School of Computer Science, McGill University, Canada
Department of Physics and Astronomy, University of Victoria, Canada
Department of Radiation Oncology, Harvard Medical School, USA
School of Computer Science, McGill University, Canada
Department of Physics and Astronomy, University of Victoria, Canada
Department of Radiation Oncology, Harvard Medical School, USA
Department of Radiation Oncology, McGill University, Canada
Department of Immunology, Genetics and Pathology, University of Uppsala, Sweden
Department of Radiology, University of British Columbia, Canada
Department of Radiation Oncology, Henry Ford Health System, USA
Laboratori Nazionali del Sud of INFN, Catania, Italy
Department or Radiation Oncology, University of Michigan, USA
Faculty of Engineering and Information Sciences, University of Wollongong, Australia
Senior Director of Science, ViewRay Incorporated, USA
Health, Environment and Energy Department, University Clermont Auvergne, France
Department of Physics, University of Liverpool, UK
Department of Industrial Engineering, Hasselt University, Belgium
Department of Physics and Astrophysics, University of Barcelona, Spain
Department of Physics, Carleton University, Canada
Department of Theoretical Physics, University of Valencia, Spain
Back to homeSee the Featured Speakers at ICCR
MCMA & ICCR Keynote Speaker
Joelle Pineau is an Associate Professor and William Dawson Scholar at McGill University where she co-directs the Reasoning and Learning Lab. She also leads the Facebook AI Research lab in Montreal, Canada. She holds a BASc in Engineering from the University of Waterloo, and an MSc and PhD in Robotics from Carnegie Mellon University.
Dr. Pineau’s research focuses on developing new models and algorithms for planning and learning in complex partially-observable domains. She also works on applying these algorithms to complex problems in robotics, health care, games and conversational agents.
She serves on the editorial board of the Journal of Artificial Intelligence Research and the Journal of Machine Learning Research and is currently President of the International Machine Learning Society. She is a recipient of NSERC’s E.W.R. Steacie Memorial Fellowship (2018), a Fellow of the Association for the Advancement of Artificial Intelligence (AAAI), a Senior Fellow of the Canadian Institute for Advanced Research (CIFAR) and in 2016 was named a member of the College of New Scholars, Artists and Scientists by the Royal Society of Canada.
Machine learning offers a powerful paradigm for automatically discovering and optimizing sequential medical treatments. I this talk I will review some of the most recent advances in AI, including deep learning, reinforcement learning and generative models. I will also examine promising methods to improve treatment planning using AI.
Examples will be drawn from several ongoing research projects on developing new treatment strategies for chronic and life-threatening diseases, including epilepsy and cancer.
MCMA Keynote Speaker
The research of Dr. Bazalova-Carter’s X-ray Cancer Imaging and Therapy Experimental (XCITE) Lab revolves around Monte Carlo simulations and experiments with kilovoltage x-rays. Apart from research in small animal radiotherapy, her lab focuses on investigations of novel x-ray imaging modalities, such as x-ray fluorescence CT and spectral CT, and novel x-ray radiotherapy techniques, such as cost-effective kilovoltage arc therapy.
Dr. Bazalova-Carter has received research funding in the United States and Canada. She is the Chair of the AAPM Working Group on Small animal radiotherapy devices and a Co-Chair of the AAPM Task Group on the Guidelines for accurate dosimetry in radiation biology experiments. Dr. Bazalova-Carter is a member of the AAPM Imaging Physics Committee and of the Board of Associate Editors for Medical Physics. She is the recipient of the 2013 AAPM Jack Fowler Junior Investigator “Award and the 2018 AAPM John S. Laughlin Young Scientist Award. She is a certified Medical Physicist by the American Board of Radiology.
In this talk, the early stages of development of two emerging radiotherapy (RT) techniques will be discussed. First, kilovoltage x-ray beam arc therapy (KVAT) will be introduced and its development from the conception using analytical calculations on phantoms through Monte Carlo (MC) simulations of patient plans to building a prototype machine will be presented. Second, RT delivered with very high-energy electron (VHEE) beams, including MC simulations, their experimental validation and its potential biological benefits will be presented.
KVAT has been proposed as a treatment modality to improve global access to RT. It is meant to be delivered with a low-energy x-ray beam generated by a high output x-ray tube. The proposed design eliminates the use of expensive linac technology and would result in reduces shielding cost. MC simulations of the KVAT system consisting of a 200 kV linear source mounted on a gantry to enable arc treatments were first performed. After initial phantom simulations, lung and partial breast irradiations on patients were simulated with MC and optimized using McGill’s Radify software. The results of these planning studies and their comparisons to current treatments in terms of dose distributions and treatment times will be presented. A simple prototype proof-of-the-principle experiment set up a table-top system and informed by MC simulations will also be demonstrated.
VHEE RT is an intriguing modality with a potential to improve patient outcomes through ultrafast FLASH therapy. Treatment plans for a machine capable of delivery of magnetically steered 60-100 MeV electron pencil beams were calculated with MC and optimized in a research version of RayStation by RaySearch Laboratories. VHEE treatment plans for a number of cases including pediatric brain, H&N, pelvis and lung cases will be compared to state-of-the-art treatments in terms of dose distributions and speed of delivery. Experimental validation of MC dose distributions for a number of VHEE pencil beams will be also presented. The potential of FLASH irradiations with VHEE beams will be discussed and future directions of experimental VHEE FLASH research at TRIUMF will be outlined.
MCMA Keynote Speaker
Dr. Schuemann is an Assistant Professor of Radiation Oncology and the Head of the Multi-scale Monte Carlo Modeling Lab at Massachusetts General Hospital and Harvard Medical School.
