- Email: [email protected]
SP-0616 ULICE – UNION OF LIGHT ION CENTRES IN EUROPE
S241
1-is an improvement of tumor response to IR? 2- is there any change in normal tissue damage? The complexity of our understanding of molecular radiobiology brings us to develop models of irradiation that more closely mimic radiotherapy such as fractionated irradiation, orthotopically implanted tumor models. In the era of personalized medicine, preclinical models have to reflect the major molecular landscapes of tumors in order to increase their predictive value. Emerging mechanisms of action targeting the tumor host component require the access to immunocompetent models. Preclinical evaluation may also lead to the identification of candidate biomarkers of tumor response to be evaluated into subsequent clinical trials. Access to similar bio-pathology and imaging platforms in mice and in humans may contribute to the optimization of ancillary assays such as circulating tumor cells, functional imaging. Last, predictive assay may contribute to provide toxicity warnings if an increase in normal tissue damage is observed. SP-0612 DO OUR MOTHERS' GENES INFLUENCE RADIATION RESPONSE? P. Lambin1, G. Nalbantov1, W. De Neve2, K. Vandecasteele2, L. Dubois1, M. van Gisbergen1, C. Oberije1, M. Starmans1,4, B. Smeets3, A. Voets1,3 1 GROW - School for Oncology and Developmental Biology, Radiation Oncology, Maastricht, The Netherlands 2 University Hosptial Ghent, Radiation Oncology, Ghent, Belgium 3 GROW - School for Oncology and Developmental Biology, Genetics and Cell Biology, Maastricht, The Netherlands 4 Ontario Institute for Cancer Research, Informatics and Biocomputing Platform, Toronto, Canada Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria, structures within eukaryotic cells that extract energy from food and convert this into adenosine triphosphate (ATP). In human, mtDNA is inherited from the mother. It can be regarded as the smallest chromosome and was the first significant part of the human genome to be sequenced. The mtDNA codes for 13 subunits of the oxidative phosphorylation system, responsible for aerobic ATP production. The remaining subunits are encoded by the DNA residing in the cellular nucleus (nDNA). Mutations of the (mtDNA or nDNA encoded) of the genes involved in oxydative phosphorylation (OXPHOS) have been associated with decreased ATP production and increased oxidative stress. Data from studies on multiple from studies on several solid cancers show that the mtDNA of cancer cells are riddled with mutations. These findings could be revolutionary within cancer research, providing new targets for treatment, diagnosis and monitoring of cancer. These mutations could contribute to the changed metabolism typical of cancer cells. Many cancers obtain their energy from glycolysis within the cytoplasm (this is why FDG PET scan is working) rather than via aerobic respiration from mitochondria. Non-cancerous cells use glycolysis for energy only upon oxygen deprivation, because it is inefficient. Despite this, glycolysis is thought to be beneficial for cancer cells because it also delivers the chemical building blocks for cellular proliferation which enables cancer cells to grow rapidly. Furthermore, mitochondrial dysfunction due to mtDNA mutations could also play a role in carcinogenesis as a result of the release of free radicals, which are by-products of aerobic respiration, eventually leading to nuclear DNA mutations. What about normal tissue tolerance? mtDNA has been seen as a marker for vitality; in oocytes the amount of mitochondria and mtDNA define fertility. It has been shown that one of the mechanisms within the aging process is due to deterioration of the mtDNA (quantitatively and qualitatively) and associated deficits in energy metabolism. Environmental factors (viral infection, drugs…) can lead to mitotoxicity, increased Reactive Oxygen Species (ROS) production and trigger more severe disease manifestations. Variation in the mtDNA sequence is common and every individual carries between 10 and 60 variants. In a preliminary study, we tested the assumption that either mtDNA variants could be associated with radiation induced toxicity or that extensive mtDNA variation might reflect the status of poor repair, mtDNA maintenance or increased ROS damage, which subsequently could lead to increased radiation induced long term toxicity. We will present a review of the most recent literature as well as our first results based on a dataset of Maastricht and Ghent.
