Search PubMed⌕ Search

Biomedical subjects

P Dupont

Publications and source records attributed to P Dupont.

At least 19 recordsLinked to original sources
PubMed2002

[A new cause of false positives when analyzing expired air carbon monoxide].

INTRODUCTION: Measurement of expired air carbon monoxide expired is an essential examination to be conducted in smokers during consultation. However, this can be the source of errors, such as that identified in the case report we present here. OBSERVATION: A 65 year-old man, wishing to stop smoking, consumed a large quantity of polyol-rich sweets and exhibited increased expired air carbon monoxide levels, intestinal gases and increased volume of his liver. All these signs regressed when he stopped taking the sweets. COMMENTS: The production of intestinal gases related to polyol and isomalt contained in some products may be the cause of error in the measurement of expired air carbon monoxide.

Aged↗
PubMed2002

[Nicotine substitution therapy: 10 years later].

To be efficient, nicotine substitution therapy (NST) must be part of a global strategy comprising several stages. The first consists in evaluating and re-enforcing motivation, since smoking cessation is impossible unless the patient is clearly motivated. The second stage is the withdrawal period that lasts for several days or months. NST is the first medicinal treatment that has demonstrated its efficacy in controlled studies: it reduces the withdrawal syndrome and doubles the chances of success at the end of the standard 3-month treatment. Recent studies have shown that the results can be improved: by adapting the dose to the degree of dependency and by using higher doses and/or associating two types of nicotine substitutes; by prolonging NST for as long as the withdrawal syndrome persists; by treating the anxiety and depression, often present in heavy smokers. The third stage is aimed at avoiding relapses, by ensuring prolonged follow-up and treating the various possible causes: eating disorders and weight gain, acute or chronic stress, depression, environment.... At all the stages of care, behavioural and cognitive therapy enhances the chances of success.

Administration, Cutaneous↗
PubMed2002

The neural substrate of orientation short-term memory and resistance to distractor items.

We used Positron Emission Tomography to map the neural substrate of human short-term memory for orientation, defined as retaining a single orientation in memory over a long delay, by comparing a successive discrimination task with a 6-s delay to the same task with a brief 0.3 s delay and to an identification control task. Short-term memory engaged the superior parietal lobe bilaterally, the middle occipital gyrus bilaterally and the left dorsolateral prefrontal cortex. In addition, we studied the resistance to a distractor item by comparing the successive discrimination task with long delay, with and without an intervening distractor stimulus. This manipulative process engaged left ventral premotor cortex and left dorsolateral prefrontal cortex. The activation of left dorsolateral prefrontal cortex is interpreted as reflecting co-ordination between task components. These results, combined with those of two previous studies using an identical reduction strategy, underscore the functional heterogeneity in the prefrontal cortex during short-term and working memory.

Adolescent↗
PubMed2002

Early restaging positron emission tomography with ( 18)F-fluorodeoxyglucose predicts outcome in patients with aggressive non-Hodgkin's lymphoma.

BACKGROUND: Less than half of all patients with aggressive non-Hodgkin's lymphoma (NHL) are cured with standard chemotherapy. Therefore, it is important to distinguish between responders to standard treatment and non-responders who may benefit from an early change to a more effective therapy. This study was intended to assess the value of a midtreatment fluorine-18 fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) scan to predict clinical outcome in patients with aggressive NHL. PATIENTS AND METHODS: Seventy newly diagnosed patients with aggressive NHL, who were treated with doxorubicin-containing chemotherapy, underwent a [(18)F]FDG-PET scan at midtreatment. Presence or absence of abnormal [(18)F]FDG uptake was related to progression-free survival (PFS) and overall survival (OS) using Kaplan-Meier survival analysis. Multivariate analysis was performed to evaluate the effect of the International Prognostic Index (IPI) and early [(18)F]FDG-PET findings on PFS and OS. RESULTS: At midtreatment, 33 patients showed persistent abnormal [(18)F]FDG uptake and none of these patients achieved a durable complete remission (CR), whereas 37 patients showed a negative scan; 31/37 remained in CR, with a median follow-up of 1107 days. Only 6/37 patients either achieved a partial response or relapsed. Comparison between groups indicated a statistically significant association between [(18)F]FDG-PET findings and PFS (P <1 x 10(-5)) and OS (P <1 x 10(-5)). In multivariate analysis, [(18)F]FDG-PET at midtreatment was a stronger prognostic factor for PFS (P <1 x 10(-7)) and OS (P <9 x 10(-6)) than the IPI (P <0.11 and P <0.03, respectively). CONCLUSIONS: Early restaging [(18)F]FDG-PET may be used to tailor induction chemotherapy in patients with aggressive NHL.

