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Radiation Oncology Physics a handbook for teachers

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Radiation Oncology Physics: A Handbook for Teachers and Students E.B. Podgorsak Technical Editor Sponsored by the IAEA and endorsed by the COMP/CCPM, EFOMP, ESTRO, IOMP, PAHO and WHOCover photograph courtesy of E. IzewskiRADIATION ONCOLOGY PHYSICS: A HANDBOOK FOR TEACHERS AND STUDENTSThe following States are Members of the International Atomic Energy Agency: AFGHANISTAN GREECE PAKISTAN ALBANIA GUATEMALA PANAMA ALGERIA HAITI PARAGUAY ANGOLA HOLY SEE PERU ARGENTINA HONDURAS PHILIPPINES ARMENIA HUNGARY POLAND AUSTRALIA ICELAND PORTUGAL AUSTRIA INDIA QATAR AZERBAIJAN INDONESIA REPUBLIC OF MOLDOVA BANGLADESH IRAN, ISLAMIC REPUBLIC OF ROMANIA BELARUS IRAQ RUSSIAN FEDERATION BELGIUM IRELAND SAUDI ARABIA BENIN ISRAEL SENEGAL BOLIVIA ITALY SERBIA AND MONTENEGRO BOSNIA AND HERZEGOVINA JAMAICA SEYCHELLES BOTSWANA JAPAN SIERRA LEONE BRAZIL JORDAN SINGAPORE BULGARIA KAZAKHSTAN SLOVAKIA BURKINA FASO KENYA SLOVENIA CAMEROON KOREA, REPUBLIC OF SOUTH AFRICA CANADA KUWAIT SPAIN CENTRAL AFRICAN KYRGYZSTAN SRI LANKA REPUBLIC LATVIA SUDAN CHILE LEBANON SWEDEN CHINA LIBERIA SWITZERLAND COLOMBIA LIBYAN ARAB JAMAHIRIYA SYRIAN ARAB REPUBLIC COSTA RICA LIECHTENSTEIN TAJIKISTAN CÔTE D’IVOIRE LITHUANIA THAILAND CROATIA LUXEMBOURG THE FORMER YUGOSLAV CUBA MADAGASCAR REPUBLIC OF MACEDONIA CYPRUS MALAYSIA TUNISIA CZECH REPUBLIC MALI TURKEY DEMOCRATIC REPUBLIC MALTA UGANDA OF THE CONGO MARSHALL ISLANDS UKRAINE DENMARK MAURITANIA UNITED ARAB EMIRATES DOMINICAN REPUBLIC MAURITIUS UNITED KINGDOM OF ECUADOR MEXICO GREAT BRITAIN AND EGYPT MONACO NORTHERN IRELAND EL SALVADOR MONGOLIA UNITED REPUBLIC ERITREA MOROCCO OF TANZANIA ESTONIA MYANMAR UNITED STATES OF AMERICA ETHIOPIA NAMIBIA URUGUAY FINLAND NETHERLANDS UZBEKISTAN FRANCE NEW ZEALAND VENEZUELA GABON NICARAGUA VIETNAM GEORGIA NIGER YEMEN GERMANY NIGERIA ZAMBIA GHANA NORWAY ZIMBABWE The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is “to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world’’.RADIATION ONCOLOGY PHYSICS: A HANDBOOK FOR TEACHERS AND STUDENTS INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2005COPYRIGHT NOTICE All IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952 (Berne) and as revised in 1972 (Paris). The copyright has since been extended by the World Intellectual Property Organization (Geneva) to include electronic and virtual intellectual property. Permission to use whole or parts of texts contained in IAEA publications in printed or electronic form must be obtained and is usually subject to royalty agreements. Proposals for non-commercial reproductions and translations are welcomed and will be considered on a case by case basis. Enquiries should be addressed by email to the Publishing Section, IAEA, at sales.publicationsiaea.org or by post to: Sales and Promotion Unit, Publishing Section International Atomic Energy Agency Wagramer Strasse 5 P.O. Box 100 A-1400 Vienna Austria fax: +43 1 2600 29302 tel.: +43 1 2600 22417 http://www.iaea.org/books © IAEA, 2005 Printed by the IAEA in Austria July 2005 STI/PUB/1196 IAEA Library Cataloguing in Publication Data Radiation oncology physics : a handbook for teachers and students / editor E. B. Podgorsak ; sponsored by IAEA … et al.. — Vienna : International Atomic Energy Agency, 2005. p.; 24 cm. STI/PUB/1196 ISBN 92–0–107304–6 Includes bibliographical references. 1. Radiation dosimetry — Handbooks, manuals, etc. 2. Dosimeters — Handbooks, manuals, etc. 3. Radiation — Measurement — Handbooks, manuals, etc. 4. Radiation — Dosage — Handbooks, manuals, etc. 5. Radiotherapy — Handbooks, manuals, etc. 6. Photon beams. 7. Electron beams. 8. Radioisotope scanning. I. Podgorsak, E. B., ed. II. International Atomic Energy Agency. IAEAL 05–00402FOREWORD In the late 1990s the IAEA initiated for its Member States a systematic and comprehensive plan to support the development of teaching programmes in medical radiation physics. Multiple projects were initiated at various levels that, together with the well known short term training courses and specialization fellowships funded by the IAEA Technical Cooperation programme, aimed at supporting countries to develop their own university based master of science programmes in medical radiation physics. One of the early activities of the IAEA in this period was the development of a syllabus in radiotherapy physics, which had the goal of harmonizing the various levels of training that the IAEA provided. This was carried out during 