ESTRO 31
SP-0613 USE IN CLINICAL TRIALS J. Overgaard Aarhus University Hospital, Aarhus, Denmark Abstract not received
SYMPOSIUM: EU PROJECTS 2 SP-0614 THE ROLE OF RADIATION PROTECTION IN RADIATION THERAPY CONSEPTS AND LEGISLATION, T. Knöös Lund University, Hospital, Lund, Sweden Abstract not received SP-0615 THE STATUS OF RADIATION PROTECTION TRAINING IN EUROPE - THE MEDRAPET SURVEY D. Olsen1 1 University of Bergen, Facully of Mathematics and Natural Sciences, Bergen, Norway MEDRAPET, medical radiation protection – education and training, is a European project of which ESTRO and other scientific and professional societies in Europe have participated. The overall has been to identify the for needs radiation protection training. One component of the project has been to conduct a survey on the education and training in radiation protection in Europe. The survey included professional/scientific societies, universities and regulatory bodies. The overall response rate was low (25%), whereas 41% of the national radiation oncology societies responded to the survey. The response rate amongst universities was 19% and 57% for regulatory bodies. According to the EURATOM 97/43 (MED) directive requirements for education and training in radiation protection should be included in the national legislation. Still, almost 50% of the respondents report that radiation protection education and training is not required for students and residents in their country. Moreover, 45% of the regulatory bodies report that the do not ensure that radiation oncologists have relevant competency in radiation protection. Less than 30% of the national radiation oncology societies classify the practical training in radiation protection as ‘good’. Clearly, creating legislation and providing guidelines at EU or national level is by itself not enough to create a radiation protection safety culture amongst health professionals. SP-0616 ULICE - UNION OF LIGHT ION CENTRES IN EUROPE J. Debus1, M. Dosanjh2, R. Orecchia3, R. Pötter4, C. Bono5 1 University Hospital of Heidelberg, ULICE transnational activities coordinator, Heidelberg, Germany 2 CERN, ULICE networking activities coordinator, Geneva, Switzerland 3 Centro Nazionale di Adroterapia Oncologica, ULICE coordinator, Milan, Italy 4 Medical University of Vienna, ULICE joint research activities coordinator, Vienna, Austria 5 Centro Nazionale di Adroterapia Oncologica, ULICE central project office, Milan, Italy ULICE is a 4 years project joining 20 leading European research organizations cooperating to deepen all the clinical, radiobiological, medical physics and physical aspects of hadrontherapy. One of the main goal of the project is the transnational access that it is to say offering greater free access to hadrontherapy facilities for particle therapy research, both from a preclinical and a clinical perspective, to those researchers working in countries where such a facility doesn’t exist. The two up to now running facilities involved in ULICE - CNAO Centro Nazionale di Adroterapia Oncologica in Italy and HIT Heidelberg Ion Therapy Center in Germany - are providing a certain number of beam time hours to external researchers. In the frame of the project, some clinical protocols are settled and following them, clinicians have the opportunity to treat their patients and then to get data on the role of hadron treatments. The clinical trials have to be approved of course by the local ethics committees. A dedicated international selection panel has been organized to evaluate the submitted research proposals and the best facility where they can
S242
take place. The committee selects the proposals taking in consideration some criteria defined for clinical and preclinical researches as the scientific relevance of the proposal, the expertise of the researcher in the field and the ability to take part to the clinical activity, the feasibility of the project, the potential impact on patient referral, the potential to improve existing facilities, the impact on hadron therapy on the whole. The facilities will provide personnel, training courses, equipment and labs to satisfy the needs of the research groups. Researchers going to CNAO or HIT for clinical researches may bring or not patients but they will act as observers if they are not entitled by national laws to perform medical activities. In the website of the ULICE project, researchers concerned find instructions on the application and on the rules about transnational access to the facilities. More details can be addressed to [email protected].
