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New hybrid radiotherapy treatment systems combining an MRI scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging. In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying electron paramagnetic resonance imaging (EPRI). Air-filled fused quartz tubes (inner diameter 3 or 4 mm) mimic small air cavities and serve as model systems. The tubes were irradiated inside a PMMA phantom by a 6 MV photon beam. The irradiations were performed in the presence or absence of a transverse, magnetic field providing a magnetic field strength of 1.0 Tesla. The spatial distributions of radiation induced paramagnetic defects in the quartz tubes were subsequently determined by applying field-swept echo-detected EPRI and were then converted to relative dose distributions. The transverse magnetic field leads to considerable local dose enhancements and reductions (up to 35%) with respect to the mean dose within the quartz tubes. The experimentally determined dose distributions are in good quantitative agreement with Monte Carlo radiation transport simulations. The results of this work demonstrate the feasibility of field-swept echo-detected EPRI to measure magnetic field induced perturbations of dose distributions within a sub-millimeter thick surface layer at the dosimeter-air interface. ispartof: PHYSICS IN MEDICINE AND BIOLOGY vol:64 issue:17 ispartof: location:England status: published

The patients with non small cell lung cancer (NSCLC) treated with definitive conformal radiotherapy (RT) were evaluated in terms of side effects and survival. Normal tissue complication probability (NTCP) was calculated for 68 patients treated between 2009 and 2012. Clinical and dosimetric factors were analyzed. The median dose of 63 Gy (range: 54 to 70 Gy) was given with conformal RT with blocks (n = 37), 3-dimensional conformal RT (3DCRT) (n =11), or intensity-modulated RT (IMRT) (n = 20). Acute grade 1 to 2 radiation pneumonitis (RP) was seen in 13% of the patients. No significant relationship was found between RP and treatment and dosimetric factors (p > 0.05). There was a positive correlation between median "mean lung dose" (MLD) (17 Gy), lung V30 (20.5%), and NTCP (14%) (p < 0.001). Median and 2-year overall survival (OS) and progression-free survival (PFS) were 27 and 18 months and 51% and 42%, respectively. In univariate analysis, significant dose range for survival was found between 59.4 and 63 Gy (p < 0.01). In multivariate analysis, response (p = 0.001), fraction dose of 1.8 Gy (p = 0.002), MLD 59.4 Gy (p = 0.01), and tumor biologically effective dose (BED)3(Gy) 5100.8 (p = 0.01) for PFS were found to be favorable factors. In our study, we found a linear correlation between NTCP and MLD for RP risk estimation in patients with NSCLC. Therapeutic dose range where MLD can be kept under 20 Gy with significant survival benefit was found between 59.4 and 63 Gy. Increased therapeutic efficacy will be possible using risk-adaptive RT techniques.

Highlights • The degradation of nominal 4 MeV electron energy from Elekta Versa HD was analyzed. • Filter and collimator were used for uniform dose distribution with steep penumbra. • The dosimetric characteristics and absolute output factors were analyzed. • Degradation method seem to be suitable treatment for small superficial skin tumors., Uniform dose distribution with steep lateral gradient within depth range of 0–0.5 cm is crucial to be able to treat small skin lesions. The standard nominal 4 MeV electron beam from Elekta Versa HD linear accelerator was modified with degrading filter to remove the lateral scatter from treatment head and minimize the penumbra. The energy degrading method was verified based on dosimetric properties and output factors (OFs) with comparison of four types of measurement methods. The properties of degraded 4 MeV electron beam and developed electron applicators seem optimal for treating small targets near the skin surface.

Purpose. Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from being fully implemented in a clinical setting. This study investigates the combination of using fast MC simulations to predict scatter distributions with a ray tracing algorithm to allow calibration between simulated and clinical CBCT images. Material and methods. An EGSnrc-based user code (egs_cbct), was used to perform MC simulations of an Elekta XVI CBCT imaging system. A 60keV x-ray source was used, and air kerma scored at the detector plane. Several variance reduction techniques (VRTs) were used to increase the scatter calculation efficiency. Three patient phantoms based on CT scans were simulated, namely a brain, a thorax and a pelvis scan. A ray tracing algorithm was used to calculate the detector signal due to primary photons. A total of 288 projections were simulated, one for each thread on the computer cluster used for the investigation. Results. Scatter distributions for the brain, thorax and pelvis scan were simulated within 2% statistical uncertainty in two hours per scan. Within the same time, the ray tracing algorithm provided the primary signal for each of the projections. Thus, all the data needed for MC-based scatter correction in clinical CBCT imaging was obtained within two hours per patient, using a full simulation of the clinical CBCT geometry. Conclusions. This study shows that use of MC-based scatter corrections in CBCT imaging has a great potential to improve CBCT image quality. By use of powerful VRTs to predict scatter distributions and a ray tracing algorithm to calculate the primary signal, it is possible to obtain the necessary data for patient specific MC scatter correction within two hours per patient.

Ion channels control the electrical properties of cells by opening and closing (gating) in response to a wide palette of environmental and physiological stimuli. Endowing ion channels with the possibility to be gated by remotely applied stimuli, such as light, provides a tool for in vivo control of cellular functions in behaving animals. We have engineered a synthetic light-gated potassium (K+) channel by connecting an exogenous plant photoreceptor LOV2 domain to the K+ channel pore Kcv. Here, we describe the experimental strategy that we have used to evolve the properties of the channel toward full control of light on pore gating. Our method combines rational and random mutagenesis of the channel followed by a yeast-based screening system for light-activated K+ conductance. © Springer Science+Business Media LLC 2017.

