- Email: [email protected]
Educational accreditation in medical physics: is it important?
Abstracts / Physica Medica 30 (2014) e1ee15
e7
requirements of the above Directives are met for automatic professional recognition. The purpose of this presentation is to give a brief account of the efforts made by EFOMP and the requirements that need to be met, at the national level, in order for both the CQMPs and MPEs can be automatically recognised by the European Union. References [1] Directive 2005/36/EC of the European Parliament and of the Council of 7 September 2005 on the recognition of professional qualifications, OJ L255, 30.9.2005, pp 22-142. [2] Directive 2013/55/EU of the European Parliament and of the Council of 20 November 2013 amending Directive 2005/36/EC on the recognition of professional qualifications and Regulation (EU) No 1024/2012 on administrative cooperation through the Internal Market Information System (‘the IMI Regulation’), OJ L354, 28.12.2013, pp 132-170. [3] Council Directive 2013/59/Euratom of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom, OJ L13, 17.1.2014, pp. 1-73. [4] European Commission, Radiation Protection Report 174, “Guidelines on Medical Physics Expert”, Directorate-General Energy, Luxembourg, 2014, available from: http://ec.europa.eu/energy/nuclear/radiation_protection/ doc/publication/174.pdf (last accessed on the 11th of May 2014).
continuous and fast, increasing the demand for high level scientists and experts in the field. To ensure that ionizing radiation is safely used, the presence of the medical physicist is essential. The medical physicist has therefore become part of an indispensable “core team” within the hospital to ensure safe and proficient use of medical equipment. His presence is growing also within the industry and/or regulatory authority environment. In order to meet all these demands, sufficient education and training is indispensable. Collaboration and innovation in this field is imperative for the appropriate professional response to all these challenges. The European Commission has for a number of years recognized the need for adequate theoretical and practical training of medical physicists for the purpose of radiological practices. This is clearly stated in a number of European directives as well as in the latest European Basic Safety Standards. A number of questions arise based on all these facts. Do we have sufficient number of adequately trained medical physicists or medical physics experts to address the needs of the increasing number of medical procedures in Europe? Is the education and training of such scientists harmonized across Europe, that will facilitate in easier and mutual recognition as well as improved cross-border mobility of medical physicists? The present paper will attempt to answer these questions using the most recent information within Europe.
THE CURRENT STATUS OF MEDICAL PHYSICS RECOGNITION IN THE MIDDLE EAST
Lama Sakhnini. Department of Physics, College of Science, University of Bahrain, Sakhir, PO. Box 32038, Kingdom of Bahrain
Ibrahim Duhaini. Chief Medical Physicist & RSO, Rafik Hariri University Hospital, Beirut - Lebanon & President of the Middle East Federation of Organizations of Medical Physicists (MEFOMP), Lebanon
Education: The Department of Physics at University of Bahrain offers a B.Sc. in medical physics program. The program produces B.Sc. degree graduates with a broad knowledge of fundamental and applied physics. With a specialization in medical physics, the graduates will be eligible for employment in hospitals, clinics, environmental establishments or industrial health care centers. Students should also be suitably prepared to carry out research in medical physics leading to a higher degree. The B.Sc. in Medical Physics degrees gives the opportunity to study the many medical applications of advanced physics. Medical physics courses, taught by staff of the department of Physics, are supplemented by specialist lectures given by senior practicing medical physicists and doctors from Salmaniya medical complex and Bahrain Defense force hospital. The B.Sc. programs in Medical Physics shares many common courses with the B.Sc. program in Physics, but nearly 48 credit hours include courses which are specific to Medical Physics program. A total of 42 female students graduated from the program so far, only 3 students managed to get jobs in the medical sector. Training: The B.Sc. in Medical Physics program ensures that the students go through clinical training at hospitals in the Kingdom of Bahrain or in the Kingdom of Saudi Arabia. In an ideal situation; the student spends a minimum of 2 months of hospital training to complete a clinical rotation in radiation therapy, diagnostic imaging and nuclear medicine. The student observes and practices clinical procedures under the direct supervision of a senior clinical medical physicist. The student is required to write a progress report on the clinical procedures. However there is no well designed training program in the hospitals. Hence there is a disparate need for a “Residency Program” which is aimed at both educating and providing practical experience so that the medical physicist would be ready to practice in a hospital setting and obtain board certification. Training for our students faced many challenges, as most hospitals do not have medical physicists, most hospital administrators do not know the rule of medical physicists, many hospitals have no quality management program and rely on the medical supplier of their equipment to do yearly maintenance.