SYMPOSIUM: MC PLATFORMS, GETTING MC EASY FOR ROUTINE USE IN MP SP-0617 SMCP - AN EFFICIENT MONTE CARLO TREATMENT PLANNING SYSTEM P. Manser1 1 Inselspital Universität Bern, Div. of Med. Radiation Physics, Bern, Switzerland Monte Carlo (MC) methods are seen as the most accurate method to calculate dose distributions in radiation therapy. Due to its statistical nature, however, MC methods lack of efficiency and thus its clinical implementation is limited. Several approaches were developed in order to improve efficiency while not compromising the accuracy. As an example, the macro MC method [1] for electron beams was developed and successfully implemented in clinical routine. Nevertheless, for photon beams, the need to speed up MC simulations is even more pronounced. Thus, in this presentation, the Swiss Monte Carlo Plan (SMCP) [2] is used to demonstrate the potential of an efficient and accurate MC treatment planning system. SMCP is an efficient and flexible MC platform for dose calculations of photon beams. It is based on a GUI-framework with different methods for the simulation of the radiation transport in a linear accelerator’s treatment head. By this means, not only 3DCRT but also more complex delivery techniques such as IMRT or VMAT [3] can be managed. Dose calculation within the patient is performed using different radiation transport methods and is linked to a commercially available treatment planning system (Eclipse, Varian Medical Systems). References: [1] H. Neuenschwander et al., Phys. Med. Biol., 107-25, 1992 [2] M.K. Fix et al., Phys. Med. Biol., N425-N437, 2007 [3] P. Manser et al., Med. Phys., 3240, 2010
ESTRO 31
radiotherapy dosimetry problems. These problems include the investigation of perturbation effects and the generation of correction factors for absolute and relative dosimetry. The methodology to assess the contribution of systematic uncertainties to results is explained. Some features of the new EGSnrc release with relevance for ion chamber calculations are discussed. SP-0619 PRIMO: A GRAPHICAL ENVIRONMENT FOR THE AUTOMATIC SIMULATION OF VARIAN AND ELEKTA LINACS WITH PENELOPE L. Brualla1, M. Rodriguez2, J. Sempau2 1 Universitätsklinikum Essen, Strahlenklinik, Essen, Germany 2 Universitat Politècnica de Catalunya, Institut de Tècniques Energètiques, Barcelona, Spain Purpose: The accurate Monte Carlo simulation of a linac requires a detailed description of its geometry and the application of elaborate variance-reduction techniques (VRTs). Here, we introduce a new system based on the codes PENELOPE, penEasy, penEasyLinac and a graphical user interface (GUI) that encompasses all these pieces in a single user-friendly environment, called PRIMO. Methods: PENELOPE is a set of general-purpose subroutines for the Monte Carlo simulation of electron and photon transport. penEasy is a general-purpose, well structured, main program for PENELOPE that includes several source models, tallies, VRTs and the possibility of combining quadric and voxelised geometries. penEasyLinac is a complementary tool that generates the input files required for the simulation of certain Varian and Elekta linacs with PENELOPE/penEasy. PRIMO is the uppermost layer of the simulation system (see figure). It consists of a GUI that allows users to define the configuration of the simulated machine, that is, irradiation mode, beam nominal energy, jaw positions, position of every leaf of the multileaf collimator (photon mode) or type of electron applicator (electron mode). All the other parameters, those of the simulation and application of VRTs, are automatically selected by the system without user intervention. Users can edit and modify configuration files if desired. The automatically selected parameters are optimised for each particular linac configuration. Finally, PRIMO incorporates graphical and numerical tools for the analysis of phase-space files and dose distributions tallied during the simulations.
SP-0618 EGSNRC FOR THE INVESTIGATION OF IONIZATION CHAMBERS IN RADIOTHERAPY DOSIMETRY J. Wulff1 1 Technische Hochschule Mittelhessen, Institut fuer Medizinische Physik und Strahlenschutz, Giessen, Germany The EGSnrc code system has been used for the investigation of ion chamber dosimetry in electron/photon radiotherapy for more than a decade. Already the very first version of EGSnrc included the elaborate electron transport algorithm capable of calculating artifactfree ion chamber response at the 0.1% level (relative to crosssections). This made EGSnrc one of the few general purpose codes available for these types of simulations. Since its initial release several enhancements have been made to the physics back-end, but more importantly a C++ interface with a geometry and particle source library was incorporated into the system. Subsequently tailored applications for efficient calculation of ion chamber response have been released. In conjunction with the functionality of BEAMnrc to calculate the fluence output of typical radiotherapy machines, the system can be understood as a valuable tool for dosimetry research. The simulation setup is mainly text-file based and requires some syntax learning, but the platform allows the investigation of complex problems in photon/electron dosimetry even for a novice user. This talk summarizes the features of EGSnrc for accurate ion chamber calculations and explains how different variance reduction techniques are employed for an efficient simulation of ion chambers in typical
