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Biomedical subjects

S Richard

Publications and source records attributed to S Richard.

At least 19 recordsLinked to original sources
PubMed2007

[Surgical treatment of stress urinary incontinence by suburethral transobturator tape].

OBJECTIVE: Assessment of the suburethral transobturator tape in the treatment of female urinary stress incontinence. PATIENTS AND METHODS: Retrospective evaluation of 39 slings. Three patients (7%) were lost to follow-up. Analysis was carried on 19 out/in procedures (mainly ObTape and Uratape slings) and 17 in/out procedures (TVT-O slings). Nine patients (25%) had a history of previous stress incontinence surgery. In 21 cases (58%) there was a concomitant surgical procedure, including genital prolapse repair (12) and total hysterectomy (6). Phone interviews were conducted with the validated questionnaires MHU and Ditrovie short form. RESULTS: The mean operative time was 17 minutes (10-30). Three vaginal wounds (8%) were immediately repaired. Two urinary retentions (5%) were managed by suprapubic catheterization for more than 10 days. With a mean follow-up of 12 months (4-23) the subjective effectiveness on stress incontinence was 89% (cure: 58%; improvement: 31%). Urge incontinence symptoms were cured in 47% of mixed incontinences. Two patients reported an important dysuria. Two sling exposures occurred. Quality of life scores were significantly improved (mean 1,7 versus 3,2, p=0,002). The level of satisfaction reached 89% (very satisfied: 50%; satisfied: 39%). DISCUSSION AND CONCLUSION: This technique is safe and effective. Our results are nevertheless inferior to those previously reported. Prospective randomised studies comparing the two surgical routes are required.

Aged↗
PubMed2006

A simple, direct method for x-ray scatter estimation and correction in digital radiography and cone-beam CT.

X-ray scatter poses a significant limitation to image quality in cone-beam CT (CBCT), resulting in contrast reduction, image artifacts, and lack of CT number accuracy. We report the performance of a simple scatter correction method in which scatter fluence is estimated directly in each projection from pixel values near the edge of the detector behind the collimator leaves. The algorithm operates on the simple assumption that signal in the collimator shadow is attributable to x-ray scatter, and the 2D scatter fluence is estimated by interpolating between pixel values measured along the top and bottom edges of the detector behind the collimator leaves. The resulting scatter fluence estimate is subtracted from each projection to yield an estimate of the primary-only images for CBCT reconstruction. Performance was investigated in phantom experiments on an experimental CBCT bench-top, and the effect on image quality was demonstrated in patient images (head, abdomen, and pelvis sites) obtained on a preclinical system for CBCT-guided radiation therapy. The algorithm provides significant reduction in scatter artifacts without compromise in contrast-to-noise ratio (CNR). For example, in a head phantom, cupping artifact was essentially eliminated, CT number accuracy was restored to within 3%, and CNR (breast-to-water) was improved by up to 50%. Similarly in a body phantom, cupping artifact was reduced by at least a factor of 2 without loss in CNR. Patient images demonstrate significantly increased uniformity, accuracy, and contrast, with an overall improvement in image quality in all sites investigated. Qualitative evaluation illustrates that soft-tissue structures that are otherwise undetectable are clearly delineated in scatter-corrected reconstructions. Since scatter is estimated directly in each projection, the algorithm is robust with respect to system geometry, patient size and heterogeneity, patient motion, etc. Operating without prior information, analytical modeling, or Monte Carlo, the technique is easily incorporated as a preprocessing step in CBCT reconstruction to provide significant scatter reduction.

Algorithms↗
PubMed2005

Spin-induced forbidden evanescent states in III-V semiconductors.

Within the band gap of a semiconductor no electronic propagating states are allowed, but there exist evanescent states which govern charge transport such as tunneling. In this Letter, we address the issue of their spin dependence in III-V semiconductors. Taking into account the spin-orbit interaction, we treat the problem using a k . p 14 x 14 Hamiltonian that we numerically compute for GaAs. Our results show that the removed spin degeneracy in the band gap can lead to giant energy splittings and induces forbidden zones in space where evanescent states are suppressed.

Journal Article↗
PubMed2005

Toward a detailed characterization of feline immunodeficiency virus-specific T cell immune responses and mediated immune disorders.

