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WOS:000395847500002; International audience; Rheometers with specific impellers, developed to characterize the behavior of cement-based suspensions in the fresh state, are used to limit the heterogeneities induced during shearing but they make the identification of the rheological parameters less straightforward compared to conventional rheometers. This paper presents the inverse analysis method and discusses the quality of this identification procedure when applied to such materials. The procedure includes a CFD simulation based on the finite element method using a Herschel-Bulkley model. Two kinds of optimization algorithms are used: a deterministic simplex method and a stochastic genetic method. As a first step of a larger study, the procedure reported in this paper used 2D synthetic data, i.e. 2D numerically generated experimental data. Two numerical vis-coplastic materials, characterized by shear-thinning and shear-thickening, were selected and studied. The results obtained with the two algorithms are systematically compared to the known parameter solution. Three approaches corresponding to three levels of user's knowledge about the material under study are considered successively: (1) the user has no a priori knowledge about the material, (2) the user knows whether the material is shear-thinning or shear-thickening and (3) the user is able to estimate the behavior index. The time-consuming genetic method appears to be suitable when the a priori knowledge of the material is slight, whereas the simplex method gives a reliable solution in a few iterations when the level of knowledge is higher. Both algorithms encounter more difficulties with the shear-thinning material than with the shear-thickening one. In this paper, the advantage provided by the genetic method regarding the non-uniqueness of the identification procedure for real experimental data is also highlighted: this method provides a collection of satisfactory solutions among which the user can select the optimal one based on his scientific background and/or on further experimental test results.

The gas permeability of the thin liquid films which separate neighbouring bubbles in a liquid foam plays a key role in foam coarsening. Different approaches have been developed in the past to measure the film permeability, relying on measurements either on individual films/bubbles or on bulk foams. While the first approach may not be sufficiently representative of a real foam film, the latter is hardly feasible due to a lack of quantitative description of the coarsening of bulk foams with non-negligible liquid content. Here we show that a good compromise between these approaches can be achieved by investigating the coarsening of quasi-two-dimensional foams. More precisely, we propose a particularly simple approach in which we follow the evolution of the number of bubbles of an initially monodisperse foam. In this case, a large number of bubbles disappear simultaneously, leading to a “catastrophic” event, which can be identified easily and accurately related to the film permeability. We demonstrate the potential of this technique by using aqueous foams stabilised by sodium dodecyl sulfate having different liquid fractions and containing different gases. The experiments are compared to Surface Evolver simulations.

Transplant renal artery stenosis (TRAS) is a common complication of kidney transplantation but attempts to identify predisposing risk factors for TRAS have yielded conflicting results. In order to determine the predisposing factors for transplant (TRAS), we retrospectively reviewed the records of 29 renal allograft recipients with TRAS treated with percutaneous transluminal angioplasty (PTA). The TRAS group was compared with a case-control group of 58 patients. Predisposing factors for TRAS included CMV infection (41.4% vs. 12.1% p = 0.0018) and initial delayed graft function (DGF) (48.3% vs. 15.5% p = 0.0018), respectively in the TRAS and the control group. Acute rejection occurred more frequently in patients from the TRAS group (48.3%) compared with the control group (27.6%), although the difference was not significant (p = 0.06). In a multivariate analysis, only CMV infection (p = 0.005) and DGF (p = 0.009) appear to be significantly and independently associated with TRAS. The long-term graft survival was significantly higher in the control group, compared with the TRAS group (p = 0.03). Our study suggests that CMV infection and DGF are two reliable risk factors for TRAS. Despite treatment by PTA with primary successful results, TRAS significantly affects long-term graft outcome.

The study included 140 patients with Parkinson’s disease (PD) and 280 non-Parkinson age-matched controls to evaluate environmental risk factors associated with PD. The effect of exposure to environmental and dietary factors was determined using conditional logistic regression. This multivariate analysis showed that PD in first-degree relatives and tea drinking were the main risk factors for PD. Smoking appeared to be a protective factor. Exposure to toxic compounds was not a significant risk factor. Further research is needed to validate that tea consumption increases the risk of PD.