Results: A demanding test for a linac simulator is the computation of absorbed dose distributions produced by relatively small far-from-axis photon fields. As an example, we have simulated a 3x5 cm2 field located 12 cm away from the beam axis of a Varian Clinac 2100 C/D. This field requires the largest possible over-travel distances for both set of jaws. Comparison of the simulated results with experimental data via the gamma test shows that there are no voxels with gamma index larger than unity using the 0.2 cm and 2% criteria. The simulation of this off-axis field, starting at the bremsstrahlung target and ending with the dose estimation in a water phantom reached 2%
1-is an improvement of tumor response to IR? 2- is there any change in normal tissue damage? The complexity of our understanding of molecular radiobiology brings us to develop models of irradiation that more closely mimic radiotherapy such as fractionated irradiation, orthotopically implanted tumor models. In the era of personalized medicine, preclinical models have to reflect the major molecular landscapes of tumors in order to increase their predictive value. Emerging mechanisms of action targeting the tumor host component require the access to immunocompetent models. Preclinical evaluation may also lead to the identification of candidate biomarkers of tumor response to be evaluated into subsequent clinical trials. Access to similar bio-pathology and imaging platforms in mice and in humans may contribute to the optimization of ancillary assays such as circulating tumor cells, functional imaging. Last, predictive assay may contribute to provide toxicity warnings if an increase in normal tissue damage is observed. SP-0612 DO OUR MOTHERS' GENES INFLUENCE RADIATION RESPONSE? P. Lambin1, G. Nalbantov1, W. De Neve2, K. Vandecasteele2, L. Dubois1, M. van Gisbergen1, C. Oberije1, M. Starmans1,4, B. Smeets3, A. Voets1,3 1 GROW - School for Oncology and Developmental Biology, Radiation Oncology, Maastricht, The Netherlands 2 University Hosptial Ghent, Radiation Oncology, Ghent, Belgium 3 GROW - School for Oncology and Developmental Biology, Genetics and Cell Biology, Maastricht, The Netherlands 4 Ontario Institute for Cancer Research, Informatics and Biocomputing Platform, Toronto, Canada Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria, structures within eukaryotic cells that extract energy from food and convert this into adenosine triphosphate (ATP). In human, mtDNA is inherited from the mother. It can be regarded as the smallest chromosome and was the first significant part of the human genome to be sequenced. The mtDNA codes for 13 subunits of the oxidative phosphorylation system, responsible for aerobic ATP production. The remaining subunits are encoded by the DNA residing in the cellular nucleus (nDNA). Mutations of the (mtDNA or nDNA encoded) of the genes involved in oxydative phosphorylation (OXPHOS) have been associated with decreased ATP production and increased oxidative stress. Data from studies on multiple from studies on several solid cancers show that the mtDNA of cancer cells are riddled with mutations. These findings could be revolutionary within cancer research, providing new targets for treatment, diagnosis and monitoring of cancer. These mutations could contribute to the changed metabolism typical of cancer cells. Many cancers obtain their energy from glycolysis within the cytoplasm (this is why FDG PET scan is working) rather than via aerobic respiration from mitochondria. Non-cancerous cells use glycolysis for energy only upon oxygen deprivation, because it is inefficient. Despite this, glycolysis is thought to be beneficial for cancer cells because it also delivers the chemical building blocks for cellular proliferation which enables cancer cells to grow rapidly. Furthermore, mitochondrial dysfunction due to mtDNA mutations could also play a role in carcinogenesis as a result of the release of free radicals, which are by-products of aerobic respiration, eventually leading to nuclear DNA mutations. What about normal tissue tolerance? mtDNA has been seen as a marker for vitality; in oocytes the amount of mitochondria and mtDNA define fertility. It has been shown that one of the mechanisms within the aging process is due to deterioration of the mtDNA (quantitatively and qualitatively) and associated deficits in energy metabolism. Environmental factors (viral infection, drugs…) can lead to mitotoxicity, increased Reactive Oxygen Species (ROS) production and trigger more severe disease manifestations. Variation in the mtDNA sequence is common and every individual carries between 10 and 60 variants. In a preliminary study, we tested the assumption that either mtDNA variants could be associated with radiation induced toxicity or that extensive mtDNA variation might reflect the status of poor repair, mtDNA maintenance or increased ROS damage, which subsequently could lead to increased radiation induced long term toxicity. We will present a review of the most recent literature as well as our first results based on a dataset of Maastricht and Ghent.