Infection of domestic cats with feline immunodeficiency virus (FIV) is associated with the development of an acquired immunodeficiency syndrome (AIDS). The pathogenesis of FIV is not fully understood but it has been reported that the immune system is progressively impaired during disease progression. As a result, anti-FIV specific immune response will usually not clear the virus and the acute stage is followed by a chronic asymptomatic phase. The overall objective of this study was to characterized FIV-induced immune cellular responses and -mediated immune disorder following the first weeks post-infection. Using both cytokine ELISpot and intracellular staining assays, FIV-specific T cells were monitored at 6, 9 and 12 weeks post-infection. We demonstrated that both IFNgamma(+) and, CD4 and CD8 TNFalpha(+) T cells specifically respond to FIV antigens. These responses were found to reach a peak at 9 weeks post-infection. It was further shown that the TNFalpha(+)CD8(+) responding T cells were contained within a CD8beta(low)CD62L(-) T cell subpopulation, expanded in FIV-infected cats. This T cell subpopulation which present features of activated CD8 T cells was further shown to be susceptible to spontaneous apoptosis following a short-term in vitro culture. Moreover, it was observed that cell death by apoptosis of this T cell subset was increased following FIV antigen-recognition. Therefore, FIV might alter immune homeostasis in inducing chronic activation of TNFalpha(+)CD8(+) T cells which eventually will die following antigen contact while deleting CD4(+) T cells. Interestingly, this study confirmed the strong similarity between FIV and HIV pathogenesis.

Animals↗
PubMed2005

Impact of plasmid supercoiling on the efficacy of a rabies DNA vaccine to protect cats.

As of today, most DNA vaccination trials have been performed with plasmid preparations highly enriched in supercoiled molecules (sc) and the importance of supercoiled versus open circular (oc) plasmid isoforms for vaccine immunogenicity has only received limited attention. This study demonstrated that a single rabies DNA vaccination fully protected cats against a lethal rabies challenge as early as 3 weeks post vaccination provided that the proportion of supercoiled isoform in the vaccinal solution is at least 48%. In contrast, vaccination with a plasmid containing only 20% of supercoiled molecules induced significant but only partial protection. Further, a single rabies DNA vaccination with plasmids containing at least 70% of supercoiled molecules triggered statistically significant specific antibody titers and specific Th-1 oriented cell-based immunity as early as 2 and 3 weeks post vaccination, respectively. It is concluded that the oc isoforms are less efficient than supercoiled isoforms at inducing a complete profile of immune responses. Therefore, it is proposed that the target threshold of supercoiling that must be met by a rabies DNA vaccine to guarantee optimal immune responses and protection, be set at 70% of supercoiled molecules in the vaccine solution.

Animals↗
PubMed2005

[Von Hippel-Lindau disease: recent advances in genetics and clinical management].

Von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome that predisposes to the development of a panel of highly vascularized tumors including CNS and retinal hemangioblastomas, endolymphatic sac tumors, clear-cell renal cell carcinomas (RCC), pheochromocytomas and pancreatic neuroendocrine tumors. CNS hemangioblastomas and RCC are the two main life-threatening manifestations. The disease is caused by germline mutations in the VHL tumor-suppressor gene that plays a major role in regulating the oxygen-sensing pathway by targeting the hypoxia-inducible factor HIF for degradation in proteasome. Somatic inactivation of the VHL gene occurs also in most sporadic RCC and sporadic CNS hemangioblastomas. The demonstration of the critical role of VHL in angiogenesis is paving the way for the development of new specific drugs that could represent an attractive potential treatment for VHL but also for sporadic RCC and other cancers.

Humans↗
PubMed2005

Generalized DQE analysis of radiographic and dual-energy imaging using flat-panel detectors.

Analysis of detective quantum efficiency (DQE) is an important component of the investigation of imaging performance for flat-panel detectors (FPDs). Conventional descriptions of DQE are limited, however, in that they take no account of anatomical noise (i.e., image fluctuations caused by overlying anatomy), even though such noise can be the most significant limitation to detectability, often outweighing quantum or electronic noise. We incorporate anatomical noise in experimental and theoretical descriptions of the "generalized DQE" by including a spatial-frequency-dependent noise-power term, S(B), corresponding to background anatomical fluctuations. Cascaded systems analysis (CSA) of the generalized DQE reveals tradeoffs between anatomical noise and the factors that govern quantum noise. We extend such analysis to dual-energy (DE) imaging, in which the overlying anatomical structure is selectively removed in image reconstructions by combining projections acquired at low and high kVp. The effectiveness of DE imaging in removing anatomical noise is quantified by measurement of S(B) in an anthropomorphic phantom. Combining the generalized DQE with an idealized task function to yield the detectability index, we show that anatomical noise dramatically influences task-based performance, system design, and optimization. For the case of radiography, the analysis resolves a fundamental and illustrative quandary: The effect of kVp on imaging performance, which is poorly described by conventional DQE analysis but is clarified by consideration of the generalized DQE. For the case of DE imaging, extension of a generalized CSA methodology reveals a potentially powerful guide to system optimization through the optimal selection of the tissue cancellation parameter. Generalized task-based analysis for DE imaging shows an improvement in the detectability index by more than a factor of 2 compared to conventional radiography for idealized detection tasks.