1997–1998, and the result of this work was released as a report used for designing IAEA training courses. In 1999–2000 a more detailed teachers’ guide was developed, in which the various topics in the syllabus were expanded to form a detailed ‘bullet list’ containing the basic guidelines of the material to be included in each topic so that lectures to students could be prepared accordingly. During the period 2001–2002 E.B. Podgorsak (Canada) was appointed editor of the project and redesigned the contents so that the book became a comprehensive handbook for teachers and students, with coverage deeper than a simple teachers’ guide. The initial list of topics was expanded considerably by engaging an enhanced list of international contributors. The handbook was published as working material in 2003 and placed on the Internet in order to seek comments, corrections and feedback. This handbook aims at providing the basis for the education of medical physicists initiating their university studies in the field. It includes the recent advances in radiotherapy techniques; however, it is not designed to replace the large number of textbooks available on radiotherapy physics, which will still be necessary to deepen knowledge in the specific topics reviewed here. It is expected that this handbook will successfully fill a gap in the teaching material for medical radiation physics, providing in a single manageable volume the largest possible coverage available today. Its wide dissemination by the IAEA will contribute to the harmonization of education in the field and will be of value to newcomers as well as to those preparing for their certification as medical physicists, radiation oncologists, medical dosimetrists and radiotherapy technologists. Endorsement of this handbook has been granted by the following international organizations and professional bodies: the International Organization for Medical Physics (IOMP), the European Society for Therapeutic Radiology and Oncology (ESTRO), the European Federation of Organisations for Medical Physics (EFOMP), the World Health Organization (WHO), the Pan American Health Organization (PAHO), the Canadian Organization of Medical Physicists (COMP) and the Canadian College of Physicists in Medicine (CCPM). The following international experts are gratefully acknowledged for making major contributions to the development of an early version of the syllabus: B. Nilsson (Sweden), B. Planskoy (United Kingdom) and J.C. Rosenwald (France). The following made major contributions to this handbook: R. Alfonso (Cuba), G. Rajan (India), W. Strydom (South Africa) and N. Suntharalingam (United States of America). The IAEA scientific officers responsible for the project were (in chronological order) P. Andreo, J. Izewska and K.R. Shortt. EDITORIAL NOTE Although great care has been taken to maintain the accuracy of information contained in this publication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use. The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. The authors are responsible for having obtained the necessary permission for the IAEA to reproduce, translate or use material from sources already protected by copyrights.PREFACE Radiotherapy, also referred to as radiation therapy, radiation oncology or therapeutic radiology, is one of the three principal modalities used in the treatment of malignant disease (cancer), the other two being surgery and chemotherapy. In contrast to other medical specialties that rely mainly on the clinical knowledge and experience of medical specialists, radiotherapy, with its use of ionizing radiation in the treatment of cancer, relies heavily on modern technology and the collaborative efforts of several professionals whose coordinated team approach greatly influences the outcome of the treatment. The radiotherapy team consists of radiation oncologists, medical physicists, dosimetrists and radiation therapy technologists: all professionals characterized by widely differing educational backgrounds and one common link — the need to understand the basic elements of radiation physics, and the interaction of ionizing radiation with human tissue in particular. This specialized area of physics is referred to as radiation oncology physics, and proficiency in this branch of physics is an absolute necessity for anyone who aspires to achieve excellence in any of the four professions constituting the radiotherapy team. Current advances in radiation oncology are driven mainly by technological development of equipment for radiotherapy procedures and imaging; however, as in the