Twenty-two patients with 25 cases of focal nodular hyperplasia (FNH) proved with pathologic study were imaged with a TurboFLASH (fast low angle shot) sequence combined with bolus administration of gadolinium tetraazacyclododecanetetraacetic acid (DOTA), spin-echo (SE) T2-weighted sequences, and postcontrast T1-weighted sequences. FNH-liver signal-difference-to-noise ratios were quantified; the features of the central scar were qualitatively analyzed. On SE T2-weighted images, all FNHs were hyperintense; in two cases the central scar exhibited a high signal intensity associated with hypointense areas corresponding to fibrous tissue within the branches of the scar. Unenhanced TurboFLASH images always demonstrated the FNHs as hypointense and always depicted the central scar as a hypointense area within the lesion. After bolus injection, arterial enhancement of FNH was clearly seen, and in 10 of 25 lesions, enhancement within the scar was seen 40-80 seconds after injection. Both unenhanced and enhanced TurboFLASH sequences produced the best signal-difference-to-noise ratios in comparison with T2-weighted images.

Cirrhosis is a chronic liver disease characterized by the presence of diffuse parenchymal necrosis, reactive fibrosis and nodular regeneration. These regenerative nodules may evolve into dysplastic nodules and finally nodules of hepatocellular carcinoma (HCC). Improved survival of cirrhotic patients with HCC depends on eligibility to liver transplantation. The purpose of this paper is to review the imaging features of liver nodules within cirrhotic liver and to propose the imaging strategies when considering the possibility of liver transplantation.

Under vacuum conditions, the accumulation of low fluence laser pulses generally leads to an organic contamination of the surface irradiated. This phenomenon reduces the optical component lifetime. Experimental conditions such as laser characteristics, environment composition and structure of the coating strongly influence the contamination mechanisms. Silica being the most employed material for optical coatings, this study aims at describing the laser-induced contamination influence of silica coatings deposition techniques. E-Beam evaporated and Ion Beam Sputtered silica thin films have been exposed to several billions 600 mJ/cm2 - 532 nm laser pulses under vacuum. This paper presents the observations made on laser-induced contamination and discusses the physical mechanisms involved.

It is still assumed that optical components submitted to laser fluences orders of magnitude below their laser induced damage threshold (LIDT) will last for ever. However, depending upon environmental conditions, the accumulation of low fluence laser pulses leads to a progressive contamination and eventually to a damage of the optical components. In order to study the physics of the laser induceded contamination, a laser test bench has been developed. The experimental cell is dry-pumped and a mass spectrometer controls the environment around the optical component. An infrared camera diagnosis follows the sample surface temperature. This paper contains preliminary results obtained on anti-reflective coatings on fused silica tested at 532 nm with a pulse repetition rate of 10 kHz and a pulse width of 100 ns.

The study included 140 patients with Parkinson's disease (PD) and 280 non-Parkinson age-matched controls to evaluate environmental risk factors associated with PD. The effect of exposure to environmental and dietary factors was determined using conditional logistic regression. This multivariate analysis showed that PD in first-degree relatives and tea drinking were the main risk factors for PD. Smoking appeared to be a protective factor. Exposure to toxic compounds was not a significant risk factor. Further research is needed to validate that tea consumption increases the risk of PD.

This article focuses on the main clinicopathologic and MR findings in the more frequent benign liver lesions (excluding hemangiomas) such as cysts, focal nodular hyperplasia, hepatocellular adenoma, and fatty tumors. These entities raise several questions concerning their pathogenesis, differential diagnosis from various malignant tumors or pseudotumoral hepatic lesions, and management that remain frequently controversial.

