Point Kernel Research Articles

Fast three-dimensional radiation field characterization in large-scale nuclear installations

The requirement of the fast three-dimensional radiation field calculation is raised during the decommissioning of large-scale nuclear installations. The most often used methods, such as the Monte Carlo and the discrete ordinates methods, have shortcomings in their simulations of such problems. The coupled Monte Carlo–point kernel computational scheme is developed to meet the requirement. The facility is separated into the source region and the bulk shielding region, with a common interface. The transport within the source region is simulated using the Monte Carlo method, which is by nature good at treating complex geometries. The radiation field in the bulk shielding region is treated by the point kernel approach to avoid the extremely expensive computation for deep penetration problems. The flow rate through the interface, which is given by the Monte Carlo simulation, is considered as the equivalent surface source for the point kernel calculation. Test calculations from simplified typical waste storage facilities have been performed to validate the coupled scheme by comparing them with the results conducted by the Monte Carlo method directly. The good agreement of the results, as well as the significant saving in computing time, indicates that the coupled method is suitable for the fast three-dimensional radiation field calculation.

Absorbed dose evaluation of Auger electron-emitting radionuclides: impact of input decay spectra on dose point kernels and S-values

The aim of this study was to investigate the impact of decay data provided by the newly developed stochastic atomic relaxation model BrIccEmis on dose point kernels (DPKs - radial dose distribution around a unit point source) and S-values (absorbed dose per unit cumulated activity) of 14 Auger electron (AE) emitting radionuclides, namely 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn, 119Sb, 123I, 124I, 125I, 135La, 195mPt and 201Tl.Radiation spectra were based on the nuclear decay data from the medical internal radiation dose (MIRD) RADTABS program and the BrIccEmis code, assuming both an isolated-atom and condensed-phase approach. DPKs were simulated with the PENELOPE Monte Carlo (MC) code using event-by-event electron and photon transport. S-values for concentric spherical cells of various sizes were derived from these DPKs using appropriate geometric reduction factors.The number of Auger and Coster–Kronig (CK) electrons and x-ray photons released per nuclear decay (yield) from MIRD-RADTABS were consistently higher than those calculated using BrIccEmis. DPKs for the electron spectra from BrIccEmis were considerably different from MIRD-RADTABS in the first few hundred nanometres from a point source where most of the Auger electrons are stopped. S-values were, however, not significantly impacted as the differences in DPKs in the sub-micrometre dimension were quickly diminished in larger dimensions.Overestimation in the total AE energy output by MIRD-RADTABS leads to higher predicted energy deposition by AE emitting radionuclides, especially in the immediate vicinity of the decaying radionuclides. This should be taken into account when MIRD-RADTABS data are used to simulate biological damage at nanoscale dimensions.

Dosimetry applications in GATE Monte Carlo toolkit

PurposeMonte Carlo (MC) simulations are a well-established method for studying physical processes in medical physics. The purpose of this review is to present GATE dosimetry applications on diagnostic and therapeutic simulated protocols. There is a significant need for accurate quantification of the absorbed dose in several specific applications such as preclinical and pediatric studies. MethodsGATE is an open-source MC toolkit for simulating imaging, radiotherapy (RT) and dosimetry applications in a user-friendly environment, which is well validated and widely accepted by the scientific community. In RT applications, during treatment planning, it is essential to accurately assess the deposited energy and the absorbed dose per tissue/organ of interest, as well as the local statistical uncertainty. Several types of realistic dosimetric applications are described including: molecular imaging, radio-immunotherapy, radiotherapy and brachytherapy. ResultsGATE has been efficiently used in several applications, such as Dose Point Kernels, S-values, Brachytherapy parameters, and has been compared against various MC codes which are considered as standard tools for decades. Furthermore, the presented studies show reliable modeling of particle beams when comparing experimental with simulated data. Examples of different dosimetric protocols are reported for individualized dosimetry and simulations combining imaging and therapy dose monitoring, with the use of modern computational phantoms. ConclusionsPersonalization of medical protocols can be achieved by combining GATE MC simulations with anthropomorphic computational models and clinical anatomical data. This is a review study, covering several dosimetric applications of GATE, and the different tools used for modeling realistic clinical acquisitions with accurate dose assessment.