Adolescent↗
PubMed2002

18-FDG PET scan in the staging of recurrent melanoma: additional value and therapeutic impact.

Staging of melanoma patients by means of whole body functional imaging in a single evaluation session using positron emission tomography (PET) with fluorine-18- labelled deoxy-d-glucose (FDG) as a metabolic tracer has created much interest over the last decade. After enthusiastic pilot studies, more attention has been paid to the false-negative and false-positive results of this technique than to its true therapeutic impact. This study aimed to evaluate (1) the sensitivity and specificity of this technique at a single lesion level compared with conventional screening procedures (CSP) - both of these accompanied by careful clinical examination; and (2) the additional value of the PET scan at the level of the individual patient and its therapeutic impact for different types of melanoma recurrence. A consecutive series of 100 PET scans performed on 84 melanoma patients with regional or distant recurrence according to CSP (89 PET scans) or suspicion of recurrence, i.e. inconclusive CSP (11 PET scans), were retrospectively analysed and compared with the CSP results. At the single lesion level, PET scan and CSP showed a sensitivity of 85 and 81%, a specificity of 90 and 87% and an accuracy of 88 and 84%, respectively. PET provided false-negative results for small skin metastases and brain involvement; false-positive results were associated with unrelated benign or malignant tumours and peripheral soft tissue and bone uptake. PET scan showed an additional value over and above CSP at the individual patient's level by true upstaging in 10 cases, true downstaging in 24 cases and depiction of more lesions within the same stage of disease in 15 cases. The overall therapeutic impact reached 26%: 17 out of 71 (24%) cases with regional recurrence, one out of 18 cases (5.5%) with distant metastasis and eight out of 11 cases (73%) with suspicion of recurrence where CSP remained doubtful. However, in 19 cases comparison between CSP and PET resulted in discordant findings, suggesting upstaging in one area and downstaging at another site within the same patient. In conclusion, PET scan has an additional value in the staging of recurrent melanoma, providing it is accompanied by careful clinical examination and specific brain imaging. However, in the absence of evidence of metastasis or unrelated conditions at the same site on CSP, PET spots may represent false-positive images, which would falsely upgrade a patient to an incurable state, or they may be early true-positive findings, which will become evident during close follow-up.

Adult↗
PubMed2002

[Developmental lumbar stenosis in eleven French Antilles patients].

PURPOSE OF THE STUDY: Developmental lumbar stenosis is a rare entity, exceptionally described in the literature. No study has been directly devoted to this condition. The purpose of the present study was to examine specific features, particularly clinical and anatomic expression, observed in a series of operated patients. MATERIAL AND METHODS: Eleven patients from the French Antilles were treated for developmental lumbar stenosis between 1996 and 2000. The Verbiest criteria were used to define canal narrowness. Signs of degeneration and presence of discal herniation were exclusion criteria. Epidemiological and clinical data were collected for the 11 patients. The degree of sagittal stenosis (fixed diameter at the bone level and mobile diameter at the discal level) was measured on computed tomography images. Transverse stenosis was determined by measuring the interpedicular and interapophyseal distances. Lateral stenosis was determined by measuring the depth of the recessus. RESULTS: These patients were young (mean age 42.4 years). Most of the clinical signs were monoradicular. Discal level stenosis predominated, generally at level L4-L5. It was generally central and lateral, sagittal and transverse. The interpedicular distance was the only diameter that remained within normal limits. Soft tissues (yellow ligaments and joint capsules) played an important role in the stenosis. DISCUSSION: The rare reports of developmental lumbar stenosis describe decompensated stenosis due to discal herniation in the adolescent. Developmental lumbar stenosis is considered to be a genetic disease and its particular high frequency in the French Antilles favors this hypothesis. The stenosis results from bony (short pedicles, hypertrophic lateral masses) and ligament (hypertrophy of the yellow ligament and joint capsules) structures. CONCLUSION: Developmental lumbar stenosis produces a global (sagittal, transverse, central, lateral) narrowing of the lumbar canal where soft tissue structures apparently play a greater role than usually thought. A prospective study examining the impact of ethnic origin is required to analyze the genetic hypothesis.