Dr. Schuemann’s research revolves around the transport and simulation of radiation for cancer treatment, in particular for proton therapy. Dr. Schuemann is one of the core developers of the TOPAS (Tool for Particle Simulations) simulation framework for clinical Monte Carlo simulations. He further heads the TOPAS-nBio collaboration, an extension to TOPAS to investigate the connection between physics and biology at the cell and sub-cellular scale. Dr. Schuemann’s experimental research focusses on new technologies to advance radiation therapy, e.g. gold nanoparticles and extreme dose rate irradiations (FLASH).
Dr. Schuemann was awarded a German Academic Exchange Service (DAAD) scholarship for his PhD research in particle physics and received the Feodor Lynen fellowship from the Alexander von Humboldt-Foundation and a fellowship from the Japanese Society for the Promotion of Science (JSPS) for his postdoctoral studies. In 2010 Dr. Schuemann joined the team at MGH to work on the TOPAS Monte Carlo system and later the extension to TOPAS-nBio. His work was recognized in 2018 with the Michael J. Fry award by the Radiation Research Society (RRS), and in late 2018, he received the Damon Runyon-Rachleff Innovation Award. In addition, Dr. Schuemann is on the editorial board of Cancer Nanotechnology and on the governing board of the RRS.
Monte Carlo simulations (MCS) are the gold standard for radiation transport calculations. Typically, MCS were a tool accessible only to programming specialists and required hours of computational time to calculate a patient dose distribution for a single field with adequate statistical accuracy. However, over the past decade, MCS have become more widely available to the general medical physics community through developments such as the TOPAS application, a more intuitive interface to the Geant4 general purpose Monte Carlo toolkit. At the same time, specialized GPU-based Monte Carlo systems have been developed that are able to calculate dose distributions in seconds, rivaling the speed of analytical algorithms. Consequently, several vendors now offer MCS within their treatment planning software for proton and photon therapy.
With MCS on the verge of becoming a standard tool in clinical practice, development efforts have shifted from providing accurate dose distributions in patients to investigating new imaging modalities (e.g. prompt-gamma) and understanding radiation therapy at a more fundamental level. The latter relates microscopic energy depositions to a macroscopic biologically observed effect. These simulations can involve simple extrapolations from lineal energy transfer distributions (the microscopic pendant to the macroscopic linear energy transfer) up to complex estimations of outcome, correlating energy depositions on DNA strands to the induction of double strand breaks (DSBs) followed by mechanistic modeling of cell repair that is then integrated over treatment volumes. Currently, such simulations typically still require programming expertise and hours of calculation time.
Here I will discuss current use of Monte Carlo simulations for patient treatment simulations, efforts to simulate the microscopic scale of radiation damage and the potential future translation of these efforts in treatment planning.
MCMA Plenary Speaker
Shirin Abbasinejad Enger is an Assistant Professor in the Gerald Bronfman Department of Oncology, Division of Radiation Oncology and the head of the Novel Patient-Specific Brachytherapy and Detector Technology lab at McGill University. She received her PhD degree from Uppsala University in 2009, and from 2009 to 2011 was a postdoctoral fellow at Université Laval. She joined McGill University in 2014.
Dr. Abbasinejad Enger research involves development of applied technology and addressing current limitations in radiation oncology and imaging. Her research group has developed a novel radiation source and a radiation delivery system, AIM-Brachy, that enables intensity modulated brachytherapy. One of the detectors developed by her group, BetaSense, is currently being tested in several university hospitals and will be used in upcoming clinical trials. In addition, Dr. Abbasinejad Enger and her group have developed a complete Monte Carlo based treatment planning system, RapidBrachyMCTPS that will be released as an opensource code in 2019, as well as a Monte Carlo based simulation package for microdosimetry applications.
Dr. Abbasinejad Enger has several patents and has received competitive funding to develop her innovations from proof of concept to clinical trials. In 2018, her AIM-Brachy project was selected by the European Society for Radiotherapy and Oncology as one of five innovative projects in the research area of brachytherapy. The project was published in the ESTRO conference report “Report on ESTRO 37: Innovation for value and access”. She has received multiple awards from the Uppsala Innovation Center for her outstanding research which has commercial development opportunities in the field of Monte Carlo calculations in medical physics. Dr. Abbasinejad Enger is the recipient of the Moses and Sylvia Greenfield Award for the best paper published in Medical Physics in 2014. She is a member of AAPM/ESTRO/ABG Working Group on Model-Based Dose Calculation Algorithms in Brachytherapy.
ICCR & MCMA Invited Speaker
Issam El Naqa received his BSc (1992) and MSc (1995) in Electrical and Communication Engineering from the University of Jordan, Jordan. He worked as a software engineer at the Computer Engineering Bureau (CEB), Jordan, 1995-1996. He was awarded a DAAD scholarship to Germany, where he was a visiting scholar at the RWTH Aachen, 1996-1998. He completed his PhD (2002) in Electrical and Computer Engineering from Illinois Institute of Technology, Chicago, IL, USA, receiving highest academic distinction award for his PhD work. He completed an MA (2007) in Biology Science from Washington University in St. Louis, St. Louis, MO, USA, where he was pursuing a post-doctoral fellowship in medical physics and was subsequently hired as a Instructor (2005-2007) and then an Assistant Professor (2007-2010) at the departments of radiation oncology and the division of biomedical and biological sciences and was an adjunct faculty at the department of Electrical engineering. He became an Associate Professor at McGill University Health Centre/Medical Physics Unit (2010-2015) and associate member of at the departments of Physics, Biomedical Engineering, and Experimental medicine, where he was a designated scholar.
He is currently an Associate Professor of Radiation Oncology at the University of Michigan at Ann Arbor and associate member in Applied Physics. He is a certified Medical Physicist by the American Board of Radiology.