We report 9 cases of febrile aseptic arthritis which occurred in 6 adults presenting with major sickle cell disease. The monoarticular arthritis affected the knee in 8 cases and the ankle in 1 case. Body temperature ranged from 38 degrees C to 39.5 degrees C in 7 cases, and neutrophilia (12.7 to 24 x 10(9)/l) was noted on six occasions. The always sterile synovial fluid contained 100 to 1700 cells/mm3 in 6 cases and 5200 to 12,500 cell/mm3 in 3 cases. Uricacidaemia was normal, and a search for crystals in the synovial fluid gave negative results. Bone scintigraphy and magnetic resonance imaging, performed in 3 patients, revealed the presence of a juxta-articular cortical bone infarct, whereas standard radiography was normal. In all patients, a brief immobilization and treatment with non-steroidal anti-inflammatory drugs resulted in complete cure in less than 10 days. These cases illustrate the characteristics of sickle cell arthritis, a rare complication of major sickle cell disease. Clinically, the condition resembles septic arthritis, being febrile and showing granulocytosis, but articular needle aspiration corrects the diagnosis. The mechanisms underlying these disorders have not yet been elucidated, but the bone scintigraphy and MRI performed in our patients are in favour of a reaction to a juxta-articular bone infarct.

To determine the efficacy of fat-suppressed sequences and contrast-enhanced MR imaging for the detection of focal spinal lesions caused by multiple myeloma, we obtained MR images in 32 patients with newly diagnosed myeloma who had back pain.All patients had biopsy-proved myeloma and had MR imaging at the painful level of the spine. Spin-echo T1-weighted, T2-weighted, and short TI inversion-recovery (STIR) images; dynamic ultrafast low-angle shot (turbo-FLASH) images after IV injection of a bolus of paramagnetic contrast material; and contrast-enhanced T1-weighted images were obtained. We qualitatively compared the signal intensities and contrast enhancement of focal lesions with those of the surrounding vertebral bodies.Multiple lesions were detected in all but two of the 32 patients. On T2-weighted and STIR images, all lesions had homogeneously high signal intensity. On T1-weighted images, the lesions were visible as hypointense areas compared with surrounding bone in all except four patients, in whom the lesions were isointense or hyperintense. All tumor nodules enhanced on turbo-FLASH images obtained in the arterial phase. No additional lesions were seen on STIR or contrast-enhanced images. MR findings resulted in a change in the staging of the disease in one patient and led to prompt treatment in five patients with epidural involvement.MR imaging appears to be helpful in detecting spinal involvement in patients with multiple myeloma. The diagnosis of spinal lesions is best achieved by using either fat-suppressed or T2-weighted images. Although myeloma lesions enhanced in all patients, contrast material appears to be of no value for the detection of additional lesions.

On chest radiographs, the precise assessment of thoracic injuries consecutive to blunt trauma is often compromised by the nonspecific appearance of many lesions. Furthermore, significant injuries are frequently overlooked. However, the management of the patients with chest trauma is still often based primarily upon clinical and radiographic findings and Computed Tomography (CT) is often performed secondarily on the basis of unexplained clinical signs or suspected radiographic abnormality. Some authors have reported that CT was a highly sensitive method for detecting thoracic lesions frequently not seen or underestimated on conventional supine chest radiographs. However, the value that these new CT findings could have in the therapeutic management of these patients, have not been systematically investigated to our knowledge, except in a limited series suggesting that the course of critically ill patients could be substantially altered after thoracic CT. In order to estimate the role of early CT in the management of patient care, we report the therapeutic consequences of CT findings in forty patients who we report the therapeutic consequences of CT findings in forty patients who had a thoracic CT within few hours following a chest injury. We showed that early thoracic CT scan in patients with blunt trauma detected significantly more lesions than did chest X-Ray and appreciably modified the treatment modalities in 70% of our patients. We then recommend that all the patients admitted in ICU after chest trauma undergo a thoracic CT scan as soon as possible in order to optimize their treatment modalities.

The pathologic changes resulting from liver irradiation include congestion, fibrosis, and veno-occlusive disease. We report an unusual complication of radiation induced injury: acute thrombosis of a main hepatic vein within the radiation port. CT and MR features are described and the etiology of this unusual complication is discussed.

