Dynamique sub-picoseconde de l'interaction laser de puissance – agrégats de gaz rare : émission intense de rayons X et production d'ions multichargés.

National audienceLors de campagnes d'expériences réalisées sur le Laser Ultra Court Accordable du CEA/Saclay, nous avons étudié le rayonnement X, tant qualitativement (spectroscopie et énergie moyenne des photons) que quantitativement (taux absolus et lois d'évolution), émis lors de l'interaction d'un jet effusif d'agrégats de gaz rare (Ar, Kr, Xe comprenant entre 10^4 et 10^6 atomes/agrégat) avec un laser femtoseconde de puissance (éclairement jusqu'à quelques 10^17 W/cm2). Les résultats présentés dans ce manuscrit sont uniquement dédiés aux agrégats d'Ar pour lesquels nous avons observé un rayonnement X issu d'ions fortement multichargés (jusqu'à l'Ar16+) présentant des lacunes en couches K. La technique de spectroscopie X utilisée a permis de déterminer pour la première fois des taux absolus ainsi que les lois d'évolution de l'émission X en fonction de l'ensemble des paramètres gouvernant l'interaction (intensité, polarisation, longueur d'onde et durée du pulse laser aussi bien que taille, densité et numéro atomique des agrégats)

Exposure of the French population to ionizing radiations from medical diagnostic procedures in 2012

International audienceMonitoring the exposure of the population to ionizing radiation is a European Union requirement. This article presents the exposure of the French population originating from medical diagnostic procedures performed in 2012. The number of procedures was established from a joint health insurances database. The effective dose associated with each procedure was estimated from various sources (national DRL, recent surveys, guides of procedures). The number of procedures was approximately 81.8 million, representing an average of 1247 examinations per 1000 inhabitants. The mean effective dose per inhabitant originating from medical diagnosis exposure was 1.6 mSv. When restricted to the population actually exposed, the average number of examinations was 2760 per 1000 individuals and the mean effective dose per exposed individual was 3.4 mSv. 70% of exposed individuals received less than 1 mSv. Mean individual exposure strongly increased with age below 1 mSv before the age of 20, around 7 mSv at 75 years. 44% of the French population (49% of the women, 39% of the men) has benefited from at least one diagnosis procedure. Conventional radiology, dental radiology and computed tomography represented respectively 54%, 34% and 10.5% of the number of procedures and contributed to 18%, 0.2% and 71% of the collective effective dose, respectively. A 20% increase of the average effective dose per inhabitant was observed, when compared to the year 2007. While efforts are still needed in the optimization of delivered dose and in the harmonization of practices, whatever the imaging field, specific interest should be paid to the justification of certain examinations which have particularly increased in numbers. © 2017 EDP Sciences

A new Monte Carlo tool for organ dose estimation in computed tomography

The constant increase of computed tomography (CT) exams and their major contribution to the collective dose led to international concerns regarding patient dose in CT imaging. Efforts were made to manage radiation dose in CT, mostly with the use of the CT dose index (CTDI). However CTDI does not give access to organ dose information, while Monte Carlo (MC) simulation can provide it if detailed information of the patient anatomy and the source are available. In this work, the X-ray source and the geometry of the GE VCT Lightspeed 64 were modelled, based both on the manufacturer technical note and some experimental data. Simulated dose values were compared with measurements performed in homogeneous conditions with a pencil chamber and then in CIRS ATOM anthropomorphic phantom using both optically stimulated luminescence dosimeters (OSLD) for point doses and XR-QA Gafchromic® films for relative dose maps. Organ doses were ultimately estimated in the ICRP 110 numerical female phantom and compared to data reported in the literature. Comparison of measured and simulated values show that our tool can be used for a patient specific and organ dose oriented radiation protection tool in CT medical imaging

Patient dose evaluation in computed tomography: A French national study based on clinical indications

International audiencePurpose. A national survey was performed to assess patient dose indicators based on clinical indication and on patient morphology for most common adult computed tomography (CT) examinations in France. Methods. Seventeen groups of clinical indications (GCIs) for diagnostic CT in adult patients were considered based on their frequency and on image quality requirements. Data was collected for 15-30 consecutive examinations performed between 2015 and 2017, per CT scanner and GCI. Distributions of total examination Dose-Length Product (DLP) and Volume CT Dose Index (CTDIvol) were assessed for each GCI as a function of patient gender or patient Body Mass Index (BMI) for head/neck and trunk examinations, respectively.Results. 6610 examinations were analysed. Median total exam DLP values were higher for men compared to women patients for head and neck examinations: difference ranged from 6% for ear trauma indication (577 vs 543 mGy·cm, p=0.01) to 35% for brain tumour GCI (1472 vs 1093 mGy·cm, p<0.01). For trunk examinations, total exam DLP increased consistently with patient’s BMI. For normal-BMI patients, median CTDIvol and DLP differed significantly between different GCIs for single-phase CT of the chest (3 mGy and 112 mGy·cm, respectively, for chronic obstructive pulmonary disease group vs 5.8 mGy and 207 mGy·cm for pulmonary embolism group, p<0.05) and of the abdomen-pelvis (5.6 mGy and 284 mGy·cm, respectively, in renal colic group vs 9.5 mGy and 463 mGy·cm in occlusive syndrome group, p<0.05). Conclusion. This study provides morphological- and clinical-based patient dose indicators in CT as a practical tool for clinical practices optimisation

Patient radiation doses in paediatric interventional cardiology procedures A review