past, these advances rely heavily on the underlying physics. This book is dedicated to students and teachers involved in programmes that train professionals for work in radiation oncology. It provides a compilation of facts on the physics as applied to radiation oncology and as such will be useful to graduate students and residents in medical physics programmes, to residents in radiation oncology, and to students in dosimetry and radiotherapy technology programmes. The level of understanding of the material covered will, of course, be different for the various student groups; however, the basic language and knowledge for all student groups will be the same. The text will also be of use to candidates preparing for professional certification examinations, whether in radiation oncology, medical physics, dosimetry or radiotherapy technology. The intent of the text is to serve as a factual supplement to the various textbooks on medical physics and to provide basic radiation oncology physics knowledge in the form of a syllabus covering all modern aspects of radiation oncology physics. While the text is mainly aimed at radiation oncology professionals, certain parts of it may also be of interest in other branches of medicine that use ionizing radiation not for the treatment of disease but for the diagnosis of disease (diagnostic radiology and nuclear medicine). The contents may also be useful for physicists who are involved in studies of radiation hazards and radiation protection (health physics). This book represents a collaborative effort by professionals from many different countries who share a common goal of disseminating their radiation oncology physics knowledge and experience to a broad international audience of teachers and students. Special thanks are due to J. Denton-MacLennan for critically reading and editing the text and improving its syntax. E.B. PodgorsakCONTRIBUTORS Andreo, P. University of Stockholm, Karolinska Institute, Sweden Evans, M.D.C. McGill University Health Centre, Canada Hendry, J.H. International Atomic Energy Agency Horton, J.L. University of Texas MD Anderson Cancer Center, United States of America Izewska, J. International Atomic Energy Agency Mijnheer, B.J. Netherlands Cancer Institute, Netherlands Mills, J.A. Walsgrave Hospital, United Kingdom Olivares, M. McGill University Health Centre, Canada Ortiz López, P. International Atomic Energy Agency Parker, W. McGill University Health Centre, Canada Patrocinio, H. McGill University Health Centre, Canada Podgorsak, E.B. McGill University Health Centre, Canada Podgorsak, M.B. Roswell Park Cancer Institute, United States of America Rajan, G. Bhabha Atomic Research Centre, India Seuntjens, J.P. McGill University Health Centre, Canada Shortt, K.R. International Atomic Energy Agency Strydom, W. Medical University of Southern Africa, South Africa Suntharalingam, N. Thomas Jefferson University Hospital, United States of America Thwaites, D.I. University of Edinburgh, United Kingdom Tolli, H. International Atomic Energy AgencyBLANKCONTENTS CHAPTER 1. BASIC RADIATION PHYSICS . . . . . . . . . . . . . . . . . . . 1 1.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1. Fundamental physical constants (rounded off to four significant figures) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.2. Important derived physical constants and relationships . . 1 1.1.3. Physical quantities and units . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.4. Classification of forces in nature . . . . . . . . . . . . . . . . . . . . . 4 1.1.5. Classification of fundamental particles . . . . . . . . . . . . . . . . 4 1.1.6. Classification of radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1.7. Classification of ionizing photon radiation . . . . . . . . . . . . . 6 1.1.8. Einstein’s relativistic mass, energy and momentum relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1.9. Radiation quantities and units . . . . . . . . . . . . . . . . . . . . . . . 7 1.2. ATOMIC AND NUCLEAR STRUCTURE . . . . . . . . . . . . . . . . . . 7 1.2.1. Basic definitions for atomic structure . . . . . . . . . . . . . . . . 7 1.2.2. Rutherford’s model of the atom . . . . . . . . . . . . . . . . . . . . . 9 1.2.3. Bohr’s model of the hydrogen atom . . . . . . . . . . . . . . . . . . 10 1.2.4. Multielectron atoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2.5. Nuclear structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.2.6. Nuclear reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.2.7. Radioactivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.2.8. Activation of nuclides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.2.9. Modes of radioactive decay . . . . . . . . . . . . . . . . . . . . . . . . 