Medical physics is the branch of physics concerned with the application of physics to medicine, particularly in the diagnosis and treatment of human diseases. From the time when Wilhelm Roentgen and other physicists made the discoveries which led to the development of Diagnostic Radiology, Radiotherapy, Brachytherapy and Nuclear Medicine, Medical Physicists have played a pivotal role in the development of new technologies that have revolutionized the way medicine is practiced. In today's health care scene, the medical physicist is essential to the safe and cost effective operation of any creditable medical institution. Medical Physics in the Middle East Region has passed in different stages. In particular the ISEP Conference held in Bahrain in November 2007 and the 16 th ICMP Conference held in Dubai in 2008. During these conferences, there were several meetings for all the medical physics societies in the Middle East. The result was the establishment in September 2009 of the Middle East Federation of Organizations in Medical Physics (MEFOMP) which is part of the International Organization of Medical Physics IOMP. The following countries have signed up for this chapter: Bahrain, Iran, Iraq, Jordan, KSA, Lebanon, Oman, Qatar, Syria, UAE and Yemen. Ever since then, the medical physics profession has gone the first mile in the road of recognition in most of the ME countries. Governmental entities and University bodies started looking deeply into the need of promoting MP activities across the region. Now, Medical physicists in the ME region are considered scientists who through science are able to identify problems and unveil deficiencies. It is also through science that they solve the problems and correct the deficiencies encountered in the diagnosis and treatment of diseases. There will be exciting and difficult challenges not only in the field of health care but also in the race for nuclear power in the ME region. Countries will be counting on the science of Medical Physics to help meet these challenges. Keywords: IOMP, MEFOMP, Middle East, Medical Physics, Recognition. EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN EUROPE V. Tsapaki. Konstantopoulio General Hospital, Athens, Greece Background: Medical exposure represents the utmost and fastest growing contribution to manmade radiation exposure not only in Europe but also across the world. Furthermore, the evolution of medical equipment is
EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN MIDDLE EAST KINGDOM OF BAHRAIN AS AN EXAMPLE
EDUCATIONAL IMPORTANT?
ACCREDITATION
IN
MEDICAL
PHYSICS:
IS
IT
John Damilakis. Professor of Medical Physics, Greece An increasing number of higher education institutions have in recent years started to offer courses on Medical Physics. Moreover, Continuing Professional Development (CPD) for medical physicists is of great professional interest. CPD courses is an excellent way to ensure that Medical Physicists
e8
Abstracts / Physica Medica 30 (2014) e1ee15
become knowledgeable about all current issues in their field and to provide the necessary knowledge, skills and competences for certified Medical Physicists to become Medical Physics Experts. However, external assessment of the quality of education or training provision is needed. Accreditation is the formal recognition that education and training on medical physics provided by an institution meets acceptable levels of quality. Accreditation should be based upon standards and guidelines. Requirements for accreditation of a training programme should take into account several aspects including facilities, staff, educational material and teaching methods. In Europe, ENQA (European Network for Quality Assurance) promotes European co-operation in the field of Quality Assurance in higher education. ENQA members are national agencies and organizations, which play a major role in the accreditation process. A European organization is needed to offer accreditation of medical physics CPD and training programs. Certification is the recognition of knowledge of a professional who has completed his/her education or training. The EC has developed tools and frameworks to promote training and facilitate mobility. ECVET is a European system of accumulation and transfer of credits designed for vocational education and training in Europe. IMAGE-GUIDED RADIATION THERAPY IN THE PRECLINICAL SETTING Ross Berbeco PhD. Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, USA Current clinical radiation therapy is delivered with multiple collimated beams and accurate radiation dose calculation based on CT imaging. Additional advances in image-guided delivery techniques have saturated a majority of modern clinics. Therefore, modern translational research of radiation biology and radiation physics using in vivo models of cancer requires a preclinical therapy platform that has the same capabilities as modern clinical linear accelerators. In 2010, we established a preclinical radiation biophysics laboratory at the Dana-Farber Cancer Institute and Harvard Medical School (Boston, MA USA). The cornerstone of this facility is a Small Animal Radiation Research Platform (SARRP) which was developed by researchers at Johns Hopkins University (Baltimore, MD USA) and commercialized by Xtrahl, Inc. (Surrey, UK). The SARRP combines a conventional x-ray tube with brass collimators to enable delivery of photon beams as narrow as 0.5 mm at 220 kVp. Precise (sub-mm) image-guided setup is performed using cone-beam CT imaging combined with a robotic motion stage. Absolute dose output is measured with an ADCL-traceable ion chamber. Percentage depth-dose and beam profiles are measured for each collimator with EBT3 film. Monte Carlo modeling of the SARRP is performed using EGSnrc. The phase space files are used in a GPU-driven 3D dose calculation engine with the 3D Slicer platform for visualization (Brigham and Women’s Hospital Surgical Planning Laboratory, Boston, MA USA). Collimator size, gantry and collimator angles, and target prescription are given and a 3D isodose distribution is calculated. Measurements in heterogeneous media have validated the dose calculation accuracy. Routine quality assurance procedures have been developed, based on those employed for clinical radiation devices. The laboratory has facilities for animal surgery, housing, anesthesia and injection. Our SARRP has been outfitted with a tube for continuous isoflurane delivery during imaging and therapy procedures. To date, more than 1,000 preclinical procedures on live animals have been performed in the laboratory. Examples of current translational research applications include genetic dependence of radiation resistance, chemical radiation sensitizers, metabolic modifiers of radiation therapy efficacy, metallic nanoparticles for enhanced radiation therapy and imaging contrast, and dermatologic studies. We anticipate that by utilizing a research instrument that provides accurate and precise radiation delivery, the results will have high translational relevance. Funding for these projects has come from the United States Department of Defense, the National Institutes of Health, philanthropic foundations and internal sources. THE GEANT4-DNA PROJECT: OVERVIEW AND STATUS bastien Incerti. CNRS, Bordeaux University, France Se On behalf of the Geant4-DNA collaboration
Understanding and prediction of adverse effects of ionizing radiation at the cellular and sub-cellular scale remains a challenge of today’s radiobiology research. In this context, a large experimental and modeling activity is currently taking place, aimed at better understanding the biological effects of ionizing radiation at the sub-cellular scale. The “Geant4-DNA” project was initiated by the European Space Agency [1]. It aims to develop an experimentally validated simulation platform for the modeling of early DNA damage induced by ionizing radiation, using modern computing tools and techniques. The platform is based on the general-purpose and opensource “Geant4” Monte Carlo simulation toolkit, and benefits from the toolkit’s full transparency and free availability [2]. This project proposes to develop specific functionalities in Geant4 allowing: 1) The modeling of elementary physical interactions between ionizing particles and biological media, during the so-called “physical” stage. 2) The modeling of the “physico-chemical and chemical” stages corresponding to the production, the diffusion and the chemical reactions occurring between chemical species. During the “physico-chemical” stage, the water molecules that have been excited and ionized during the physics stage may de-excite and dissociate into initial water radiolysis products. In the “chemical stage”, these chemical species diffuse in the medium surrounding the DNA. They may eventually react among themselves or with the DNA molecule. 3) The introduction of detailed biological target geometry models, where the two above stages are combined with a geometrical description of biological targets (such as chromatin segments, cell nuclei…). The Geant4DNA physics processes and models are fully integrated into the Geant4 toolkit and can be combined with Geant4 geometry modeling capabilities. In particular, it becomes possible to implement the geometry of biological targets with a high resolution at the sub-micrometer scale and fully track particles within these geometries using the Geant4-DNA physics processes. These geometries represent a significant improvement of the geometrical models used so far for dosimetry studies with the Geant4 toolkit at the biological cell scale. The current status of the project will be presented, as well as on-going