The development of two-phase three-node model used to simulate the transport of ACPs

Activated corrosion products (ACPs) are the dominant radiation hazard in water-cooled fusion reactor under normal operation conditions, and directly determine the occupational radiation exposure during operation and maintenance. In this paper, a two-phase three-node model is set up, and code CATE V2.0 is developed. Compared to the two-phase homogeneous model used in CATE V1.0, it is capable to analyze the spatial distribution of the ACPs along the cooling loops, and has the ability to deal with pulse of neutron flux, and almost all the radionuclides produced in the loop can be simulated. In the paper, the LIM-OBB loop of ITER is simulated by CATE V2.0. Different pulse handling methods applied to the simulation are compared. The spatial distribution of the composition and activity of ACPs along the loop is presented. And then the dose rate of the LIM-OBB loop is calculated by point kernel code ARShield.

A New Point Kernel Sampling Scheme and Monte Carlo Transport

Starting from an existing point kernel intergrated over the bounding surface of a volume source [1], the present contribution proposes a new point kernel sampling scheme. This sampling scheme is shown to be more effcient than the standard one because the integration proceeds from line segment sources instead of point sources. A new kind of Monte Carlo transport process is proposed. It is called flux transport from a line source and is expected to be more effcient than the standard source transport.

Evaluation of ACPs in China Fusion Engineering Test Reactor Using CATE 2.1 Code

Activated corrosion products (ACPs) are the dominant radiation hazard in water-cooled fusion reactor under normal operation conditions and directly determine the occupational radiation exposure during operation and maintenance. Recently, the preliminary design of China Fusion Engineering Test Reactor (CFETR) has been just completed. Evaluation of ACPs is an important work for the safety of CFETR. In this paper, the ACPs analysis code CATE 2.1 was used to simulate the spatial distribution of ACPs along the blanket cooling loop of CFETR, in which the influence of adopting different pulse handling methods was researched. At last, the dose rate caused by ACPs around the blanket cooling loop was calculated using the point kernel code ARShield. The results showed that the dose rate under normal operation for 1.2 years at contact is 1.02 mSv/h and at 1 m away from pipe is 0.45 mSv/h. And after shutting down the reactor, there will be a rapid decrease of dose rate, because of the rapid decay of short-lived ACPs.

A brief look at model-based dose calculation principles, practicalities, and promise.

Model-based dose calculation algorithms (MBDCAs) have recently emerged as potential successors to the highly practical, but sometimes inaccurate TG-43 formalism for brachytherapy treatment planning. So named for their capacity to more accurately calculate dose deposition in a patient using information from medical images, these approaches to solve the linear Boltzmann radiation transport equation include point kernel superposition, the discrete ordinates method, and Monte Carlo simulation. In this overview, we describe three MBDCAs that are commercially available at the present time, and identify guidance from professional societies and the broader peer-reviewed literature intended to facilitate their safe and appropriate use. We also highlight several important considerations to keep in mind when introducing an MBDCA into clinical practice, and look briefly at early applications reported in the literature and selected from our own ongoing work. The enhanced dose calculation accuracy offered by a MBDCA comes at the additional cost of modelling the geometry and material composition of the patient in treatment position (as determined from imaging), and the treatment applicator (as characterized by the vendor). The adequacy of these inputs and of the radiation source model, which needs to be assessed for each treatment site, treatment technique, and radiation source type, determines the accuracy of the resultant dose calculations. Although new challenges associated with their familiarization, commissioning, clinical implementation, and quality assurance exist, MBDCAs clearly afford an opportunity to improve brachytherapy practice, particularly for low-energy sources.

Impact of dose calculation models on radiotherapy outcomes and quality adjusted life years for lung cancer treatment: do we need to measure radiotherapy outcomes to tune the radiobiological parameters of a normal tissue complication probability model?

