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Medical physics challenges within the Microbeam Radiation Therapy (MRT) project
Abstracts / Physica Medica 30 (2014) e1ee15
way that using available perturbation factors is not appropriate. Furthermore, changes in energy spectrum with field size, the fact that on some modern radiotherapy equipment conventional reference conditions cannot be realised or that the flattening filter is not present, means that current dosimetry codes of practice do not provide recommendations for dosimetry in such fields. Results & Discussion: The new formalism for dose determination in small and non-standard photon fields developed by the IAEA/AAPM is explained2. Some results on detector-specific beam quality corrections factors are presented. References 1. Aspradakis, M.M., Byrne, J. P., Palmans, H., Conway, J., Rosser, K., Warrington, A. P., Duane, S. IPEM report 103: 'Small Field MV Photon Dosimetry'. 2010, York, UK: Institute of Physics and Engineering in Medicine (IPEM). ISBN 978 1 903613 45 0 2. Palmans, H, Dosimetry of small fields: Present status and future guidelines by IAEA, Radiotherapy & Oncology, Vol 111, Supp 1, April 2014, ISSN 01678140 MEDICAL PHYSICS CHALLENGES WITHIN THE MICROBEAM RADIATION THERAPY (MRT) PROJECT €uer-Krisch a, f, C. Nemoz a, f, T. Brochard a, f, M. Renier a, f, H. E. Bra Requardt a, f, R. Serduc b,f, G. LeDuc a, f, A. Bravin a, f, S. Bartzsch c, f, P. Fournier d, a, f, I. Cornelius d, f, P. Berkvens a, f, J.C. Crosbie d, f, M.L.F. Lerch d, f, A.B. Rosenfeld d, f, M. Donzelli a, c, f, U.Oelfke c, f, A. Bouchet e, f, H. Blattmann g, f, B. Kaser-Hotz h, f, J.A. Laissue i, f. aEuropean Synchrotron Radiation Facility, B.P.220, F-38043 Grenoble Cedex, France; bINSERM unit 836, CHU Grenoble, Grenoble, France; cIm Neuenheimer Feld 280,69120 Heidelberg,Germany; dCMRP, Northfields Ave., Wollongong, 2500, NSW, €t Bern Institut für Anatomie Baltzerstrasse 2CH-3000 Australia; eUniversita Bern 9, Switzerland; f CHU Grenoble, Grenoble, France; gNiederwiesstr. 13c 5417 Untersiggenthal, Switzerland; hAnimal Oncology and Imaging Center, Rothusstr. 2, CH-6331 Huenenberg/CH,.Switzerland; iUniversity of Bern ,Faculty of Medicine, Murtenstrasse 11, CH-3010 Bern, Switzerland Background: Microbeam Radiation Therapy (MRT) uses a spatially fractionated filtered white X-ray beam from a high energy wiggler Synchrotron Source (energies 50-350keV) with extremely high dose rates (up to about 20kGy/s). The typical planar beam width in an array is 25-100mm with 100-400mm wide spaces between beams. Such beams are very well tolerated by the tissue, even the high “peak” doses delivered in the path of the microbeams, when respecting a dose prescription in the “valley’ that corresponds to a dose used of conventional Radiation Therapy (RT) converted to a single exposure . The superior tumor control when compared to that realized by conventional RT is achieved by differential effects of MRT on the normal tissue vasculature versus the tumor vasculature. Materials and Methods: The MRT technique has been technically set up, tested and successfully applied during the last 20 years on various tumor models. Presently, the project is mature enough to be used for the treatment of spontaneous tumors in pets. Unified efforts from several teams with very different expertise now permit Microbeam Radiation Therapy in animal patients with a high degree of safety, in pursuit of the ultimate goal of clinical applications in humans. Results: The MRT trials for animal pets as tumor patients required substantial work for developing, upgrading and progressively implementing instrumentation, dosimetry protocol, as well as the crucial patient safety systems. Progress on the homogenous dose measurements using ionisation chambers and Alanine dosimetry as well as the comparison of high resolution dosimeters with the dose calculations based on a novel tumor planning system will be summarized. A general overview on the different achievements will be presented as well as a vision for possible human trials. TEXTURE AS IMAGING BIOMARKER Costaridou Lena. Department of Medical Physics, School of Medicine, University of Patras, Rion Patras 26504, Greece Quantitative image analysis involves derivation of quantitative measures (extraction of image features), aiming to capture image manifestations of
