Dupont.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Value of MRCP for detection of choledocholithiasis in symptomatic patients: one-year experience with a standardized high resolution breath-hold technique].

In our institution, MRCP is actually replacing diagnostic ERCP. This study is addressing its accuracy in the diagnosis of symptomatic choledocholithiasis. 137 MRCP were performed in patients with upper abdominal pain and biological anomalies (n = 48), pain with cholelithiasis at sonography (n = 69) or non-alcoholic acute pancreatitis (n = 20) on a 1.5 T system with high gradients using a standardized combination of breath-hold HASTE and RARE sequences. We included in our study 74 patients who underwent as second test ERCP (n = 36), peroperative cholangiography (n = 13), or extensive follow-up with laboratory tests and/or sonography (n = 25). All examinations were judged as diagnostic, discrepancies between direct cholangiography and MRCP being noted in 4 patients (5.4%). Lithiasis was misinterpreted on MRCP as bubbles in 2 patients after sphincterotomy or surgery. We had two false positive diagnoses on MRCP: in one patient peroperative cholangiography was negative and in the other one ERCP was negative. With a sensitivity and PPV of 92%, a specificity and NPV of 96% MRCP in our experience is shown as an accurate diagnostic tool for the detection of stone in the common bile duct replacing ERCP.

Adolescent↗
PubMed2000

Utility of positron emission tomography for the staging of patients with potentially operable esophageal carcinoma.

PURPOSE: A prospective study of preoperative tumor-node-metastasis staging of patients with esophageal cancer (EC) was designed to compare the accuracy of 18-F-fluoro-deoxy-D-glucose (FDG) positron emission tomography (PET) with conventional noninvasive modalities. PATIENTS AND METHODS: Seventy-four patients with carcinomas of the esophagus (n = 43) or gastroesophageal junction (n = 31) were studied. All patients underwent attenuation-corrected FDG-PET imaging, a spiral computed tomography (CT) scan, and an endoscopic ultrasound (EUS). RESULTS: FDG-PET demonstrated increased activity in the primary tumor in 70 of 74 patients (sensitivity: 95%). False-negative PET images were found in four patients with T1 lesions. Thirty-four patients (46%) had stage IV disease. FDG-PET had a higher accuracy for diagnosing stage IV disease compared with the combination of CT and EUS (82% v 64%, respectively; P: =.004). FDG-PET had additional diagnostic value in 16 (22%) of 74 patients by upstaging 11 (15%) and downstaging five (7%) patients. Thirty-nine (53%) of the 74 patients underwent a 2- or 3-field lymphadenectomy in conjunction with primary curative esophagectomy. In these patients, tumoral involvement was found in 21 local and 35 regional or distant lymph nodes (LN). For local LN, the sensitivity of FDG-PET was lower than EUS (33% v 81%, respectively; P: =.027), but the specificity may have been higher (89% v 67%, respectively; P: = not significant [NS]). For the assessment of regional and distant LN involvement, compared with the combined use of CT and EUS, FDG-PET had a higher specificity (90% v 98%, respectively; P: =. 025) and a similar sensitivity (46% v 43%, respectively; P: = NS). CONCLUSION: PET significantly improves the detection of stage IV disease in EC compared with the conventional staging modalities. PET improves diagnostic specificity for LN staging.

Adenocarcinoma↗
PubMed2000

Self-injection ictal SPECT during partial seizures.

The authors compared ictal SPECT injection performed by medical personnel with self-injection ictal SPECT in six patients with refractory temporal lobe epilepsy. Self-injection was safe and started faster. Self-injection subtraction ictal SPECT coregistered to MRI (SISCOM) was localizing in three patients who had a complex partial seizure, but only one of three patients who had a simple partial seizure, which may limit its usefulness in clinical practice. The localizing information of self-injection was better in three patients, and obviated the need for depth-EEG studies in one patient.

Adult↗
PubMed2000

Quantitative distribution studies in animals: cross-validation of radioluminography versus liquid-scintillation measurement.

The results of a cross-validation of the radioluminography (RLG) and liquid scintillation counting (LSC) methods are presented. The methods for the determination of radioactivity concentrations were compared in 16 organs, after administration of (14)C-labeled substances to rats. LSC measurements of two kinds were used as reference methods for RLG: (1) quantitative determination of radioactivity after conventional dissection (interindividual comparison) and (2) quantitative determination of radioactivity in tissue punches taken from the whole-body sections after they had undergone RLG measurement (intraindividual comparison). Blood standards containing known concentrations were used for calibration. For statistical evaluation log-linear regression analysis of paired concentration values and organ-specific 95% confidence intervals of the log-transformed RLG/LSC concentration quotients were compared. For most organs, the slopes of the regression lines and the means of the concentration quotients were within the defined equivalence range of 0.80-1.25. Deviations were distinctly smaller in the intraindividual comparison. For some organs, however, it became clear that found concentrations were affected by self-absorption (RLG) and by differences in sample preparation (LSC). In conclusion, quantification with RLG is a reliable and reproducible method with comparable measurement precision and greater accuracy in respect of tissue localization, compared to LSC (dissection).