developments. [1] S. Incerti et al., “Comparison of Geant4 very low energy cross section models with experimental data in water“ , Med. Phys. 37, 4692-4708 (2010) [2] S. Agostinelli et al., “Geant4-a simulation toolkit”, Nucl. Instrum. Methods. Phys. Res. A. 506, 250-303 (2003) FIELD-CYCLING MRI: A NEW IMAGING MODALITY? David J. Lurie, Lionel M. Broche, Gareth R. Davies, Nicholas Payne, Kerrin J. Pine, P. James Ross, Vasileios Zampetoulas. Aberdeen Biomedical Imaging Centre, University of Aberdeen, AB25 2ZD, Scotland, UK Much of the contrast in conventional MRI arises from differences in the NMR relaxation times, especially the spin-lattice relaxation time, T-1. It is also well known, from in vitro measurements on small tissue samples, that the variation of T1 with the strength of the applied magnetic field B0 (known as T-1-dispersion) is tissue-dependent, and that the shape of a tissue’s T-1-dispersion curve is altered in disease. However, T-1-dispersion is invisible to conventional MRI scanners, because each scanner can only operate at its own native magnetic field (e.g. 1.5 T, 3.0 T). The aim of our work is to exploit T-1-dispersion as a new MRI contrast mechanism, by building new types of MRI scanner which make use of Fast Field-Cycling (FFC) [1]. In FFC, the applied magnetic field is switched rapidly, while the sample (or patient) is inside the scanner. Thus, the nuclear magnetisation can be made to evolve at a range of magnetic field strengths, allowing the measurement of T-1-dispersion. The magnetic field is always switched to the same value prior to measurement of the NMR signals, so that the instrument’s radiofrequency system does not require retuning during the procedure. In our laboratory we have built two whole-body human sized FFC-MRI scanners, one of which makes use of a dual magnet in order to achieve field switching [1,2]. The detection field of 59 mT is provided by a vertical-field, permanent magnet. Inside its bore is located a resistive magnet which generates an opposing magnetic field; field-cycling is achieved by switching the current in the resistive magnet coil.
e7
requirements of the above Directives are met for automatic professional recognition. The purpose of this presentation is to give a brief account of the efforts made by EFOMP and the requirements that need to be met, at the national level, in order for both the CQMPs and MPEs can be automatically recognised by the European Union. References [1] Directive 2005/36/EC of the European Parliament and of the Council of 7 September 2005 on the recognition of professional qualifications, OJ L255, 30.9.2005, pp 22-142. [2] Directive 2013/55/EU of the European Parliament and of the Council of 20 November 2013 amending Directive 2005/36/EC on the recognition of professional qualifications and Regulation (EU) No 1024/2012 on administrative cooperation through the Internal Market Information System (‘the IMI Regulation’), OJ L354, 28.12.2013, pp 132-170. [3] Council Directive 2013/59/Euratom of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom, OJ L13, 17.1.2014, pp. 1-73. [4] European Commission, Radiation Protection Report 174, “Guidelines on Medical Physics Expert”, Directorate-General Energy, Luxembourg, 2014, available from: http://ec.europa.eu/energy/nuclear/radiation_protection/ doc/publication/174.pdf (last accessed on the 11th of May 2014).
continuous and fast, increasing the demand for high level scientists and experts in the field. To ensure that ionizing radiation is safely used, the presence of the medical physicist is essential. The medical physicist has therefore become part of an indispensable “core team” within the hospital to ensure safe and proficient use of medical equipment. His presence is growing also within the industry and/or regulatory authority environment. In order to meet all these demands, sufficient education and training is indispensable. Collaboration and innovation in this field is imperative for the appropriate professional response to all these challenges. The European Commission has for a number of years recognized the need for adequate theoretical and practical training of medical physicists for the purpose of radiological practices. This is clearly stated in a number of European directives as well as in the latest European Basic Safety Standards. A number of questions arise based on all these facts. Do we have sufficient number of adequately trained medical physicists or medical physics experts to address the needs of the increasing number of medical procedures in Europe? Is the education and training of such scientists harmonized across Europe, that will facilitate in easier and mutual recognition as well as improved cross-border mobility of medical physicists? The present paper will attempt to answer these questions using the most recent information within Europe.
THE CURRENT STATUS OF MEDICAL PHYSICS RECOGNITION IN THE MIDDLE EAST
Lama Sakhnini. Department of Physics, College of Science, University of Bahrain, Sakhir, PO. Box 32038, Kingdom of Bahrain
Ibrahim Duhaini. Chief Medical Physicist & RSO, Rafik Hariri University Hospital, Beirut - Lebanon & President of the Middle East Federation of Organizations of Medical Physicists (MEFOMP), Lebanon
Education: The Department of Physics at University of Bahrain offers a B.Sc. in medical physics program. The program produces B.Sc. degree graduates with a broad knowledge of fundamental and applied physics. With a specialization in medical physics, the graduates will be eligible for employment in hospitals, clinics, environmental establishments or industrial health care centers. Students should also be suitably prepared to carry out research in medical physics leading to a higher degree. The B.Sc. in Medical Physics degrees gives the opportunity to study the many medical applications of advanced physics. Medical physics courses, taught by staff of the department of Physics, are supplemented by specialist lectures given by senior practicing medical physicists and doctors from Salmaniya medical complex and Bahrain Defense force hospital. The B.Sc. programs in Medical Physics shares many common courses with the B.Sc. program in Physics, but nearly 48 credit hours include courses which are specific to Medical Physics program. A total of 42 female students graduated from the program so far, only 3 students managed to get jobs in the medical sector. Training: The B.Sc. in Medical Physics program ensures that the students go through clinical training at hospitals in the Kingdom of Bahrain or in the Kingdom of Saudi Arabia. In an ideal situation; the student spends a minimum of 2 months of hospital training to complete a clinical rotation in radiation therapy, diagnostic imaging and nuclear medicine. The student observes and practices clinical procedures under the direct supervision of a senior clinical medical physicist. The student is required to write a progress report on the clinical procedures. However there is no well designed training program in the hospitals. Hence there is a disparate need for a “Residency Program” which is aimed at both educating and providing practical experience so that the medical physicist would be ready to practice in a hospital setting and obtain board certification. Training for our students faced many challenges, as most hospitals do not have medical physicists, most hospital administrators do not know the rule of medical physicists, many hospitals have no quality management program and rely on the medical supplier of their equipment to do yearly maintenance.
Medical physics is the branch of physics concerned with the application of physics to medicine, particularly in the diagnosis and treatment of human diseases. From the time when Wilhelm Roentgen and other physicists made the discoveries which led to the development of Diagnostic Radiology, Radiotherapy, Brachytherapy and Nuclear Medicine, Medical Physicists have played a pivotal role in the development of new technologies that have revolutionized the way medicine is practiced. In today's health care scene, the medical physicist is essential to the safe and cost effective operation of any creditable medical institution. Medical Physics in the Middle East Region has passed in different stages. In particular the ISEP Conference held in Bahrain in November 2007 and the 16 th ICMP Conference held in Dubai in 2008. During these conferences, there were several meetings for all the medical physics societies in the Middle East. The result was the establishment in September 2009 of the Middle East Federation of Organizations in Medical Physics (MEFOMP) which is part of the International Organization of Medical Physics IOMP. The following countries have signed up for this chapter: Bahrain, Iran, Iraq, Jordan, KSA, Lebanon, Oman, Qatar, Syria, UAE and Yemen. Ever since then, the medical physics profession has gone the first mile in the road of recognition in most of the ME countries. Governmental entities and University bodies started looking deeply into the need of promoting MP activities across the region. Now, Medical physicists in the ME region are considered scientists who through science are able to identify problems and unveil deficiencies. It is also through science that they solve the problems and correct the deficiencies encountered in the diagnosis and treatment of diseases. There will be exciting and difficult challenges not only in the field of health care but also in the race for nuclear power in the ME region. Countries will be counting on the science of Medical Physics to help meet these challenges. Keywords: IOMP, MEFOMP, Middle East, Medical Physics, Recognition. EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN EUROPE V. Tsapaki. Konstantopoulio General Hospital, Athens, Greece Background: Medical exposure represents the utmost and fastest growing contribution to manmade radiation exposure not only in Europe but also across the world. Furthermore, the evolution of medical equipment is
EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN MIDDLE EAST KINGDOM OF BAHRAIN AS AN EXAMPLE
EDUCATIONAL IMPORTANT?