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Major current efforts within Committee 2 of the International Commission on Radiological Protection (ICRP) involve the development of dose coefficients for inhalation and ingestion of radionuclides, and those for exposure to environmental radiation fields. These efforts build upon changes in radiation and tissue weighting factors (Publication 103), radionuclide decay schemes (Publication 107), computational phantoms of the adult reference male and female (Publication 110), external dose coefficients for adult reference workers for idealised radiation fields (Publication 116), models of radionuclide intake (Publications 66, 100 and 130), and models of radionuclide systemic biokinetics (Publication 130). This paper will review the overall computational framework for both internal and external dose coefficients. For internal exposures, the work entails assessment of organ self-dose and cross-dose from monoenergetic particle emissions (specific absorbed fraction), absorbed dose per nuclear transformation (S value), time-integrated activity of the radionuclide in source tissues (inhalation, ingestion, and systemic biokinetic models), and their numerical combination to yield the organ equivalent dose or effective dose per activity inhaled or ingested. Various challenges are reviewed that were not included in the development of Publication 30 dose coefficients, which were based upon much more simplified biokinetic models and computational phantoms. For external exposures, the computations entail the characterisation of environmental radionuclide distributions, the transport of radiation particles through that environment, and the tracking of energy deposition to the organs of the exposed individual. Progress towards the development of dose coefficients to members of the general public (adolescents, children, infants and fetuses) are also reviewed. © 2016, © The International Society for Prosthetics and Orthotics.

In this study, a Monte Carlo program has been developed to simulate the response function of the NaI(Tl) detector with all features for Co-60 and Cs-137 and to investigate the effects of detector housing material on response function. The pulse height spectra in a 2aEuro(3) x 2aEuro(3) NaI(Tl) detector due to these gamma ray sources have been measured. Comparison of the experimentally obtained and simulated spectra shows that there is good agreement between both spectra. Energy distributions of gamma photons that generate the backscattering peak in the response function were obtained and the contribution of single, double and multiple Compton scattering events to these distributions was investigated.

ObjectiveThe hippocampus and prefrontal cortex (PFC) are important for memory and executive functioning and are known to be sensitive to radiotherapy (RT). Radiation dosimetry relates radiation exposure to specific brain areas. The effects of various pituitary RT techniques were studied by relating detailed dosimetry of the hippocampus and PFC to cognitive performance.MethodsIn this cross-sectional design, 75 non-functioning pituitary macroadenoma (NFA) patients (61±10 years) participated and were divided into irradiated (RT+, n=30) and non-irradiated (RT−, n=45) groups. The RT+ group (who all received 25 fractions of 1.8 Gy; total dose: 45 Gy) consisted of three RT technique groups: three-field technique, n=10; four-field technique, n=15; and five-field technique, n=5. Memory and executive functioning were assessed by standardized neuropsychological tests. A reconstruction of the dose distributions for the three RT techniques was made. The RT doses on 30, 50, and 70% of the volume of the left and right hippocampus and PFC were calculated.ResultsCognitive test performance was not different between the four groups, despite differences in radiation doses applied to the hippocampi and PFC. Age at RT, time since RT, and the use of thyroid hormone varied significantly between the groups; however, they were not related to cognitive performance.ConclusionThis study showed that there were no significant differences on cognitive performance between the three-, four-, and five-field RT groups and the non-irradiated patient group. A dose–response relationship could not be established, even with a radiation dose that was higher on most of the volume of the hippocampus and PFC in case of a four-field RT technique compared with the three- and five-field RT techniques.

Objective This radiotherapy planning study evaluated tumour delineation using both optimally respiratory gated and nongated fluorine-18 fluorodeoxyglucose-PET (18F-FDG-PET). Methods For 22 non-small-cell lung tumours, both scans were used to create the nongated and gated (g) gross tumour volumes (GTVg) together with the accompanying clinical target volumes (CTV) and planning target volumes (PTV). The size of the target volumes (TV) was evaluated and the accompanying radiotherapy plans were created to study the radiation doses to the organs at risk (OAR). Results The median volumes of GTVg, CTVg and PTVg were statistically significantly smaller compared with the corresponding nongated volumes, resulting in a median TV reduction of 0.5 cm3 (interquartile range 0.1-1.2), 1.5 cm3 (-0.2 to 7.0) and 2.3 cm3 (-0.5 to 11.3) for the GTVg, CTVg and PTVg, respectively. For the OAR, only the percentage of lung (GTV included) receiving at least 35 Gy was significantly smaller after gating, with a median difference in lung volume receiving at least 35 Gy of 5.7 cm3 (interquartile range -0.8 to 30.50). Conclusion Compared with nongated 18F-FDG-PET, the TVs obtained with optimally respiratory gated 18F-FDG-PET were significantly smaller, however, without a clinically relevant difference in radiation dose to the OAR. Nucl Med Commun 37:66-73

External radiotherapy is a major component of cancer treatment. Its objective is to deliver a high measure of radiation to tumors while minimizing the dose inflicted to healthy tissues. Protons have the ability to deliver a peak of energy (the "Bragg peak") in a precise location depending on the atomic composition and densities of the tissues in their path, making them highly suitable for radiotherapy. Because the anatomy of the patient is continuously changing during the course of the treatment that may last more than 30 days, the position of the Bragg peak is subject to uncertainties, which may have dramatic consequences for the patient. The goal of this master thesis is to tune the treatment to day-to-day anatomical changes by performing the so-called "adaptive planning". We submit an original strategy where the treatment plan, optimized before the start of the treatment and approved by a radiation oncologist, is adjusted to the new anatomy. Three test cases have been designed: 1) anatomical changes around a tumor with unmodified position and shape; 2) tumor displacement; and 3) tumor reduction. The evaluation of a plan is conducted by analysing the dose volume histogram of the predicted dose by a Monte Carlo algorithm. Except for the tumor reduction, our adapted plans manage to produce a dose close to the desired one. In conclusion, non-rigid deformation of treatment plan could be used in addition of other method to perform efficient adaptive protontherapy. Master [120] : ingénieur civil biomédical, Université catholique de Louvain, 2016