Algorithms↗
PubMed2004

Somatic mutations of KIT in familial testicular germ cell tumours.

Somatic mutations of the KIT gene have been reported in mast cell diseases and gastrointestinal stromal tumours. Recently, they have also been found in mediastinal and testicular germ cell tumours (TGCTs), particularly in cases with bilateral disease. We screened the KIT coding sequence (except exon 1) for germline mutations in 240 pedigrees with two or more cases of TGCT. No germline mutations were found. Exons 10, 11 and 17 of KIT were examined for somatic mutations in 123 TGCT from 93 multiple-case testicular cancer families. Five somatic mutations were identified; four were missense amino-acid substitutions in exon 17 and one was a 12 bp in-frame deletion in exon 11. Two of seven TGCT from cases with bilateral disease carried KIT mutations compared with three out of 116 unilateral cases (P=0.026). The results indicate that somatic KIT mutations are implicated in the development of a minority of familial as well as sporadic TGCT. They also lend support to the hypothesis that KIT mutations primarily take place during embryogenesis such that primordial germ cells with KIT mutations are distributed to both testes.

DNA Mutational Analysis↗
PubMed2004

Critical temperature of a trapped, weakly interacting Bose gas.

We report on measurements of the critical temperature of a harmonically trapped, weakly interacting Bose gas as a function of atom number. Our results exclude ideal-gas behavior by more than two standard deviations, and agree quantitatively with mean-field theory. At our level of sensitivity, we find no additional shift due to critical fluctuations. In the course of this measurement, the onset of hydrodynamic expansion in the thermal component has been observed. Our thermometry method takes this feature into account.

Journal Article↗
PubMed2004

[Disease management programs in Germany. Current focus and further development].

The structure of the German healthcare system impedes well-coordinated long-term care of the chronically ill. Based on centrally defined standards, German sickness funds have implemented nationwide disease management programs for patients with diabetes. Breast cancer programs are underway. The programs are evidence based. Performance standards are centrally defined and subject to accreditation by a federal office. The programs are designed to improve the coordination of care between the different sectors, but the associated administration costs are often criticized.

Breast Neoplasms↗
PubMed2004

Spektr: a computational tool for x-ray spectral analysis and imaging system optimization.

A set of computational tools are presented that allow convenient calculation of x-ray spectra, selection of elemental and compound filters, and calculation of beam quality characteristics, such as half-value layer, mR/mAs, and fluence per unit exposure. The TASMIP model of Boone and Seibert is adapted to a library of high-level language (Matlab) functions and shown to agree with experimental measurements across a wide range of kVp and beam filtration. Modeling of beam filtration is facilitated by a convenient, extensible database of mass and mass-energy attenuation coefficients compiled from the National Institute of Standards and Technology. The functions and database were integrated in a graphical user interface and made available online at http:// www.aip.org/epaps/epaps.html. The functionality of the toolset and potential for investigation of imaging system optimization was illustrated in theoretical calculations of imaging performance across a broad range of kVp, filter material type, and filter thickness for direct and indirect-detection flat-panel imagers. The calculations reveal a number of nontrivial effects in the energy response of such detectors that may not have been guessed from simple K-edge filter techniques, and point to a variety of compelling hypotheses regarding choice of beam filtration that warrant future investigation.

Algorithms↗
PubMed2004

The influence of antiscatter grids on soft-tissue detectability in cone-beam computed tomography with flat-panel detectors.