The capability for studying noninvasively vessels has been dramatically improved with the use of gradient echo sequences. Twenty-one patients presenting a suspected inferior vena cava obstruction on cavography underwent MR examination with axial, sagittal and coronal gradient echo images. Eighteen patients were also imaged with ultrasound and/or CT. Gradient echo sequences visualized a thrombus in 19 cases and a normal vein in the remaining 2 cases. The potential MR pitfalls are illustrated and the two cases of false positive on cavography are discussed. Gradient echo sequences allow a fast and performant examination of the vessels.

Unlike other major abdominal organs, infarctions affecting the liver is extremely rare. In humans, the rarity of hepatic infarction is explained commonly on the basis of the double blood supply via the hepatic artery and portal vein. The imaging studies and clinical records of seven patients with hepatic infarcts were reviewed. These infarctions were essentially observed during post-operative periods: after aortoceliac graft and after accidental ligation of the hepatic artery (4 cases). The other etiologies included: acute hypovolemic shock in patients with atherosclerosis (2 cases) and finally one case of acute thrombocytosis. Dynamic CT was performed initially in all the cases and during the evolution, demonstrating peripheral low attenuation areas without enhancement. Associated splenic infarcts were present in 4 patients and renal infarcts in two. While the clinical and laboratory findings in hepatic infarction can be completely mimicked by hepatic abscess, CT-guided aspirations were performed in 6 patients demonstrating in only one case the presence of infection.

Duplication of the stomach is a rare congenital malformation. Most reported cases involve infants or young children. On the basis of 3 cases identified at a later age, we describe the CT appearance of this malformation. Those 3 cases were demonstrated by the histological study of the surgical specimen.

Two out of nine patients in which inferior vena cava interruption was performed with a Gunther filter developed a recurrent pulmonary embolism. In both cases, the filter had moved down and the anchoring legs had perforated the wall of the vena cava. The source of the pulmonary embolism was a clotted basket filter. Anticoagulation was given for two weeks in one patient and six months in the other after insertion of the filter, but it had been stopped before the thrombotic event leading to the recurrent pulmonary embolism. The formation of the thrombi had probably been caused by the migration of the filter and the subsequent perforation, which may have been facilitated by the cessation of the anticoagulation.

In this chapter the acquired abnormalities of the pulmonary vessels (including the systemic arteries, which contribute to pulmonary vascularization), the superior vena cava, and the azygos vein are described.

Sonographic and computed tomographic (CT) examinations have modified the investigation of hepatic, splenic and pancreatic tumors. Because of advances in non-invasive diagnostic procedures, these different benign or malignant tumors are now more frequently detected and surgically treated. However, for these different lesions sonography is the gold standard imaging technique. The different indications for CT and magnetic resonance imaging are discussed for each tumor. For the diagnostic imaging of an acutely injured patient, sonography remains the useful examination in emergencies. The indications for CT scans are limited to the difficulties of sonographic diagnosis in stable trauma patients.

Purpose: Intrahepatic thrombus is usually associated with either cirrhosis or hepato-cellular carcinoma (HCC). Most HCCs enhance after the administration of MnDPDP (Teslascan). Our objective was to analyze the enhancement characteristics of tumour portal vein thrombi. Material and Methods: Thrombi affecting the main or segmental portal veins (17 cases) and the suprahepatic inferior vena cava (1 case) were retrospectively selected from a series of 128 patients studied with MR imaging before and after the administration of MnDPDP. Enhancement was assessed qualitatively and quantitatively. Results: All tumour thrombi enhanced after MnDPDP administration. The enhancement was more conspicuous in the GRE images. On the quantitative evaluation, the portal thrombus enhancement was greater for GRE images than SE images. Portal thrombi enhanced more than the liver and the HCCs. There was a significant difference between the enhancement of the HCCs and the thrombi with both MR imaging techniques. Conclusion: The greater enhancement of the tumour thrombus associated with the liver and HCC may suggest that other mechanisms, apart from accumulation of the contrast medium within the hepatocytes inside the thrombi, are involved in thrombus enhancement.