Purpose: Respiratory motion can lead to treatment errors in the delivery of radiotherapy treatments. Respiratory gating can assist in better conforming the beam delivery to the target volume.We present a study of the technical aspects of a real time positron emission tracking system for potential use in gated radiotherapy. Methods: The tracking system, called PeTrack, uses implanted positron emission markers and position sensitive gamma ray detectors to track breathing motion in real time. PeTrack uses an expectation-maximization algorithm to track the motion of fiducial markers. A normalized least mean squares adaptive filter predicts the location of the markers a short time ahead to account for system response latency. The precision and data collection efficiency of a prototype PeTrack system were measured under conditions simulating gated radiotherapy. The lung insert of a thorax phantom was translated in the inferior-superior direction with regular sinusoidal motion and simulated patient breathing motion (maximum amplitude of motion -10 mm, period 4 s). The system tracked the motion of a 22Na fiducial marker (0.34 MBq) embedded in the lung insert every 0.2 s. The position of the was marker was predicted 0.2 s ahead. For sinusoidal motion, the equation used to model the motion was fitted to the data. The precision of the tracking was estimated as the standard deviation of the residuals. Software was also developed to communicate with a Linac and toggle beam delivery. In a separate experiment involving a Linac, 500 monitor units of radiation were delivered to the phantom with a 3×3 cm photon beam and with 6 and 10 MV accelerating potential. Radiochromic films were inserted in the phantom to measure spatial dose distribution. In this experiment, the period of motion was set to 60 s to account for beam turn-on latency. The beam was turned off when the marker moved outside of a 5-mm gating window. Results: The precision of the tracking in the IS direction was 0.53 mm for a sinusoidally moving target, with an average count rate -250 cps. The average prediction error was 1.1 0.6 mm when the marker moved according to irregular patient breathing motion. Across all beam deliveries during the radiochromic film measurements, the average prediction error was 0.8 0.5 mm. The maximum error was 2.5 mm and the 95th percentile error was 1.5 mm. Clear improvement of the dose distribution was observed between gated and nongated deliveries. The full-width at halfmaximum of the dose profiles of gated deliveries differed by 3 mm or less than the static reference dose distribution. Monitoring of the beam on/off times showed synchronization with the location of the marker within the latency of the system. Conclusions: PeTrack can track the motion of internal fiducial positron emission markers with submillimeter precision. The system can be used to gate the delivery of a Linac beam based on the position of a moving fiducial marker. This highlights the potential of the system for use in respiratory-gated radiotherapy. © 2016 American Association of Physicists in Medicine.

Internal dosimetry is the science of assessing the amount and distribution of radionuclides in the body, and calculating resulting radiation doses to internal organs or tissues over specific time periods. Because the ionizing radiation energy deposited in a particular organ from radionuclides incorporated in the body cannot be measured directly, internal doses are estimated or inferred principally from in vivo or in vitro bioassay. As a matter of fact, in an effort to implement effective programmes in internal dosimetry, since internal dosimetry programmes exist, the internal dosimetry laboratories have always tried to develop new capabilities for these techniques or achieve the harmonisation in individual monitoring for occupational exposures. The primary goal of this paper is to categorise the principal trends made in recent developments in these fields regarding their potential and eligibility for the routine monitoring community and discuss the main aspects, which aims at a comprehensive assessment of these techniques. Secondly, starting from these data, their potential improvements are compared to the currently employed monitoring techniques used in routines. © The Author 2007. Published by Oxford University Press. All rights reserved.

The objective of the present study was to identify advantages and limitations of the application of microdosimetric concepts for inhaled radon progeny activities in the lungs. The methods employed for this analysis were a recently developed Monte-Carlo microdosimetry code for the calculation of energy deposition in bronchial target cells and the Probability Per Unit Track Length (PPUTL) model, which relates these microdosimetric parameters to cellular radiation effects. The major advantages of internal microdosimetry of radon progeny in bronchial airways are: (i) quantitative characterisation of non-uniform dose distributions and identification of target sites with enhanced carcinogenic potential, (ii) quantification of low doses of alpha particles by the number of cells hit and the dose received by those cells, (iii) illustration of the random variations of cellular doses by specific energy distributions and (iv) establishment of a direct link to cellular radiobiological effects. At present, a major limitation of microdosimetry is the extrapolation of the response of individual cells to the resulting tissue response, which is still not fully explored. © The Author 2007. Published by Oxford University Press. All rights reserved.

The EUropean RAdiation DOSimetry Group (EURADOS) initiated in 2005 the CONRAD Project, a Coordinated Network for Radiation Dosimetry funded by the European Commission (EC), within the 6th Framework Programme (FP). The main purpose of CONRAD is to generate a European Network in the field of Radiation Dosimetry and to promote both research activities and dissemination of knowledge. The objective of CONRAD Work Package 5 (WP5) is the coordination of research on assessment and evaluation of internal exposures. Nineteen institutes from 14 countries participate in this action. Some of the activities to be developed are continuations of former European projects supported by the EC in the 5th FP (OMINEX and IDEAS). Other tasks are linked with ICRP activities, and there are new actions never considered before. A collaboration is established with CONRAD Work Package 4, dealing with Computational Dosimetry, to organise an intercomparison on Monte Carlo modelling for in vivo measurements of 241Am deposited in a knee phantom. Preliminary results associated with CONRAD WP5 tasks are presented here. © The Author 2007. Published by Oxford University Press. All rights reserved.