The equivalent uniform dose (EUD) radiobiological model can be applied for lung cancer treatment plans to estimate the tumor control probability (TCP) and the normal tissue complication probability (NTCP) using different dose calculation models. Then, based on the different calculated doses, the quality adjusted life years (QALY) score can be assessed versus the uncomplicated tumor control probability (UTCP) concept in order to predict the overall outcome of the different treatment plans. Nine lung cancer cases were included in this study. For the each patient, two treatments plans were generated. The doses were calculated respectively from pencil beam model, as pencil beam convolution (PBC) turning on 1D density correction with Modified Batho's (MB) method, and point kernel model as anisotropic analytical algorithm (AAA) using exactly the same prescribed dose, normalized to 100% at isocentre point inside the target and beam arrangements. The radiotherapy outcomes and QALY were compared. The bootstrap method was used to improve the 95% confidence intervals (95% CI) estimation. Wilcoxon paired test was used to calculate P value. Compared to AAA considered as more realistic, the PBCMB overestimated the TCP while underestimating NTCP, P<0.05. Thus the UTCP and the QALY score were also overestimated. To correlate measured QALY's obtained from the follow-up of the patients with calculated QALY from DVH metrics, the more accurate dose calculation models should be first integrated in clinical use. Second, clinically measured outcomes are necessary to tune the parameters of the NTCP model used to link the treatment outcome with the QALY. Only after these two steps, the comparison and the ranking of different radiotherapy plans would be possible, avoiding over/under estimation of QALY and any other clinic-biological estimates.

Evaluating the Application of Tissue-Specific Dose Kernels Instead of Water Dose Kernels in Internal Dosimetry: A Monte Carlo Study.

The aim of this work is to evaluate the application of tissue-specific dose kernels instead of water dose kernels to improve the accuracy of patient-specific dosimetry by taking tissue heterogeneities into consideration. Tissue-specific dose point kernels (DPKs) and dose voxel kernels (DVKs) for yttrium-90 (90Y), lutetium-177 (177Lu), and phosphorus-32 (32P) are calculated using the Monte Carlo (MC) simulation code GATE (version 7). The calculated DPKs for bone, lung, adipose, breast, heart, intestine, kidney, liver, and spleen are compared with those of water. The dose distribution in normal and tumorous tissues in lung, liver, and bone of a Zubal phantom is calculated using tissue-specific DVKs instead of those of water in conventional methods. For a tumor defined in a heterogeneous region in the Zubal phantom, the absorbed dose is calculated using a proposed algorithm, taking tissue heterogeneity into account. The algorithm is validated against full MC simulations. The simulation results indicate that the highest differences between water and other tissue DPKs occur in bone for 90Y (12.2% ± 0.6%), 32P (18.8% ± 1.3%), and 177Lu (16.9% ± 1.3%). The second highest discrepancy corresponds to the lung for 90Y (6.3% ± 0.2%), 32P (8.9% ± 0.4%), and 177Lu (7.7% ± 0.3%). For 90Y, the mean absorbed dose in tumorous and normal tissues is calculated using tissue-specific DVKs in lung, liver, and bone. The results are compared with doses calculated considering the Zubal phantom water equivalent and the relative differences are 4.50%, 0.73%, and 12.23%, respectively. For the tumor in the heterogeneous region of the Zubal phantom that includes lung, liver, and bone, the relative difference between mean calculated dose in tumorous and normal tissues based on the proposed algorithm and the values obtained from full MC dosimetry is 5.18%. A novel technique is proposed considering tissue-specific dose kernels in the dose calculation algorithm. This algorithm potentially enables patient-specific dosimetry and improves estimation of the average absorbed dose of 90Y in a tumor located in lung, bone, and soft tissue interface by 6.98% compared with the conventional methods.

Statistic and dosimetric criteria to assess the shift of the prescribed dose for lung radiotherapy plans when integrating point kernel models in medical physics: are we ready?

