Electron emission spectra of a thin gold foil after photon interaction were measured over the energy range between 50 eV and 9500 eV to provide reference data for Monte Carlo radiation-transport simulations. Experiments were performed with the HAXPES spectrometer at the PETRA III high-brilliance beamline P22 at DESY (Hamburg, Germany) for photon energies just below and above each of the gold L-edges, that is, at 11.9 keV, 12.0 keV, 13.7 keV, 13.8 keV, 14.3 keV, and 14.4 keV. The data were analyzed to obtain the absolute values of the particle radiance of the emitted electrons per incident photon flux. Simulations of the experiment were performed using the Penelope and Geant4 Monte Carlo radiation-transport codes. Comparison of the measured and simulated results shows good qualitative agreement. On an absolute scale, the experiments tend to produce higher electron radiance values at the lower photon energies studied as well as at the higher photon energies for electron energies below the energy of the Au L-3 photoelectron. This is attributed to the linear polarization of the photon beam in the experiments, something which is not considered in the simulation codes.

BACKGROUND:In Targeted Radionuclide Therapy (TRT), the continuous technological effort in imaging tumor phenotypes (i.e. sub-volumes with different phenotypic characteristics) and in precise radiopharmaceutical tumor-targeting, is allowing for a better dosimetric optimization at the tumor phenotype level. The aim of this study was to evaluate the dosimetric efficiency (considering strategic absorbed dose delivery to the phenotypes) of personalized TRT directed to the tumor phenotypes.METHODS:The dosimetric assessment was performed using a four-phenotype realistic tumor model implemented within the ICRP reference voxel phantom and simulations using the state-of-the-art Monte Carlo program PENELOPE. The dose assessment was performed for five radionuclides commonly used in therapy and/or diagnostic procedures: 125I, 99mTc, 177Lu, 161Tb and 67Ga. Two irradiation scenarios were considered: (i) the Whole Tumor Treatment Planning Scenario (WTTPS), i.e. the four phenotypes irradiated with the same radionuclide; (ii) the Phenotype Treatment Planning Scenario (PTPS), i.e. each phenotype irradiated by a single radionuclide. The optimal radionuclide configurations were studied considering the maximization of the absorbed dose delivered to the tumor and the minimization of dose to healthy tissues.RESULTS:In WTTPS, 125I outperforms the other radionuclides in terms of the ratio of the maximum absorbed dose delivered to the tumor and the minimum absorbed dose delivered to healthy tissues. In the PTPS, the use of 161Tb in combination with the other radionuclides maximizes the absorbed dose in the tumor tissues while simultaneously minimizing dose to healthy tissue, compared to the WTTPS. In agreement with recent pre-clinical studies, our computational results confirm and indicate the beneficial additive dosimetric effects of Auger and conversion electrons of 161Tb with respect to 177Lu, when considering the same cumulated activity for both. Interestingly, in considering a realistic tumor model, the better dosimetric performances of 161Tb were confirmed also for tumor volumes ranging from 1.98 cm3 to 33.32 cm3.CONCLUSIONS:Dose assessment in realistic non-homogeneous tumor models could provide more insights with respect to consider only homogenous water-spheres tumor models and should be taken into account in dosimetry-based TRT planning studies.

This paper summarizes the results of an intercomparison on the use of the ICRP Reference Computational Phantoms with radiation transport codes, which was organized by EURADOS working group 6. Three exercises are described: exposure to an anterior-posterior (AP) photon point source, exposure to an AP neutron point source, and exposure to two typical medical X-ray examinations. The three exercises received 17, 8 and 8 so-lutions, respectively. Participants originated from fifteen different countries, and used a wide range of Monte Carlo codes. Due to difficulties in defining the precise source location unambiguously in the exercise description, agreement to within ~10% of the reference solution was considered satisfactory for a given participant's results. Although some participants provided initial solutions in good agreement with the reference solutions, differences of several tens of percent, or even several orders of magnitude, were exhibited for many of the others. Following feedback and suggestions from the organizers, revised solutions were submitted by some of the participants for the photon exercises; in general, agreement was improved. The overall observations from these three inter comparison exercises are summarized and discussed.

EURADOS Working Group 6 has organized an intercomparison exercise on the use of the ICRP Reference Computational Phantoms with radiation transport codes. This paper summarizes the results of a specific task from the intercomparison exercise modelling internal radiation sources. The quantities to be calculated were absorbed fractions and specific absorbed fractions for monoenergetic photon and electron sources as well as S-values for two radionuclides in four source organs. Twelve participants from eleven countries participated in this specific task using the Monte Carlo radiation transport codes FLUKA, Geant4, the MCNP code family, PenEasy, TRIPOLI-4 and VMC. Although some participants provided initial solutions in good agreement with the master solution evaluated by the organizers, differences of factors or even orders of magnitude were also found. Following feedback from the organizer, most participants submitted revised solutions that were mostly in better agreement with the master solution, although this was not always the case. Some initial and revised results are discussed in detail in this paper, and the reasons of mistakes are described as far as they were revealed by the participants. A full account of all results is presented in specific annexes as supplemental material.