The Grup de Física de les Radiacions (GFR) of the Universitat Autònoma de Barcelona (UAB), in collaboration with the Institute for Radiological Protection and Nuclear Safety (IRSN), has developed a passive Bonner sphere system (UAB-BSS), with gold foils as thermal neutron detectors, for application in pulsed neutron fields or in mixed neutron-photon fields with high photon intensities. In such fields, active devices suffer from saturation and dead-time effects. The MCNPX Monte-Carlo code has been used to determine the response to neutrons of different energies of each polyethylene sphere belonging to the BSS. The passive UAB-BSS system was characterised with the ISO 252Cf reference source at the IRSN facilities. The energy distribution of the reference source neutron fluence was folded with the response functions for comparison with the experimental data. A good agreement between the experimental and calculated count rates was found. © The Author 2007. Published by Oxford University Press. All rights reserved.

Workplace neutron spectra from nuclear facilities obtained within the European project EVIDOS are compared with those of the simulated workplace fields CANEL and SIGMA and fields set-up with radionuclide sources at the PTB. Contributions of neutrons to ambient dose equivalent and personal dose equivalent are given in three energy intervals (for thermal, intermediate and fast neutrons) together with the corresponding direction distribution, characterised by three different types of distributions (isotropic, weakly directed and directed). The comparison shows that none of the simulated workplace fields investigated here can model all the characteristics of the fields observed at power reactors. © The Author 2007. Published by Oxford University Press. All rights reserved.

Objective: With the increasing life expectancy for patients with cystic fibrosis (CF), and a known predisposition to certain cancers, cumulative radiation exposure from radiologic imaging is of increasing significance. This study explores the estimated cumulative effective radiation dose over a 17-year period from radiologic procedures and changing trends of imaging modalities over this period. Methods: Estimated cumulative effective dose (CED) from all thoracic and extrathoracic imaging modalities and interventional radiology procedures for both adult and pediatric patients with CF, exclusively attending a nationally designated CF center between 1992-2009 for > 1 year, was determined. The study period was divided into three equal tertiles, and estimated CED attributable to all radiologic procedures was estimated for each tertile. Results: Two hundred thirty patients met inclusion criteria (2,240 person-years of follow-up; 5,596 radiologic procedures). CED was > 75 mSv for one patient (0.43%), 36 patients (15.6%) had a CED between 20 and 75 mSv, 56 patients (24.3%) had a CED between 5 and 20 mSv, and in 138 patients (60%) the CED was estimated to be between 0 and 5 mSv over the study period. The mean annual CED per patient increased consecutively from 0.39 mSv/y to 0.47 mSv/y to 1.67 mSv/y over the tertiles one to three of the study period, respectively (P < .001). Thoracic imaging accounted for 46.9% of the total CED and abdominopelvic imaging accounted for 42.9% of the CED, respectively. There was an associated 5.9-fold increase in the use of all CT scanning per patient (P < .001). Conclusions: This study highlights the increasing exposure to ionizing radiation to patients with CF as a result of diagnostic imaging, primarily attributable to CT scanning. Increased awareness of CED and strategies to reduce this exposure are needed.

The evaluation of uncertainties in doses from intakes of radionuclides is one of the most difficult problems in internal dosimetry. In this paper, the process of assessing internal doses from monitoring measurements is reviewed and the major sources of uncertainty are discussed. Methods developed independently at HPA and at IRSN for the determination of uncertainties in internal doses assessed from monitoring measurements are described. Both use a Monte Carlo simulation approach. Results are described for three illustrative examples. An alternative method developed at the Los Alamos National Laboratory that uses Bayesian statistical methods is also described briefly. Copyright © 2006 Oxford University Press.

This paper aims at comparing dosimetric assessments performed with three Monte Carlo codes: EGS4, MCNP4c2 and MCNPX2.5e, using a realistic voxel phantom, namely the Zubal phantom, in two configurations of exposure. The first one deals with an external irradiation corresponding to the example of a radiological accident. The results are obtained using the EGS4 and the MCNP4c2 codes and expressed in terms of the mean absorbed dose (in Gy per source particle) for brain, lungs, liver and spleen. The second one deals with an internal exposure corresponding to the treatment of a medullary thyroid cancer by 131I-labelled radiopharmaceutical. The results are obtained by EGS4 and MCNPX2.5e and compared in terms of S-values (expressed in mGy per kBq and per hour) for liver, kidney, whole body and thyroid. The results of these two studies are presented and differences between the codes are analysed and discussed. © The Author 2005. Published by Oxford University Press. All rights reserved.

Purpose: Knowing the contribution of neutron to collateral effects in treatments is both a complex and a mandatory task. This work aims to present an operative procedure for neutron estimates in any facility using a neutron digital detector.Methods: The authors previous work established a linear relationship between the total second cancer risk due to neutrons (TRn) and the number of MU of the treatment. Given that the digital detector also presents linearity with MU, its response can be used to determine the TRn per unit MU, denoted as m, normally ssociated to a generic Linac model and radiotherapy facility. Thus, from the number of MU of each patient treatment, the associated risk can be estimated. The feasibility of the procedure was tested by applying it in eight facilities; patients were evaluated as well. ©2015 Am. Assoc. Phys. Med.Results: From the reading of the detector under selected irradiation conditions, m values were obtained for different machines, ranging from 0.25×l10-4% per MU for an Elekta Axesse at 10 MV to 6.5×10-4% per MU for a Varian Clinac at 18 MV. Using these values, TRn of patients was estimated in each facility and compared to that from the individual evaluation. Differences were within the range of uncertainty of the authors methodology of equivalent dose and risk estimations.Conclusions: The procedure presented here allows an easy estimation of the second cancer risk due to neutrons for any patient, given the number of MU of the treatment. It will enable the consideration of this information when selecting the optimal treatment for a patient by its implementation in the treatment planning system. © 2015 American Association of Physicists in Medicine