He is a recognized expert in the fields of image processing, bioinformatics, computational radiobiology, and treatment outcomes modelling and has published extensively in these areas with more than 150 peer-reviewed journal publications and 3 edited textbooks. He has been an acting member of several academic and professional societies. His research has been funded by several federal and private grants and serves as a peer-reviewer and editorial board member for several leading international journals in his areas of expertise.
Radiobiological models play a pivotal role in radiotherapy. These models can help to understand the underlying biology of cancer response to radiation treatment. They can also approximate the treatment environment and be used to develop decision support tools for oncologists that can provide guidance for treatment planning or design of future clinical trials. These models can be divided into top-down approaches (statistical data analytics) and bottom-up approaches, which start from first principles of physics, chemistry, and biology to model cellular damage temporally and spatially up to the observed clinical phenomena. Here, we will provide an overview on how MC methods can be employed to estimate the molecular spectrum of radiation damage in clustered and non-clustered DNA lesions (Gbp-1 Gy-1). We will briefly discuss the temporal and spatial evolution of the effects of ionizing radiation across the three phases (physical, chemical, and biological) and contrast the available MC codes that aim to emulate these phases along the molecular and cellular scales to varying extents. Will highlight future directions and prospects in radiotherapy.
MCMA Invited Speaker
Anders Ahnesjö is professor at the Medical Radiation Sciences program at Uppsala University. He began working in medical physics in the early 80’ies by developing treatment planning system for stereotactic radiation surgery and engaged then in development of 3D treatment planning systems for external therapy with the Helax company. He took a lead in researching dose calculation algorithms, resulting in a PhD 1991 at Karolinska Inst., Stockholm, achieving two Farrington Daniels Awards for his thesis papers. Dr. Ahnesjö continued to work as a research scientist with the treatment planning industry, eventually in combination with positions as adjunct professor at the universities of Umeå and Uppsala until 2012 when he was appointed professor at Uppsala University.
Dr. Ahnesjö has researched dose calculation algorithms and the associated beam modelling and verification framework forming the basis in present treatment planning systems. His current research interest includes multiscale approaches to RBE modelling for particle beams, development of image evidence-based dose painting models for robust TCP maximization, probabilistic planning and patient interplay with scanned beams. Dr. Ahnesjö has authored 70 peer-reviewed papers and supervised 10 PhD thesis. He has served on the AAPM task groups TG-36, TG-106 and TG-155 and long been engaged in the ESTRO school on dose modelling and verification issues.
Accurate calculation of the radiation transport in an irradiated object is a necessity for determination of dosimetric quantities such as dose, fluence, stopping power ratios, etc. For dose calculations in treatment planning systems (TPS) beam modelling is critical for dose accuracy, and is an obligatory step in the commissioning procedures for any dose algorithm, hence not unique for Monte Carlo (MC) simulations. However, since MC can explicitly provide all of the above exemplified dosimetric quantities, it’s beam modelling process might require extra awareness. MC is also a convenient tool to investigate various limitations of approximations in clinical TPS, which can make beam modelling critical.
Beam modelling for MC require explicit generation of full particle phase spaces, while beam modelling for semi-analytical dose calculations in a TPS rely on macroscopic quantities such as fluence and energy spectrum, where (spatial) correlations between the two is often neglected. Certain MC packages provide detailed interfaces for describing the geometry of the treatment head/beam nozzle and are thus able to generate a beam phase space at a beam reference plane downstream of all beam shaping/collimating devices. The beam properties upstream of the beam shaping devices are important for the outcome, but not accessible for MC simulation per se, thus requiring iterative approaches for validation of assumed properties. The common modelling approaches for photon and particle beams will be reviewed and a comparison to clinical TPS modelling approaches made to highlight critical areas. Collimating devices with partial leakage, scattering and generation of secondary particles can be challenging to commonly used approximations in clinical TPS and thus be of interest for more detailed MC analysis. The penumbra regions also yield gradients in dosimetric quantities of importance for detector response calculations.
MCMA Invited Speaker
Anna Celler is a Professor Emeritus in the Department of Radiology at the University of British Columbia (UBC) Vancouver, Canada. She is also the Head of the Medical Imaging Research Group (MIRG) associated with the Vancouver Coastal Health Research Institute, an Adjunct Professor at the Department of Mathematics, Simon Fraser University, and an Associate Member at the Department of Physics and Astronomy, UBC. She has been awarded several research grants (NSERC, CIHR, NRC-ITAP, NIH and others), and has single-handedly created a medical imaging research program that is now into its third decade.
Dr. Celler’s main expertise is in nuclear and medical physics, quantitative and dynamic image reconstruction and analysis, dosimetry for radionuclide therapies, cyclotron production of medical radioisotopes, and the use of sophisticated mathematics for different aspects of imaging. She is the author of more than 350 peer-reviewed articles, abstracts and book chapters and serves on many committees and review boards.
In 2018, Dr. Celler was awarded the 2018 COMP Gold Medal by the Canadian Organization of Medical Physicists in recognition of her contributions to medical physics, her leadership in various medical physics organizations, and her role in guiding the professional and career development of junior medical physicists in Canada. Dr. Celler’s other prestigious awards include the NSERC Brockhouse Canada Prize for Interdisciplinary Research in Science and Engineering (2015) and the World Council on Isotopes President’s Award for TRIUMF-ITAP Consortium (2017).
Monte Carlo (MC) simulations play an important role in nuclear medicine (NM) research, in both single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Simulations are routinely used in the design of new imaging systems, development and validation of image reconstruction algorithms as well as data processing and analysis methods. Further, applications of MC simulations include calculations of internal radiation doses absorbed as a result of diagnostic procedures and, more importantly, in radionuclide therapies. Finally, they are also used in the investigations of cyclotron production of medical radioisotopes. The research program of our Medical Imaging Research Group covers all these areas. In my talk I will discuss all these applications and present examples of MC simulation studies performed by us and others.