e5
underlying pathophysiological processes, with the ultimate goal to identify image-based biomarkers and improve patient-specific disease management. While features capturing lesion contrast and shape, also mimicking radiologists’ used image attributes, have been extensively studied in the framework of image-based computer aided diagnosis texture analysis, not directly intuitive to radiologists, is an emerging approach. In addition, the tissue appearance modeling and classification task has been recently enriched, encompassing tasks, such as prognosis, monitoring disease progression and response to therapy, as well as cancer risk assessment. Prognosis imaging biomarkers assess neoplasm aggressiveness, in terms of their relationship to pathology and molecular classification, while treatment response imaging biomarkers could help early identification of responders/non responders to neo-adjuvant chemotherapy schemes prior to surgical decisions. In this review, texture analysis methodologies exploited towards the identification of potential imaging biomarkers will be considered. Representative texture analysis approaches will be reviewed across imaging modalities, with reference to methodological and technological aspects and challenges. The advent of multimodality imaging with near isotropic 3-dimensional spatial resolution modalities, including anatomical and functional modalities, is expected to enhance characterization and quantification of naturally occurring textures, as well as their scale and orientation properties, while casting insight to texture dynamics, provided by imaging tissue volume times series (spatiotemporal data). TECHNICAL CHALLENGES AND CLINICAL RESEARCH APPLICATIONS OF ULTRAHIGH FIELD MRI Andrew Webb. Leiden University Medical Center, Radiology Department, The Netherlands With the rapid spread of 7 Tesla whole body MRI systems throughout the world there has been significant recent progress in both clinical and clinical research applications. Although predominantly in the neurological area, there have also been many developments in the areas of musculoskeletal, cardiac and ocular imaging. Increased magnetic susceptibility contrast, enhanced magnetic resonance angiography, and much higher signal-to-noise in spectroscopy and heteronuclear imaging/spectroscopy have been the driving forces for much of this progress. The major challenges have been, and continue to be, increased image inhomogeneity, power deposition, and motion-induced artifacts. Many hardware advances have already been necessary to deal with these problems, and many future advances are required to keep the field moving forward. Examples which will be presented include: (i) the use of navigator echoes and phase imaging for high resolution MRI in Alzheimers patients, (ii) the use of high dielectric materials to improve neuroimaging and spectroscopy at high field, (iii) diffusion weighted metabolite spectroscopy in the brain, (iv) high field cardiac and musculoskeletal imaging, and (v) the design of new types of RF coil specifically for high field. DOSIMETRY IN SUPPORT OF PATIENT PROTECTION IN DIAGNOSTIC RADIOLOGY - A VALEDICTORY VIEW FROM THE UK Dr Paul C. Shrimpton. Formerly Leader of Medical Dosimetry Group, Public Health England, Chilton, OX11 0RQ, UK Invited lecture in relation to EFOMP Medal Award Ceremony The increasingly widespread use of x-rays in diagnostic radiology provides not only enormous benefits to patients, but also significant radiation exposure for populations. The protection of patients against potential radiation harm requires the elimination of all unnecessary x-ray exposure in relation to effective clinical diagnosis. Dosimetry is an essential management tool for patient safety by allowing the assessment of typical radiation risks in support of the justification of procedures, and the routine monitoring and comparison of typical doses in pursuit of the optimisation of patient protection. Periodic assessment of patient doses should form an integral part of quality assurance in x-ray departments and is best based on practical measurements that provide useful characterisation of patient exposure, such as entrance surface dose, dose-area product and, for CT, volume-weighted CT dose index and dose-length product. Mean values determined in a department for these practical dose monitoring quantities, from patient samples for each type of examination and patient group,
