Biomedical subjects

F Thibault

Publications and source records attributed to F Thibault.

At least 19 recordsLinked to original sources

PubMed2006

Rotranslational state-to-state rates and spectral representation of inelastic collisions in low-temperature molecular hydrogen.

Inelastic collisions in natural H2 are studied from the experimental and theoretical points of view between 10 and 140 K. Rotational populations and number densities measured by Raman spectroscopy along supersonic expansions of H2 provide the link between experimental and theoretical rotranslational state-to-state rate coefficients of H2 in the vibrational ground state. These rates are calculated in the close-scattering approach with the MOLSCAT code employing a recent ab initio H2-H2 potential. The calculated rates are assessed by means of a master equation describing the time evolution of the experimental rotational populations. The feasibility for obtaining the rates on the sole basis of the experiment is discussed. The dominant processes j(1)j(2)-->j'(1)j'(2) in the investigated thermal range are found to be 21-->01 >30-->12 >31-->11, proving the importance of double processes such as 30-->12. Good agreement is found between theory and experiment, as well as with earlier ultrasonic measurements of relaxation times. A spectral representation is proposed in order to visualize quantitatively the collisional contributions in any nonequilibrium time evolving process.

Journal Article↗

PubMed2006

Efficient diode-pumped Yb3+:Y2SiO5 and Yb3+:Lu2SiO5 high-power femtosecond laser operation.

We report the mode-locked operation of two new Yb-doped oxyorthosilicates, Y2SiO5 (YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 fs with 410 mW of output power at 1041 nm. More than 2.6 W of average output power, for pulse durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided. These are, to our best knowledge, the highest values ever obtained and the most efficient mode-locked laser in such a classic fiber-coupled diode-pumping configuration.

Journal Article↗

PubMed2005

Inelastic collisions in para-H2: translation-rotation state-to-state rate coefficients and cross sections at low temperature and energy.

We report an experimental determination of the k(00-->02) rate coefficient for inelastic H(2):H(2) collisions in the temperature range from 2 to 110 K based on Raman spectroscopy data in supersonic expansions of para-H(2). For this purpose a more accurate method for inverting the master equation of rotational populations is presented. The procedure permits us to reduce the measured k(00-->02) rate coefficient to the corresponding sigma(00-->02) cross section in the range of precollisional energy from 360 to 600 cm(-1). Numerical calculations of sigma(00-->02) carried out in the frame of the coupled channel method are also reported for different intermolecular potentials of H(2). A good agreement is found between the experimental cross section and the numerical one derived from Diep and Johnson's potential [J. Chem. Phys. 112, 4465 (2000)].

Journal Article↗

PubMed2004

Digital detectors for mammography: the technical challenges.

This paper reviews the different techniques available and competing for full-field digital mammography. The detectors are described in their principles: photostimulable storage phosphor plates inserted as a cassette in a conventional mammography unit, dedicated active matrix detectors (i.e., flat-panel, thin-film transistor-based detectors) and scanning systems, using indirect and direct X-ray conversion. The main parameters that characterize the performances of the current systems and influence the quality of digital images are briefly explained: spatial resolution, detective quantum efficiency and modulation transfer function. Overall performances are often the result of compromises in the choice of technology.

Equipment Design↗

PubMed2004

Experimental and theoretical study of line mixing in NH3 spectra. II. Effect of the perturber in infrared parallel bands.

In a previous paper [J. Chem. Phys. 116, 7544 (2002) (Paper I)] a model, based on the energy corrected sudden approximation, was proposed for the construction of the line-mixing relaxation matrix. It was successfully tested by comparisons with measured infrared spectra of ammonia-helium mixtures. The present paper extends this preliminary study by considering mixtures of NH3 with H2 and Ar. Measurements have been made at room temperature in the regions of the nu2 and nu1 bands for pressures up to several hundred atmospheres. As in Paper I, the relaxation operator is constructed, within the impact approximation, using the ECS approximation. The data required are dynamical factors (which can be predicted from the NH3-X potential energy surface) and a scaling length (adjusted using line broadening data). Comparisons between measured and calculated absorptions demonstrate the quality of the model which satisfactory corrects for the large deviations with respect to the purely Lorentzian behavior. Line-mixing effects for NH3-Ar and NH3-H2 are qualitatively similar to those observed for NH3-He but quantitative differences exist, particularly when intra- and interbranch couplings are considered. Finally, the proposed model leads to very satisfactory results in the wings of both the purely rotational and nu2 bands of NH3 diluted in H2, opening promising perspectives for the remote sensing study of planetary atmospheres.

Journal Article↗

PubMed2004

[New developments in breast imaging].

