93 research outputs found

    Use of polyethylene glycol coatings for optical fibre humidity sensing

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    Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystal line structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed. (C) 2008 The Optical Society of Japan

    Set up of a methodology for participatory plant breeding in bread wheat in France

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    In Organic Agriculture, cultivation environments and agronomic practices are very diverse. This diversity can be handled with decentralized selection based on the knowledge of farmers and scientists. A collaborative work between associations from Réseau Semences Paysannes and the DEAP team from INRA du Moulon set up an innovative breeding approach on farm based on decentralization and participation of farmers. This approach makes it possible to (i) create new population varieties of bread wheat locally adapted (genetic innovation) (ii) set up an organizational scheme based on decentralization and co construction between actors (societal innovation) and (iii) develop experimental designs, create statistical and data management tools which stimulate these genetic and societal innovations

    Individual participant data meta-analysis of LR-5 in LI-RADS version 2018 versus revised LI-RADS for hepatocellular carcinoma diagnosis

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    Background A simplification of the Liver Imaging Reporting and Data System (LI-RADS) version 2018 (v2018), revised LI-RADS (rLI-RADS), has been proposed for imaging-based diagnosis of hepatocellular carcinoma (HCC). Single-site data suggest that rLI-RADS category 5 (rLR-5) improves sensitivity while maintaining positive predictive value (PPV) of the LI-RADS v2018 category 5 (LR-5), which indicates definite HCC. Purpose To compare the diagnostic performance of LI-RADS v2018 and rLI-RADS in a multicenter data set of patients at risk for HCC by performing an individual patient data meta-analysis. Materials and Methods Multiple databases were searched for studies published from January 2014 to January 2022 that evaluated the diagnostic performance of any version of LI-RADS at CT or MRI for diagnosing HCC. An individual patient data meta-analysis method was applied to observations from the identified studies. Quality Assessment of Diagnostic Accuracy Studies version 2 was applied to determine study risk of bias. Observations were categorized according to major features and either LI-RADS v2018 or rLI-RADS assignments. Diagnostic accuracies of category 5 for each system were calculated using generalized linear mixed models and compared using the likelihood ratio test for sensitivity and the Wald test for PPV. Results Twenty-four studies, including 3840 patients and 4727 observations, were analyzed. The median observation size was 19 mm (IQR, 11–30 mm). rLR-5 showed higher sensitivity compared with LR-5 (70.6% [95% CI: 60.7, 78.9] vs 61.3% [95% CI: 45.9, 74.7]; P < .001), with similar PPV (90.7% vs 92.3%; P = .55). In studies with low risk of bias (n = 4; 1031 observations), rLR-5 also achieved a higher sensitivity than LR-5 (72.3% [95% CI: 63.9, 80.1] vs 66.9% [95% CI: 58.2, 74.5]; P = .02), with similar PPV (83.1% vs 88.7%; P = .47). Conclusion rLR-5 achieved a higher sensitivity for identifying HCC than LR-5 while maintaining a comparable PPV at 90% or more, matching the results presented in the original rLI-RADS study

    Hepatic hemangiomas: Factors associated with T2 shine-through effect on diffusion-weighted MR sequences.

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    PURPOSE: To determine the frequency and factors associated with the presence of T2 shine-through effect in hepatic hemangiomas on diffusion-weighted (DW) magnetic resonance (MR) sequences. MATERIALS AND METHODS: This retrospective study was approved by institutional review board with waiver of informed consent. One hundred forty-nine consecutive patients with 388 hepatic hemangiomas who underwent a liver MR between January 2010 and November 2011 were included. MR analysis evaluated the lesion characteristics (signal intensities and enhancement patterns (classical, rapidly filling, delayed filling)), the presence of T2 shine-through effect on DW sequences (b values of 0, 150, and 600s/mm(2)), and apparent diffusion coefficient (ADC) values. Multivariate analysis was performed to study the factors associated with the T2 shine-through effect. RESULTS: T2 shine-through effect was observed in 204/388 (52.6%) of hepatic hemangiomas and in 100 (67.1%) patients. Mean ADC value of hemangiomas with T2 shine-through effect was significantly lower than hemangiomas without (2.0±0.48 vs 2.38±0.45, P&lt;.0001). On multivariate analysis, high signal intensity on fat-suppressed T2-weighted fast spin-echo images, hemangiomas with classical or delayed enhancement, and the ADC of the liver were the only significant factors associated with T2 shine-through effect. CONCLUSION: T2 shine-through effect is commonly observed in hepatic hemangiomas and is related to hemangiomas characteristics. Radiologists should be aware of this phenomenon which could lead to misdiagnosis. Its presence should not question the diagnosis of hemangiomas when typical MR findings are found

    Baseline values of DCE-CT of liver in patients with colorectal cancer

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    Purpose: Assessment of baseline values in CT perfusion (CTp) studies is as much difficult as it plays a crucial role for an accurate computation of perfusion parameters. Besides that, the unenhanced stage of CTp provides repeated measures of baseline. This study aims at computing and analysing the voxel-based baseline values of normal liver in a set of patients with colorectal cancer. Methods and Materials: 40 patients with colorectal cancer, free from any hepatic diseases, underwent axial CTp examinations of liver at colorectal cancer diagnosis. A large region of interest (ROI) was drawn on one central section of the liver, avoiding large vessels. Baseline portion (BP) of each time concentration curve (TCC) of the ROI was determined through the use of an adaptive 3D filtering and the relative baseline value (HU) was computed as the mean of the TCC values over BP. Mean, median, and standard deviation values were computed for each patient as well as for the entire cohort. Results: For each patient, mean and median baseline values coincide, this suggesting quite symmetric distributions. The average and standard deviation (std) of baseline mean values of all patients are 61.7HU (range 32\uf779HU), and 10.1, with 73% of values within one std interval (51\uf771HU). Moreover, baseline colorimetric maps showed a high spatial correlation. Conclusion: Baseline values of normal liver of patients with colorectal cancer are compliant with values of normal liver in healthy subjects reported in the literature. The spatial coherence of maps hints at a local similarity of tissue features

    Multicentre analysis of blood flow values of normal liver in CT perfusion examinations of patients with colorectal cancer

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    Purpose: Despite CT perfusion (CTp) has already proved to be a useful tool in oncology, the lack of standardization prevents its use in the clinical practice, and especially using different equipment. In this multicentre study, we wanted to estimate to what extent using different CT machines can affect computation of perfusion values in normal liver. Methods and Materials: These patients belong to a large multicentre study on CTp (PIXEL). 30 patients (age range 46-85 years) with colorectal cancer, free from any liver disease, who did not develop liver metastases in the follow-up, underwent liver axial CTp in three Centres (10 patients each), with the same acquisition protocol. A large region of interest was drawn on one section, and voxel-based blood flow (BF) values were calculated using the same software. Mean BF values of each patient were computed and Tukey test (p-value 640.05) was applied to evaluate whether Centres introduce variability on computation of the averaged perfusion values. Results: Mean BF (mL/min/100g) values for each Centre were 34.4\ub17.8, 38.4\ub19.9, 30.8\ub16.3, respectively, with ranges 22.8\uf747.4, 26.4\uf751.2, 21.4\uf737.5. Statistical tests assessed that the mean perfusion values of the second and third Centre differ, and this difference was not to be attributed to within-patients variability. Conclusion: Perfusion values of normal liver in patients with colorectal cancer are often used as the \u201ccontrol\u201d to check for the existence of predictive biomarkers. Despite using the same software, the preliminary results of this multicentre study suggest that a normalization has to be performed before comparing results between Centres
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