MCMA Invited Speaker
Dr. Chetty is Professor and Division Head of Medical Physics in the Department of Radiation Oncology at Henry Ford Hospital, a position in which he has served since 2007. He oversees the operations for a large group of medical physicists (>30) working to provide routine clinical medical physics services, and actively engaged in research development. During his PhD at UCLA, Dr. Chetty specialized in the area Monte Carlo-based dose calculations for lung cancer. When he joined the University of Michigan in 2000, he developed a strong research track record in the area of dose calculations and motion management for patients with lung cancers. In 2005, he was awarded a NIH/NCI R01 grant to investigate correlations of dose with outcome for patients with lung cancers. He served as the Chair of the AAPM Task Group No. 105 on the use of Monte Carlo methods for radiotherapy dose calculations in 2007, and more recently has been actively engaged in the efforts of AAPM Task Group No. 157 on beam modelling for Monte Carlo dose calculations. Dr. Chetty has amassed a significant amount of experience in the area of dose calculations, motion management and image-guided radiation therapy (IGRT) for the treatment of lung cancers. Over the past 10 years his research has focused on the investigation of deformable image registration and dose accumulation for adaptive radiotherapy. He is also involved in research pertaining to quantitative image analysis (in particular, radiomics) as well as the use of artificial and augmented intelligence for various tasks in radiotherapy, such as automated contouring. Dr. Chetty has published over 150 peer-reviewed articles and is Fellow of both AAPM and ASTRO.
The use of Monte Carlo -based dose algorithms has become mainstream in the clinic today. Several major commercially available treatment planning systems incorporate Monte Carlo algorithms for photon and electron transport. New delivery technologies, such as the MRI-linac systems include the use of MC-based dose algorithms for treatment planning. Clinical examples motivating the need for MC-based dose algorithms will be presented for photon and electron beams. This session will include discussion of issues, such as dose reporting methods (dose-to-water or medium), statistical uncertainties and dose denoising. Methods for modeling of the treatment head geometry will be reviewed based on the AAPM Task Group Report No. 157, aimed to provide guidance to clinical physicists on the tasks of acceptance testing and commissioning of MC-based treatment planning systems for photon and electron beam dose calculation. The specific recommendations on methods and practical procedures to clinically accept and commission source models for treatment planning systems employing MC-based dose algorithms will be discussed, along with clinical examples.
MCMA Invited Speaker
Dr. Cirrone Giuseppe Antonio Pablo was born in Catania on August 20, 1974. He received his Master Degree in Nuclear Physics on April 1998 discussing a thesis on the application of the plastic scintillators in medical physics.
In 1998 entered in the Medical Physics school of the Florence University where he get his degree as Qualified Medical Physicist in 2000 discussing a work thesis on the use of the natural and synthetic diamond as dosimetric system for ionizing radiation.
In 2000 he started the PhD course at the Catania University. The PhD work was completely dedicated to the use and application of the Monte Carlo approach in proton and ion therapy. He get his PhD title in 2003 discussing a thesis on the use of the Monte Carlo Geant4 code in hadrontherapy applications.
Dr. Cirrone is expert of the use of proton and ion in radiation treatment and of absolute and relative dosimetry in electron, photon and ion beam. He is expert of the development and test of detectors for medical applications. He is expert of the development and use of Monte Carlo-based techniques for the simulation of problems related to the medical physics and nuclear fields. He is expert in the beamline transport and diagnostic of laser-driven ion beams.
Since 2002 he belongs to the Geant4 Collaboration being responsible for the development and maintenance of an example for the simulation of iontherapy related problems. Since 2006 is member of the Geant4 Steering Board as responsible of the “Advanced Examples” working group and since 2008 is responsible of the validation activity of the Geant4 “Low Energy” working Group.
Since 2007 he is the responsible of the protontherapy beam line and of the interdisciplinary beam-line at the Laboratori Nazionali del Sud of INFN coordinating and supporting various experimental groups.
In 2006 he was local spokeperson of the PRIMA INFN project dedicated to the development and design of a proton computed tomography. In 2010 was local spokesperson of the LILIA INFN project dedicated to the study and detection of proton beams accelerated by high power ladder beams to be used in medical application. Since 2010 is national spokeperson of the MC-INFN project, dedicated to the development of the Geant4 toolkit and Monte Carlo simulation for medical physics.
Since 2012 he is responsible of the ELIMED (ELI-Beamline MEDical applications) project. ELIMED will realize a Users’ transport beamline and associated diagnostic for laser-accelerated beams. The beamline will be installed at ELI-Beamlines (Prague, CZ) whitin the end of 2017.
He is currently the local Coordinator of the multidisciplinary Committee of INFN.
He is President of the Tecnical Board of the COMETA consortium, a National research Institution dedicated to the high perrformance computing and related applications. He belong to the coordination staff of the PhD in Physics of University of Catania as INFN representative
He was a member of the scientific committees and organization of national and international conferences. He presented reports in international conference and national and international workshops. He was a referee of experiments and scientific articles in international journals.
Computer simulations are used in many areas of research and development.
Specifically, Monte Carlo simulations allow the precise simulation of experimental conditions.
A properly benchmarked Monte Carlo system can thus save beam time for experiments or create potential scenarios that are difficult to create experimentally. Computer simulations are particularly important in a field such as radiation therapy where it is important to evaluate the dose to a patient before the irradiation.
In particle therapy, in particular, Monte Carlo simulations are used for different tasks such as the evaluation of the dose delivered to patients, study the physics of proton/ion beams, design the beamlines, design of the treatment heads, quality assurance and finally, many other specific research issues.