20 1.3. ELECTRON INTERACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.3.1. Electron–orbital electron interactions . . . . . . . . . . . . . . . . 23 1.3.2. Electron–nucleus interactions . . . . . . . . . . . . . . . . . . . . . . . 23 1.3.3. Stopping power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1.3.4. Mass scattering power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.4. PHOTON INTERACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.4.1. Types of indirectly ionizing photon radiation . . . . . . . . . . . 26 1.4.2. Photon beam attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.4.3. Types of photon interaction . . . . . . . . . . . . . . . . . . . . . . . . . 28 1.4.4. Photoelectric effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 1.4.5. Coherent (Rayleigh) scattering . . . . . . . . . . . . . . . . . . . . . . 291.4.6. Compton effect (incoherent scattering) . . . . . . . . . . . . . . . 30 1.4.7. Pair production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 1.4.8. Photonuclear reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 1.4.9. Contributions to attenuation coefficients . . . . . . . . . . . . . . 34 1.4.10. Relative predominance of individual effects . . . . . . . . . . . 36 1.4.11. Effects following photon interactions . . . . . . . . . . . . . . . . . 37 1.4.12. Summary of photon interactions . . . . . . . . . . . . . . . . . . . . . 38 1.4.13. Example of photon attenuation . . . . . . . . . . . . . . . . . . . . . 40 1.4.14. Production of vacancies in atomic shells . . . . . . . . . . . . . . . 41 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 CHAPTER 2. DOSIMETRIC PRINCIPLES, QUANTITIES AND UNITS . . . . . . . . . . . . . . . . . . . . . . 45 2.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.2. PHOTON FLUENCE AND ENERGY FLUENCE . . . . . . . . . . . . 45 2.3. KERMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 2.4. CEMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 2.5. ABSORBED DOSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 2.6. STOPPING POWER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 2.7. RELATIONSHIPS BETWEEN VARIOUS DOSIMETRIC QUANTITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2.7.1. Energy fluence and kerma (photons) . . . . . . . . . . . . . . . . . 54 2.7.2. Fluence and dose (electrons) . . . . . . . . . . . . . . . . . . . . . . . . 56 2.7.3. Kerma and dose (charged particle equilibrium) . . . . . . . . 57 2.7.4. Collision kerma and exposure . . . . . . . . . . . . . . . . . . . . . . . 60 2.8. CAVITY THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 2.8.1. Bragg–Gray cavity theory . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 2.8.2. Spencer–Attix cavity theory . . . . . . . . . . . . . . . . . . . . . . . . . 62 2.8.3. Considerations in the application of cavity theory to ionization chamber calibration and dosimetry protocols . 64 2.8.4. Large cavities in photon beams . . . . . . . . . . . . . . . . . . . . . . 66 2.8.5. Burlin cavity theory for photon beams . . . . . . . . . . . . . . . . 66 2.8.6. Stopping power ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70CHAPTER 3. RADIATION DOSIMETERS . . . . . . . . . . . . . . . . . . . . . 71 3.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2. PROPERTIES OF DOSIMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2.1. Accuracy and precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.2.1.1. Type A standard uncertainties . . . . . . . . . . . . . . 72 3.2.1.2. Type B standard uncertainties . . . . . . . . . . . . . . 73 3.2.1.3. Combined and expanded uncertainties . . . . . . . 73 3.2.2. Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 3.2.3. Dose rate dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 3.2.4. Energy dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 3.2.5. Directional dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 3.2.6. Spatial resolution and physical size . . . . . . . . . . . . . . . . . . . 76 3.2.7. Readout convenience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 3.2.8. Convenience of use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 3.3. IONIZATION CHAMBER DOSIMETRY SYSTEMS . . . . . . . . . 77 3.3.1. Chambers and electrometers . . . . . . . . . . . . . . . . . . . . . . . . 77 3.3.2. Cylindrical (thimble type) ionization chambers . . . . . . . . 78 3.3.3. Parallel-plate (plane-parallel) ionization chambers . . . . . 