A platform for multi-point fiber optic base dosimetry

Radiotherapy is in a period of rapid scientific and clinical development and the increasing complexity of modern treatment modalities has also introduced a more comprehensive patient-specific quality assurance programme (QA) to verify an individual patient delivery. Optical fibers offer a solution for in vivo radiotherapy dosimetry with many advantages over currently employed clinical dosimetry systems. A new technology is based on the use of luminescent materials with a plastic optical fiber, acting as light guides, to create a multi-point dosimeter. In this study, two different types of optical fibers with a core diameter of 1mm were used in all the characterization measurements. In both cases the inorganic radiation sensor is based on europium-doped yttrium oxide and emits light slightly above 600nm. In both configurations, the fibers were connected to a small portable reader. Optical fibers were irradiated in a water equivalent slab phantom, at the nominal photon energy of a 6MV clinical accelerator for a fixed dose of 1Gy. Field Output Factors (OF) for photon small beams were measured using the two fibers and a ionization chamber. Several measurements of the signal were performed to test the stability over time and repeatability. The comparison of OF measurements between the two fibers and the ion chamber was performed. In our preliminary measurements optical fibers have been demonstrated to be able to perform accurate radiotherapy dosimetric measurements

Full Geant4 and FLUKA Simulations of an e-LINAC for its Use in Particle Detectors Performance Tests

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges is from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.Comment: 10 pages, 10 figures, 2 table

On the use of highly pixellated CMOS imagers to measure therapeutic beam profile

The characterization of high-intensity charged-particle and photon beams at medical accelerators is often a time-consuming task. In this work, we discuss the possibility to use highly segmented CMOS imagers as a way to measure the fluxes with high spatial precision and in a short time. Quite recently CMOS imagers, designed to collect visible light, have been used to detect ionizing radiation, either charged particles (electron, proton) or photons. These devices, due to the very low single pixel noise, have a very high detection efficiency, once the interaction between radiation and silicon has taken place, and act primarily as counting detectors. We will show how it is possible to extract a precise beam shape using as a test case a therapeutic electron beam delivered by an Elekta e-LINAC at the S. Maria Hospital in Terni (Italy), and as sensors commercial off-the-shelf (COTS) CMOS imagers

Coastline changes and sedimentation related with the opening of an artificial channel: the Valo Grande Delta, SE Brazil

The role played by human activity in coastline changes indicates a general tendency of retreating coasts, especially deltaic environments, as a result of the recent trend of sea level rise as well as the blockage of the transfer of sediments towards the coast, especially due to the construction of dams. This is particularly important in deltaic environments which have been suffering a dramatic loss of area in the last decades. In contrast, in this paper, we report the origin and evolution of an anthropogenic delta, the Valo Grande delta, on the south-eastern Brazilian coast, whose origin is related to the opening of an artificial channel and the diversion of the main flow of the Ribeira de Iguape River. The methodology included the analysis of coastline changes, bathy metry and coring, which were used to determine the sedimentation rates and grain-size changes over time. The results allowed us to recognize the different facies of the anthropogenic delta and establish its lateral and vertical depositional trends. Despite not being very frequent, anthropogenic deltas represent a favorable environment for the record of natural and anthropogenic changes in historical times and, thus, deserve more attention from researchers of different subjects.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [06/04344-2]info:eu-repo/semantics/publishedVersio

The Mycobacterial LysR-Type Regulator OxyS Responds to Oxidative Stress and Negatively Regulates Expression of the Catalase-Peroxidase Gene