In this talk, I will try to illustrate the status of the art in the use of Monte Carlo simulations in particle therapy reporting experiences from different groups around the world.
MCMA Invited Speaker
Susanna Guatelli is Associate Professor at the School of Physics, University of Wollongong, NSW, Australia. She is Theme Leader in “Monte Carlo Simulations” at the Centre for Medical Radiation Physics (CMRP). She has a PhD in physics, awarded in 2006 at the University of Genova, Italy, after a Master in Physics in 2002, awarded in the same University.
Dr. Guatelli has extensive expertise in the use of Geant4 from dosimetry to micro- and nano-dosimetry, performing several studies from the verification of clinical Treatment Planning Systems to the characterization and optimization of silicon microdosimeters in radiation protection and hadron therapy Quality Assurance. She has extensive expertise in the characterization of beamlines used in hadron therapy (BNCT, proton and carbon ion therapy), conventional X-ray radiotherapy and Microbeam Radiation Therapy by means of Geant4. Since 2005 she contributes to the development and validation of Geant4 for medical physics applications, including the Geant4-DNA extensions. In addition, Dr. Guatelli has expertise in the theoretical characterization of the radio-enhancement in X-ray radiotherapy by means of high atomic number nanoparticles. In this respect, in 2017 she was awarded with an Australian Research Council Discovery Project Grant (2017-2019) to develop in Geant4-DNA track structure physics models describing more accurately electron processes in gold nanoparticles.
Since 2018 Dr. Guatelli is Coordinator of the Geant4 Advanced Examples Working Group, Coordinator of the Geant4 Medical Physics Benchmarking Group (G4MSBG) and member of the Geant4 Steering Board. She regularly organizes international Geant4 short courses and Monte Carlo workshops at the UOW, focused on medical physics applications.
Dr. Guatelli has been chair/co-chair of several international workshops and conference sessions dedicated to Monte Carlo codes applied to medical physics. In 2017 she was selected as Australian Chair of the Symposium dedicated to the Australia Japan Emerging Research Leaders Exchange Program, administered by the Australian Academy of Technological Sciences and Engineering (ATSE) and the Engineering Academy of Japan (EAJ).
Dr. Guatelli is Associate Editor of Physica Medica and of Applied Radiation and Isotopes. She is member of the Australian Institute of Physics. In 2016 she was selected as researcher profile showcased in the “Women of Impact” publication of the University of Wollongong.
Microdosimetry is an effective approach to determine the effect of a mixed radiation field at cellular level. Monte Carlo codes, modelling particle interactions with matter, are extensively used in the scientific community to perform in-silico microdosimetric calculations for radiation protection in space and aviation and for hadron therapy Quality Assurance. This talk will show how to use one of these Monte Carlo codes, Geant4, in this domain.
In particular the talk will be focused on the use of Geant4 to support the development of novel Silicon-On-Insulator (SOI) microdosimeters, performed at the Centre for Medical Radiation (CMRP), University of Wollongong, as alternative technology to address the shortcomings of traditional Tissue Equivalent Proportional Counters. It will be shown how the Monte Carlo simulations aided the improvement of the design of the device, in addition to the definition of a methodology to convert microdosimetric measurements in silicon to tissue.
Comparisons of Geant4-based microdosimetric spectra against experimental measurements performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC, Japan), using CMRP devices, quantified the reliability of this Monte Carlo code for microdosimetry. Geant4 was also used successfully to determine the RBE10 in the case of proton and carbon ion therapy, with good agreement with experimental measurements. Finally, guidelines will be provided to start to use Geant4 for microdosimetry.
MCMA Invited Speaker
Iwan Kawrakow is the Senior Director of Science for ViewRay.
He received a PhD in physics from the University of Leipzig in 1994, where he then continued to work as a research assistant until 1996.
Dr. Kawrakow held several roles with the National Research Council of Canada: postdoctoral researcher from 1996 to 1998, Research Officer from 1998 to 2003, and Senior Research Officer from 2003 to 2010. He was the main developer of the widely-used EGSnrc code and his fast Monte Carlo code VMC++ is now the engine in different commercial Monte Carlo treatment planning systems.
He worked as a Senior Key Expert for Siemens RO for a couple years before joining ViewRay in 2012.
The presentation will examine the requirements on a Monte Carlo (MC) based Dose Computation Engine (DCE) for use in Radiation Therapy (RT). The focus will be on RT with external photon beams in the context of (i) Offline treatment plan preparation, (ii) Online plan adaptation before treatment delivery, (iii) Real-time dose accumulation, and (iv) Real-time plan adaptation during treatment delivery. To satisfy the requirements of (i) and (ii), a DCE must provide the ability to a) Compute the dose of a treatment plan, b) Compute the dose for each segment in a treatment plan and c) Compute the dose from discretized fluence elements from the beams involved in the treatment plan on typically static representations of the patient anatomy. To be able to accommodate (iii) and (iv), the DCE must be also capable of performing a-c) on time-dependent and rapidly changing patient anatomies, in addition to being able to quickly pause and resume simulations to allow for the execution of other computationally intensive tasks such as real-time tissue tracking, deformable image registration, dose accumulation, and treatment plan optimization. The merits of parallel implementations on modern multi-core CPU’s and GPU’s will be discussed and specific examples illustrating the respective performance will be presented.
MCMA Invited Speaker
Lydia Maigne is associate professor at University Clermont Auvergne (UCA, http://see.lpc.uca.fr) since 2007. She is a team leader in modelling and simulations in medical physics at Health, Environment and Energy Department of the Physics Laboratory of Clermont (CNRS-IN2P3). She obtained a PhD in particle physics in 2005, she has been qualified as medical physicist in 2007.
Dr. Lydia Maigne has developed an expertise in the fields of e-science through the development of applications and services relevant to imaging and healthcare in grid and cloud environments. Active member in European grid projects (DataGrid, EGEE II and III and EGI), in 2011, she received a grant from the French National Research Agency for the deployment of a distributed infrastructure for epidemiology studies and medical data transfers related to breast and colon cancers.
Involved in the OpenGATE collaboration (www.opengatecollaboration.org) since the beginning of her PhD in 2003; she is participating to the development and validation of multi-scale simulations using the open source GATE platform based on the Geant4 toolkit in the field of radiation therapy physics and imaging. She became a member of the steering committee in 2008 and has been elected as the new spokesperson of the collaboration in 2018. She has been awarded twice in 2009 and 2015, with the other collaboration members, for their two collaboration papers that have received the largest number of citations in the preceding five years in the Physics in Medicine and Biology journal.
She started her research career in validating Geant4 charged particle processes in external radiation therapy and brachytherapy. In 2011 and 2013, she received two grants from the French Cancer Research National Program to improve dosimetry simulations associated to innovative radiopharmaceuticals in internal radiation therapy before studying the potentializing effect of gadolinium nanoparticles for particularly high resistant cancer cells. To that purpose, she got involved with biologists, chemists and computer scientists into the developments of programs to tackle how energy depositions are allocated to biological endpoints (cells, DNA) when using clinical and low-energy radiation beams. To that purpose, her group developed the PDB4DNA (http://pdb4dna.in2p3.fr) and CPOP (http://cpop.in2p3.fr) Geant4 applications that have been used to validate low-energy processes within the Geant4-DNA project (http://geant4-dna.org).
In 2017, she focused on the deployment and validation of biophysical models into the GATE platform for the simulation of the biological dose in ion beam therapy. Through her involvement in an Excellence Laboratory dedicated to Physics, Radiobiology, Medical Imaging and Simulation (https://primes.universite-lyon.fr), her group is collaborating with researchers (IPNL-IN2P3) and clinical partners (MedAustron in Austria, Centre Antoine Lacassagne in France) involved in hadrontherapy.
Lydia Maigne dedicates part of her time in organizing practical tutorials using the GATE platform in the Medical Physics Graduate Program at UCA and international workshops. As new spokesperson of the OpenGATE collaboration, she has made one of her priority to increase the organization of dedicated schools and workshops together with e-learning courses to improve the learning of medical physics through the GATE platform.
Monte Carlo simulations are the researcher’s allies in medical imaging for the optimization of various imaging detectors, the improvement of resolution and detection sensitivity, or the development of new imaging systems such as multi-spectral CT, phase-contrast CT, proton imaging, Compton camera, in vivo range monitoring in ion therapy, etc. In order to propose computationally efficient simulations, researchers are proposing hardware acceleration solutions but also variance reduction techniques as hybrid modeling approaches combining either Monte Carlo and analytical simulations or using advanced machine learning processes such like artificial neural networks (ANN) or Generative Adversarial Networks (GAN). We will illustrate some last advances in the field on Monte Carlo simulations for medical imaging and dosimetry applications with the GATE Monte Carlo simulation platform. We will consider some developments related to theranostic approaches accounting for the simulation of dynamic processes and different resolution scales. We will show how the modelling of light transport in scintillation detectors plays an increasingly important role in detector design, we will illustrate how ANN can be used to model photon tracking in SPECT imaging or how GAN are used to replace phase space files usually produced to collect particles emerging from a voxelised patient geometry to simulate an imaging process. All presented methods are available in the open-source and collaborative GATE platform based on Geant4.
MCMA Invited Speaker
Born in 1949 in Manchester UK. He studied physics at Oxford University and received his PhD at Edinburgh University, on Monte Carlo methods applied to the chemical and ionometric dosimetry of megavoltage electron and photon beams. Dr. Nahum worked as researcher and lecturer on various aspects of radiation dosimetry and on radiobiological modelling and treatment-plan bio-optimization at Umeå University (Sweden), National Research Council of Canada, Ottawa (3-month sabbatical), Institute of Cancer Research (London), Fox-Chase Cancer Center (Philadelphia), Reggio Emilia (Italy), and Clatterbridge Cancer Centre (CCO – near Liverpool). He published around 140 peer-reviewed papers, and co-edited/co-wrote seven books including ‘Handbook of Radiotherapy Physics’ with Philip Mayles and Jean-Claude Rosenwald (Taylor & Francis, 2nd Edition due 2019) and ‘Fundamentals of ionizing Radiation Dosimetry’ (Wiley, 2017) with Pedro Andreo, David Burns and Jan Seuntjens. Dr. Nahum supervised 18 PhD theses; set up and taught professional-level courses on radiotherapy physics (ICR/Royal Marsden) and radiobiology and radiobiological modelling (Clatterbridge). In addition, he created and distributed free radiobiological-modelling software BIOPLAN with Beatriz Sanchez-Nieto and BioSuite with Julian Uzan. He retired in 2015.
In the 1970s condensed-history (CH) Monte-Carlo (MC) codes yielded depth-dependent electron fluence spectra in megavoltage electron beams and thereby water-to-air stopping-power ratios (SPRs) sw,air (Berger et al 1975); Nahum (1978) subsequently extended this to bremsstrahlung (MV) beams, yielding depth-dependent unrestricted (‘Bragg-Gray’) and ‘track-end corrected’ Spencer-Attix (SA) for varying D. Correlation between and TPR20/10 was demonstrated by the MC work of Andreo and Brahme (1986), superseding ‘MV’; Burns et al (1996) showed that R50 performed an equivalent role for electron beams.