79 3.3.4. Brachytherapy chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.3.5. Extrapolation chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.4. FILM DOSIMETRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.4.1. Radiographic film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.4.2. Radiochromic film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5. LUMINESCENCE DOSIMETRY . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.5.1. Thermoluminescence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3.5.2. Thermoluminescent dosimeter systems . . . . . . . . . . . . . . . 86 3.5.3. Optically stimulated luminescence systems . . . . . . . . . . . . 88 3.6. SEMICONDUCTOR DOSIMETRY . . . . . . . . . . . . . . . . . . . . . . . . 89 3.6.1. Silicon diode dosimetry systems . . . . . . . . . . . . . . . . . . . . . 89 3.6.2. MOSFET dosimetry systems . . . . . . . . . . . . . . . . . . . . . . . . 90 3.7. OTHER DOSIMETRY SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.7.1. Alanine/electron paramagnetic resonance dosimetry system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.7.2. Plastic scintillator dosimetry system . . . . . . . . . . . . . . . . . . 92 3.7.3. Diamond dosimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923.7.4. Gel dosimetry systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 3.8. PRIMARY STANDARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 3.8.1. Primary standard for air kerma in air . . . . . . . . . . . . . . . . . 95 3.8.2. Primary standards for absorbed dose to water . . . . . . . . . 95 3.8.3. Ionometric standard for absorbed dose to water . . . . . . . . 96 3.8.4. Chemical dosimetry standard for absorbed dose to water 96 3.8.5. Calorimetric standard for absorbed dose to water . . . . . . 97 3.9. SUMMARY OF SOME COMMONLY USED DOSIMETRIC SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 CHAPTER 4. RADIATION MONITORING INSTRUMENTS . . . . 101 4.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.2. OPERATIONAL QUANTITIES FOR RADIATION MONITORING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 4.3. AREA SURVEY METERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.3.1. Ionization chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.3.2. Proportional counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.3.3. Neutron area survey meters . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.3.4. Geiger–Müller counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.3.5. Scintillator detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 4.3.6. Semiconductor detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 4.3.7. Commonly available features of area survey meters . . . . 108 4.3.8. Calibration of survey meters . . . . . . . . . . . . . . . . . . . . . . . . 108 4.3.9. Properties of survey meters . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.3.9.1. Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.3.9.2. Energy dependence . . . . . . . . . . . . . . . . . . . . . . . 110 4.3.9.3. Directional dependence . . . . . . . . . . . . . . . . . . . . 111 4.3.9.4. Dose equivalent range . . . . . . . . . . . . . . . . . . . . 111 4.3.9.5. Response time . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 4.3.9.6. Overload characteristics . . . . . . . . . . . . . . . . . . . 111 4.3.9.7. Long term stability . . . . . . . . . . . . . . . . . . . . . . . 112 4.3.9.8. Discrimination between different types of radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 4.3.9.9. Uncertainties in area survey measurements . . . 112 4.4. INDIVIDUAL MONITORING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.4.1. Film badge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1134.4.2. Thermoluminescence dosimetry badge . . . . . . . . . . . . . . . . 115 4.4.3. Radiophotoluminescent glass dosimetry systems . . . . . . . 116 4.4.4. Optically stimulated luminescence systems . . . . . . . . . . . . 116 4.4.5. Direct reading personal monitors . . . . . . . . . . . . . . . . . . . . 117 4.4.6. Calibration of personal dosimeters . . . . . . . . . . . . . . . . . . . 118 4.4.7. Properties of personal monitors . . . . . . . . . . . . . . . . . . . . . . 118 4.4.7.1. Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 4.4.7.2. Energy dependence . . . . . . . . . . . . . . . . . . . . . . . 119 4.4.7.3. Uncertainties in personal monitoring measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 4.4.7.4. Equivalent dose range . . . . . . . . . . . . . . . . . . . . . 119 4.4.7.5. Directional dependence . . . . . . . . . . . . . . . . . . . 