Protection against oxidative stress is one of the primary defense mechanisms contributing to the survival of Mycobacterium tuberculosis in the host. In this study, we provide evidence that OxyS, a LysR-type transcriptional regulator functions as an oxidative stress response regulator in mycobacteria. Overexpression of OxyS lowers expression of the catalase-peroxidase (KatG) gene in M. smegmatis. OxyS binds directly with the katG promoter region and a conserved, GC-rich T-N11-A motif for OxyS binding was successfully characterized in the core binding site. Interestingly, the DNA-binding activity of OxyS was inhibited by H2O2, but not by dithiothreitol. Cys25, which is situated at the DNA-binding domain of OxyS, was found to have a regulatory role for the DNA-binding ability of OxyS in response to oxidative stress. In contrast, the other three cysteine residues in OxyS do not appear to have this function. Furthermore, the mycobacterial strain over-expressing OxyS had a higher sensitivity to H2O2.Thus, OxyS responds to oxidative stress through a unique cysteine residue situated in its DNA-binding domain and negatively regulates expression of the katG gene. These findings uncover a specific regulatory mechanism for mycobacterial adaptation to oxidative stress

The association between frailty and MRI features of cerebral small vessel disease

Abstract: Frailty is a common syndrome in older individuals that is associated with poor cognitive outcome. The underlying brain correlates of frailty are unclear. The aim of this study was to investigate the association between frailty and MRI features of cerebral small vessel disease in a group of non-demented older individuals. We included 170 participants who were classified as frail (n = 30), pre-frail (n = 85) or non-frail (n = 55). The association of frailty and white matter hyperintensity volume and shape features, lacunar infarcts and cerebral perfusion was investigated by regression analyses adjusted for age and sex. Frail and pre-frail participants were older, more often female and showed higher white matter hyperintensity volume (0.69 [95%-CI 0.08 to 1.31], p = 0.03 respectively 0.43 [95%-CI: 0.04 to 0.82], p = 0.03) compared to non-frail participants. Frail participants showed a non-significant trend, and pre-frail participants showed a more complex shape of white matter hyperintensities (concavity index: 0.04 [95%-CI: 0.03 to 0.08], p = 0.03; fractal dimensions: 0.07 [95%-CI: 0.00 to 0.15], p = 0.05) compared to non-frail participants. No between group differences were found in gray matter perfusion or in the presence of lacunar infarcts. In conclusion, increased white matter hyperintensity volume and a more complex white matter hyperintensity shape may be structural brain correlates of the frailty phenotype

Inhibitor of apoptosis proteins, NAIP, cIAP1 and cIAP2 expression during macrophage differentiation and M1/M2 polarization

Monocytes and macrophages constitute the first line of defense of the immune system against external pathogens. Macrophages have a highly plastic phenotype depending on environmental conditions; the extremes of this phenotypic spectrum are a pro-inflammatory defensive role (M1 phenotype) and an anti-inflammatory tissue-repair one (M2 phenotype). The Inhibitor of Apoptosis (IAP) proteins have important roles in the regulation of several cellular processes, including innate and adaptive immunity. In this study we have analyzed the differential expression of the IAPs, NAIP, cIAP1 and cIAP2, during macrophage differentiation and polarization into M1 or M2. In polarized THP-1 cells and primary human macrophages, NAIP is abundantly expressed in M2 macrophages, while cIAP1 and cIAP2 show an inverse pattern of expression in polarized macrophages, with elevated expression levels of cIAP1 in M2 and cIAP2 preferentially expressed in M1. Interestingly, treatment with the IAP antagonist SMC-LCL161, induced the upregulation of NAIP in M2, the downregulation of cIAP1 in M1 and M2 and an induction of cIAP2 in M1 macrophages.This work was supported by Universidad de Granada, Plan Propio 2015;#P3B: FAM, VMC (http://investigacion.ugr.es/pages/planpropio/2015/ resoluciones/p3b_def_28072015); Universidad de Granada CEI BioTic;#CAEP2-84: VMC (http:// biotic.ugr.es/pages/resolucionprovisional enseaanzapractica22demayo/!); and Canadian nstitutes of Health Research;#231421, #318176, #361847: STB, ECL, RK (http://www.cihr-irsc.gc. ca/e/193.html). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript