Multicentre survey on patient dose in paediatric imaging and proposal for updated diagnostic reference levels for France. Part 2: plain radiography and diagnostic fluoroscopy.

OBJECTIVES: To report on a dose survey conducted by the French societies of radiology and paediatric imaging (SFR and SFIPP) and the French public service expert in nuclear and radiological risks (IRSN), and to suggest new diagnostic reference levels (DRLs) for paediatric plain radiography and diagnostic fluoroscopy. METHODS: Dose reports concerning four radiography procedures and three diagnostic fluoroscopy procedures performed in 2015-2016 on children aged 0-15 years were collected from 16 imaging departments on a voluntary basis. Air kerma-area product (PKA) was recorded for at least 10 patients per procedure, per centre and per age group. New DRLs were calculated as the 3rd quartiles of the distributions of the median values. RESULTS: Results from 2249 radiography examinations and 1235 diagnostic fluoroscopy procedures were obtained. A noticeable variability in patient exposure between facilities was observed in diagnostic fluoroscopy and to a lesser extent in plain radiography. DRLs are proposed for each procedure and each age group. CONCLUSIONS: This study showed that the applicable national DRLs in plain radiography were obsolete and its results have been recently used by the French authorities to update them. In diagnostic fluoroscopy, large differences of doses were observed, even among departments accustomed to paediatric procedures. The new national DRLs will be useful for optimising diagnostic practice. KEY POINTS: • New national diagnostic reference levels (DRLs) are proposed for several paediatric procedures in plain radiography and diagnostic fluoroscopy. • Even between departments accustomed to paediatric procedures, substantial differences of practice were observed, especially in diagnostic fluoroscopy.

Long-term experience and analysis of data on diagnostic reference levels: the good, the bad, and the ugly.

OBJECTIVES: To analyze 11-year data of France for temporal trends in dose indices and dose optimization and draw lessons for those who are willing to work on creation and update of diagnostic reference levels (DRLs). METHODS: The data from about 3000 radiology departments leading to about 750,000 imaging exams between 2004 and 2015 was analyzed, and patterns of reductions in dose for those below and above the DRLs were estimated and correlated with technology change. RESULTS: Dose optimization achieved was important and significant in departments which were above or just below the DRL (p = .006) but not in those which were around half of the DRL values. The decrease in 75th percentile value of Kerma air product (KAP) for chest radiography by 27.4% between 2004 and 2015 was observed with the number of flat panel detectors increase from 6 to 43%. A good correlation between the detector type distribution and the level of patient radiation exposure is observed. Otherwise, setting DRLs for standard-sized patient excludes patients lower and higher weighted than "standard." CONCLUSIONS: The concept of DRL may become obsolete unless lessons drawn from the experience of users are taken into account. While establishing DRLs should be part of the regulations, setting up and updating values should be governed by bodies whose decision-making cycle is short, at the most 1 year. A local rather than national approach, taking into account body habitus and image quality, needs to be organized. KEY POINTS: • The technology changes faster than regulations. Requirement of DRL establishment should be part of the regulations; however, setting and updating values should be the role of professional societies. • The concept of DRL, highlighting the 75th percentile values and dedicated to standard-sized adult, misses optimization opportunities in the majority of patients who are below the 75th percentile value and outside the range of standard-sized adult. • The ugly aspects of the DRL concept include its non-applicability to individuals, no customization to clinical indications, and lack of consideration of image quality.

Multicentre survey on patient dose in paediatric imaging and proposal for updated diagnostic reference levels for France. Part 1: computed tomography.

OBJECTIVES: To report on a dose survey conducted by the French societies of radiology and paediatric imaging (SFR and SFIPP) and the French public service expert in nuclear and radiological risks (IRSN), and to suggest new diagnostic reference levels (DRLs) for paediatric CT. METHODS: Dose reports concerning children aged 0-15 years and five CT procedures (brain, petrous bone, mediastinum, lung and abdomen-pelvis) performed in 2015-2016 were collected from 15 imaging departments on a voluntary basis. Volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded for at least 10 patients per procedure, per centre and per age group. New DRLs were calculated as the 3rd quartiles of the distributions of the median values. RESULTS: Results from 3253 CT examinations were obtained. The exposure levels observed were much lower than for the previous surveys (2007-2008 and 2010-2013) and among the lowest values currently published. A good homogeneity between facilities was also observed. New DRLs are proposed for each procedure and age group. CONCLUSIONS: This new survey contributes to the continuing optimisation process in French paediatric CT practice. Its results have been recently used to update the national paediatric CT DRLs. KEY POINTS: • New national diagnostic reference levels (DRLs) are proposed for several paediatric CT procedures. • The DRLs proposed for brain, chest and abdomen-pelvis procedures are among the lowest published worldwide.