To apply the statistical bootstrap analysis and dosimetric criteria's to assess the change of prescribed dose (PD) for lung cancer to maintain the same clinical results when using new generations of dose calculation algorithms. Nine lung cancer cases were studied. For each patient, three treatment plans were generated using exactly the same beams arrangements. In plan 1, the dose was calculated using pencil beam convolution (PBC) algorithm turning on heterogeneity correction with modified batho (PBC-MB). In plan 2, the dose was calculated using anisotropic analytical algorithm (AAA) and the same PD, as plan 1. In plan 3, the dose was calculated using AAA with monitor units (MUs) obtained from PBC-MB, as input. The dosimetric criteria's include MUs, delivered dose at isocentre (Diso) and calculated dose to 95% of the target volume (D95). The bootstrap method was used to assess the significance of the dose differences and to accurately estimate the 95% confidence interval (95% CI). Wilcoxon and Spearman's rank tests were used to calculate P values and the correlation coefficient (ρ). Statistically significant for dose difference was found using point kernel model. A good correlation was observed between both algorithms types, with ρ>0.9. Using AAA instead of PBC-MB, an adjustment of the PD in the isocentre is suggested. For a given set of patients, we assessed the need to readjust the PD for lung cancer using dosimetric indices and bootstrap statistical method. Thus, if the goal is to keep on with the same clinical results, the PD for lung tumors has to be adjusted with AAA. According to our simulation we suggest to readjust the PD by 5% and an optimization for beam arrangements to better protect the organs at risks (OARs).

Dosimetry of non-uniform activity distribution: possibility to use the local energy deposition approach at the voxel level in radionuclide therapy

Non-uniform activity distribution plays an important role in dosimetry of organs treated with radionuclides. Tumor control probability and normal tissue complication probability depend on radionuclide distribution in treated organ/tissue. In this paper a rule for considering the local energy deposition (LED) hypothesis is presented. This allows us to use a straightforward method for the 3D absorbed dose calculation instead of the more complicated Monte Carlo, Dose Point Kernel or MIRD approach at the voxel level (MIRD 17 method). A comparison between the dose volume histograms (DVHs) evaluated by using the MIRD 17 method and a new normalized average absorbed dose (NAAD) approach in a simulated spherical target lesion, in which the activity is randomly distributed, is presented for 90Y, 131I, 153Sm, and 177Lu. The calculation was performed considering six different values of homogeneity of distributed activity (0.42, 0.38, 0.34, 0.31, 0.29, 0.27) corresponding to the relative standard-deviation of the counts in the voxels into the lesion. For 90Y the fractional difference between DVHs calculated by MIRD 17 and NAAD method ranges between 0.21 (corresponding to ) and 0.06 (corresponding to ); for 131I it ranges between 0.12 and 0.09; for 153Sm between 0.09 and 0.02 and for 177Lu between 0.05 and 0.01. The NAAD method, like the others usable in the LED hypothesis, can be used in the most cases allowing us to bypass the mathematical problems due to the convolution of 3D arrays.

High resolution digital autoradiographic and dosimetric analysis of heterogeneous radioactivity distribution in xenografted prostate tumors

The first main aim of this study was to illustrate the absorbed dose rate distribution from 177Lu in sections of xenografted prostate cancer (PCa) tumors using high resolution digital autoradiography (DAR) and compare it with hypothetical identical radioactivity distributions of 90Y or 7 MeV alpha-particles. Three dosimetry models based on either dose point kernels or Monte Carlo simulations were used and evaluated. The second and overlapping aim, was to perform DAR imaging and dosimetric analysis of the distribution of radioactivity, and hence the absorbed dose rate, in tumor sections at an early time point after injection during radioimmunotherapy using 177Lu-h11B6, directed against the human kallikrein 2 antigen. Male immunodeficient BALB/c nude mice, aged 6-8 w, were inoculated by subcutaneous injection of ∼107 LNCaP cells in a 200 μl suspension of a 1:1 mixture of medium and Matrigel. The antibody h11B6 was conjugated with the chelator CHX-A″-DTPA after which conjugated h11B6 was mixed with 177LuCl3. The incubation was performed at room temperature for 2 h, after which the labeling was terminated and the solution was purified on a NAP-5 column. About 20 MBq 177Lu-h11B6 was injected intravenously in the tail vein. At approximately 10 h postinjection (hpi), the mice were sacrificed and one tumor was collected from each of the five animals and cryosectioned into 10 μm thick slices. The tumor slices were measured and imaged using the DAR MicroImager system and the M3Vision software. Then the absorbed dose rate was calculated using a dose point kernel generated with the Monte Carlo code gate v7.0. The DAR system produced high resolution images of the radioactivity distribution, close to the resolution of single PCa cells. The DAR images revealed a pronounced heterogeneous radioactivity distribution, i.e., count rate per area, in the tumors, indicated by the normalized intensity variations along cross sections as mean ± SD: 0.15 ± 0.15, 0.20 ± 0.18, 0.12 ± 0.17, 0.15 ± 0.16, and 0.23 ± 0.22, for each tumor section, respectively. The absorbed dose rate distribution for 177Lu at the time of dissection 10 hpi showed a maximum value of 2.9 ± 0.4 Gy/h (mean ± SD), compared to 6.0 ± 0.9 and 159 ± 25 Gy/h for the hypothetical 90Y and 7 MeV alpha-particle cases assuming the same count rate densities. Mean absorbed dose rate values were 0.13, 0.53, and 6.43 Gy/h for 177Lu, 90Y, and alpha-particles, respectively. The initial uptake of 177Lu-h11B6 produces a high absorbed dose rate, which is important for a successful therapeutic outcome. The hypothetical 90Y case indicates a less heterogeneous absorbed dose rate distribution and a higher mean absorbed dose rate compared to 177Lu, although with a potentially increased irradiation of surrounding healthy tissue. The hypothetical alpha-particle case indicates the possibility of a higher maximum absorbed dose rate, although with a more heterogeneous absorbed dose rate distribution.

