417 research outputs found
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Correction of megavoltage cone-beam CT images of the pelvic region based on phantom measurements for dose calculation purposes.
Megavoltage cone-beam CT (MVCBCT) is an imaging technology that provides a 3D representation of the patient in treatment position. Because it is a form of x-ray tomography, MVCBCT images give information about the attenuation coefficients of the imaged tissues, and thus could be used for dose calculation. However, the cupping and missing data artifacts seen on MVCBCT images can cause inaccuracies in dose calculations. To eliminate these inaccuracies, a correction method specific to pelvis imaging and based on phantom measurements has been devised. Pelvis-shaped water phantoms of three different sizes were designed and imaged with MVCBCT. Three sets of correction factors were created from the artifacts observed in these MVCBCT images by dividing the measured CT number by the predefined CT number for water. Linear interpolation is performed between the sets of correction factors to take into account the varying size of different patients. To compensate for the missing anatomy due to the limited field of view of the MVCBCT system, the MVCBCT image is complemented with the kilovoltage CT (kVCT) image acquired for treatment planning.When the correction method is applied to an anthropomorphic pelvis phantom, the standard deviation between dose calculations performed with kVCT and MVCBCT images is 0.6%, with 98% of the dose points agreeing within +/- 3%.With uncorrected MVCBCT images this percentage falls to 75%. An example of dose calculation performed with a corrected clinicalMVCBCT image of a prostate cancer patient shows that changes in anatomy of normal tissues result in variation of the dose distribution received by these tissues.This correction method enablesMVCBCT images to be used for the verification of the daily dose distribution for patients treated in the pelvis region
ITGA1 (integrin, alpha 1)
The α1 integrin subunit (SU) belongs to a large family of α and β subunits that are noncovalently linked to constitute αβ transmembrane units. To date, 18 α and 8 β subunits are known to form 24 αβ units (Takada et al., 2007; Barczyk et al., 2010) which are involved in cell-cell and cell-matrix attachment and can drive inside-out and outside-in cell signaling (Shattil et al., 2010). Integrins are known to participate in different cell processes including cell shape, differentiation, migration, survival and proliferation (Giancotti, 1997; Vachon, 2011; Beauséjour et al., 2012). The &alpha ;1 SU was discovered in 1986 as the Very Late Antigen 1 (VLA1) and is highly expressed in activated lymphocytes in the joints of patients with rheumatoid arthritis (Hemler et al., 1986). In fibroblasts, α1 is known to activate the RAS/ERK proliferative pathway and has a pro-invasive function in certain cancers. In megakaryocyte differentiation α1 is silenced by DNA methylation but not histone modification (Cheli et al., 2007). Different transcription factors involved in cancer progression can bind to the ITGA1 promoter. Integrin α1 transcriptional regulation remains to be further defined
Which interventions with youths counter ageism toward older adults? : results from a realist review
Abstract : Age-related social biases â ageism â are developed at an early age. Interventions to counter ageism have been identified but little is known about their mechanisms, particularly in children. This study aimed to provide a comprehensive understanding of which interventions in youths are most effective, under which circumstances, how, and with what outcomes. Using 46 keywords in 6 databases, a realist review identified 24 studies published between 2000 and 2022 targeting youths under 18. A content analysis of these studies led to the construction of a Context-Mechanisms-Outcomes explanatory model. Contextual facilitators triggering mechanisms for changing stereotypes, prejudices and discrimination were: 1) enhancing knowledge about aging and older adults by providing nuanced information, 2) improving the quality of intergenerational contacts, 3) increasing opportunities to apply previously acquired knowledge in intergenerational interactions, and 4) promoting reflective thinking about experiences with older adults. However, stereotypes and prejudices appeared to be resistant and changes difficult to generalize. Insufficiently advanced cognitive development in children or viewing healthy and socially engaged older adults as unrepresentative of their age group were obstacles that reduced intervention effectiveness. Future studies should explore how advancing age influences interventions as well as the characteristics of older adults involved
