Physics of Radiology

Author:  Anthony B. Wolbarst
ISBN:  9780944838952
Published:  1993 | 461 pp. | Hardcover



SCOPE  |  June 2004

SCOPE, vol 13, issue 2, June 2004 SCOPE, vol 13, issue 2, June 2004

Book Reviews Editor: Geraint Lewis


The Physics of Radiotherapy X-Rays from Linear Accelerators

ISBN 0-944838-75-8 (hardcover) $119.95 ISBN 0-944838-76-6 (softcover) $98.95

and The Q Book: Problems & Solutions ISBN 0-944838-86-3 (softcover) $33.95

Peter Metcalfe, Tomas Kron and Peter Hoban
Medical Physics Publishing, Madison, Wisconsin, 1997

I consider this a superb radiotherapy physics textbook. It does not replace the widely accepted 'classics' (John's and Cunningham, Attix, Kahn, Williams and Thwaites and others), but complements them and is strikingly different in many aspects. The book concentrates on the physics of external megavoltage beams, placing emphasis on the use of modern technology tools and concepts (some not presented in other textbooks) and employing simple mathematical formalisms to explain these. The Q Book is a companion workbook with questions and answers, and some additional information (good viva preparation material for trainees…)

Chapter 1 briefly but clearly outlines the operation of modern linacs. The reader will find that very recent advances in linac technology (IMRT delivery features, etc.) are missing, but this is simply because the book was published in 1997 (written a few years before?) and many commercial solutions appeared soon after this.

The presentation of basic physics concepts in Chapter 2 is refreshing. This is the first textbook to my knowledge that includes a definition of terma together with kerma, collision kerma and dose. Carefully selected figures showing data generated from Monte Carlo simulations are used to demonstrate differences between photon spectra at different energies and depths in water, kerma and dose for different beam energies, etc.

Chapter 3, the longer chapter, contains ample information and comparisons between detectors used for absolute reference and in vivo dosimetry. I found the tables with the properties of commonly used detectors a useful reference. This chapter also contains a section on calibration protocols, where although the general formalism for absolute dosimetry is appropriate and well written, the subsections that follow are less so. The HPA 1983 code of practice has been long superseded by the IPSM 1990 and IAEA 1987 (TRS 277) with the IAEA 2000 (TRS 398).

Chapter 4 entitled 'Linear accelerator x-ray beam properties' essentially describes the data usually acquired during linac photon beam commissioning. The sections on dose measurements in the build-up region, percentage depth dose and profiles are particularly good. The last two subsections in this chapter are dedicated to linac room shielding and some limited space is allocated to quality assurance.

Chapter 5 concentrates on principles of treatment planning and monitor unit calculations (fixed and isocentric setups, with examples). A section on treatment volume definition is included here, and the paragraphs on the relation of CT numbers to electron density are appropriately placed. The reader is briefly introduced to some modern tools, such as dose volume histograms (DVHs), CT simulation and electronic portal imaging and other imaging techniques used in diagnosis and planning. The section on treatment planning techniques is short and only gives a flavour of the problems encountered in the planning room. Some space is dedicated to stereotactic radiosurgery and radiotherapy but none to inverse planning and intensity-modulated beam delivery.

The best is kept for last! Those (both trainees and more experiences radiotherapy physicists) who would like to understand the principles on photon dose calculation algorithms would most definitely appreciate the effort expended by the authors in chapters 6 and 7. Chapter 6 describes broad beam data models and traditional inhomogeneity correction methods whereas chapter 7 gives a simple overview of Monte Carlo calculations to radiation transport problems in radiotherapy (using the EGS4 code as an example), as well as the basics of convolution/superposition methods.

Finally, chapter 8 on radiobiological models is an introduction to a fascinating topic, with the section on the linear quadratic model a most enjoyable reading.

This book deserves a place in one's library because it presents and clarifies concepts in an original way. It contains a very good selection of graphs and tables to aid understanding and extensive bibliography for those wanting to find out more. Everyone should read chapters 4, 6, 7 and 8. The copy that I bought had some errors (an errata list was provided) but this is a minor criticism for an otherwise excellent effort!

Marla Manla Aspradakis

Regional Medical Physics Department

Newcastle upon Tyne