In 2004, breast cancer screening will be effective in France. This evolution has a strong impact on our mammographic practice that becomes a real mission of public health. Digital mammography, compared to screen-film mammography, provides the same results for the detection of breast cancer, computer-aided detection systems represent the most relevant application of this technology at this time. The setting up of a quality control will allow the introduction of this technology in screening during 2004. Percutaneous imaging-guided procedures are now currently used for the diagnosis of nonpalpable breast lesions and allow the selection of patients for surgery. These procedures have emphasized the need for a multidisciplinary approach of the patients. Indications of MRI have not changed because of its moderated specificity and no relevant development of interventional-guided procedures. Work on standardization of radiological reports and assessment categories goes on. This classification is already applied for mammography, and new classifications for lesions detected by ultrasound or MRI will be published by the American College of Radiology (Breast Imaging Reporting and Data System, 4th edition, available in 2003).

Aged↗

PubMed2003

[Interventional radiology in nonpalpable lesions of the breast].

The increasing number of nonpalpable breast lesions found at screening mammography has induced the development of percutaneous imaging-guided procedures to reduce the number of surgical biopsies. After a description of the indications (classification of the American College of Radiology), the different types of sampling procedures (fine needle aspiration, core and large-core biopsies) will be described and the material used also. Depending on the type of breast lesions (mass, clustered microcalcifications), ultrasound--guided and stereotactic--guided biopsies will be explained. Clear information to the patients, efficient quality control and multidisciplinary approach are mandatory for the success of these percutaneous diagnostic procedures.

Biopsy, Fine-Needle↗

PubMed2002

[Using BI-RADS in French].

BI-RADStrade mark is the referral lexicon in the United States for the classification of terms which are used for reporting breast imaging. The purpose of this chapter is to present and summarize the French version.

Breast Diseases↗

PubMed2001

Critical clinicopathologic analysis of 23 cases of fine-needle breast sampling initially recorded as false-positive. The 44-year experience of the Institut Curie.

BACKGROUND: Because false-positive cytologic diagnoses in breast tumors are rare, few cases have been reported, although their consequences may be highly detrimental to the patient. The authors report the Institut Curie's experience, by using a multidisciplinary approach. METHODS: Of 9334 benign breast tumors examined preoperatively for cytologic diagnosis by fine-needle sampling (FNS), the 23 (0.25%) FNS cases considered to be false-positive were retrospectively reviewed and analyzed. RESULTS: Tumors were situated close to the nipple in 7 cases and away from the nipple in 16 cases. Tumor stage was T0 for 1 case, T1 for 18 cases, and T2 for 4 cases. Radiologically, six tumors were classified as malignant, seven as indeterminate or suspicious, and nine as benign. Three of six tumors studied by flow cytometry were DNA aneuploid. Based on a multidisciplinary clinicopathologic review, 20 FNS cases were finally classified as false-positive, and the remaining 3 tumors with malignant FNS and subsequent benign histology were classified as true-positive, because local and/or metastatic progression was observed in the short term. CONCLUSIONS: The authors' review suggests two categories of false-positive cases: the first in which cytologic benign patterns are overdiagnosed, and the second in which atypical morphologic criteria were present. Nevertheless, as shown by the malignant course in three cases, patients with malignant preoperative FNS and corresponding benign histology always require close clinical follow-up. Finally, surgical overtreatment rate could be decreased if all radiologically benign tumors with positive/suspicious FNS were subject to intraoperative frozen section examination.

Adult↗

PubMed2000

Diagnostic accuracy of sonography and combined sonographic assessment and sonographically guided cytology in nonpalpable solid breast lesions.

PURPOSE: The aim of this study was to assess the diagnostic accuracy of sonography alone and combined sonographic assessment and sonographically guided fine-needle aspiration cytology in solid, nonpalpable lesions of the breast. METHODS: We retrospectively evaluated the sonograms from a series of 174 consecutive nonpalpable masses that were cytologically diagnosed using fine-needle aspiration under sonographic guidance and then histologically verified through surgical excision. We examined the relationships between the findings from sonography, combined sonographic assessment and cytopathology, and histology. RESULTS: Histologically, 95 lesions (55%) were malignant and 79 (45%) were benign. The overall sensitivity of sonography alone for diagnosing cancer was 98. 9% (94 of 95 lesions), and the specificity was 45.6% (36 of 79 lesions). One (3%) of 37 masses considered at sonography to be benign was correctly diagnosed on cytologic examination to be cancer. By establishing the benign status of 11 of 13 masses that were indeterminate at sonography, cytology increased the specificity of the combined method (to 56.3%). Cytology appropriately suspected or confirmed malignancy in 79 (84%) of 94 carcinomas considered at sonography to be suspicious or malignant. CONCLUSIONS: In this study, sonography alone demonstrated a high sensitivity but limited specificity in evaluating nonpalpable breast masses. The addition of sonographically guided cytology substantially increased the specificity of the combined method without compromising sensitivity.