The influence of antiscatter x-ray grids on image quality in cone-beam computed tomography (CT) is evaluated through broad experimental investigation for various anatomical sites (head and body), scatter conditions (scatter-to-primary ratio (SPR) ranging from approximately 10% to 150%), patient dose, and spatial resolution in three-dimensional reconstructions. Studies involved linear grids in combination with a flat-panel imager on a system for kilovoltage cone-beam CT imaging and guidance of radiation therapy. Grids were found to be effective in reducing x-ray scatter "cupping" artifacts, with heavier grids providing increased image uniformity. The system was highly robust against ring artifacts that might arise in CT reconstructions as a result of gridline shadows in the projection data. The influence of grids on soft-tissue detectability was evaluated quantitatively in terms of absolute contrast, voxel noise, and contrast-to-noise ratio (CNR) in cone-beam CT reconstructions of 16 cm "head" and 32 cm "body" cylindrical phantoms. Imaging performance was investigated qualitatively in observer preference tests based on patient images (pelvis, abdomen, and head-and-neck sites) acquired with and without antiscatter grids. The results suggest that although grids reduce scatter artifacts and improve subject contrast, there is little strong motivation for the use of grids in cone-beam CT in terms of CNR and overall image quality under most circumstances. The results highlight the tradeoffs in contrast and noise imparted by grids, showing improved image quality with grids only under specific conditions of high x-ray scatter (SPR> 100%), high imaging dose (Dcenter> 2 cGy), and low spatial resolution (voxel size > or = 1 mm).

Artifacts↗
PubMed2003

Momentum spectroscopy of 1D phase fluctuations in Bose-Einstein condensates.

We measure the axial momentum distribution of Bose-Einstein condensates with an aspect ratio of 152 using Bragg spectroscopy. We observe the Lorentzian momentum distribution characteristic of one-dimensional phase fluctuations. The temperature dependence of the width of this distribution provides a quantitative test of quasicondensate theory. In addition, we observe a condensate length consistent with the suppression of density fluctuations, even when phase fluctuations are large.

Journal Article↗
PubMed2003

Aromatase activity modulation by lindane and bisphenol-A in human placental JEG-3 and transfected kidney E293 cells.

Aromatase is the cytochrome P-450 involved in converting androgens to estrogens. The cytochrome P-450 family plays a central role in the oxidative metabolism of compounds including environmental pollutants. Since lindane and bisphenol-A (BPA) are two well-characterized endocrine disruptors that have been detected in animals and humans, it was important to learn whether they could affect aromatase activity and consequently estrogen biosynthesis. The present study investigates the effects of BPA and lindane on cytotoxicity, aromatase activity and mRNA levels in human placental JEG-3 cells and transfected human embryonal kidney 293 cells. Both cell lines were exposed to increasing concentrations of lindane (25, 50 and 75 microM) and bisphenol-A (25, 50 and 100 microM) over different time periods (10 min-18 h). As a result, none of these concentrations showed cytotoxicity. After short pre-incubation times (10 min-6 h), aromatase activity was enhanced by both compounds. Longer time incubation (18 h), however, produced dose-related inhibition. Lindane and BPA had no significant effects on CYP19 mRNA levels. Therefore, lindane and BPA modulate aromatase activity suggesting an interaction with the cytochrome P-450 aromatase. This study highlights the endocrine-modulating properties of lindane and bisphenol-A.

Adult↗
PubMed2003

Epidural corticosteroid injections for sciatica: a randomised, double blind, controlled clinical trial.

OBJECTIVE: To determine the efficacy of epidural corticosteroid injections for sciatica. METHODS: Three epidural injections (two day intervals) of 2 ml prednisolone acetate (50 mg) or 2 ml isotonic saline were administered to patients with sciatica presumably due to a disk herniation lasting 15-180 days. Self evaluation was the main judgment criterion at day 20. Patients who recovered or showed marked improvement were considered as success. Pain measured by VAS, the SLR test, Schober's test, Dallas pain questionnaire, and the Roland-Morris index were evaluated at days 0, 5, 20, and 35. Only analgesics were authorised, patients requiring non-steroidal anti-inflammatory drugs (NSAIDs) before day 20 were considered as failure. RESULTS: 42 patients were included in the control group (CG), 43 in the steroid group (SG). On an intention to treat analysis 15/42 (36%) in the CG and 22/43 (51%) in the SG (p=0.15) were considered as success (difference 15.5%, 95% CI (-5.4 to 36.3)). Among the 48 failures, 14 patients (6 CG, 8 SG) required NSAIDs, 3 (2 CG, 1 SG) required surgery, and 7 (3 CG, 4 SG) other treatments. On analysis according to protocol, in 74 remaining patients 12/35 (34%) in the CG and 22/39 (56%) in the SG (p=0.057) were considered as success (difference 22.1%, 95% CI (0.0 to 44.2)). For all secondary end points intragroup improvement with time was significant, but intergroup differences were not. CONCLUSION: The efficacy of isotonic saline administered epidurally for sciatica cannot be excluded, but epidural steroid injections provide no additional improvement.

Adult↗