McDermott - Tutorials in radiotherapy physics: advanced topics with problems and solutions

TUTORIALS IN
RADIOTHERAPY
PHYSICS

TUTORIALS IN
RADIOTHERAPY
PHYSICS

Advanced Topics with Problems and Solutions

Patrick N. McDermott

CRC Press

Taylor & Francis Group

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Version Date: 20151008

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Monica McDermott

My wife, who sees something in me, although I am still not quite sure what it is. This project would not have been possible without her support.

CONTENTS

This book is intended to be a textbook covering selected advanced topics that are not covered in depth in any of the standard medical physics texts. The prerequisite is a bachelors degree in physics and a graduate-level course in radiological physics at the level found in the textbooks by Attix (1986), Khan and Gibbons (2014), Podgorsak (2010), and Metcalfe et al. (2007). A course in radiobiology would be helpful for but is not essential. This book is not meant to be a comprehensive review of the topics presented. Review articles already exist for some (but not all) of these topics, and they are summaries of current research. Fundamental, systematic, mathematical development is missing in such articles. This book is the place where one should begin when learning these topics. Reading review articles should then follow.

Many of these important topics are not well known or understood even by board-certified medical physicists with years of experience. Reading the scant existing literature is an exercise in frustration. While there are a few notable exceptions, problems are all too common: poor, nonexistent, or incomplete derivations and explanations; numerous errors; poor equation typography; failure to clearly and carefully define all mathematical symbols (if they are defined at all); internal contradictions or inconsistencies; nonsequiturs; and so forth. Physics is difficult enough to learn without these obstacles. I certainly do not claim perfection, but I have been very careful to try to minimize these problems. My approach is to start from first principles rather than writing down immaculately conceived equations whose provenance is mysterious. The material in this book cannot be found in any one place. It is a synthesis from a large variety of sources using consistent mathematical notation.

This book can be used for self-study, or it could be used by students in graduate medical physics programs or physics residency programs. It may also be of use in vendor training for linacs or treatment planning systems. The chapters can be read independently, although there are some links between them. It is my contention that a single course in radiation therapy physics ( la Khan) is not adequate for radiation therapy physicist preparation. Indeed, many graduate programs do have an advanced course. There are efforts underway by the American Association of Physicists in Medicine to improve teaching of graduate medical physics students. One of the biggest problems, however, is a lack of well-written texts covering topics that medical physicists need to know. This was frustrating for me as a student, and it continues to be a problem today.

Problems and questions appear at the end of each chapter. The solutions to the problems are given in the back of the book. I urge you to give the problems considerable thought before looking at the solutions. The struggle to solve problems is, after all, one of the ways that we learn. I believe that if you can solve the problems, you will have a good quantitative understanding of the material.

, The Physics of Electron Acceleration in Medical Linacs, is for those physicists who are tired of comic book explanations about electrons surfing on waves and desire a real understanding of the mechanism of microwave acceleration of electrons. Commonly cited books in the medical physics literature do not provide a satisfactory explanation of this topic. The monograph by Karzmark, Nunan, and Tanabe (Medical Electron Accelerators) does provide some explanation; however, it is from an engineering perspective, and this book is now out of print. Basic physics textbooks on electromagnetic theory (e.g., Jackson) do not extend the discussion of waveguides to a consideration of their use in accelerating charged particles. The accelerator physics literature helps some, but the discussion there is concentrated on high-energy physics applications, not medical linacs. Medical linacs are different than those used for other applications. They have to be able to produce both x-ray beams and electron beams. They usually offer multiple beam energies, and they are mounted on a gantry that can rotate around a patient.