A kernel-based dose calculation algorithm for kV photon beams with explicit handling of energy and material dependencies

Objective:Mimicking state-of-the-art patient radiotherapy with high-precision irradiators for small animals is expected to advance the understanding of dose–effect relationships and radiobiology in general. We work on the implementation of intensity-modulated radiotherapy-like irradiation schemes for small animals. As a first step, we present a fast analytical dose calculation algorithm for keV photon beams.Methods:We follow a superposition–convolution approach adapted to kV X-rays, based on previous work for microbeam therapy. We assume local energy deposition at the photon interaction point due to the short electron ranges in tissue. This allows us to separate the dose calculation into locally absorbed primary dose and the scatter contribution, calculated in a point kernel approach. We validate our dose model against Geant4 Monte Carlo (MC) simulations and compare the results to Muriplan (XStrahl Ltd, Camberley, UK).Results:For field sizes of (1 mm)2 to (1 cm)2 in water, the depth dose curves show a mean disagreement of 1.7% to MC simulations, with the largest deviations in the entrance region (4%) and at large depths (5% at 7 cm). Larger discrepancies are observed at water-to-bone boundaries, in bone and at the beam edges in slab phantoms and a mouse brain. Calculation times are in the order of 5 s for a single beam.Conclusion:The algorithm shows good agreement with MC simulations in an initial validation. It has the potential to become an alternative to full MC dose calculation.Advances in knowledge:The presented algorithm demonstrates the potential of kernel-based dose calculation for kV photon beams. It will be valuable in intensity-modulated radiotherapy and inverse treatment planning for high precision small-animal radiotherapy.

Implementation of new physics models for low energy electrons in liquid water in Geant4-DNA

A new alternative set of elastic and inelastic cross sections has been added to the very low energy extension of the Geant4 Monte Carlo simulation toolkit, Geant4-DNA, for the simulation of electron interactions in liquid water. These cross sections have been obtained from the CPA100 Monte Carlo track structure code, which has been a reference in the microdosimetry community for many years. They are compared to the default Geant4-DNA cross sections and show better agreement with published data.In order to verify the correct implementation of the CPA100 cross section models in Geant4-DNA, simulations of the number of interactions and ranges were performed using Geant4-DNA with this new set of models, and the results were compared with corresponding results from the original CPA100 code. Good agreement is observed between the implementations, with relative differences lower than 1% regardless of the incident electron energy.Useful quantities related to the deposited energy at the scale of the cell or the organ of interest for internal dosimetry, like dose point kernels, are also calculated using these new physics models. They are compared with results obtained using the well-known Penelope Monte Carlo code.

