Wavelet-Based Processing of Angular Measurements: Application to Realistic Display Aspect Simulation

In this paper, we describe a new wavelet-based data processing that performs simultaneously compression and fast multidimensional interpolation of hemispherical angular features. This algorithm is applied for display aspect simulation to allow predicting the rendering of any content on a given display under any illuminations conditions. Such rendering is based on a complex set of data composed of emitting display properties as a function of angle as well as its reflective behavior (BRDF). This record was migrated from the OpenDepot repository service in June, 2017 before shutting down

Fourier optics technology for viewing angle measurements: past, present and future

The proposed paper will explain the technical bases of the Fourier Optics Technology (OFT) for viewing angle measurement of displays and the evolution of the ELDIM systems over the years. There multiple capacities to obtain luminance, color, spectral, polarization or reflection data will be explained and illustrated by various application examples. New OFT systems dedicated to the characterization ofNIR light sources will be also presented

Investigation of the feasibility of a simple method for verifying the motion of a binary multileaf collimator synchronized with the rotation of the gantry for helical tomotherapy

In this paper, we suggest a new method for verifying the motion of a binary multileaf collimator (MLC) in helical tomotherapy. For this we used a combination of a cylindrical scintillator and a general-purpose camcorder. The camcorder records the light from the scintillator following photon irradiation, which we use to track the motion of the binary MLC. The purpose of this study is to demonstrate the feasibility of this method as a binary MLC quality assurance (QA) tool. First, the verification was performed using a simple binary MLC pattern with a constant leaf open time; secondly, verification using the binary MLC pattern used in a clinical setting was also performed. Sinograms of simple binary MLC patterns, in which leaves that were open were detected as "open" from the measured light, define the sensitivity which, in this case, was 1.000. On the other hand, the specificity, which gives the fraction of closed leaves detected as "closed", was 0.919. The leaf open error identified by our method was -1.3 +/- 7.5%. The 68.6% of observed leaves were performed within +/- 3% relative error. The leaf open error was expressed by the relative errors calculated on the sinogram. In the clinical binary MLC pattern, the sensitivity and specificity were 0.994 and 0.997, respectively. The measurement could be performed with -3.4 +/- 8.0% leaf open error. The 77.5% of observed leaves were performed within +/- 3% relative error. With this method, we can easily verify the motion of the binary MLC, and the measurement unit developed was found to be an effective QA tool.ArticleJOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS. 13(1):27-43 (2012)journal articl

Cold Leak Tests of LHC Beam Screens

In order to guide the high energy proton beams inside its two 27 km long vacuum rings, the Large Hadron Collider (LHC) at CERN, Geneva, makes use of superconducting technology to create the required magnetic fields. More than 4000 beam screens, cooled at 7 20 K, are inserted inside the 1.9 K beam vacuum tubes to intercept beam induced heat loads and to provide dynamic vacuum stability. As extremely high helium leak tightness is required, all beam screens have been leak tested under cold conditions in a dedicated test stand prior to their installation. After describing the beam screen design and its functions, this report focuses on the cold leak test sequence and discusses the results

Typologie des hospitalisations multiples de patients diabétiques au CHU de Grenoble