Air-kerma based reference-dose determination in kilovoltage x-ray (kV) beams has been significantly advanced by MC-derived Backscatter Factors (BSFs) and water-to-air ratios for the Half-Value Layers (HVLs) and kVps encountered in therapeutic and diagnostic use (Grosswendt 1984; Knight 1996). MCM work by Ma and Nahum (1991) demonstrated that Farmer-type ion chambers do not behave as Bragg-Gray cavities in kV beams.
Nath and Schulz (1981) applied MC to direct computation of the (air) dose in an ion chamber; their counter-intuitive results spurred Bielajew and Rogers (1987) to develop the EGS4/PRESTA code, whereby electron steplengths could be reduced close to region boundaries. MC simulation of (gas-filled) ion chambers was only completely solved when Kawrakow (2000) added ‘event by event’ electron histories to EGSnrc and demonstrated zero perturbation in a medium-filled, gaseous ‘Fano’ cavity. EGSnrc-derived ion-chamber perturbation factors Pwall (Buckley and Rogers 2006) and Peff (Tessier and Kawrakow 2010) revealed the inadequacies of (non-MC) P-values in Codes of Practice.
In ‘small’, sub-equilibrium (megavoltage photon) fields ion chambers no longer behave as Bragg-Gray cavities (IPEM 2010). By replacing the true composition of various detectors by water of the same mass-density the MCM work by Scott et al (2012) revealed that detector-response variation with increasingly small field size (in MV-irradiated water) depended primarily on detector density. This led to MC-guided design of quasi-perturbation-free composite-wall small-field detectors (Underwood et al 2013).
The constancy of the MCM-derived electron-fluence spectrum per unit dose at energies below around 10 keV is consistent with the quasi-constant RBE of all megavoltage beams (Nahum 1999); this suggests that MCM has a role to play in investigating how cellular radiosensitivity varies with radiation quality.
MCMA Invited Speaker
Brigitte Reniers is an Associate Professor in the Nuclear Technology Center in Hasselt University in Belgium since 2016. She obtained her PhD in Medical Physics in 2005 from the Catholic University of Louvain. Her PhD research focused on Monte Carlo studies of dosimetric and microdosimetric properties of low energy photon sources.
Dr. Reniers has been working most of her career both as a researcher and as a clinical medical physicist. Consequently, her research interests cover not only brachytherapy, which has always stayed her main topic, but also research problems that where identified from her clinical tasks such as the evaluation of a Monte Carlo algorithm for electron planning or the dose accumulation from different fractions in brachytherapy. She has authored more than 50 peer-reviewed journal publications and book chapters.
Dr. Reniers is since 2012 in charge of an audit in external beam for VMAT, arc therapy and stereotaxy for Belgium financed by the Belgian Federal Public Service. This audit is based on the use of alanine electron paramagnetic detector and Gafchromic films. Since her appointment in Hasselt University she is also working on experimental microdosimetry.
MCMA Invited Speaker
Francesc Salvat is the leader of the group at the University of Barcelona that develops and maintains the general-purpose electron-photon transport code PENELOPE (an acronym for PENetration and Energy LOss of Positrons and Electrons), which has found a wide variety of applications in radiation metrology, dosimetry, radiotherapy, electron microscopy, x-ray source design, etc. The first version of this program was released in 1996, and since then the group has progressively improved the physics interaction models and the numerical sampling algorithms. Dr. Salvat has specialized in the development of theoretical models for the interactions of radiation with matter, and on the production of reference databases calculated from these models. His group has produced a database for elastic scattering of electrons and positrons (which is distributed as part of the Report 77 of the ICRU, and as the NIST Standard Reference Database 64), a database of cross sections for ionization of atoms by electron and positron impact (distributed as the NIST Standard Reference database 164), as well as other databases that are part of the PENELOPE code system.
After decades of development and practice, the physics interaction models implemented in electron-photon Monte Carlo codes have become quite homogeneous, at least those referring to electromagnetic interactions. I will summarize the theoretical basis of models currently in use for photon, electron/positron, and proton transport simulation, and discuss their limitations and associated uncertainties. For energies lower than about 1 GeV, the tendency is to use either numerical databases of calculated differential cross sections (DCSs) or analytical models with parameters determined empirically. Photon interactions are frequently modeled by using total cross sections from the Evaluated Photon Data Library, which is frequently complemented with approximate angular distributions, electron shell Compton profiles, empirical electron binding energies, etc. Elastic collisions of electrons/positrons with atoms are simulated from DCS calculated by the partial-wave expansion method; in the case of protons and heavier charged particles, partial-wave calculations are unfeasible and the DCS is calculated (to a similar degree of accuracy) by the eikonal approximation, which was first used by Molière in the formulation of his popular multiple-scattering theory. The description of inelastic interactions of charged particles with atoms is the main dissimilarity between the various codes; a consistent simulation scheme requires modeling the response of individual electron shells to account for the correlation between inelastic collisions and x-ray and Auger-electron emission. Unfortunately, several codes still consider mixed schemes that combine the continuous slowing down approximation and the DCS for close collisions with stationary free electrons or, even less reliably, an energy-straggling distribution of Landau’s or Vavilov’s type. The process of bremsstrahlung emission is relevant only for electrons and positrons; it is usually described by means of the extensive tabulations by Seltzer and Berger. With the most elaborate databases available, simulations of photons, electrons, and positrons are expected to meet essentially all practical needs for energies higher than about 1 keV; proton simulations are expected to be reliable for energies higher than about 1 MeV.