ESTRO 31
SP-0613 USE IN CLINICAL TRIALS J. Overgaard Aarhus University Hospital, Aarhus, Denmark Abstract not received
SYMPOSIUM: EU PROJECTS 2 SP-0614 THE ROLE OF RADIATION PROTECTION IN RADIATION THERAPY CONSEPTS AND LEGISLATION, T. Knöös Lund University, Hospital, Lund, Sweden Abstract not received SP-0615 THE STATUS OF RADIATION PROTECTION TRAINING IN EUROPE - THE MEDRAPET SURVEY D. Olsen1 1 University of Bergen, Facully of Mathematics and Natural Sciences, Bergen, Norway MEDRAPET, medical radiation protection – education and training, is a European project of which ESTRO and other scientific and professional societies in Europe have participated. The overall has been to identify the for needs radiation protection training. One component of the project has been to conduct a survey on the education and training in radiation protection in Europe. The survey included professional/scientific societies, universities and regulatory bodies. The overall response rate was low (25%), whereas 41% of the national radiation oncology societies responded to the survey. The response rate amongst universities was 19% and 57% for regulatory bodies. According to the EURATOM 97/43 (MED) directive requirements for education and training in radiation protection should be included in the national legislation. Still, almost 50% of the respondents report that radiation protection education and training is not required for students and residents in their country. Moreover, 45% of the regulatory bodies report that the do not ensure that radiation oncologists have relevant competency in radiation protection. Less than 30% of the national radiation oncology societies classify the practical training in radiation protection as ‘good’. Clearly, creating legislation and providing guidelines at EU or national level is by itself not enough to create a radiation protection safety culture amongst health professionals. SP-0616 ULICE - UNION OF LIGHT ION CENTRES IN EUROPE J. Debus1, M. Dosanjh2, R. Orecchia3, R. Pötter4, C. Bono5 1 University Hospital of Heidelberg, ULICE transnational activities coordinator, Heidelberg, Germany 2 CERN, ULICE networking activities coordinator, Geneva, Switzerland 3 Centro Nazionale di Adroterapia Oncologica, ULICE coordinator, Milan, Italy 4 Medical University of Vienna, ULICE joint research activities coordinator, Vienna, Austria 5 Centro Nazionale di Adroterapia Oncologica, ULICE central project office, Milan, Italy ULICE is a 4 years project joining 20 leading European research organizations cooperating to deepen all the clinical, radiobiological, medical physics and physical aspects of hadrontherapy. One of the main goal of the project is the transnational access that it is to say offering greater free access to hadrontherapy facilities for particle therapy research, both from a preclinical and a clinical perspective, to those researchers working in countries where such a facility doesn’t exist. The two up to now running facilities involved in ULICE - CNAO Centro Nazionale di Adroterapia Oncologica in Italy and HIT Heidelberg Ion Therapy Center in Germany - are providing a certain number of beam time hours to external researchers. In the frame of the project, some clinical protocols are settled and following them, clinicians have the opportunity to treat their patients and then to get data on the role of hadron treatments. The clinical trials have to be approved of course by the local ethics committees. A dedicated international selection panel has been organized to evaluate the submitted research proposals and the best facility where they can
S242
take place. The committee selects the proposals taking in consideration some criteria defined for clinical and preclinical researches as the scientific relevance of the proposal, the expertise of the researcher in the field and the ability to take part to the clinical activity, the feasibility of the project, the potential impact on patient referral, the potential to improve existing facilities, the impact on hadron therapy on the whole. The facilities will provide personnel, training courses, equipment and labs to satisfy the needs of the research groups. Researchers going to CNAO or HIT for clinical researches may bring or not patients but they will act as observers if they are not entitled by national laws to perform medical activities. In the website of the ULICE project, researchers concerned find instructions on the application and on the rules about transnational access to the facilities. More details can be addressed to [email protected].