Animals↗
PubMed2000

Tumour necrosis factor (TNF) gene polymorphism in Crohn's disease (CD): influence on disease behaviour?

Crohn's disease (CD) is a multifactorial disease with genetic heterogeneity. TNF-alpha plays a key role in the development of the mucosal lesions. The aim of our work was to study a single base pair polymorphism located in the promoter region of TNF gene, in a large population of CD patients with well defined phenotypes. One hundred and ninety-three patients with CD and 98 ethnically matched controls were studied. The -308 single base pair polymorphism of TNF gene was studied using an allele-specific polymerase chain reaction. Genotype and allelic frequencies were compared between patients and controls and between subgroups of patients defined by sex, age at diagnosis, familial history, location of disease, type of disease, extra-intestinal manifestations, and response to steroid treatment. In 29 patients a measure of TNF-alpha production by colonic biopsies was performed. The frequency of the allele TNF2 as well as the proportion of carriers of the allele TNF2 were slightly but not significantly lower in CD than in controls (11.9% versus 14.8% and 21.5% versus 27.6%, respectively). A more prominent difference in frequencies of allele TNF2 and in proportions of TNF2 carriers was found when comparing subgroups of patients. The frequency of allele TNF2 was significantly higher in steroid-dependent than in non-steroid-dependent disease (28.1% versus 10.3%; Delta = 17.8%, 95% confidence interval (CI) = 6.3-29.5%, P = 0.0027) and tended to be higher in colonic than in small bowel disease and in fistulizing than in stricturing disease. Furthermore, TNF2 carriers tended to be more frequent in patients with steroid-dependent than non-steroid-dependent disease (43.8% versus 19.3%; Delta = 24.5%, 95% CI = 3.6-45.4%, P = 0.022), in patients with fistulizing than stricturing disease (26.5% versus 9.6%; Delta = 16.9%, 95% CI = 1. 1-32.6%, P = 0.036), and in patients with colonic than small bowel disease (26.5% versus 11.1%; Delta = 15.4%, 95% CI = -0.8-31.6%, P = 0.063). Finally, patients carrying at least one copy of allele 2 were found to produce slightly more TNF-alpha at the colonic level. The -308 TNF gene polymorphism may have a slight influence on the behaviour of CD. The carriage of allele 2 may favour steroid-dependent disease and to a lesser extent fistulizing and colonic disease, possibly secondary to a more intense TNF-alpha-driven inflammatory reaction at the mucosal level.

Adult↗
PubMed2000

Maintaining and shifting attention within left or right hemifield.

Positron emission tomography (PET) was used to examine two questions: (i) which structures of the intact human brain change their activity with the direction of attention to left or right visual field; and (ii) how does activity in these structures, and in parietal cortex in particular, depend on the frequency of attentional shifts? Subjects were required to discriminate the orientation of peripheral gratings. The two main experimental variables were the attended hemifield (left or right) and the proportion of trials requiring a shift within that hemifield (20% or 80%). A detection control condition was also included. Behaviourally, subjects were less accurate and significantly slower when a trial required a shift than when it did not. Ventral and lateral occipital areas showed significantly higher blood flow levels contralateral to the direction of attention. Replicating previous work, there was also a significant main effect of the direction of attention in left lateral prefrontal cortex: blood flow levels were higher during leftward attention in comparison both to baseline and to rightward attention. This left frontal effect reached significance in single subjects in whom several activation sites could be distinguished within left middle and inferior frontal gyrus. Right and left parietal cortex were activated during both left- and right-field attention conditions, with a tendency for higher activity levels when attention was directed contralaterally. Contrary to the experimental hypothesis, however, parietal regions were not activated differentially by high versus low numbers of attentional shifts. The current experiment confirms that left frontal convexity is sensitive to manipulations of the direction of visuospatial attention. The results do not indicate a specific role of parietal cortex in attentional shifting.

Adult↗
PubMed1999

Decreased corticosensitivity in quiescent Crohn's disease: an ex vivo study using whole blood cell cultures.