Experimental evaluation of seven quality control phantoms for digital breast tomosynthesis.

PURPOSES: 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.

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

Radiation 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.

PATIENT EXPOSURE FROM NUCLEAR MEDICINE IN FRANCE: NATIONAL FOLLOW-UP AND INFLUENCE OF THE TECHNOLOGY THROUGH DIAGNOSTIC REFERENCE LEVELS DATA ANALYSIS.

The Nuclear Safety and Radiation Protection French Institute (IRSN) presents its latest assessment from up-to-date diagnostic reference levels (DRL) national data in nuclear medicine (NM). NM departments annually send data to IRSN to estimate the representativeness of current DRLs. Complementary analyses of the data have been performed to evaluate the influence of equipment evolution on practice and patient radiation exposure. Based on data from almost 90% of the French NM departments, some DRL update are proposed. The analysis of positron emission tomography data show that the more the time of flight technology is available on equipment, the lower is the administered activity to the patient. IRSN recommends updating DRL regulation with current and relevant examination data. The influence of technology evolution appeared to be positive for patient exposure and the results showed an obvious involvement of professionals in the radiation dose optimisation process.

Using diagnostic reference levels to evaluate the improvement of patient dose optimisation and the influence of recent technologies in radiography and computed tomography.

OBJECTIVES: Twelve years since the implementation of Diagnostic Reference Levels (DRL) process in France, the Nuclear Safety and Radiation Protection French Institute (IRSN) presents its latest analyses performed on the most recent national data. METHODS: Statutorily, each year, medical imaging departments must perform patient exposure evaluation from their clinical practice for at least 2 types of radiographic and computed tomography (CT) examinations freely chosen in the regulatory list. The samples of dosimetric data used for the evaluations must be sent to IRSN for national assessment using a dedicated and secured web portal. The analyses of collected data for radiography and CT allow IRSN to estimate the representativeness of current DRLs in terms of target practices and examinations, dosimetric quantities and numerical values. Technical data are transmitted, such as detector type in radiography or commissioning date of CT, and are included in some complementary analyses in order to evaluate their influence on patient exposure. RESULTS: Since 2004 the involvement of professionals in the DRL process has highly increased in CT (about 80% in 2015) but remains quite weak in radiography (almost 30%). Analyses show some discordance between regulation references and clinical practice leading to clinical doses data which are 40% lower than DRLs in 2015. As a consequence, the list of examinations types and some numerical values should be updated in the regulation. Focused analyses show a significant patient exposure reduction when digital radiography is used and when CT equipment is under five years old. CONCLUSIONS: Based on these findings, IRSN recommends to update DRL regulation with current and relevant examination lists, dosimetric quantities and numerical values. In addition, this study shows that technology and generation of equipment, such as detector type in radiography or image reconstruction algorithm in CT, take an important place in the dose optimisation process, enabling significant patient exposure reduction when it is associated with protocols optimisation.

Patient dose in interventional radiology: a multicentre study of the most frequent procedures in France.

OBJECTIVES: A national retrospective survey on patient doses was performed by the French Society of Medical physicists to assess reference levels (RLs) in interventional radiology as required by the European Directive 2013/59/Euratom. METHODS: Fifteen interventional procedures in neuroradiology, vascular radiology and osteoarticular procedures were analysed. Kerma area product (KAP), fluoroscopy time (FT), reference air kerma and number of images were recorded for 10 to 30 patients per procedure. RLs were calculated as the 3rd quartiles of the distributions. RESULTS: Results on 4600 procedures from 36 departments confirmed the large variability in patient dose for the same procedure. RLs were proposed for the four dosimetric estimators and the 15 procedures. RLs in terms of KAP and FT were 90 Gm.cm2 and 11 mins for cerebral angiography, 35 Gy.cm2 and 16 mins for biliary drainage, 75 Gy.cm2 and 6 mins for lower limbs arteriography and 70 Gy.cm2 and 11 mins for vertebroplasty. For these four procedures, RLs were defined according to the complexity of the procedure. For all the procedures, the results were lower than most of those already published. CONCLUSIONS: This study reports RLs in interventional radiology based on a national survey. Continual evolution of practices and technologies requires regular updates of RLs. KEY POINTS: • Delivered dose in interventional radiology depends on procedure, practice and patient. • National RLs are proposed for 15 interventional procedures. • Reference levels (RLs) are useful to benchmark practices and optimize protocols. • RLs are proposed for kerma area product, air kerma, fluoroscopy time and number of images. • RLs should be adapted to the procedure complexity and updated regularly.