An addendum to the AAPM's TG-51 protocol for the determination of absorbed dose to water in megavoltage photon beams is presented. This addendum continues the procedure laid out in TG-51 but new kQ data for photon beams, based on Monte Carlo simulations, are presented and recommendations are given to improve the accuracy and consistency of the protocol's implementation. The components of the uncertainty budget in determining absorbed dose to water at the reference point are introduced and the magnitude of each component discussed. Finally, the consistency of experimental determination of N D,w coefficients is discussed. It is expected that the implementation of this addendum will be straightforward, assuming that the user is already familiar with TG-51. The changes introduced by this report are generally minor, although new recommendations could result in procedural changes for individual users. It is expected that the effort on the medical physicist's part to implement this addendum will not be significant and could be done as part of the annual linac calibration.

This article represents the first results of the natural radionuclides in the Maritza and Tundja river sediments, in the vicinity of Edirne city, Turkey. The aim of the article is to describe the natural radioactivity concentrations as a baseline for further studies and to obtain the distribution patterns of radioactivity in trans-boundary river sediments of the Maritza and Tundja, which are shared by Turkey, Bulgaria and Greece. Sediment samples were collected during the period of August 2007-April 2010. The riverbank sediment samples were analyzed firstly for their pH, organic matter content and soil texture. The gross alpha/beta and 238U, 232Th and 40K activity concentrations were then investigated in the collected sediment samples. The mean and standard error of mean values of gross alpha and gross beta activity concentrations were found as 91 ± 11, 410 ± 69 Bq/kg and 86 ± 11, 583 ± 109 Bq/kg for the Maritza and Tundja river sediments, respectively. Moreover, the mean and standard error of mean values of 238U, 232Th and 40K activity concentrations were determined as 219 ± 68, 128 ± 55, 298 ± 13 and as 186 ± 98, 121 ± 68, 222 ± 30 Bq/kg for the Maritza and Tundja River, respectively. Absorbed dose rates (D) and annual effective dose equivalent s have been calculated for each sampling point. The average value of adsorbed dose rate and effective dose equivalent were found as 191 and 169 nGy/h; 2 and 2 mSv/y for the Maritza and the Tundja river sediments, respectively. © 2012 Copyright Taylor and Francis Group, LLC.

An inverse technique has been designed to unfold the x-ray tube spectrum from the measurement of the photons scattered by a target interposed in the path of the beam. A special strategy is necessary to circumvent the ill-conditioning of the forward transport algebraic problem. The proposed method is based on the calculation of both, the forward and adjoint analytical solutions of the Boltzmann transport equation. After testing the method with numerical simulations, a simple prototype built at the Operational Unit of Health Physics of the University of Bologna was used to test the method experimentally. The reconstructed spectrum was validated by comparison with a straightforward measurement of the X-ray beam. The influence of the detector was corrected in both cases using standard unfolding techniques. The method is capable to accurately characterize the intensity distribution of an X-ray tube spectrum, even at low energies where other methods fail.

Objective: Inflammatory response associated with radiation-induced lung injury (RILI) results in an increased 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography/computed tomography (PET/CT). In this study, we aimed to analyze the degree of FDG uptake within specific isodose regions (IR) of the irradiated lung using standardized uptake value (SUV) measurements, and to correlate posttreatment FDG uptake with radiotherapy (RT) dose parameters, patient characteristics and the imaging time interval after RT completion. Material and Methods: Data from 30 patients with non-small cell lung cancer (NSCLC) who underwent FDG PET/CT imaging at least 12 weeks (72-668 days) after completion of RT were evaluated. In each patient, side-by-side visual registration of the treatment planning CT slices including IR curves with the corresponding PET/CT slices was performed. Using SUV measurements, FDG uptake levels were analyzed within specific IRs of the irradiated lung. The statistical difference between SUVmax of each IR was determined. The RT dose parameters, patient characteristics and time interval between RT and PET/CT were tested for correlation with SUVmax of IRs. Results: The mean SUVmax in the IRs of the lung that received 2000-4000cGy was 1.51 +/- 0.66 (mean +/- SD) (mm-max: 0.69-2.84), 4000-6000cGy was 2.67 +/- 1.16 (min-max: 0.71-6.0), and >6000Gy was 3.55 +/- 1.09 (min-max: 1.2-5.72). We found statistically significant differences between the SUVmax values of all IRs (SUV2000 vs. SUV4000, p = 0.001; SUV2000 vs. 6000, p = 0.002; SUV4000 vs. 6000, p = 0.001). No statistically significant correlation was found between SUVmax and the other variables. Conclusion: The findings of this study showed that, although some overlap occurs between IRs, the degree of radiation-related parenchymal FDG uptake gets higher with increasing dose levels. Persistent high FDG uptake levels may be observed in radiation fibrosis areas on PET/CT even several months after RT. Amaç: Radyasyona bağlı akciğer hasarı (RBAH) ile ilişkili inflamatuvar yanıt pozitron emisyon tomografisi/bilgisayarlı tomografide (PET/BT) artmış 18F-florodeoksiglukoz (FDG) tutulumu ile sonuçlanır. Bu çalışmada, standardize tutulum değeri (standard uptake value; SUV) ölçümlerini kullanarak ışınlanmış akciğerin belirli izodoz alanlarında (İA) FDG tutulumunun derecesini incelemeyi ve tedavi sonrası FDG tutulumu ile radyoterapi (RT) doz parametreleri, hasta özellikleri ve RT tamamlandıktan sonra görüntüleme zamanı aralığı arasında bağıntı kurmayı amaçladık. Gereç ve Yöntemler: RT tamamlandıktan en az 12 hafta (72-668 gün) sonra FDG PET/BT yapılan küçük hücreli dışı akciğer kanserli (KHDAK) 30 hastanın verileri değerlendirildi. Her hastada, PET/BT kesitlerine karşılık gelen ve İA eğrilerini içeren tedavi planlama BT kesitlerinin yan yana görsel kaydı yapıldı. SUV ölçümleri kullanılarak, ışınlanmış akciğerin belirli İA içindeki FDG tutulum düzeyleri incelendi. Her ışınlanmış bölgenin SUVmax arasındaki istatistiksel fark belirlendi. İAnın SUVmax ile korelasyonu için RT doz parametreleri, hasta özellikleri ve RT ile PET/BT arasındaki zaman aralığı istatistiksel olarak test edildi. Bulgular: 2000-4000 cGy alan akciğer İAdaki ortalama SUVmax 1.51 ± 0.66 (mean ± SS) (min-max: 0.69-2.84) idi, 4000-6000 cGy ve >6000 alanlarda sırasıyla 2.67 ± 1.16 (min-max: 0.71-6.0) ve 3.55 ± 1.09 (min-max: 1.2-5.72) idi. Tüm İAnın SUVmax değerleri arasında istatistiksel olarak anlamlı farklar bulduk (SUV2000 ile SUV4000, p= 0.001; SUV2000 ile SUV6000, p= 0.002; SUV4000 ile SUV6000, p=0.001). SUVmax ve diğer değişkenler arasında istatistiksel olarak anlamlı ilişki bulunmadı. Sonuç: Bu çalışmanın sonuçları, izodoz alanları arasında bir miktar çakışma olmakla birlikte, radyasyonla ilişkili parankimal FDG tutulumunun derecesinin artan dozlarla arttığını göstermiştir. RT bitiminden aylar sonra bile, radyasyona bağlı fibrozis gelişen alanlarda yüksek düzeylerde FDG tutulumunun sebat ettiği görülebilmektedir.