Adult↗

PubMed2000

Hepatic regenerating nodules: a mimic of recurrent cancer in children.

BACKGROUND: Pseudometastatic lesions of the liver may be discovered incidentally in children previously treated for malignant tumour. OBJECTIVE: To describe the radiological pattern of these lesions and to analyse their pathogenesis. MATERIALS AND METHODS: Nine children, 2-12 years' old at the time of diagnosis, are described in this retrospective multicentre report. The primary tumours were: nephroblastoma (n = 2), neuroblastoma (n = 2), Ewing's tumour/PNET (n = 2), non-Hodgkin's lymphoma (n = 1), and osteosarcoma (n = 2), treated by surgery (8/9), chemotherapy (9/9), intensive chemotherapy and bone-marrow transplantation (5/9), and radiotherapy (7/9). Three children suffered veno-occlusive disease (VOD) during treatment. The hepatic assessment was performed by sonography (8/9), Doppler (7/9), multiphase spiral CT (8/9) and MRI (7/9). RESULTS: Lesions were discovered 15 months to 16 years after completing treatment. CT was the most sensitive modality for diagnosis. Lesions were multiple in eight cases, measured 2-50 mm, and appeared hypervascular on the arterial phase of CT and/or MRI in every case. Metastases were excluded on the basis of histological verification (n = 2) and clinical and radiological follow-up. CONCLUSION: Pseudometastatic hypervascular hepatic nodules can appear after treatment of a malignant tumour in children. The hypothesis of benign regenerative lesions secondary to treatment and/or VOD is considered.

Child↗

PubMed2000

Computerized ultrasound B-scan characterization of breast nodules.

The ability of computerized parameters to discriminate benign from malignant breast nodules from digitized ultrasonic acquisitions has been assessed. The images of 75 lesions, including 19 lesions proved to be malignant at histology and 56 found to be benign, were digitized and characterized by morphometric and texture parameters. The texture parameters, derived from first-order statistics, run-length matrices and co-occurrence matrices, were computed in the entire lesion and in a ring-shape region surrounding the contour of the lesion. The strongest features were found to be issued from the second region. Further investigations confirmed that the discriminant information was contained in the external part of the lesion and, to a lesser extent, in the neighboring tissue. A linear discriminant analysis using three features yielded a sensitivity of 94.7% for a specificity of 80.4% and the "leave-one-out" technique confirmed the results. Comparison with the classifications given by radiologists let us assume that information revealed by texture features is able to help the physician in reducing the number of unnecessary biopsies.

Breast Diseases↗

PubMed1999

Spectral Lineshape Parameters Revisited for HF in a Bath of Argon.

Previous measurements of asymmetries of the profiles of argon-broadened HF lines at moderate perturber densities (pressures higher than 10 atm) have been confirmed and extended by high-resolution Fourier transform spectroscopy. In some cases, the asymmetries observed here are of opposite sign when compared to the results obtained at much lower densities (pressures lower than 1 atm). By comparing all the available experiments, the competition between the various mechanisms leading to asymmetries has been analyzed as function of the perturber pressure and the vibrational transitions considered. Copyright 1999 Academic Press.

Journal Article↗

PubMed1998

Stereotactic fine-needle aspiration cytology of nonpalpable breast lesions: Institut Curie's experience of 243 histologically correlated cases.

BACKGROUND: The early diagnosis of nonpalpable breast lesions is a medical challenge because of the low specificity of different radiologic modalities. Fine-needle aspiration cytology (FNAC) assisted by a stereotactic guidance is an adjunctive diagnostic approach in the management of these lesions. The primary purpose of this article was to assess the diagnostic accuracy of FNAC in patients with nonpalpable breast lesions. METHODS: Three hundred and seventy-one lesions from 357 patients (all female) underwent FNAC using the stereotactically guided technique. Of these cases, 243 lesions from 238 patients subsequently were acquired by surgical excisional biopsies and formed the basis of this study. Statistical analyses of the cytologic and the histologic diagnoses of these cases were performed. RESULTS: Histologically, 107 lesions (44%) were benign and 136 lesions (56%) were malignant. Of the 136 malignant lesions, cytology was concordant in 73 lesions (53.7%), suspicious in 15 lesions (11.0%), false-negative in 12 lesions (8.8%) (benign), and unsatisfactory in 36 lesions (26.5%). Among the 107 benign lesions, cytology was concordant with histology in 75 lesions (70.1%), whereas 4 lesions (3.7%) and 28 lesions (26.2%) were cytologically suspicious and unsatisfactory, respectively. No false-positive cytologies were found in the current series. CONCLUSIONS: The current prospective study indicates that mammography combined with FNAC provides an accurate and practical diagnostic approach for the majority of nonpalpable lesions. Patients with unsatisfactory and false-negative lesions should undergo excisional biopsy.