Adult↗
PubMed2001

The neural substrate of orientation working memory.

We have used positron emission tomography (PET) to identify the neural substrate of two major cognitive components of working memory (WM), maintenance and manipulation of a single elementary visual attribute, i.e., the orientation of a grating presented in central vision. This approach allowed us to equate difficulty across tasks and prevented subjects from using verbal strategies or vestibular cues. Maintenance of orientations involved a distributed fronto-parietal network, that is, left and right lateral superior frontal sulcus (SFSl), bilateral ventrolateral prefrontal cortex (VLPFC), bilateral precuneus, and right superior parietal lobe (SPL). A more medial superior frontal sulcus region (SFSm) was identified as being instrumental in the manipulative operation of updating orientations retained in the WM. Functional connectivity analysis revealed that orientation WM relies on a coordinated interaction between frontal and parietal regions. In general, the current findings confirm the distinction between maintenance and manipulative processes, highlight the functional heterogeneity in the prefrontal cortex (PFC), and suggest a more dynamic view of WM as a process requiring the coordinated interaction of anatomically distinct brain areas.

Adult↗
PubMed2001

Human brain regions involved in heading estimation.

Observer motion in a stationary visual environment results in an optic flow pattern on the retina, which in simple situations can be used to determine the direction of self motion or heading. The present study, using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), investigated the human cerebral activation pattern, elicited when subjects viewing a ground plane optic flow pattern actively judged heading. Several successive experiments controlled for visual input, visuospatial attention, and motor response effects. Results indicate that the network specifically involved in heading consists of only two motion sensitive areas: human MT/V5+, including an inferior satellite, and dorsal intraparietal sulcus area (DIPSM/L), predominantly in the right hemisphere, plus a dorsal premotor region bilaterally. These results suggest possible homologies with the dorsal part of the medial superior temporal area and area 7a in the monkey.

Brain↗
PubMed2001

Prognostic value of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose ([18F]FDG) after first-line chemotherapy in non-Hodgkin's lymphoma: is [18F]FDG-PET a valid alternative to conventional diagnostic methods?

PURPOSE: A complete remission (CR) after first-line therapy is associated with longer progression-free survival (PFS). However, defining CR is not always easy because of the presence of residual masses. Metabolic imaging with fluorine-18 fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) offers the ability to differentiate between viable and fibrotic inactive tissue. In this study, we evaluated the value of PET in detecting residual disease and, hence, predicting relapse after first-line treatment in patients with non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: Ninety-three patients with histologically proven NHL, who underwent a whole-body [18F]FDG-PET study after completion of first-line chemotherapy and who had follow-up of at least 1 year, were included. Persistence or absence of residual disease on PET was related to PFS using Kaplan-Meier survival analysis. RESULTS: Sixty-seven patients showed a normal PET scan after first-line chemotherapy; 56 of 67 remained in CR, with a median follow-up of 653 days. Nine of these patients with a residual mass considered as unconfirmed CR received additional radiotherapy. Only 11 of 67 patients relapsed (median PFS, 404 days). Persistent abnormal [18F]FDG uptake was seen in 26 patients, and all of them relapsed (median PFS, 73 days). Because standard restaging also suggested residual disease, 12 patients received immediate secondary treatment. In 14 of 26 patients, only PET predicted persistent disease. From these patients, relapse was proven either by biopsy (n = 8) or by progressive disease on computed tomography or magnetic resonance imaging (n = 6). CONCLUSION: Persistent abnormal [18F]FDG uptake after first-line chemotherapy in NHL is highly predictive for residual or recurrent disease. In relapsing patients, PFS was significantly shorter after a positive scan than after a negative scan.

Adolescent↗
PubMed2001

Is cellular fibronectin a biological marker for pre-eclampsia?