Evaluation of Seismicity Using Density Analysis of 2000-2015 Earthquakes in The West Coastal Zone of Anatolia (Turkey) And Its Correlation with Geothermal Areas

The purpose of the study is to evaluate the seismic activity using the density analysis methods (point density and Kernel density analysis) for 2000-2015 earthquake catalogue belonging to the study area surrounded by Qanakkale to the north, Fethiye to the south and Denizli (Buharkent) to the east, and also to apply its correlation with geothermal regions. The earthquake data, in total 6.675 earthquakes with M>3 magnitudes were obtained from DDA Catalogue of Prime Ministry Disaster & Emergency Management Authority (AFAD) official website. In this survey, data analysis and maps were prepared using ArcGIS (version_10.1) program. The analysis maps present (1) the intensity clustered earthquakes dominant in Sigacik and Gokova Gulfs, (2) regions which have high seismic risk were determined according to Buffer analysis for 2 km distance, (3) geothermal areas (21.4-153°C) in the west coastal zone of Anatolia were mapped, (4) regions the most affected by seismic activity for the last 15 years were detected from 2015 population data, and as latest (5) Seferihisar, Urla, Gulbahge, Demircili, Bodrum, and Datga provinces are identified as areas having high seismic activity for the last 15 years. Consequently, all analysis results were compared with the geothermal areas, and the review made that earthquake catalogue has not the relationship with hot regions and also these shocks triggered by active faults in this region using ArcGIS program. the author recommends that these regions should be investigated the earthquake sensitivity analysis in the near future.

GPS &amp; GIS In Road Accident Mapping And Emergency Response Management

Road accidents is a major cause of mortality worldwide with urgent action required to mitigate against the negative impacts. A comprehensive accident recording and analysis system can provide a GISbased solution for control and management of accident events as a real-time monitoring system. This paper presents a GIS approach to road accident management based on spatial autocorrelation. It goes further to analyzing the spatial viability of emergency services offered to the accident victims. The study starts with the identification of the accident prone zones along Waiyaki Way in Nairobi, Kenya using GPS and GIS. For this purpose, the road accident data for the years 2013, 2014 and 2015 pertaining to Waiyaki Way was obtained from the traffic police department and used for analysis. Accident particulars like date, location, number of victims (fatal, serious and slight injuries), classes of victims (drivers, motor cyclists, pedal cyclists, passengers, pedestrians) were included in the GIS database. The “Density” function available in the spatial analyst extension of the Arc GIS software was applied to identify the accident prone areas during the years 2013, 2014 and 2015. Assessment of spatial clustering of accidents and hotspots spatial densities was carried out following Moran‟s I method of spatial autocorrelation, and point Kernel density functions. An effort was made to develop a comprehensive accident information management system that can provide a GIS-based solution for control and management of accident events. This system will inform clients about accident locations, accident and service diagnosis, reducing the number of accidents based on the accident reports thus increasing the level of road safety and fast delivery of emergency services. Keywords; Accidents, GIS, AIMS

Using GATE for radiation therapy applications

Monte Carlo (MC) simulations is a standard method for studying physical processes in medical physics, worldwide. GATE is an open-source platform for simulating imaging, radiotherapy (RT) and dosimetry applications in a user-friendly environment. In RT applications, during the treatment planning, it is essential to accurately assess the deposited energy and the absorbed dose per tissue or organ of interest, as well as the local statistical uncertainty. Several types of realistic dosimetric applications are described including: molecular radiotherapy, radio-immunotherapy, brachytherapy, particle and external beam therapy. GATE is a MC toolkit which is well validated and is widely accepted by the scientific community. More specifically, it has been efficiently used in several applications, such as Dose Point Kernels, S-values, Brachytherapy parameters (anisotropy and radial dose function), and compared against a variety of MC codes which are considered as standard tools for decades. Furthermore, comparison studies reported reliable modelling of electron, photon and proton beams comparing experimental with simulated data. Personalization of medical protocols can be achieved by combining GATE MC simulations with anthropomorphic computational models and clinical anatomical data. High statistics obtained by speeding up these computationally demanding simulations (GPU, Grids, Variance Reduction Techniques, Phase-Space), can lead to accurate dosimetric assessment in clinical applications. In the present study, examples of validated RT applications are presented, describing the structure of such simulations and examples of recently funded H2020 projects (i.e. ERROR) are given. Monte Carlo (MC) simulations is a standard method for studying physical processes in medical physics, worldwide. GATE is an open-source platform for simulating imaging, radiotherapy (RT) and dosimetry applications in a user-friendly environment. In RT applications, during the treatment planning, it is essential to accurately assess the deposited energy and the absorbed dose per tissue or organ of interest, as well as the local statistical uncertainty. Several types of realistic dosimetric applications are described including: molecular radiotherapy, radio-immunotherapy, brachytherapy, particle and external beam therapy. GATE is a MC toolkit which is well validated and is widely accepted by the scientific community. More specifically, it has been efficiently used in several applications, such as Dose Point Kernels, S-values, Brachytherapy parameters (anisotropy and radial dose function), and compared against a variety of MC codes which are considered as standard tools for decades. Furthermore, comparison studies reported reliable modelling of electron, photon and proton beams comparing experimental with simulated data. Personalization of medical protocols can be achieved by combining GATE MC simulations with anthropomorphic computational models and clinical anatomical data. High statistics obtained by speeding up these computationally demanding simulations (GPU, Grids, Variance Reduction Techniques, Phase-Space), can lead to accurate dosimetric assessment in clinical applications. In the present study, examples of validated RT applications are presented, describing the structure of such simulations and examples of recently funded H2020 projects (i.e. ERROR) are given.