Quelles pratiques diffĂ©renciĂ©es pour lâenseignement de lâorthographe lexicale ? Une recension des Ă©crits
MalgrĂ© la quantitĂ© dâĂ©crits sur la diffĂ©renciation pĂ©dagogique, peu dâentre eux visent Ă appliquer son cadre conceptuel Ă des contenus scolaires. Cet article propose de croiser les pratiques en orthographe lexicale et ce cadre. Une recension des Ă©crits a Ă©tĂ© effectuĂ©e dans diffĂ©rentes bases de donnĂ©es. LâanasynthĂšse a Ă©tĂ© employĂ©e pour analyser les donnĂ©es recueillies et Ă©laborer une modĂ©lisation de la diffĂ©renciation en orthographe lexicale. De nombreuses pistes de diffĂ©renciation pĂ©dagogique sont proposĂ©es Ă la suite de cette catĂ©gorisation dans les quatre axes de la diffĂ©renciation pĂ©dagogique : contenu,processus, structure et production
Non-negative Matrix Factorization using Partial Prior Knowledge for Radiation Dosimetry
Hyperspectral unmixing aims at decomposing a given signal into its spectral
signatures and its associated fractional abundances. To improve the accuracy of
this decomposition, algorithms have included different assumptions depending on
the application. The goal of this study is to develop a new unmixing algorithm
that can be applied for the calibration of multi-point scintillation dosimeters
used in the field of radiation therapy. This new algorithm is based on a
non-negative matrix factorization. It incorporates a partial prior knowledge on
both the abundances and the endmembers of a given signal. It is shown herein
that, following a precise calibration routine, it is possible to use partial
prior information about the fractional abundances, as well as on the
endmembers, in order to perform a simplified yet precise calibration of these
dosimeters. Validation and characterization of this algorithm is made using
both simulations and experiments. The experimental validation shows an
improvement in accuracy compared to previous algorithms with a mean spectral
angle distance (SAD) on the estimated endmembers of 0.0766, leading to an
average error of % on dose measurements.Comment: 11 pages, 6 figure
P-glycoprotein of blood brain barrier: cross-reactivity of MAb C219 with a 190 kDa protein in bovine and rat isolated brain capillaries
AbstractP-glycoprotein (P-gp), an active efflux pump of antitumor drugs, is strongly expressed in endothelial cells of the blood brain barrier (BBB). Two proteins (155 and 190 kDa) were detected by Western blot analysis of beef and rat capillaries with the monoclonal antibody (MAb) C219. In order to characterize the nature of these proteins, their profile of solubilization by different detergents was established and compared with that of P-gp from the CHRC5 tumoral cell line. The 155 kDa protein (p155) of capillaries and the P-gp of CHRC5 cells were well solubilized by deoxycholate and Elugent, whereas the 190 kDa protein (p190) was only solubilized by sodium dodecylsulfate (SDS). Both proteins have different patterns of extraction by Triton X-114, p155 partitioning as a membrane protein, while p190 was insoluble. Deglycosylation of capillary proteins resulted in a 27â28 kDa decrease in the apparent molecular weight of p155, similar to that observed for the P-gp of CHRC5 cells, but a decrease of only 7â8 for p190. Only p155 was immunoprecipitated by MAb C219. These results suggest that only p155 is the P-gp in BBB and that MAb C219 cross-reacts with a 190 kDa MDR-unrelated glycosylated protein. Consequently, the use of this antibody, which is frequently used to detect P-gp in tumors, could be a pitfall of immunohistochemistry screening for cancer tissues and lead to false positive in the diagnosis of MDR
MIQE précis: Practical implementation of minimum standard guidelines for fluorescence-based quantitative real-time PCR experiments
The conclusions of thousands of peer-reviewed publications rely on data obtained using fluorescence-based quantitative real-time PCR technology. However, the inadequate reporting of experimental detail, combined with the frequent use of flawed protocols is leading to the publication of papers that may not be technically appropriate. We take the view that this problem requires the delineation of a more transparent and comprehensive reporting policy from scientific journals. This editorial aims to provide practical guidance for the incorporation of absolute minimum standards encompassing the key assay parameters for accurate design, documentation and reporting of qPCR experiments (MIQE précis) and guidance on the publication of pure 'reference gene' articles
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