cited By 5; Typical patient radiation doses in diagnostic imaging Radiologists should be able to appreciate the radiation dose delivered to patients for routine diagnostic procedures. The radiology report should include data necessary to calculate the patient dose in Gray. Using the effective dose, it is possible to compare with other source of radiation exposure. Simple formulas, taking into account different anatomical regions, derived from dose-area product (conventional radiography) or dose-length product (CT) are provided to calculate the effective dose in Sievert. For conventional (non-interventional) radiography, the effective dose for a given exam is inferior or equal to the yearly background radiation. For CT, the effective dose corresponds to 1 to 10 years of yearly background radiation. © 2010. Éditions Françaises de Radiologie.; Il est essentiel que tout radiologue soit capable d’apprécier le niveau de la dose délivrée par les explorations usuelles. La transcription sur le compte-rendu d’examen des éléments permettant de connaître la dose délivrée est obligatoire. À partir de ces données, il est possible par des calculs d’évaluer le niveau de dose et ainsi de connaître l’ordre de grandeur de l’irradiation exprimée en Gray ou sous multiples. La comparaison avec les autres sources d’exposition est possible par l’appréciation de la dose efficace qui tient compte de l’effet biologique attendu. Des formules simples tenant compte de la région anatomique sont proposées à partir des produits dose-surface (radiologie conventionnelle) et dose-longueur (TDM) pour évaluer cette dose efficace, qui s’exprime en sievert et sous-multiples (mSv). En radiographie conventionnelle (non interventionnelle), la dose efficace délivrée par une exploration est inférieure ou égale au niveau de l’irradiation naturelle annuelle. En tomodensitométrie, la dose efficace délivrée par une exploration représente, selon les régions anatomiques, de 1 à 10 ans d’irradiation naturelle.

cited By 16; The purpose of this study was to evaluate the in vivo dose-response relation of chromosome aberration formation and distribution in a context of localised and fractionated radiotherapy. Cytogenetic analysis was applied to eight patients, all treated for the same tumour localisation; the same localisation was used to prevent the variability usually observed between patients treated with radiotherapy and to allow the corresponding roles of the size of irradiation field and of the dose rate to be studied. The yield of dicentrics, centric rings and fragments was measured in blood samples taken before treatment, during the course of radiotherapy and up to 6 months after. After the first fraction of radiotherapy, we observed that the whole-body dose estimated from the yield of dicentrics and rings was higher (0.35±0.2 Gy) than the calculated equivalent whole-body dose (0.07±0.04 Gy). By contrast, the partial-body dose derived from the Qdr (quotient of dicentrics and rings) model was estimated to be 2.2±0.3 Gy, which agreed quite well with the dose delivered to the tumour (2.1±0.1 Gy). We also found a correlation between the yield of induced chromosome aberrations and the target field size (p=0.014). U-value analysis showed that the distribution of dicentrics and rings was overdispersed, despite the fractionation of the exposure, and a positive correlation between the U-value and the dose rate was observed (p=0.017). Overall, these results suggest that the proportion of undamaged lymphocytes could increase with the dose rate. © 2010 The British Institute of Radiology.

The Monte Carlo (MC) method can be applied to simulate brachytherapy treatment planning. The MCNP5 code gives, together with results, a statistical uncertainty associated with them. However, the latter is not the only existing uncertainty related to the simulation and other uncertainties must be taken into account. A complete analysis of all sources of uncertainty having some influence on results of the simulation of brachytherapy treatment is presented in this paper. This analysis has been based on the recommendations of the American Association for Physicist in Medicine (AAPM) and of the International Standard Organisation (ISO)., This work received financial support from the Generalitat Valenciana as well as from the Research Vice-Rector Office of the "Universidad Politecnica de Valencia" (Spain) for the stay of Isabelle Gerardy in Valencia at the "Departamento de Ingenieria Quimica y Nuclear" of the "Universidad Politecnica de Valencia".