Adult↗

PubMed1998

Ultrasound-guided fine-needle aspiration cytology of nonpalpable breast lesions: Institut Curie's experience with 198 histologically correlated cases.

BACKGROUND: The value of ultrasound-guided fine-needle aspiration cytology (FNAC) in the diagnosis of nonpalpable breast lesions remains a subject of debate. To determine the accuracy of this procedure in these lesions, a comparative analysis with open surgical biopsy in 188 patients was performed. METHODS: Six hundred and fifty-four nonpalpable breast lesions detected by ultrasound in 585 patients were subjected to FNAC. Of these, 198 lesions (30.3%) from 188 patients were surgically excised. RESULTS: Histologically, 105 lesions (53%) were malignant and 93 (47%) were benign. Among carcinomas, 65 cases (61.9%) were concordant, whereas 21 cases (20%) were suspicious, 12 cases (11.4%) were false-negative (benign), and 7 cases (6.7%) were unsatisfactory for diagnosis. Among benign lesions, 80 cases (86%) were concordant, whereas 5 cases (5.4%) were suspicious, and 8 cases (8.6%) were unsatisfactory. No false-positive diagnoses were made. The sensitivity of the FNAC method was 87.8%, the specificity was 94.5%, and the positive predictive value was 94.6%. CONCLUSIONS: These results indicate that, with the exception of random microcalcified lesions, ultrasound-guided FNAC is a valuable and reliable technique in the diagnosis of nonpalpable breast lesions.

Adult↗

PubMed1998

[Pulmonary melioidosis].

Melioidosis is most frequently encountered in pulmonary localization. Melioidosis is an infectious disease caused by Burkholderia pseudomallei first described by Whitmore in 1912 in Burma. B. pseudomallei is a Gram negative rod belonging to the Pseudomonadaceae family. Soil and water are the natural reservoirs for the germ which is a specific pathogen for several mammal species. Long endemic in Southeast Asia and several tropical zones, B. pseudomallei has recently been found in temperate zones, including France. Human contamination occurs via the transcutaneous route and often leads to dormant inapparent infection. Many conditions, such as diabetes, renal lithiasis, various circumstances of immunodepression or stress, facilitate clinical manifestations which vary greatly. Pulmonary manifestations may be acute and extensive, producing a torpid pseudo-tuberculous condition or a variety of clinical and radiological features mimicking other diseases. Bacteriological and serological tests may be negative. Exposure in an endemic zone, the notion of a favorable context, weight loss, cavitary images on successive chest x-rays and the presence of extra-pulmonary localizations may be suggestive. Ceftazidime or the amoxicillin-clavulanic acid combination are indicated, but mortality in acute forms still reaches 40%. Relapse can be expected if the treatment duration is too short.

Amoxicillin↗

PubMed1998

[Diagnostic difficulties and limits in imaging].

Fine-needle cytology and core biopsy of the breast done under mammographic or ultrasonographic guidance can assist in decision-making (monitoring, diagnostic or therapeutic procedures). Cytologic studies and histologic evaluation of core biopsies have their own limitations: the samples are small in size, and the histopathological features of the lesions are often complex. Each step of an image-guided diagnostic procedure contributes to the reliability of the method. The characteristics of the mammogram and/or ultrasonogram image provide initial orientation. Whether they are concordant with the results of the cytologic or histologic study is an important factor. The main limitations of stereotactically-guided biopsies are ballistic with targets that are difficult to circumscribe (fine microcalcifications or ill-defined density). With ultrasonography, verification of the sampling site in the target is essential. The performances of these procedures are closely dependent on the experience of the operators and on the quality of the cooperation between clinicians, radiologists and pathologists.

Biopsy↗

PubMed1997

Line-Mixing Effects in Q Branches of CO2

A theoretical model based on the energy corrected sudden (ECS) approximation is used in order to account for line-mixing effects in Delta left and right arrow Pi infrared Q branches of 12C16O2. Its quality is demonstrated by comparisons with numerous laboratory spectra of CO2-He and CO2-N2 mixtures: three Q branches in the 4 and 17 μm regions are investigated at room temperature in a wide pressure range. The influence of mixing between Q(J) lines associated with odd and even values of the rotational quantum number J is demonstrated and analyzed in detail. It is shown that, in contrast to available fitting law approaches, the ECS model correctly predicts the influence of the parity of the rotational quantum numbers J and J' on coupling between the Q(J) and Q(J') lines. Comparisons between the effects of collisions of CO2 with N2 and He are made and analyzed. They show that these two systems involve different line couplings within the Q branch. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