Corticosensitivity influences the degree and the duration of an inflammatory reaction by altering target cell responses to endogenous and/or exogenous glucocorticoids. Indeed, different clinical responses to glucocorticoids have been observed among patients with Crohn's disease, suggesting different degrees of corticosensitivity in these subjects. The purpose of this study was to compare the corticosensitivity of patients with quiescent Crohn's disease to that of healthy subjects (HS). Nineteen patients with quiescent Crohn's disease and 14 HS were studied; all patients were steroid-free for at least six months; 7 of the 19 were corticosteroid-dependent (CSD) and treated with nonglucocorticoid immunosuppressants at the time of the study. Corticosensitivity was measured by the inhibition of LPS-induced cytokine secretion in whole blood cell cultures treated with increasing concentrations (10(-9) to 10(-6) M) of dexamethasone. Tumor-necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1 beta (IL-1 beta) were measured using specific immunoassays. Crohn's disease patients had a markedly decreased dexamethasone-mediated inhibition of TNF-alpha (P < 0.01), IL-6 (P < 0.001), and IL-1 beta (P < 0.01) compared to healthy subjects, with a shift of the dexamethasone dose-response curve to the right. No significant differences in the basal and LPS-stimulated secretion of the three cytokines were observed between CSD and non-CSD patients, and both subgroups of patients had similar degrees of dexamethasone-mediated cytokine inhibition. We conclude that patients with Crohn's disease have a significant decrease in the corticosensitivity of their leukocytes. This may be related to a specific genetic/constitutional background and/or could be acquired, due to inflammation-related endocrine and/or immune factors.

Adult↗
PubMed1999

Regional brain activity during shape recognition impaired by a scopolamine challenge to encoding.

In the present positron emission tomography (PET) study, we examine the effect of a scopolamine-induced challenge to encoding upon the pattern of regional cerebral blood flow during recognition of a list of abstract visual shapes 3 days after encoding of these shapes. This study was conducted to test hypotheses concerning the fusiform and thalamic contributions to object recognition arising from a previous imaging study of impaired recognition. In that study, we demonstrated that activity in the fusiform cortex and the thalamus during shape recognition was modulated by memory challenges. These memory challenges included, on one hand, impaired storage as a consequence of diazepam administration during encoding, and, on the other hand, impaired retrieval caused by a perceptual challenge. Activation in the fusiform cortex decreased during impaired recognition, irrespective of the type of challenge. In contrast, thalamic activation increased only when the recognition deficit resulted from impaired memory storage. Based on these results, we hypothesized that fusiform activation during recognition reflects the matching of an incoming stimulus with a stored one, whereas thalamic activation reflects retrieval attempts. These hypotheses would receive considerable support if scopolamine, which also impairs memory storage, induced similar modulations of fusiform and thalamic activation. In the present study, we observed that a scopolamine challenge to encoding does indeed modulate the activity in the very same regions that were previously modulated by a diazepam challenge. Hence, a similar memory deficit, although primarily effected through different neurochemical pathways, was paralleled by a similar modulation of activity in the same set of nodes in the shape recognition network. In the fusiform cortex, scopolamine decreased recognition-related activity, as did the sensory challenge of retrieval. Furthermore, covariate analysis demonstrated that the level of fusiform activity linearly correlates with behavioural performance. In the thalamus, activation increased following impaired encoding. This is in accordance with the idea that enhanced thalamic activity reflects increased effort expended in retrieval. In addition, in the intraparietal sulcus, differential activation also increased following impaired memory storage, possibly reflecting enhanced visuospatial attention in an effort to compensate for impaired performance.

Administration, Oral↗
PubMed1999

Brain activity underlying stereotyped and non-stereotyped retrieval of learned stimulus-response associations.

When humans retrieve learned stimulus-response associations in a stereotyped manner the necessary brain structures may differ from those required when the same associations must be retrieved and adapted to new circumstances. We tested this hypothesis by means of tasks that resembled those employed in monkeys, using positron emission tomography (PET). Stimuli consisted of abstract two-dimensional shapes. Stereotyped retrieval of learned stimulus-response associations was studied by the use of a concurrent discrimination task with fixed pairing. This was contrasted with conditions requiring retrieval and adaptation of learned associations: forced-choice recognition, response reversal and concurrent discrimination with random pairing. Visuomotor control, passive viewing and fixation conditions were also included. During concurrent discrimination with fixed pairing, the left lower precentral gyrus and rostral anterior cingulate demonstrated higher blood flow levels in comparison with recognition, concurrent discrimination with random pairing, and to a lesser degree, response reversal. In the left lower precentral gyrus these blood flow levels were also higher in comparison with control conditions. Conversely, during recognition, concurrent discrimination with random pairing and reversal, a single region within the right inferior frontal gyrus demonstrated higher blood flow levels in comparison with concurrent discrimination with fixed pairing and control conditions. This right inferior frontal gyrus activation did not depend on the need for active familiarity judgements or response inhibition. To conclude, the left lower precentral gyrus is more active during stereotyped retrieval of learned stimulus-response associations and the right inferior prefrontal cortex is more active when a learned stimulus-response association must be retrieved and adapted to new circumstances.