ACCREDITATION
IN
MEDICAL
PHYSICS:
IS
IT
John Damilakis. Professor of Medical Physics, Greece An increasing number of higher education institutions have in recent years started to offer courses on Medical Physics. Moreover, Continuing Professional Development (CPD) for medical physicists is of great professional interest. CPD courses is an excellent way to ensure that Medical Physicists
e8
Abstracts / Physica Medica 30 (2014) e1ee15
become knowledgeable about all current issues in their field and to provide the necessary knowledge, skills and competences for certified Medical Physicists to become Medical Physics Experts. However, external assessment of the quality of education or training provision is needed. Accreditation is the formal recognition that education and training on medical physics provided by an institution meets acceptable levels of quality. Accreditation should be based upon standards and guidelines. Requirements for accreditation of a training programme should take into account several aspects including facilities, staff, educational material and teaching methods. In Europe, ENQA (European Network for Quality Assurance) promotes European co-operation in the field of Quality Assurance in higher education. ENQA members are national agencies and organizations, which play a major role in the accreditation process. A European organization is needed to offer accreditation of medical physics CPD and training programs. Certification is the recognition of knowledge of a professional who has completed his/her education or training. The EC has developed tools and frameworks to promote training and facilitate mobility. ECVET is a European system of accumulation and transfer of credits designed for vocational education and training in Europe. IMAGE-GUIDED RADIATION THERAPY IN THE PRECLINICAL SETTING Ross Berbeco PhD. Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, USA Current clinical radiation therapy is delivered with multiple collimated beams and accurate radiation dose calculation based on CT imaging. Additional advances in image-guided delivery techniques have saturated a majority of modern clinics. Therefore, modern translational research of radiation biology and radiation physics using in vivo models of cancer requires a preclinical therapy platform that has the same capabilities as modern clinical linear accelerators. In 2010, we established a preclinical radiation biophysics laboratory at the Dana-Farber Cancer Institute and Harvard Medical School (Boston, MA USA). The cornerstone of this facility is a Small Animal Radiation Research Platform (SARRP) which was developed by researchers at Johns Hopkins University (Baltimore, MD USA) and commercialized by Xtrahl, Inc. (Surrey, UK). The SARRP combines a conventional x-ray tube with brass collimators to enable delivery of photon beams as narrow as 0.5 mm at 220 kVp. Precise (sub-mm) image-guided setup is performed using cone-beam CT imaging combined with a robotic motion stage. Absolute dose output is measured with an ADCL-traceable ion chamber. Percentage depth-dose and beam profiles are measured for each collimator with EBT3 film. Monte Carlo modeling of the SARRP is performed using EGSnrc. The phase space files are used in a GPU-driven 3D dose calculation engine with the 3D Slicer platform for visualization (Brigham and Women’s Hospital Surgical Planning Laboratory, Boston, MA USA). Collimator size, gantry and collimator angles, and target prescription are given and a 3D isodose distribution is calculated. Measurements in heterogeneous media have validated the dose calculation accuracy. Routine quality assurance procedures have been developed, based on those employed for clinical radiation devices. The laboratory has facilities for animal surgery, housing, anesthesia and injection. Our SARRP has been outfitted with a tube for continuous isoflurane delivery during imaging and therapy procedures. To date, more than 1,000 preclinical procedures on live animals have been performed in the laboratory. Examples of current translational research applications include genetic dependence of radiation resistance, chemical radiation sensitizers, metabolic modifiers of radiation therapy efficacy, metallic nanoparticles for enhanced radiation therapy and imaging contrast, and dermatologic studies. We anticipate that by utilizing a research instrument that provides accurate and precise radiation delivery, the results will have high translational relevance. Funding for these projects has come from the United States Department of Defense, the National Institutes of Health, philanthropic foundations and internal sources. THE GEANT4-DNA PROJECT: OVERVIEW AND STATUS bastien Incerti. CNRS, Bordeaux University, France Se On behalf of the Geant4-DNA collaboration