This paper discusses a method to determine the thickness of an absorber using the energy distribution of beta particles. An empirical relationship was obtained between the absorber thickness and the energy distribution of beta particles transmitted through. The thickness of a polyethylene radioactive source cover was determined by exploiting this relationship, which has largely been left unexploited allowing us to determine the in-situ cover thickness of beta sources in a fast, cheap and non-destructive way.

Purpose. To evaluate current exposure levels from pediatric MDCT examinations in order to issue recommendations for the routine clinical practice that may be used for establishing future diagnostic reference levels (DRL).Materials and methods. A survey was conducted at hospital sites affiliated with the SFIPP (Société Francophone d'Imagerie Pédiatrique et Prénatale). Tube potential and volume computed tomography dose index (CTDI) vol. values were obtained for three age groups (1, 5 and 10 years) for typical scanning indications of eight anatomical regions.Results. Twenty of 29 sites provided us with a copy of their protocols. All ages groups combined, 97% of protocols used a tension level ≤120 kVp. For age groups 1, 5 and 10 years respectively, the 75th percentiles of dose distributions were : 31, 39.5 and 49.5 mGy for the «head» protocol; 24, 22 and 24 mGy for «head and neck»; 11, 11, and 11mGy for «paranasal sinuses»; 46, 71 and 87 mGy for «petrous bone»; 3, 3.5 and 5.5 mGy for «chest»; 2, 3 and 4 mGy for «low dose lung»; 4, 4.5 and 7 mGy for «abdomen-pelvis»; 7, 11 and 12 mGy for «bone». The inter-center discrepancy for doses were still high.Conclusion. This study provided an evaluation of current practices in reference centers for pediatric imaging and allowed readjustment of MDCT dose recommendations. It could help in the development of DRLS for pediatric MDCT.; Objectif. Évaluer les niveaux actuels d’exposition en scanner multicoupes pédiatrique et en déduire des recommandations pour la pratique pouvant servir de base à l’élaboration de futurs niveaux de référence diagnostiques (NRD). Matériels et méthodes. Une enquête de pratique a été réalisée auprès des sites hospitaliers correspondants de la SFIPP (Société Francophone d’Imagerie Pédiatrique et Prénatale). Les valeurs protocolaires de haute tension et de dose théorique absorbée (IDSV) ont été relevées pour trois âges types (1, 5 et 10 ans) et des indications types sur huit régions anatomiques. Résultats. Vingt des 29 sites contactés ont transmis leurs protocoles. Tous âges confondus, 97 % des protocoles comportaient un niveau de haute tension ≤ 120 kV. Pour les âges de 1, 5 et 10 ans respectivement, les 75es centiles des distributions de dose étaient : 31, 39,5 et 49,5 mGy pour le protocole « crâne » ; 24, 22 et 24 mGy pour le « massif facial » ; 11, 11 et 11 mGy pour les « sinus » ; 46, 71 et 87 mGy pour les « rochers » ; 3, 3,5 et 5,5 mGy pour le « thorax standard » ; 2, 3 et 4 mGy pour le « poumon basse dose » ; 4, 4,5 et 7 mGy pour « l’abdomen-pelvis » ; 7, 11 et 12 mGy pour l’« os ». Les écarts dosimétriques intercentres restaient élevés. Conclusion. L’étude a permis d’évaluer les pratiques actuelles au sein de centres radiopédiatriques de référence et de réajuster les recommandations dosimétriques. Elle pourrait servir de base pour l’établissement de NRD en scanographie pédiatrique.

The dosimetry of internal exposure to radionuclides is performed on the basis of biokinetic and dosimetric models. For prospective purpose, the organ or effective dose resulting from potential conditions of exposure can be calculated by applying these models with dedicated software. However, it is acknowledged that a significant uncertainty is associated with such calculation due to the variability of individual cases and to the possible lack of knowledge about some factors influencing the dosimetry. This uncertainty has been studied in a range of situations by modeling the uncertainty on the model parameters by probability distributions and propagating this uncertainty onto the dose result by Monte Carlo calculation. However, while probability distributions are well adapted to model the known variability of a parameter, they may lead to an unrealistically low estimate of the uncertainty due to a lack of knowledge about some input parameters. Here we present a mathematical method, based on the Dempster-Shafer theory, to deal with such imprecise knowledge. We apply this method to the prospective dosimetry of inhaled uranium dust in the nuclear fuel cycle when its physico-chemical properties are not precisely known. The results show an increased estimation of the range of uncertainty as compared to the application of a probabilistic method. This Dempster-Shafer method may valuably be applied in future prospective dosimetry of internal exposure in order to more realistically estimate the uncertainty resulting from an imprecise knowledge of the parameters of the dose calculation. © 2009 Health Physics Society.

Estimating the dose distribution in a victim's body is a relevant indicator in assessing biological damage from exposure in the event of a radiological accident caused by an external source. This dose distribution can be assessed by physical dosimetric reconstruction methods. Physical dosimetric reconstruction can be achieved using experimental or numerical techniques. This article presents the laboratory-developed SESAME-Simulation of External Source Accident with MEdical images-tool specific to dosimetric reconstruction of radiological accidents through numerical simulations which combine voxel geometry and the radiation-material interaction MCNP(X) Monte Carlo computer code. The experimental validation of the tool using a photon field and its application to a radiological accident in Chile in December 2005 are also described. © 2009 Health Physics Society.