SYMPOSIUM: MC PLATFORMS, GETTING MC EASY FOR ROUTINE USE IN MP SP-0617 SMCP - AN EFFICIENT MONTE CARLO TREATMENT PLANNING SYSTEM P. Manser1 1 Inselspital Universität Bern, Div. of Med. Radiation Physics, Bern, Switzerland Monte Carlo (MC) methods are seen as the most accurate method to calculate dose distributions in radiation therapy. Due to its statistical nature, however, MC methods lack of efficiency and thus its clinical implementation is limited. Several approaches were developed in order to improve efficiency while not compromising the accuracy. As an example, the macro MC method [1] for electron beams was developed and successfully implemented in clinical routine. Nevertheless, for photon beams, the need to speed up MC simulations is even more pronounced. Thus, in this presentation, the Swiss Monte Carlo Plan (SMCP) [2] is used to demonstrate the potential of an efficient and accurate MC treatment planning system. SMCP is an efficient and flexible MC platform for dose calculations of photon beams. It is based on a GUI-framework with different methods for the simulation of the radiation transport in a linear accelerator’s treatment head. By this means, not only 3DCRT but also more complex delivery techniques such as IMRT or VMAT [3] can be managed. Dose calculation within the patient is performed using different radiation transport methods and is linked to a commercially available treatment planning system (Eclipse, Varian Medical Systems). References: [1] H. Neuenschwander et al., Phys. Med. Biol., 107-25, 1992 [2] M.K. Fix et al., Phys. Med. Biol., N425-N437, 2007 [3] P. Manser et al., Med. Phys., 3240, 2010
ESTRO 31
radiotherapy dosimetry problems. These problems include the investigation of perturbation effects and the generation of correction factors for absolute and relative dosimetry. The methodology to assess the contribution of systematic uncertainties to results is explained. Some features of the new EGSnrc release with relevance for ion chamber calculations are discussed. SP-0619 PRIMO: A GRAPHICAL ENVIRONMENT FOR THE AUTOMATIC SIMULATION OF VARIAN AND ELEKTA LINACS WITH PENELOPE L. Brualla1, M. Rodriguez2, J. Sempau2 1 Universitätsklinikum Essen, Strahlenklinik, Essen, Germany 2 Universitat Politècnica de Catalunya, Institut de Tècniques Energètiques, Barcelona, Spain Purpose: The accurate Monte Carlo simulation of a linac requires a detailed description of its geometry and the application of elaborate variance-reduction techniques (VRTs). Here, we introduce a new system based on the codes PENELOPE, penEasy, penEasyLinac and a graphical user interface (GUI) that encompasses all these pieces in a single user-friendly environment, called PRIMO. Methods: PENELOPE is a set of general-purpose subroutines for the Monte Carlo simulation of electron and photon transport. penEasy is a general-purpose, well structured, main program for PENELOPE that includes several source models, tallies, VRTs and the possibility of combining quadric and voxelised geometries. penEasyLinac is a complementary tool that generates the input files required for the simulation of certain Varian and Elekta linacs with PENELOPE/penEasy. PRIMO is the uppermost layer of the simulation system (see figure). It consists of a GUI that allows users to define the configuration of the simulated machine, that is, irradiation mode, beam nominal energy, jaw positions, position of every leaf of the multileaf collimator (photon mode) or type of electron applicator (electron mode). All the other parameters, those of the simulation and application of VRTs, are automatically selected by the system without user intervention. Users can edit and modify configuration files if desired. The automatically selected parameters are optimised for each particular linac configuration. Finally, PRIMO incorporates graphical and numerical tools for the analysis of phase-space files and dose distributions tallied during the simulations.
SP-0618 EGSNRC FOR THE INVESTIGATION OF IONIZATION CHAMBERS IN RADIOTHERAPY DOSIMETRY J. Wulff1 1 Technische Hochschule Mittelhessen, Institut fuer Medizinische Physik und Strahlenschutz, Giessen, Germany The EGSnrc code system has been used for the investigation of ion chamber dosimetry in electron/photon radiotherapy for more than a decade. Already the very first version of EGSnrc included the elaborate electron transport algorithm capable of calculating artifactfree ion chamber response at the 0.1% level (relative to crosssections). This made EGSnrc one of the few general purpose codes available for these types of simulations. Since its initial release several enhancements have been made to the physics back-end, but more importantly a C++ interface with a geometry and particle source library was incorporated into the system. Subsequently tailored applications for efficient calculation of ion chamber response have been released. In conjunction with the functionality of BEAMnrc to calculate the fluence output of typical radiotherapy machines, the system can be understood as a valuable tool for dosimetry research. The simulation setup is mainly text-file based and requires some syntax learning, but the platform allows the investigation of complex problems in photon/electron dosimetry even for a novice user. This talk summarizes the features of EGSnrc for accurate ion chamber calculations and explains how different variance reduction techniques are employed for an efficient simulation of ion chambers in typical
Results: A demanding test for a linac simulator is the computation of absorbed dose distributions produced by relatively small far-from-axis photon fields. As an example, we have simulated a 3x5 cm2 field located 12 cm away from the beam axis of a Varian Clinac 2100 C/D. This field requires the largest possible over-travel distances for both set of jaws. Comparison of the simulated results with experimental data via the gamma test shows that there are no voxels with gamma index larger than unity using the 0.2 cm and 2% criteria. The simulation of this off-axis field, starting at the bremsstrahlung target and ending with the dose estimation in a water phantom reached 2%