120 4.4.7.6. Discrimination between different types of radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 CHAPTER 5. TREATMENT MACHINES FOR EXTERNAL BEAM RADIOTHERAPY . . . . . . . . . . . . . . . . . . . . . . . 123 5.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.2. X RAY BEAMS AND X RAY UNITS . . . . . . . . . . . . . . . . . . . . . . . 124 5.2.1. Characteristic X rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.2.2. Bremsstrahlung (continuous) X rays . . . . . . . . . . . . . . . . . 124 5.2.3. X ray targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 5.2.4. Clinical X ray beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 5.2.5. X ray beam quality specifiers . . . . . . . . . . . . . . . . . . . . . . . 127 5.2.6. X ray machines for radiotherapy . . . . . . . . . . . . . . . . . . . . . 127 5.3. GAMMA RAY BEAMS AND GAMMA RAY UNITS . . . . . . . . 129 5.3.1. Basic properties of gamma rays . . . . . . . . . . . . . . . . . . . . . . 129 5.3.2. Teletherapy machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.3.3. Teletherapy sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.3.4. Teletherapy source housing . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.3.5. Dose delivery with teletherapy machines . . . . . . . . . . . . . . 132 5.3.6. Collimator and penumbra . . . . . . . . . . . . . . . . . . . . . . . . . 132 5.4. PARTICLE ACCELERATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 5.4.1. Betatron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 5.4.2. Cyclotron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 5.4.3. Microtron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355.5. LINACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 5.5.1. Linac generations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 5.5.2. Safety of linac installations . . . . . . . . . . . . . . . . . . . . . . . . . . 137 5.5.3. Components of modern linacs . . . . . . . . . . . . . . . . . . . . . . . 138 5.5.4. Configuration of modern linacs . . . . . . . . . . . . . . . . . . . . . . 138 5.5.5. Injection system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 5.5.6. Radiofrequency power generation system . . . . . . . . . . . . . 143 5.5.7. Accelerating waveguide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 5.5.8. Microwave power transmission . . . . . . . . . . . . . . . . . . . . . . 144 5.5.9. Auxiliary system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 5.5.10. Electron beam transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 5.5.11. Linac treatment head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 5.5.12. Production of clinical photon beams in a linac . . . . . . . . . 147 5.5.13. Beam collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 5.5.14. Production of clinical electron beams in a linac . . . . . . . . . 149 5.5.15. Dose monitoring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.6. RADIOTHERAPY WITH PROTONS, NEUTRONS AND HEAVY IONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 5.7. SHIELDING CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 152 5.8. COBALT-60 TELETHERAPY UNITS VERSUS LINACS . . . . . 153 5.9. SIMULATORS AND COMPUTED TOMOGRAPHY SIMULATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 5.9.1. Radiotherapy simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 5.9.2. Computed tomography simulator . . . . . . . . . . . . . . . . . . . . 158 5.10. TRAINING REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 CHAPTER 6. EXTERNAL PHOTON BEAMS: PHYSICAL ASPECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 6.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 6.2. QUANTITIES USED IN DESCRIBING A PHOTON BEAM . . 161 6.2.1. Photon fluence and photon fluence rate . . . . . . . . . . . . . . 162 6.2.2. Energy fluence and energy fluence rate . . . . . . . . . . . . . . . 162 6.2.3. Air kerma in air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 6.2.4. Exposure in air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 6.2.5. Dose to small mass of medium in air . . . . . . . . . . . . . . . . . . 164 6.3. PHOTON BEAM SOURCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1666.4. INVERSE SQUARE LAW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 6.5. PENETRATION OF PHOTON BEAMS INTO A PHANTOM OR PATIENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 6.5.1. Surface dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 6.5.2. Buildup region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 6.5.3. Depth of dose maximum z . . . . . . . . . . . . . . . . . . . . . . . . 