Understanding and prediction of adverse effects of ionizing radiation at the cellular and sub-cellular scale remains a challenge of today’s radiobiology research. In this context, a large experimental and modeling activity is currently taking place, aimed at better understanding the biological effects of ionizing radiation at the sub-cellular scale. The “Geant4-DNA” project was initiated by the European Space Agency [1]. It aims to develop an experimentally validated simulation platform for the modeling of early DNA damage induced by ionizing radiation, using modern computing tools and techniques. The platform is based on the general-purpose and opensource “Geant4” Monte Carlo simulation toolkit, and benefits from the toolkit’s full transparency and free availability [2]. This project proposes to develop specific functionalities in Geant4 allowing: 1) The modeling of elementary physical interactions between ionizing particles and biological media, during the so-called “physical” stage. 2) The modeling of the “physico-chemical and chemical” stages corresponding to the production, the diffusion and the chemical reactions occurring between chemical species. During the “physico-chemical” stage, the water molecules that have been excited and ionized during the physics stage may de-excite and dissociate into initial water radiolysis products. In the “chemical stage”, these chemical species diffuse in the medium surrounding the DNA. They may eventually react among themselves or with the DNA molecule. 3) The introduction of detailed biological target geometry models, where the two above stages are combined with a geometrical description of biological targets (such as chromatin segments, cell nuclei…). The Geant4DNA physics processes and models are fully integrated into the Geant4 toolkit and can be combined with Geant4 geometry modeling capabilities. In particular, it becomes possible to implement the geometry of biological targets with a high resolution at the sub-micrometer scale and fully track particles within these geometries using the Geant4-DNA physics processes. These geometries represent a significant improvement of the geometrical models used so far for dosimetry studies with the Geant4 toolkit at the biological cell scale. The current status of the project will be presented, as well as on-going developments. [1] S. Incerti et al., “Comparison of Geant4 very low energy cross section models with experimental data in water“ , Med. Phys. 37, 4692-4708 (2010) [2] S. Agostinelli et al., “Geant4-a simulation toolkit”, Nucl. Instrum. Methods. Phys. Res. A. 506, 250-303 (2003) FIELD-CYCLING MRI: A NEW IMAGING MODALITY? David J. Lurie, Lionel M. Broche, Gareth R. Davies, Nicholas Payne, Kerrin J. Pine, P. James Ross, Vasileios Zampetoulas. Aberdeen Biomedical Imaging Centre, University of Aberdeen, AB25 2ZD, Scotland, UK Much of the contrast in conventional MRI arises from differences in the NMR relaxation times, especially the spin-lattice relaxation time, T-1. It is also well known, from in vitro measurements on small tissue samples, that the variation of T1 with the strength of the applied magnetic field B0 (known as T-1-dispersion) is tissue-dependent, and that the shape of a tissue’s T-1-dispersion curve is altered in disease. However, T-1-dispersion is invisible to conventional MRI scanners, because each scanner can only operate at its own native magnetic field (e.g. 1.5 T, 3.0 T). The aim of our work is to exploit T-1-dispersion as a new MRI contrast mechanism, by building new types of MRI scanner which make use of Fast Field-Cycling (FFC) [1]. In FFC, the applied magnetic field is switched rapidly, while the sample (or patient) is inside the scanner. Thus, the nuclear magnetisation can be made to evolve at a range of magnetic field strengths, allowing the measurement of T-1-dispersion. The magnetic field is always switched to the same value prior to measurement of the NMR signals, so that the instrument’s radiofrequency system does not require retuning during the procedure. In our laboratory we have built two whole-body human sized FFC-MRI scanners, one of which makes use of a dual magnet in order to achieve field switching [1,2]. The detection field of 59 mT is provided by a vertical-field, permanent magnet. Inside its bore is located a resistive magnet which generates an opposing magnetic field; field-cycling is achieved by switching the current in the resistive magnet coil.