way that using available perturbation factors is not appropriate. Furthermore, changes in energy spectrum with field size, the fact that on some modern radiotherapy equipment conventional reference conditions cannot be realised or that the flattening filter is not present, means that current dosimetry codes of practice do not provide recommendations for dosimetry in such fields. Results & Discussion: The new formalism for dose determination in small and non-standard photon fields developed by the IAEA/AAPM is explained2. Some results on detector-specific beam quality corrections factors are presented. References 1. Aspradakis, M.M., Byrne, J. P., Palmans, H., Conway, J., Rosser, K., Warrington, A. P., Duane, S. IPEM report 103: 'Small Field MV Photon Dosimetry'. 2010, York, UK: Institute of Physics and Engineering in Medicine (IPEM). ISBN 978 1 903613 45 0 2. Palmans, H, Dosimetry of small fields: Present status and future guidelines by IAEA, Radiotherapy & Oncology, Vol 111, Supp 1, April 2014, ISSN 01678140 MEDICAL PHYSICS CHALLENGES WITHIN THE MICROBEAM RADIATION THERAPY (MRT) PROJECT €uer-Krisch a, f, C. Nemoz a, f, T. Brochard a, f, M. Renier a, f, H. E. Bra Requardt a, f, R. Serduc b,f, G. LeDuc a, f, A. Bravin a, f, S. Bartzsch c, f, P. Fournier d, a, f, I. Cornelius d, f, P. Berkvens a, f, J.C. Crosbie d, f, M.L.F. Lerch d, f, A.B. Rosenfeld d, f, M. Donzelli a, c, f, U.Oelfke c, f, A. Bouchet e, f, H. Blattmann g, f, B. Kaser-Hotz h, f, J.A. Laissue i, f. aEuropean Synchrotron Radiation Facility, B.P.220, F-38043 Grenoble Cedex, France; bINSERM unit 836, CHU Grenoble, Grenoble, France; cIm Neuenheimer Feld 280,69120 Heidelberg,Germany; dCMRP, Northfields Ave., Wollongong, 2500, NSW, €t Bern Institut für Anatomie Baltzerstrasse 2CH-3000 Australia; eUniversita Bern 9, Switzerland; f CHU Grenoble, Grenoble, France; gNiederwiesstr. 13c 5417 Untersiggenthal, Switzerland; hAnimal Oncology and Imaging Center, Rothusstr. 2, CH-6331 Huenenberg/CH,.Switzerland; iUniversity of Bern ,Faculty of Medicine, Murtenstrasse 11, CH-3010 Bern, Switzerland Background: Microbeam Radiation Therapy (MRT) uses a spatially fractionated filtered white X-ray beam from a high energy wiggler Synchrotron Source (energies 50-350keV) with extremely high dose rates (up to about 20kGy/s). The typical planar beam width in an array is 25-100mm with 100-400mm wide spaces between beams. Such beams are very well tolerated by the tissue, even the high “peak” doses delivered in the path of the microbeams, when respecting a dose prescription in the “valley’ that corresponds to a dose used of conventional Radiation Therapy (RT) converted to a single exposure . The superior tumor control when compared to that realized by conventional RT is achieved by differential effects of MRT on the normal tissue vasculature versus the tumor vasculature. Materials and Methods: The MRT technique has been technically set up, tested and successfully applied during the last 20 years on various tumor models. Presently, the project is mature enough to be used for the treatment of spontaneous tumors in pets. Unified efforts from several teams with very different expertise now permit Microbeam Radiation Therapy in animal patients with a high degree of safety, in pursuit of the ultimate goal of clinical applications in humans. Results: The MRT trials for animal pets as tumor patients required substantial work for developing, upgrading and progressively implementing instrumentation, dosimetry protocol, as well as the crucial patient safety systems. Progress on the homogenous dose measurements using ionisation chambers and Alanine dosimetry as well as the comparison of high resolution dosimeters with the dose calculations based on a novel tumor planning system will be summarized. A general overview on the different achievements will be presented as well as a vision for possible human trials. TEXTURE AS IMAGING BIOMARKER Costaridou Lena. Department of Medical Physics, School of Medicine, University of Patras, Rion Patras 26504, Greece Quantitative image analysis involves derivation of quantitative measures (extraction of image features), aiming to capture image manifestations of
e5