Radiation Doses to Patients in Interventional Coronary Procedures-Estimation of Updated National Reference Levels by Dose Audit.

The objective of this study was to estimate the French national updated reference levels (RLs) for coronary angiography (CA) and percutaneous coronary intervention (PCI) by a dose audit from a large data set of unselected procedures and in standard-sized patients. Kerma-area product (PKA), air kerma at interventional point (Ka,r), fluoroscopy time (FT), and the number of registered frames (NFs) and runs (NRs) were collected from 51 229 CAs and 42 222 PCIs performed over a 12-month period at 61 French hospitals. RLs estimated by the 75th percentile in CAs and PCIs performed in unselected patients were 36 and 78 Gy.cm² for PKA, 498 and 1285 mGy for Ka,r, 6 and 15 min for FT, and 566 and 960 for NF, respectively. These values were consistent with the RLs calculated in standard-sized patients. The large difference in dose between sexes leads us to propose specific RLs in males and females. The results suggest a trend for a time-course reduction in RLs for interventional coronary procedures.

Low-dose computed tomography screening for lung cancer in populations highly exposed to tobacco: A systematic methodological appraisal of published randomised controlled trials.

Low-dose computed tomography (LDCT) screening recommendations for lung cancer are contradictory. The French National Authority for Health commissioned experts to carry a systematic review on the effectiveness, acceptability and safety of lung cancer screening with LDCT in subjects highly exposed to tobacco. We used MEDLINE and Embase databases (2003-2014) and identified 83 publications representing ten randomised control trials. Control arms and methodology varied considerably, precluding a full comparison and questioning reproducibility of the findings. From five trials reporting mortality results, only the National Lung Screening Trial found a significant decrease of disease-specific and all-cause mortality with LDCT screening compared to chest X-ray screening. None of the studies provided all information needed to document the risk-benefit balance. The lack of statistical power and the methodological heterogeneity of European trials question on the possibility of obtaining valid results separately or by pooling. We conclude, in regard to the lack of strong scientific evidence, that LDCT screening should not be recommended in subjects highly exposed to tobacco.

[Exposure to CT scans in childhood and long-term cancer risk: A review of epidemiological studies]. / Exposition à la scanographie dans l'enfance et risque de cancer à long terme. Une synthèse des études épidémiologiques récentes.

Amongst medical exams requiring ionizing radiation, computed tomography (CT) scans are used more frequently, including in children. These CT examinations are associated with absorbed doses that are much higher than those associated with conventional radiology. In comparison to adults, children have a greater sensitivity to radiation and a longer life span with more years at cancer risks. Five epidemiological studies on cancer risks after CT scan exposure during childhood were published between 2012 and 2015. The results of these studies are consistent and show an increase of cancer risks in children who have been exposed to several CT scans. However, methodological limits due to indication bias, retrospective assessment of radiation exposure from CT scans and lack of statistical power are to be taken into consideration. International projects such as EPI-CT (Epidemiological study to quantify risks for pediatric computerized tomography and to optimize dose), with a focus on dosimetric reconstruction and minimization of bias will provide more precise results. In the meantime, available results reinforce the necessity of justification and optimization of doses.

Chest X-ray screening examinations among French uranium miners: exposure estimation and impact on radon-associated lung cancer risk.

BACKGROUND: Medical surveillance of uranium miners can include periodic chest X-ray examinations. This study aimed to assess the X-ray exposure due to occupational health monitoring in the French cohort of uranium miners, and to test whether consideration of this additional radiation exposure impacts the excess risk of lung cancer death associated with radon exposure. METHOD: X-ray exposure due to occupational health monitoring was estimated retrospectively based on review of a sample of miners' medical records and bibliographic data. Four exposure scenarios were designed, differing in their assumptions about the type of procedures performed, their frequency, and the lung dose delivered. Radon exposure and lung doses from exposure to α-particle emitters and external γ rays have previously been individually assessed. Exposure-risk and dose-risk relations were estimated by Poisson regression with a linear excess relative risk (ERR) model. RESULTS: The cohort included 5086 miners with a mean follow-up duration of 30.1 years. The mean number of chest X-ray examinations ranged from 15.1 in the lowest to 34 in the highest-exposure scenario, and produced a mean cumulative lung dose ranging from 4.6 to 34.2 mGy. The role of occupation-related imaging screening X-ray procedures in total equivalent lung dose appeared insignificant compared to α-emitter exposure. X-ray exposure was not associated with lung cancer mortality risk. The ERR associated with radon remained significantly positive when X-ray exposure was included in the multivariate analysis. CONCLUSIONS: X-ray exposure did not confound the exposure-risk relation between radon and lung cancer.