Certains patients diabétiques semblent ré-hospitalisés pour les mêmes raisons au fil des ans, ce qui questionne sur l intérêt et l impact de ces hospitalisations réitérées. Les soignants ressentent un sentiment d échec associé à une perte de motivation face à ces patients. Qu en est-il réellement de ce phénomène ? Ce travail rétrospectif sur la période Janvier 2006-Mai 2011 a permis de déterminer que les patients multi-hospitalisés (au moins deux hospitalisations) représentent un cinquième des patients admis entre ces dates dans le service de Diabétologie du CHU de Grenoble, et correspondent à 40% des séjours. Au sein de cette population : 32% de patients diabétiques de type 1 et 64% de patients diabétiques de type 2, une majorité de patients concernés par 2 ou 3 séjours, des diabètes anciens et complexes, des motifs d hospitalisations souvent récurrents et semblant pourtant sensibles à une prévention en amont. Quatre problématiques majeures ont été retrouvées et analysées: nécessité de modifier la stratégie thérapeutique, difficultés liées à la diététique, difficultés d adhérer à la proposition de prise en charge thérapeutique, et autres difficultés ayant un impact sur l équilibre du diabète (réaliser une activité physique, réaliser certains actes nécessaire à la gestion de la maladie et s adapter aux situations vécues, facteurs émotionnels). Elles peuvent faire l objet d interventions ciblées et le temps d hospitalisation pourrait être considéré comme temps spécifique d amorce ou de remobilisation structurée lors d une hospitalisation dédiée permettant d envisager la construction d un projet personnalisé en partenariat et en complémentarité avec la ville.Some diabetic patients appear to be readmitted for the same reasons over the years that questions about the relevance and impact of these repeated hospitalizations. Caregivers feel a sense of failure associated with a loss of motivation deal with these patients. What really is this phenomenon? This retrospective study over the period January 2006-May 2011 has identified that patients concerned by multiple hospitalizations (at least two hospitalizations) represent 1/5 of patients admitted between the dates in diabetology unit of Grenoble University Hospital, and correspond 40% of stay. Within this population: 32% of patients with type 1 diabetes and 64% of patients with type 2 diabetes, a majority of patients affected by two or three visits, diabetes ancient and complex, many recurrent reasons of hospitalizations that seem yet sensitive to upstream prevention. Four major problems were found and analyzed: the need to modify the therapeutic strategy, problems related to diet, difficulties to adhere to the proposed therapeutic management, and other difficulties that affect diabetes control (achieving a physical activity, perform certain acts necessary for the management of the disease and adjust to life situations, emotional factors). They can be subject to targeted interventions and hospitalization time could be considered as time-specific primer or "remobilization" structured in a stay dedicated to envisage the construction of a custom project in partnership and complementary to ambulatory cares.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

DOSIMAP: a high-resolution 2-D tissue equivalent dosemeter for linac QA and IMRT verification

International audienceNew generation of radiation therapy accelerators requires highly accurate dose measurements with high spatial resolution patterns. IMRT is especially demanding since the positioning accuracy of all the multi-leafs should be verified for each applied field and at any incidence. A new 2-D tissue equivalent dosemeter is presented with high spatial resolution that can fulfil these tasks. A plastic scintillator sheet is sandwiched between two polystyrene cubes, and the emitted light is observed by a high-resolution camera. A patented procedure allows efficient discrimination of the scintillation proportional to the dose from the parasitic Cerenkov radiation. This extraction made on the cumulated images taken during an irradiation field at a rate of 10 images s(-1) provides high-resolution mapping of the dose rate and cumulated dose in quasi real time. The dosemeter is tissue equivalent (ICRU-44) and works both for electrons and photons without complex parameter adjustment, since phantom and detector materials are identical. The calibration is simple and independent of the irradiation conditions (energy, fluence, quality and so on). The principle of the dosemeter and its calibration procedure are discussed in this paper. The results and, in particular, the dose depth profiles are compared with standard ionisation chamber measurements in polystyrene for both photons and electrons. Finally, the detector specifications are summarised and one example of complex IMRT field is discussed

The DOSIMAP, a high spatial resolution tissue equivalent 2D dosimeter for LINAC QA and IMRT verification

The continual need for more accurate and effective techniques in radiation therapy makes it necessary to devise new control means combining high spatial resolution as well as high dose accuracy. Intensity modulated radio therapy (IMRT) allows highly conformed fields with high spatial gradient and therefore requires a precise monitoring of all the multileaf positions. In response to this need, the authors have developed a new 2D tissue equivalent dosimeter with high spatial resolution. A plastic scintillator sheet is sandwiched between two polystyrene blocks and the emitted light is captured by a high resolution camera. A newly developed procedure described herein allows efficient discrimination of the scintillation from the parasitic Čerenkov radiation. This processing is applied on the cumulated image from a sequence of images taken during an irradiation field at a rate of 10 images/s. It provides a high resolution mapping of the cumulated dose in quasireal time. The dosimeter is tissue equivalent (ICRU-44) and works both for electrons and photons without complex parameter adjustment since phantom and detector materials are identical. Instrument calibration is simple and independent of the irradiation conditions (energy, fluence, quality, ...). In this article, the authors present the principle of the dosimeter and its calibration procedure. They compare the results obtained for photons and electron beams with ionization chamber measurements in polystyrene. Technical specifications such as accuracy and repeatability are precisely evaluated and discussed. Finally, they present different IMRT field measurements and compare DOSIMAP measurements to TPS simulations and dosimetric film profiles. The results confirm the excellent spatial resolution of the instrument and its capacity to inspect the leaf positions for each segment of a given field

New high spatial resolution and tissue equivalent two-dimensional dosimeter for IMRT quality control

International audienc