Cellular fibronectin (cFn) appears to be an important factor in the regulation of cell-cell interactions. It is mostly synthesised by endothelial cells and its increased circulating values are thought to correspond to the endothelial damage. As pre-eclampsia is considered a pathology of endothelial cells, our study was intended to see if this circulating protein is increased during pre-eclampsia and to determine from which moment in pregnancy these changes occur. We studied cFn longitudinally in 198 consecutive pregnant patients, with or without pathologies associated to pregnancy. We measured the cFn concentrations by ELISA four times during pregnancy with the monoclonal antibody A 134. The values of cFn increased throughout the normal pregnancy, but a significant increase was observed only after the 36th week of pregnancy (P<0.0001). The values of doubling time of cFn gradually decreased, being inverse to cFn concentrations. The values of cFn were significantly higher (3.53 microg/ml; P=0.0009) in the third trimester in the group of women who developed pre-eclampsia, as compared to normals (2.23 microg/ml). cFn could not be used as a predictor of pre-eclampsia, because the clinical symptoms of this pathology were already present at the time of measurement. Our data represent the first longitudinal study showing the increase of cFn values throughout normal and pre-eclamptic pregnancies.

Antibodies, Monoclonal↗
PubMed2001

Can positron emission tomography with [(18)F]-fluorodeoxyglucose after first-line treatment distinguish Hodgkin's disease patients who need additional therapy from others in whom additional therapy would mean avoidable toxicity?

To assess the ability of restaging positron emission tomography (PET) scanning to predict clinical outcome after first-line treatment in patients with Hodgkin's disease, we included 60 patients with histologically proven HD, who underwent whole-body [(18)F]-fluorodeoxygenase ([(18)F]-FDG)-PET studies after first-line treatment and with a follow-up of at least 1 year. Persistence or absence of residual disease on PET was related to progression-free survival (PFS) using Kaplan-Meier survival analysis. After treatment, 55 patients showed a normal [(18)F]-FDG-PET scan; 50 of 55 remained in complete remission (CR), with a median follow-up of 955 d. Only five patients relapsed (median PFS, 296 d). During follow-up in all five patients, [(18)F]-FDG-PET was the first tool that became positive for relapse. Persistent abnormal [(18)F]-FDG uptake was seen in only five patients; all of them relapsed (median PFS, 296 d). In four of five patients, only PET predicted persistent disease. All relapses were proven histologically. Two-year actuarial PFS rate for negative patients was 91% compared with 0% for positive patients. We concluded that [(18)F]-FDG-PET has an important prognostic role in the post-treatment evaluation of HD patients.

Adolescent↗
PubMed2001

Separate neural correlates for the mnemonic components of successive discrimination and working memory tasks.

We have used positron emission tomography to map the mnemonic components of two tasks at the extremes of the visual short-term/ working memory spectrum. The successive discrimination task requires only storage of a single item for very short time (ultra-short- term memory), while the 2back task requires both maintenance (i.e. storage and rehearsal) and manipulation of several items (working memory). We tested whether or not the storage component, common to the two tasks, engaged the same cerebral regions. To remove unnecessary confounds, we reduced the cues available to the subjects to a single elementary attribute, the orientation of a grating presented in central vision. This prevented subjects from using verbal strategies or vestibular cues and allowed equating of difficulty among tasks. Ultra-short-term memory for orientation engaged a large expanse of occipito-temporal cortex with a rate-dependent antero-posterior gradient: a fast trial rate engaged posterior regions, a slow trial rate anterior regions. On the other hand, working memory for orientation involved the left inferior parietal cortex, left dorsolateral prefrontal cortex and a left superior frontal sulcus region, and to a lesser degree the symmetrical right superior frontal region and a left superior parietal region. Direct comparison of the two orientation memory networks confirmed their functional segregation. We conclude that at least the storage of orientation information engages distinct regions depending on whether or not short-term memory/working memory involves rehearsal and/or manipulative processes.

Adult↗
PubMed2001

The utility of SPECT in determining the relationship between radiation dose and salivary gland dysfunction after radiotherapy.

Salivary gland scintigraphy (SGS) is used to depict salivary gland dysfunction after radiotherapy (RT). The aim of this study was to investigate the utility of SGS combined with single photon emission computed tomography (SPECT). Twenty-one patients with a carcinoma of head and neck underwent SGS before and 1 month after RT. After injection of 370 MBq 99Tcm-pertechnetate, a biplanar dynamic acquisition (12 x 1 min) was started, followed by a SPECT acquisition during 4 min. Carbachol was then injected and a second dynamic study (16 x 1 min) was performed, again followed by a SPECT acquisition. The salivary excretion fraction (SEF) was calculated both from the geometric mean planar image for each parotid and from the SPECT data for each transverse plane through the parotids. The RT-induced changes in the SEF (dSEF) were correlated with the mean radiation dose calculated using tomography-based dosimetry. The mean radiation dose to the parotids was 44 Gy (range 4.4-68.1 Gy). The mean range of the variation in radiation dose to the transverse slices within the parotids of a patient was 24 Gy (range 6.2-51.9 Gy). Considering all transverse planes through the parotids in all patients, a linear correlation was found between the dSEF calculated using SGS-SPECT and the radiation dose (r=0.45, P=0.0001). Thirteen patients had a variation in radiation dose within the parotids of more than 20 Gy. In nine of these a significant intra-individual correlation between radiation dose and the dSEF of the transverse parotid slices was found (r range 0.55-0.97; P value range 0.037-0.0001). In conclusion, SGS-SPECT can be used for monitoring radiation-induced parotid gland dysfunction. It offers the unique possibility for the assessment of intra-individual dose-dysfunction curves in patients with large variations in the radiation dose within the parotids.

Adult↗
PubMed2001

Maximum-likelihood expectation-maximization reconstruction of sinograms with arbitrary noise distribution using NEC-transformations.

The maximum-likelihood (ML) expectation-maximization (EM) [ML-EM] algorithm is being widely used for image reconstruction in positron emission tomography. The algorithm is strictly valid if the data are Poisson distributed. However, it is also often applied to processed sinograms that do not meet this requirement. This may sometimes lead to suboptimal results: streak artifacts appear and the algorithm converges toward a lower likelihood value. As a remedy, we propose two simple pixel-by-pixel methods [noise equivalent counts (NEC)-scaling and NEC-shifting] in order to transform arbitrary sinogram noise into noise which is approximately Poisson distributed (the first and second moments of the distribution match those of the Poisson distribution). The convergence speed associated with both transformation methods is compared, and the NEC-scaling method is validated with both simulations and clinical data. These new methods extend the ML-EM algorithm to a general purpose nonnegative reconstruction algorithm.

Algorithms↗
PubMed2001

An iterative maximum-likelihood polychromatic algorithm for CT.

A new iterative maximum-likelihood reconstruction algorithm for X-ray computed tomography is presented. The algorithm prevents beam hardening artifacts by incorporating a polychromatic acquisition model. The continuous spectrum of the X-ray tube is modeled as a number of discrete energies. The energy dependence of the attenuation is taken into account by decomposing the linear attenuation coefficient into a photoelectric component and a Compton scatter component. The relative weight of these components is constrained based on prior material assumptions. Excellent results are obtained for simulations and for phantom measurements. Beam-hardening artifacts are effectively eliminated. The relation with existing algorithms is discussed. The results confirm that improving the acquisition model assumed by the reconstruction algorithm results in reduced artifacts. Preliminary results indicate that metal artifact reduction is a very promising application for this new algorithm.

Algorithms↗
PubMed2001

Near-fatal gamma-butyrolactone intoxication--first report in the UK.

Gamma-hydroxybutyrate (GHB) is a compound used in the treatment of alcohol withdrawal, narcolepsy, and for induction of anaesthesia. It is also contained in many products illegally marketed as "dietary supplements" and is increasingly being recognised as a potential drug of abuse. We report the case of a 44-year-old man who suffered coma and life-threatening respiratory depression following an accidental overdose of the GHB prodrug, gamma-butyrolactone (GBL), contained in a "health drink". He made a full recovery following appropriate supportive treatment. GHB toxicity should be included in the differential diagnosis of patients with altered mental state, particularly where there is a history of recreational drug abuse.

4-Butyrolactone↗