Exposure of the French paediatric population to ionising radiation from diagnostic medical procedures in 2010.

BACKGROUND: Medical examination is the main source of artificial radiation exposure. Because children present an increased sensitivity to ionising radiation, radiology practices at a national level in paediatrics should be monitored. OBJECTIVE: This study describes the ionising radiation exposure from diagnostic medical examinations of the French paediatric population in 2010. MATERIALS AND METHODS: Data on frequency of examinations were provided by the French National Health Insurance through a representative sample including 107,627 children ages 0-15 years. Effective doses for each type of procedure were obtained from the published French literature. Median and mean effective doses were calculated for the studied population. RESULTS: About a third of the children were exposed to at least one examination using ionising radiation in 2010. Conventional radiology, dental exams, CT scans and nuclear medicine and interventional radiology represent respectively 55.3%, 42.3%, 2.1% and 0.3% of the procedures. Children 10-15 years old and babies from birth to 1 year are the most exposed populations, with respectively 1,098 and 734 examinations per 1,000 children per year. Before 1 year of age, chest and pelvis radiographs are the most common imaging tests, 54% and 32%, respectively. Only 1% of the studied population is exposed to CT scan, with 62% of these children exposed to a head-and-neck procedure. The annual median and mean effective doses were respectively 0.03 mSv and 0.7 mSv for the exposed children. CONCLUSION: This study gives updated reference data on French paediatric exposure to medical ionising radiation that can be used for public health or epidemiological purposes. Paediatric diagnostic use appears much lower than that of the whole French population as estimated in a previous study.

Characterization of MOSFET detectors for in vivo dosimetry in interventional radiology and for dose reconstruction in case of overexposure.

As MOSFET (Metal Oxide Semiconductor Field Effect Transistor) detectors allow dose measurements in real time, the interest in these dosimeters is growing. The aim of this study was to investigate the dosimetric properties of commercially available TN-502RD-H MOSFET silicon detectors (Best Medical Canada, Ottawa, Canada) in order to use them for in vivo dosimetry in interventional radiology and for dose reconstruction in case of overexposure. Reproducibility of the measurements, dose rate dependence, and dose response of the MOSFET detectors have been studied with a Co source. Influence of the dose rate, frequency, and pulse duration on MOSFET responses has also been studied in pulsed x-ray fields. Finally, in order to validate the integrated dose given by MOSFET detectors, MOSFETs and TLDs (LiF:Mg,Cu,P) were fixed on an Alderson-Rando phantom in the conditions of an interventional neuroradiology procedure, and their responses have been compared. The results of this study show the suitability of MOSFET detectors for in vivo dosimetry in interventional radiology and for dose reconstruction in case of accident, provided a well-corrected energy dependence, a pulse duration equal to or higher than 10 ms, and an optimized contact between the detector and the skin of the patient are achieved.

National survey of patient doses from whole-body FDG PET-CT examinations in France in 2011.

A national survey of patient doses from 'whole-body PET-CT' examinations was conducted within all French nuclear medicine departments in 2011. Data related to injected [(18)F]-fluorodeoxyglucose (FDG) activity and to computerised tomography (CT) parameters were received from 56 positron emission tomography (PET)-CT units (answer rate: ∼60 %). The average specific injected FDG activity was equal to 4.3 MBq kg(-1), in agreement with European recommendations. The new 'time-of-flight' technology enabled to decreasing the specific activity down to 3.5 MBq kg(-1). The results have shown that current diagnostic reference levels (DRLs) for the diagnostic trunk CT are too high for CT combined with PET, only performed in France for attenuation correction and localisation, and not for diagnostic purpose. Despite wide variations between PET-CT units (4-fold factor in CTDI(vol)), DRLs equal to 8 mGy (CTDI(vol)) and 750 mGy cm (dose-length product) could be proposed for whole-body PET-CT. The average effective dose related to whole-body PET-CT examination in France has been assessed to ∼14 mSv.