International audienceA large number of investigations into the radiation doses from x-ray guided interventional cardiology procedures in children have been carried out in recent years. A review was conducted of these studies, gathering data on kerma area product (P KA), fluoroscopic screening time (FT), air kerma, and estimates of effective dose and organ doses. The majority of studies focus on P KA and FT with no estimation of dose to the patient. A greater than ten-fold variation in average P KA was found between different studies, even where data were stratified by patient age or weight. Typical values of P KA were 0.6-10 Gy • cm2 (andlt;1 year/10 kg), 1.5-30 Gy • cm2 (1-5 years), 2-40 Gy • cm2 (5-10 years), 5-100 Gy • cm2 (10-16 years) and 10-200 Gy • cm2 (andgt;16 years). P KA was lowest for heart biopsy (0.3-10 Gy • cm2 for all ages combined) and atrial septostomy (0.4-4.0 Gy • cm2), and highest for pulmonary artery angioplasty (1.5-35 Gy • cm2) and right ventricular outflow tract dilatation (139 Gy • cm2). Most estimates of patient dose were in the form of effective dose (typically 3-15 mSv) which is of limited usefulness in individualised risk assessment. Few studies estimated organ doses. Despite advances in radiation protection, recent publications have reported surprisingly large doses, as represented by P KA and air kerma. There is little indication of a fall in these dose indicators over the last 15 years. Nor is there much suggestion of a fall in doses associated with the use of flat panel detectors, as opposed to image intensifiers. An assessment of the impact of radiation dose in the context of overall patient outcome is required. © 2016 IOP Publishing Ltd

SESAME A TOOL FOR NUMERICAL DOSIMETRIC RECONSTRUCTION OF PATIENTS OVEREXPOSURES IN INTERVENTIONAL RADIOLOGY

International audienceRadiation overexposure accidents are rare but can have severe health consequences. Evaluating the dose received by the patient is a crucial step in the medical management. For that purpose, for more than 15 years, IRSN has been developing an in-house tool named SESAME for the numerical reconstruction of radiological accidents due to external sources. Recently, two new functionalities were implemented in SESAME to allow accurate reconstructions of interventional radiology (IR) overexposures. The experimental validation of SESAME for the reconstruction of overexposures in IR is presented. First, an anthropomorphic dummy equipped with dosemeters was irradiated following conditions similar to a fluoroscopically guided interventional procedure. Then the procedure was simulated using SESAME. Finally measured doses were compared to calculated doses. Even with a limited amount of data available, SESAME can provide valuable dose information for the medical team in charge of the patient, such as skin dose mapping and dose distribution in depth. © The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email [email protected]

Experimental evaluation of seven quality control phantoms for digital breast tomosynthesis

International audiencePurposes: The introduction of digital breast tomosynthesis (DBT) into the French breast cancer screening program is forecast by the authorities. The aim of the present study was to evaluate image quality phantoms to be used as internal quality controls. Methods: Seven breast phantoms dedicated to quality control in mammography were evaluated on reconstructed DBT images: ACR Model 015, BR3D, DBT QC model 021, Mam/Digi-EPQC, MTM100, TOMOMAM® and TOMOPHAN®. Two representative image parameters of DBT images were studied: image score and z-resolution, when inserts were included in the phantom, on five DBT systems of three different brands. Three observers were involved. Results: The MTM100, Mam/Digi-EPQC, BR3D, DBT QC model 021 phantoms' images presented artefacts affecting the image score. The ACR Model 015, TOMOMAM® and TOMOPHAN® phantoms appeared to be pertinent for DBT image score analysis. Due to saturation artefacts, Z-resolution results were not coherent with the theory for all phantoms except by using aluminium beads in the TOMOMAM® phantom. Conclusions: Phantom manufacturers should be encouraged to collaborate with DBT system manufacturers in order to design universal phantoms suitable for all systems for more complete quality control. From our study we can propose several specifications for an ideal and universal phantom designed for internal quality control in DBT. Phantoms should allow sensitive image score measurements. The background structure should be realistic to avoid artefacts. Phantoms should have a standard breast-like shape and size. © 2019 Associazione Italiana di Fisica Medic

Dynamique sub-picoseconde de l'interaction laser de puissance – agrégats de gaz rare : emission intense de rayons X et production d'ions multichargés

Lors de campagnes d'expériences réalisées sur le Laser Ultra Court Accordable du CEA/Saclay, nous avons étudié le rayonnement X, tant qualitativement (spectroscopie et énergie moyenne des photons) que quantitativement (taux absolus et lois d'évolution), émis lors de l'interaction d'un jet effusif d'agrégats de gaz rare (Ar, Kr, Xe comprenant entre 10$^4$ et 10$^6$ atome/agrégat) avec un laser femtoseconde de puissance (éclairement jusqu'à quelques 10$^{17}$ W/cm$^2$). Les résultats présentés dans ce manuscrit sont uniquement dédiés aux agrégats d'Ar pour lesquels nous avons observé un rayonnement X issu d'ions fortement multichargés (jusqu'à l'Ar$^{16+}$) présentant des lacunes en couches K. La technique de spectroscopie X utilisée a permis de déterminer pour la première fois des taux absolus ainsi que les lois d'évolution de l'émission X en fonction de l'ensemble des paramètres gouvernant l'interaction (intensité, polarisation, longueur d'onde et durée du pulse laser aussi bien que taille, densité et numéro atomique des agrégats)