TU-AB-BRC-06: Dose Calculation in Curved Space

Purpose: Microbeam Radiation Therapy is a preclinical method in radiation oncology that modulates radiation fields on a micrometre scale. Dose calculation is challenging due to arising dose gradients and therapeutically important dose ranges. Monte Carlo (MC) simulations, often used as gold standard, are computationally expensive and hence too slow for the optimisation of treatment parameters in future clinical applications. On the other hand, conventional kernel based dose calculation leads to inaccurate results close to material interfaces. The purpose of this work is to overcome these inaccuracies while keeping computation times low. Methods: A point kernel superposition algorithm is modified to account for tissue inhomogeneities. Instead of conventional ray tracing approaches, methods from differential geometry are applied and the space around the primary photon interaction is locally warped. The performance of this approach is compared to MC simulations and a simple convolution algorithm (CA) for two different phantoms and photon spectra. Results: While peak doses of all dose calculation methods agreed within less than 4% deviations, the proposed approach surpassed a simple convolution algorithm in accuracy by a factor of up to 3 in the scatter dose. In a treatment geometry similar to possible future clinical situations differences between Monte Carlo and the differential geometry algorithm were less than 3%. At the same time the calculation time did not exceed 15 minutes. Conclusion: With the developed method it was possible to improve the dose calculation based on the CA method with respect to accuracy especially at sharp tissue boundaries. While the calculation is more extensive than for the CA method and depends on field size, the typical calculation time for a 20×20 mm2 field on a 3.4 GHz and 8 GByte RAM processor remained below 15 minutes. Parallelisation and optimisation of the algorithm could lead to further significant calculation time reductions.

Development and Validation of an Interactive Efficient Dose Rates Distribution Calculation Program Arshield for Visualization of Radiation Field in Nuclear Power Plants.

Point kernel integration (PKI) method is widely used in the visualization of radiation field in engineering applications because of the features of quickly dealing with large-scale complicated geometry space problems. But the traditional PKI programs have a lot of restrictions, such as complicated modeling, complicated source setting, 3Dfine mesh results statistics and large-scale computing efficiency. To break the traditional restrictions for visualization of radiation field, ARShield was developed successfully. The results show that ARShield can deal with complicated plant radiation shielding problems for visualization of radiation field. Compared with SuperMC and QAD, it can be seen that the program is reliable and efficient. Also, ARShield can meet the demands of calculation speediness and interactive operations of modeling and displaying 3D geometries on a graphical user interface, avoiding error modeling in calculation and visualization.

Survey on Algorithms for Object Tracking in Video

Object tracking is a very essential task in many applications of computer vision such as surveillance, vehicle navigation, autonomous robot navigation, etc. It contains detection of interesting moving objects and tracking of such objects from frame to frame. Its main task is to find and follow a moving object or multiple objects in image sequences. Normally there are three stages of video analysis: object detection, object tracking and object reorganization. This paper presents a brief survey of various video object tracking techniques like point tracking, kernel tracking and Silhouette tracking algorithms. General Terms Human-computer Interactions, 2D image, noise image, Proximity.