Adult↗
PubMed1999

Simultaneous maximum a posteriori reconstruction of attenuation and activity distributions from emission sinograms.

In order to perform attenuation correction in emission tomography an attenuation map is required. We propose a new method to compute this map directly from the emission sinogram, eliminating the transmission scan from the acquisition protocol. The problem is formulated as an optimization task where the objective function is a combination of the likelihood and an a priori probability. The latter uses a Gibbs prior distribution to encourage local smoothness and a multimodal distribution for the attenuation coefficients. Since the attenuation process is different in positron emission tomography (PET) and single photon emission tomography (SPECT), a separate algorithm for each case is derived. The method has been tested on mathematical phantoms and on a few clinical studies. For PET, good agreement was found between the images obtained with transmission measurements and those produced by the new algorithm in an abdominal study. For SPECT, promising simulation results have been obtained for nonhomogeneous attenuation due to the presence of the lungs.

Abdomen↗
PubMed1999

Additional value of whole-body positron emission tomography with fluorine-18-2-fluoro-2-deoxy-D-glucose in recurrent colorectal cancer.

PURPOSE: To assess the additional value of the whole-body [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) scan as a staging modality complementing conventional diagnostic methods (CDM) in patients suspected of having recurrent colorectal adenocarcinoma. PATIENTS AND METHODS: In 103 patients, the discordances between FDG-PET and CDM results were identified and related to the final diagnosis obtained by histopathology or clinical follow-up (> 1 year). All FDG-PET studies were reviewed with full knowledge of the CDM findings. RESULTS: In a region-based analysis, discordances between CDM and FDG-PET findings were found in 40 of 412 regions (10%). In these, FDG-PET had additional diagnostic value in 14 of 16 locoregional, six of seven hepatic, seven of eight abdominal, and eight of nine extra-abdominal regions. In a patient-based analysis, CDM categorized a subgroup of 60 patients as having resectable recurrent disease limited to the liver (n = 37) or locoregional region (n = 23). In 13 of these patients, there were discordant FDG-PET findings, detecting additional tumor sites in nine patients and excluding disease in three patients and yielding an additional diagnostic value in 20% of the patients. A second subgroup consisted of 13 patients with inconclusive CDM findings (n = 5) or with elevated plasma carcinoembryonic antigen levels and an otherwise negative conventional work-up (n = 8). In these patients, FDG-PET results were correct in eight of nine discordances, yielding a positive additional diagnostic value in 62% of the patients. CONCLUSION: Whole-body FDG-PET can have a clear impact on the therapeutic management in the follow-up of patients with colorectal cancer.

Abdominal Neoplasms↗
PubMed1999

[Tibia vara in adolescents. Apropos of 19 cases].

PURPOSE OF THE STUDY: Clinical, and radiological aspects and treatment of adolescent tibia have been studied in a review of 19 children native of the Caribbean. MATERIAL: 23 cases of adolescent tibia vara in 19 children have been collected (14 males and 5 females, aged from 9 to 14). METHODS: Clinical aspects (weight, lower limb axis), radiological signs (aspect of the physis, mechanical axis, epiphyseal slope) were studied pre and post-operatively. RESULTS: All the boys presented an important overweight. Pain was the first symptom, characterized by a progressive varus deformity on a leg which was previously straight. Radiological findings consisted in metaphyseal varus and widening of the medial part of the physis. Mechanical femoro-tibial axis varied from 10 degrees to 55 degrees varus, medial epiphyseal slope from 12 degrees to 30 degrees. Average mechanical femoral angle was 92 degrees and accounted for a mean femoral varus deformity of 4 degrees. 23 knees were operated, 4 after fusion of the whole physis. 10 lateral hemi-epiphysiodesis were performed with a mean correction of 4 degrees every year until fusion. In 3 cases a tibial osteotomy was made in a second time, at the end of growth. In 6 cases of late treated patients, an isolated tibial osteotomy of valgisation was performed. In 7 cases of important deformity before closure of the physis, tibial osteotomy was associated with lateral epiphysiodesis. In one case, a lateral closing wedge osteotomy was performed, associated to an elevation of the medial tibial plateau and a lateral hemi-epiphysiodesis. DISCUSSION: Histopathological examination of the physis showed similarities between adolescent tibia vara, infantile tibia vara and Slipped capital femoral epiphysis: the entire physeal plate was involved. Concerning pathogenesis of adolescent tibia vara, mechanical factors are predominant, with abnormal pressures across the medial part of the physis. CONCLUSION: Adolescent tibia vara occur in obese black children and can be considered as an epiphysiolysis of the upper end of the tibia.