Human populations and natural ecosystems are bound to be exposed to ionizing radiation from the deposition of artificial radionuclides resulting from nuclear accidents, nuclear devices or radiological dispersive devices (“dirty bombs”). On the other hand, Naturally Occurring Radioactive Material industries such as phosphate production or uranium mining, contribute to the on site storage of residuals with enhanced concentrations of natural radionuclides. Therefore, in the context of the European agreements concerning nuclear energy, namely the European Atomic Energy Community Treaty, monitoring is an essential feature of the environmental radiological surveillance. In this work, we obtain 3D maps from outdoor scenarios, and complete such maps with measured radiation levels and with its radionuclide signature. In such scenarios, we face challenges such as unknown and rough terrain, limited number of sampled locations and the need for different sensors and therefore different tasks. We propose a radiological solution for scouting, monitoring and inspecting an area of interest, using a fleet of drones and a controlling ground station. First, we scout an area with a Light Detection and Ranging sensor onboard a drone to accurately 3D-map the area. Then, we monitor that area with a Geiger–Müller Counter at a low-vertical distance from the ground to produce a radiological (heat)map that is overlaid on the 3D map of the scenario. Next, we identify the hotspots of radiation, and inspect them in detail using a drone by landing on them, to reveal its radionuclide signature using a Cadmium–Zinc–Telluride detector. We present the algorithms used to implement such tasks both at the ground station and on the drones. The three mission phases were validated using actual experiments in three different outdoor scenarios. We conclude that drones can not only perform the mission efficiently, but in general they are faster and as reliable as personnel on the ground.

Clinical dosimetry is typically performed using ion chambers calibrated in terms of absorbed dose to water. As primary measurement standards for this quantity for low and medium energy x-rays are available only since a few years, most dosimetry protocols for this photon energy range are still based on air kerma calibration. For that reason, data for beam quality correction factors kQ,Q0 , necessary for the application of dose to water based protocols, are scarce in literature. Currently the international IAEA TRS-398 Code of Practice is under revision and new kQ,Q0 factors for a large number of ion chambers will be introduced in the update of this protocol. Several international groups provided the IAEA with experimental and Monte Carlo based data for this revision. Within the European Community the EURAMET 16NRM03 RTNORM project was initiated for that purpose. In the present study, Monte Carlo based results for the beam quality correction factors in medium energy x-ray beams for six ion chambers applying different Monte Carlo codes are presented. Additionally, the perturbation factor p Q , necessary for the calculation of dose to water from an air kerma calibration coefficient, was determined. The beam quality correction factor kQ,Q0 for the chambers varied in the investigated energy range by about 4%–5%, and for five out of six chambers the data could be fitted by a simple logarithmic function, if the half-value-layer was used as the beam quality specifier. Corresponding data using different Monte Carlo codes for the same ion chamber agreed within 0.5%. For the perturbation factor p Q , the data did not obey a comparable simple relationship with the beam quality specifier. The variation of p Q for all ion chambers was in the range of 3%–4%. Compared to recently published data, our p Q data is around 1% larger, although the same Monte Carlo code has been used. Compared to the latest experimental data, there are even deviations in the range of 2%.

The beam quality correction factor, , which corrects for the difference in the ionization chamber response between the reference and clinical beam quality, is an integral part of radiation therapy dosimetry. The uncertainty of is one of the most significant sources of uncertainty in the dose determination. To improve the accuracy of available data, four partners calculated factors for 10 ionization chamber models in linear accelerator beams with accelerator voltages ranging from 6 MV to 25 MV, including flattening-filter-free (FFF) beams. The software used in the calculations were EGSnrc and PENELOPE, and the ICRU report 90 cross section data for water and graphite were included in the simulations. Volume averaging correction factors were calculated to correct for the dose averaging in the chamber cavities. A comparison calculation between partners showed a good agreement, as did comparison with literature. The values from TRS-398 were higher than our values for each chamber where data was available. The values for the FFF beams did not follow the same , relation as beams with flattening filter (values for 10 MV FFF beams were below fits made to other data on average by 0.3%), although our FFF sources were only for Varian linacs.

Radiological monitoring is fundamental for compliance with radiological protection policies in the aftermath of radiological events, such as nuclear accidents, terrorism, and out-of-commission uranium mines. An effective strategy for radiation monitoring is to use radiation detectors coupled with Unmanned Aerial Vehicles (UAVs), enabling for quicker surveillance of large areas without involving the need of human presence in the target area. The main aim of this study was to formulate the parameters for a UAV flight strategy in preparation for future field measurements using Geiger–Muller Counters (GMC) and Cadmium Zinc Telluride (CZT) spectrometers. As a proof of concept, the prepared flight strategy will be used to survey out-of-commission uranium mines in northern Portugal. Procedures to assure the calibration of the CZT and verification of the GMCs were conducted, as well as a sensitivity analysis of the sensors considering different acquisition times, distance to source, and detector response time. This article reports specific parameters, such as UAV distance to ground, time of exposition, speed, and the methodology to perform the identification and calculate the activity of possible radioactive sources. An effective flight strategy is also presented, aiming to use radiation detectors coupled with UAVs to undertake extensive monitoring of areas with enhanced levels of environmental radiation, which is of prime importance due to the lasting hazardous effects of enhanced environmental radiation in the nearby ecosystem and population.