underlying pathophysiological processes, with the ultimate goal to identify image-based biomarkers and improve patient-specific disease management. While features capturing lesion contrast and shape, also mimicking radiologists’ used image attributes, have been extensively studied in the framework of image-based computer aided diagnosis texture analysis, not directly intuitive to radiologists, is an emerging approach. In addition, the tissue appearance modeling and classification task has been recently enriched, encompassing tasks, such as prognosis, monitoring disease progression and response to therapy, as well as cancer risk assessment. Prognosis imaging biomarkers assess neoplasm aggressiveness, in terms of their relationship to pathology and molecular classification, while treatment response imaging biomarkers could help early identification of responders/non responders to neo-adjuvant chemotherapy schemes prior to surgical decisions. In this review, texture analysis methodologies exploited towards the identification of potential imaging biomarkers will be considered. Representative texture analysis approaches will be reviewed across imaging modalities, with reference to methodological and technological aspects and challenges. The advent of multimodality imaging with near isotropic 3-dimensional spatial resolution modalities, including anatomical and functional modalities, is expected to enhance characterization and quantification of naturally occurring textures, as well as their scale and orientation properties, while casting insight to texture dynamics, provided by imaging tissue volume times series (spatiotemporal data). TECHNICAL CHALLENGES AND CLINICAL RESEARCH APPLICATIONS OF ULTRAHIGH FIELD MRI Andrew Webb. Leiden University Medical Center, Radiology Department, The Netherlands With the rapid spread of 7 Tesla whole body MRI systems throughout the world there has been significant recent progress in both clinical and clinical research applications. Although predominantly in the neurological area, there have also been many developments in the areas of musculoskeletal, cardiac and ocular imaging. Increased magnetic susceptibility contrast, enhanced magnetic resonance angiography, and much higher signal-to-noise in spectroscopy and heteronuclear imaging/spectroscopy have been the driving forces for much of this progress. The major challenges have been, and continue to be, increased image inhomogeneity, power deposition, and motion-induced artifacts. Many hardware advances have already been necessary to deal with these problems, and many future advances are required to keep the field moving forward. Examples which will be presented include: (i) the use of navigator echoes and phase imaging for high resolution MRI in Alzheimers patients, (ii) the use of high dielectric materials to improve neuroimaging and spectroscopy at high field, (iii) diffusion weighted metabolite spectroscopy in the brain, (iv) high field cardiac and musculoskeletal imaging, and (v) the design of new types of RF coil specifically for high field. DOSIMETRY IN SUPPORT OF PATIENT PROTECTION IN DIAGNOSTIC RADIOLOGY - A VALEDICTORY VIEW FROM THE UK Dr Paul C. Shrimpton. Formerly Leader of Medical Dosimetry Group, Public Health England, Chilton, OX11 0RQ, UK Invited lecture in relation to EFOMP Medal Award Ceremony The increasingly widespread use of x-rays in diagnostic radiology provides not only enormous benefits to patients, but also significant radiation exposure for populations. The protection of patients against potential radiation harm requires the elimination of all unnecessary x-ray exposure in relation to effective clinical diagnosis. Dosimetry is an essential management tool for patient safety by allowing the assessment of typical radiation risks in support of the justification of procedures, and the routine monitoring and comparison of typical doses in pursuit of the optimisation of patient protection. Periodic assessment of patient doses should form an integral part of quality assurance in x-ray departments and is best based on practical measurements that provide useful characterisation of patient exposure, such as entrance surface dose, dose-area product and, for CT, volume-weighted CT dose index and dose-length product. Mean values determined in a department for these practical dose monitoring quantities, from patient samples for each type of examination and patient group,