Adolescent↗
PubMed1999

[Sagittal changes induced by knee arthroplasty: a radiologic study].

PURPOSE OF THE STUDY: To quantify the modifications occurring on the femoral side, after Total Knee Arthroplasty, we describe a method of measurements in the sagittal plane on standardized X-rays. MATERIAL AND METHODS: We report the clinical and radiologic results of a prospective study of 80 cases of Total Knee Arthroplasty performed with the same prosthesis. We eliminated twenty cases with incorrect X-rays. Measurements were done on 60 preoperative X-rays and 60 postoperative X-rays. The aim of the measure was to quantify the modifications induced by the prosthesis on the trochlear groove and on the tibio-femoral joint line in full extension and in flexion, to eliminate individual femoral diameter was used as a reference in order to cancel variations in X-rays magnification. We first validated the two perpendicular reference axis on which we based all the measurements. RESULTS: No significative difference was found on the position of the tibio-femoral joint line in flexion. The tibio-femoral joint line in extension was significantly moved distally. The prosthesis was placed too distally, therefore we changed the operative procedure. No significative difference was found on the position of the anterior trochlear groove. DISCUSSION: With this method, the anatomic variations of the femoral profiles can be quantified, therefore, further prosthesis shapes can be improved. Radiological follow-up of knee prosthesis and comparison of the influence of different prosthesis can be made by these measures.

Aged↗
PubMed1999

Abdominal aortic coarctation with splanchnic arterial occlusion.

Abdominal aortic coarctation is found in only 2% of aortic coarctation and is usually manifested by renovascular hypertension. Splanchnic arterial occlusive lesions occur in 22% of these patients and are exceptionally symptomatic. We present a case report of a young patient with abdominal aortic coarctation causing hypertension and visceral angina. The aetiopathogeny and treatment are discussed.

Adult↗
PubMed1998

Laryngeal tumor volume measurements determined with CT: a study on intra- and interobserver variability.

PURPOSE: To investigate the intra- and interobserver variability of computed tomography-based volume measurements of laryngeal tumors. METHODS AND MATERIALS: The volume of 13 laryngeal tumors was repeatedly measured by five independent observers in four different sessions, using the summation-of-areas technique. Mean tumor volume and its standard deviation were calculated for each tumor. Statistical analysis was done with analysis of variance, Spearman rank correlation, and linear regression. RESULTS: Both the effect of the observers (p < 0.0001) and the effect of the session (p < 0.01) on tumor volume was statistically significant. Interobserver variability was the most important component of total variability (89.3%). A significant rank correlation was found between mean volume and standard deviation (p < 0.01); the relationship between mean tumor volume and standard deviation can be described using linear regression [standard deviation = 0.28 volume + 0.35 (R = 0.79)]. CONCLUSION: Total variability in the computed tomography-based measurement of laryngeal tumor volume can be reduced by having the measurements done by a single trained observer.

Analysis of Variance↗
PubMed1998

Human brain activity related to speed discrimination tasks.

The regional cerebral blood-flow (rCBF) pattern of the human brain was measured using positron emission tomography (PET) while subjects viewed, detected, judged the speed of a moving random dot pattern (RDP) or compared speeds of successive RDPs. In all four conditions, retinal input was identical. Two additional conditions, continuous presentation of a moving and a stationary RDP, were included to identify human MT/V5 (hMT/V5). Both speed discrimination tasks involved the right cuneus and right lingual gyrus and to a lesser degree the left lingual gyrus and a more anterior lingual region in the right hemisphere. There was, however, little or no differential activity over hMT/V5 during either speed discrimination. Direct comparison of the two speed discrimination tasks revealed higher activity in the right middle fusiform gyrus, a result reminiscent of that obtained in earlier studies using orientation and direction as the attribute to be discriminated. These results confirm that processing in the human visual cortex is task dependent and underscore the role of the middle fusiform gyrus in temporal comparison of simple attributes.

Adult↗