Internal radiotherapy using Auger-emitting radionuclides is a relatively new technique that presents interesting advantages with respect to external radiotherapy, such as localized tumor efficacy. The aim of this study was to assess the dosimetric effectiveness in irradiating a tumor partitioned in different phenotypes, with different radionuclides directed at each tumor phenotype: Tc-99m, I-125 Tb-161, and Lu-177. State of the art Monte Carlo PENELOPE code and ICRP adult female reference voxel phantom (AFP) were used in order to mimic a lung tumor volume composed by four different phenotypes. For each radionuclide above mentioned, the decay modes (accessed through ICRP-107 data files) considered encompassed Auger electrons and beta, X and gamma radiation. Two main radiation therapy scenarios were simulated: i) the entire tumor was irradiated homogenously with each of the radionuclides; ii) each tumor phenotype was filled with a different radionuclide. The optimal dosimetric configuration was studied in terms of Dose Efficiency (DE), defined as tumor-to-healthy dose ratio. The Monte Carlo model was validated by comparing the results of SAF values in AFP and cellular S-values for I-125 with the ones present in the bibliography. In the first scenario, calculations showed that the highest DE is reached by I-125. Namely, with 1251 a gain dose factor (GDF) of about 2.8, 2.7 and 122.5 could be achieved, with respect to Lu-177, Tb-161, and Tc-99m, respectively. In the second scenario, a combination of radionuclides directed to each of the phenotypes can act as enhancement for DE or dose in the tumor tissues, with respect to using only one radionuclide in the 4 tumor phenotypes. According to this study, the hypothetical use of different electron beam qualifies directed to different tumor phenotypes of the same tumor could act as a radio-sensitizer and, at the same time, minimize dose to the surrounding healthy tissues.

The IAEA is currently coordinating a multi-year project to update the TRS-398 Code of Practice for the dosimetry of external beam radiotherapy based on standards of absorbed dose to water. One major aspect of the project is the determination of new beam quality correction factors, k Q , for megavoltage photon beams consistent with developments in radiotherapy dosimetry and technology since the publication of TRS-398 in 2000. Specifically, all values must be based on, or consistent with, the key data of ICRU Report 90. Data sets obtained from Monte Carlo (MC) calculations by advanced users and measurements at primary standards laboratories have been compiled for 23 cylindrical ionization chamber types, consisting of 725 MC-calculated and 179 experimental data points. These have been used to derive consensus k Q values as a function of the beam quality index TPR20,10 with a combined standard uncertainty of 0.6%. Mean values of MC-derived chamber-specific [Formula: see text] factors for cylindrical and plane-parallel chamber types in 60Co beams have also been obtained with an estimated uncertainty of 0.4%.

PurposeGiven the large use of computed tomography (CT) worldwide, the potential harmful effects and the radiation dose delivered to the patient have become high-interest topics among the scientific community. The main objective of this work was to modify existing three-dimensional (3D) voxel phantom models to resemble real patients as much as possible, thus trying to give a contribute towards the concept of a more personalized patient dosimetry. Moreover, comparisons were made of organ dose computed in the standard reference phantom and phantoms modified to match patient body size and organ size. This study focused essentially on one of the biggest and most radiosensitive organs in the thorax, the lungs.MethodsIn order to accomplish this objective a FORTRAN-based program was developed, which is able to semi-automatically modify the volumetric information of organs of interest in a standard voxel phantom (Female ICRP Adult Reference). Monte Carlo (MC) PENELOPE simulation code was used to mimic CT previews and, therefore, generate 2D projections, used for visual organ matching with clinical patient CT images, and calculate organ dose in both phantoms (ICRP standard and ICRP modified). Two CT scan irradiation setups were considered, namely Fan Beam CT (FBCT) and Cone Beam CT (CBCT) geometries. Validation of the implemented MC model (voxel phantom plus X-ray sources in diagnostic energy range) was accomplished through the calculation of lung-absorbed dose per fluence conversion coefficients for the Anterior-Posterior (AP) geometry setup with subsequent comparison with ICRP 116 tabulated values.ResultsThe main results reported that matching the voxel phantom's size and lungs provides organ dose values substantially different from the ones calculated in the ICRP reference phantom. According to the data presented in this study, organ dose can be up to 20% underestimated and 40% overestimated when compared to organ dose in the reference phantom, considering both irradiation setups.ConclusionsThis study demonstrates that voxel phantoms developed using single patient data could provide a better and more precise organ dose assessment by MC methods with respect to a standard phantom.