172 max 6.5.4. Exit dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 6.6. RADIATION TREATMENT PARAMETERS . . . . . . . . . . . . . . . 172 6.6.1. Radiation beam field size . . . . . . . . . . . . . . . . . . . . . . . . . . 173 6.6.2. Collimator factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 6.6.3. Peak scatter factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 6.6.4. Relative dose factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 6.7. CENTRAL AXIS DEPTH DOSES IN WATER: SOURCE TO SURFACE DISTANCE SET-UP . . . . . . . . . . . . . . . 179 6.7.1. Percentage depth dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 6.7.2. Scatter function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 6.8. CENTRAL AXIS DEPTH DOSES IN WATER: SOURCE TO AXIS DISTANCE SET-UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 6.8.1. Tissue–air ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 6.8.2. Relationship between TAR(d, A , hn) and Q PDD(d, A, f, hn) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 6.8.3. Scatter–air ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 6.8.4. Relationship between SAR(d, A , hn) and S(z, A, f, hn) . 190 Q 6.8.5. Tissue–phantom ratio and tissue–maximum ratio . . . . . . 190 6.8.6. Relationship between TMR(z, A , hn) and Q PDD(z, A, f, hn) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 6.8.7. Scatter–maximum ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 6.9. OFF-AXIS RATIOS AND BEAM PROFILES . . . . . . . . . . . . . . 194 6.9.1. Beam flatness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 6.9.2. Beam symmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 6.10. ISODOSE DISTRIBUTIONS IN WATER PHANTOMS . . . . . . . 197 6.11. SINGLE FIELD ISODOSE DISTRIBUTIONS IN PATIENTS . . 199 6.11.1. Corrections for irregular contours and oblique beam incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 6.11.1.1. Effective source to surface distance method . . . 201 6.11.1.2. Tissue–air ratio or tissue–maximum ratio method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2026.11.1.3. Isodose shift method . . . . . . . . . . . . . . . . . . . . . . 202 6.11.2. Missing tissue compensation . . . . . . . . . . . . . . . . . . . . . . . . 202 6.11.2.1. Wedge filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 6.11.2.2. Bolus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 6.11.2.3. Compensators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 6.11.3. Corrections for tissue inhomogeneities . . . . . . . . . . . . . . . . 204 6.11.4. Model based algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.12. CLARKSON SEGMENTAL INTEGRATION . . . . . . . . . . . . . . . . 206 6.13. RELATIVE DOSE MEASUREMENTS WITH IONIZATION CHAMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 6.14. DELIVERY OF DOSE WITH A SINGLE EXTERNAL BEAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 6.15. EXAMPLE OF DOSE CALCULATION . . . . . . . . . . . . . . . . . . . . 213 6.16. SHUTTER CORRECTION TIME . . . . . . . . . . . . . . . . . . . . . . . . . . 215 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 CHAPTER 7. CLINICAL TREATMENT PLANNING IN EXTERNAL PHOTON BEAM RADIOTHERAPY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 7.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 7.2. VOLUME DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 7.2.1. Gross tumour volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 7.2.2. Clinical target volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 7.2.3. Internal target volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 7.2.4. Planning target volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 7.2.5. Organ at risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 7.3. DOSE SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 7.4. PATIENT DATA ACQUISITION AND SIMULATION . . . . . . 223 7.4.1. Need for patient data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 7.4.2. Nature of patient data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 7.4.2.1. Two dimensional treatment planning . . . . . . . . 223 7.4.2.2. Three dimensional treatment planning . . . . . . . 224 7.4.3. Treatment simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 7.4.4. Patient treatment position and immobilization devices . . 226 7.4.5. Patient data requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 228 7.4.6. Conventional treatment simulation . . . . . . . . . . . . . . . . . . . 229 7.4.6.1. Simulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229