Criteria are needed to be able to judge the level of risk associated with dose rates estimated for non-human biota. In this paper, European guidance on the derivation of predicted no-effect chemical concentrations has been applied to appropriate radiation sensitivity data. A species sensitivity distribution fitted to the data for all species resulted in a generic predicted no-effect dose rate of 10 μGy h−1. Currently, data are inadequate to derive screening values for separate organism groups. A second, higher, benchmark could aid in decision making by putting results into context on the scale of no effect to a risk of ‘serious’ effect. The need for, meaning and use of such a value needs to be debated by the wider community. This paper explores potential approaches of deriving scientific input to this debate. The concepts proposed in this paper are broadly consistent with the framework for human protection.

International audience; The use of active personal dosemeters (APD) in interventional radiology was evaluated by Working Group 9 (Radiation protection dosimetry of medical staff) of the CONRAD project, which is a Coordination Action supported by the European Commission within its sixth Framework Programme. Interventional radiology procedures can be very complex and they can lead to relatively high doses to personnel who stand close to the primary radiation field and are mostly exposed to radiation scattered by the patient. For the adequate dosimetry of the scattered photons, APDs must be able to respond to low-energy [10-100 keV] and pulsed radiation with relatively high instantaneous dose rates. An intercomparison of five APD models deemed suitable for application in interventional radiology was organised in March 2007. The intercomparison used pulsed and continuous radiation beams, at CEA-LIST (Saclay, France) and IRSN (Fontenay-aux-Roses, France), respectively. A specific configuration, close to the clinical practice, was considered. The reference dose, in terms of Hp(10), was derived from air kerma measurements and from the measured and calculated energy distributions of the scattered radiation field. Additional Monte Carlo calculations were performed to investigate the energy spectra for different experimental conditions of the intercomparison. The results of this intercomparison are presented in this work and indicate which APDs are able to provide a correct response when used in the specific low-energy spectra and dose rates of pulsed X-rays encountered in interventional radiology.

Publication 100 of the International Commission on Radiological Protection (ICRP) provides a Human Alimentary Tract Model (HATM) to replace the gastrointestinal (GI) model described in Publication 30. The HATM will be used for future calculations of dose coefficients and bioassay predictions, first in a series of publications on occupational intakes of radionuclides, and subsequently in revision of dose coefficients for public exposures. This paper compares dose coefficients calculated using the new model with current values calculated using the GI model for a range of radionuclides. Colon doses are lower using the HATM in all cases considered, in some cases by significant factors. Stomach doses tend to be lower, but are in some cases higher under HATM. The extent to which these changes in doses to gut tissues impacts upon the effective dose varies among nuclides, but there is a tendency for lower effective doses. Special-case applications of the HATM are also described, considering retention on teeth or in the walls of the small intestine. Although the effect of such retention on the regional tissue dose can be large, the effective dose is not greatly changed. © The Author 2007. Published by Oxford University Press. All rights reserved.

As part of the EU Fifth Framework Programme IDEAS project 'General Guidelines for the Evaluation of Incorporation Monitoring Data', and in collaboration with the International Atomic Energy Agency, a new intercomparison exercise for the assessment of doses from intakes of radionuclides was organised. Several cases were selected, to cover a wide range of practices in the nuclear fuel cycle and medical applications. The cases were: (1) acute intake of HTO, (2) acute inhalation of the fission products 137Cs and 90Sr, (3) acute inhalation of 60Co, (4) repeated intakes of 131I, (5) intake of enriched uranium and (6) single intake of Pu isotopes and 241Am. This intercomparison exercise especially focused on the effect of the Guidelines proposed by the IDEAS project for harmonisation of internal dosimetry. © The Author 2007. Published by Oxford University Press. All rights reserved.

A didactic software, MEthodes DOsimètriques de REférence (MEDOR), is being developed to provide help in the interpretation of biological data. Its main purpose is to evaluate the pertinence of the application of different models. This paper describes its first version that is focused on inhalation exposure to actinide aerosols. With this tool, sensitivity analysis on different parameters of the ICRP models can be easily done for aerosol deposition, in terms of activity and particle number, actinide biokinetics and doses. The user can analyse different inhalation cases showing either that dose per unit intake cannot be applied if the aerosol contains a low number of particles or that an inhibition of the late pulmonary clearance by particle transport can occur which contributes to a 3-4 fold increase in effective dose as compared with application of default parameters. This underlines the need to estimate systematically the number of deposited particles, as well as to do chest monitoring as long as possible. © The Author 2007. Published by Oxford University Press. All rights reserved.

The interpretation of individual activity measurement after a contamination by 241Am or its parent nuclide 241Pu is based on the reference americium (Am) biokinetic model published by the International Commission on Radiological Protection in 1993 [International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 2 Ingestion dose coefficients. ICRP Publication 67. Ann. ICRP 23(3/4) (1993)]. The authors analysed the new data about Am biokinetics reported afterwards to propose an update of the current model. The most interesting results, from the United States Transuranium and Uranium Registries post-mortem measurement database [Filipy, R. E. and Russel, J. J. The United States Transuranium and Uranium Registries as sources for actinide dosimetry and bioeffects. Radiat. Prot. Dosim. 105(1-4), 185-187 (2003)] and the long-term follow-up of cases of inhalation intake [Malatova, I., Foltanova, S., Beckova, V., Filgas, R., Pospisilova, H. and Holgye, Z. Assessment of occupational doses from internal contamination with 241Am. Radiat. Prot. Dosim. 105(1-4), 325-328 (2003)], seemed to show that the current model underestimates the retention in the massive soft tissues and overestimates the retention in the skeleton and the late urinary excretion. However, a critical review of the data demonstrated that all were not equally reliable and suggested that only a slight revision of the model, possibly involving a change in the balance of activity between massive soft tissues, cortical and trabecular bone surfaces, may be required. © The Author 2007. Published by Oxford University Press. All rights reserved.