MCMA Invited Speaker
Rowan Thomson is an Associate Professor and Canada Research Chair in the Department of Physics at Carleton University. She holds a BSc Double Honours Mathematics and Physics from Carleton University (2003). Her PhD research was in theoretical high-energy physics (Superstring Theory) at Perimeter Institute and the University of Waterloo, and was awarded Waterloo’s Pearson Medal (2007). Post-PhD, Dr. Thomson’s research has focused on computational radiotherapy physics; she became a faculty member at Carleton in 2010.
Dr. Thomson’s research involves the development and application of computational techniques to study the interactions of radiation with matter. She is a leader in the development and application of advanced Monte Carlo dose calculation algorithms for brachytherapy, most recently developing and releasing egs_brachy as open-source code. In complement, she is very active in developing multi-scale simulation techniques, from patients to cells to subcellular length scales, and applying these to investigate novel treatment approaches and understand measurements of cellular radiation response.
Dr. Thomson has been recognized through awards including: Polanyi Prize for Physics (2011), Canada Research Chair (2013), and Ontario Early Researcher Award (2015). She is a member of the AAPM’s Therapy Physics Committee and of the Board of Associate Editors for Medical Physics. She is co-chair of AAPM TG-221 Ocular Brachytherapy and a member of other task and working groups including AAPM TG-129, joint AAPM/ESTRO/ABG TG-186 and its successor the Working Group on Model-Based Dose Calculation Algorithms in Brachytherapy.
Monte Carlo (MC) simulations are ubiquitous in medical applications for modelling radiation transport and energy deposition across length scales from patients to subcellular structures to nanodevices. With growing interest in, e.g., radiation response on subcellular length scales and developing new treatments targeting cellular structures, the range of applicability of multi-purpose MC codes is being pushed to lower energies and shorter length scales. However, these developments present challenges as the transport of electrons is generally treated ~classically with radiation quanta modelled as point-like objects undergoing sequences of free-flight interrupted by discrete interaction sites. With the electron’s wavelength increasing with its decreasing kinetic energy, coupled with the nanometre-size of biological targets of interest, the applicability of the classical trajectory MC approach becomes questionable. This presentation will focus on departures from traditional trajectory MC simulations of electron transport. We will consider the validity of trajectory MC simulations of electron transport in the context of quantum theory, and, on the basis of general arguments, describe the potential for quantum effects to emerge at sub-1 keV kinetic energies. As a full quantum theoretic treatment of electron transport in condensed (biological) media is too complex to be feasible at present, calculations within a simplified model consisting of a plane wave electron incident on a cluster of point scatterers representing a water droplet will be presented. Within this model, quantum mechanical (QM) calculations will be contrasted with the corresponding trajectory MC results, considering varying water molecule (scatterer) elastic/inelastic cross sections, droplet structure (minimum separation between molecules in the droplet constrained by some threshold or random arrangement), as well as droplet size and shape. Differences between QM and MC results are generally larger when inelastic scatter and/or medium structure are included in simulations. Across the parameter space, relative errors on MC results are typically only sub-1% once electron energy exceeds 1 keV, and hence convergence of classical MC with QM calculations only occurs near 1 keV. Ongoing research to develop more realistic models of low-energy electron transport in condensed media will be described.
MCMA Invited Speaker
Javier Vijande is a professor at the Molecular, Nuclear, and Atomic Physics department of the University of Valencia, Spain. He holds a PhD in physics from the University of Salamanca where he was an Assistant Professor before moving to Valencia to occupy a researcher position in the Theoretical Physics department.
His research focus has always been linked to computation-intensive calculation techniques. In the beginning of his scientific career he worked in developing numerical methods to approach the few- and many-body problems in hadronic physics. Nowadays, his main research interests are Monte Carlo simulations in the field of medical physics and its clinical applications.
Professor Vijande serve as a member of the American Association of Physicist in Medicine (AAPM) Brachytherapy Subcommittee and Brachytherapy Source Registry Work Group, and as Chair of the Working Group on Model-Based Dose Calculation Algorithms in Brachytherapy.
The evaluation of the absorbed dose deposited on a patient following a pre-ordained clinical plan has undergone a renaissance during the last decade. The combined role played by increasingly powerful computational architectures together with new refined algorithms allows the clinical user to reach an accuracy only dreamed of during the last decades. Among the different radiation modalities, it is brachytherapy the one that has evolved more drastically in the last few years.
Monte Carlo (MC) calculations, an advance dose calculation algorithm itself, have been used since 1994 for the evaluation of absorbed dose in clinical brachytherapy by means of the TG-43 formalism. Such formalism makes use of state-of-the-art MC simulations to obtain the absorbed dose deposited by the brachytherapy sources. However, in order to be used in clinical practice, such dose kernels are pre-obtained assuming that the patient is made of water and immersed in an infinite volume of water. Therefore, effects like interseed attenuation, tissue heterogeneities, patient geometry or applicator materials are not explicitly considered when creating a clinical plan. This implies that the role played by MC simulations until few years ago was restricted to the development and validation of new source models and applicator designs.
Fortunately, in the last years, new Model Based Dose Calculation Algorithms (MBDCAs) have been developed. In 2012, AAPM, ESTRO, ABS, and ABG released a report, TG-186, to provide guidance for early adopters of MBDCAs for brachytherapy, and to ensure clinical practice uniformity. TG186 goes one-step further, defining MC as the gold standard to which any new dose calculation algorithms should be compared and commissioned. Therefore, any MBDCA algorithm has to be verified against state-of-the-art MC calculations to ensure: i) that it reproduces correctly the “true” absorbed dose as described by MC, ii) to evaluate possible discrepancies due to the unavoidable numerical approximations required, and iii) to guide the clinical user when moving away from the current TG-43 clinical planning.
In this lecture, we will describe the new MBDCAs commercially available in clinical practice, describing their main properties and focusing on the role that MC simulations play in their commissioning.