Radioactivity and X-rays Applications and health effects by Thormod Henriksen Preface The present book is an update and extension of three previous books from groups of scientists at the University of Oslo. The books are: I. Radioaktivitet – Stråling – Helse Written by; Thormod Henriksen, Finn Ingebretsen, Anders Storruste and Erling Stranden. Universitetsforlaget AS 1987 ISBN 82-00-03339-2 I would like to thank my coauthors for all discussions and for all the data used in this book. The book was released only a few months after the Chernobyl accident. II. Stråling og Helse Written by Thormod Henriksen, Finn Ingebretsen, Anders Storruste, Terje Strand, Tove Svendby and Per Wethe. Institute of Physics, University of Oslo 1993 and 1995 ISBN 82-992073-2-0 This book was an update of the book above. It has been used in several courses at The University of Oslo. Furthermore, the book was again up- dated in 1998 and published on the Internet. The address is: www.afl.hitos.no/mfysikk/rad/straling_innh.htm III. Radiation and Health Written by Thormod Henriksen and H. David Maillie Taylor & Francis 2003 ISBN 0-415-27162-2 This English written book was mainly a translation from the books above. I would like to take this opportunity to thank David for all help with the translation. The three books concentrated to a large extent on the basic properties of ionizing radiation. Efforts were made to describe the background ra- diation as well as the release of radioactivity from reactor accidents and fallout from nuclear explosions in the atmosphere. These subjects were of high interest in the aftermath of the Chernobyl accident. During the later years a large amount of research and interesting new results within radiobiology have emerged. The purpose of the present is book is therefore to include some interesting applications of radiation in medicine as well as some of the exciting mechanisms in radiobiology. In this update the basic radiation physics and radiobiology is included. Furthermore, some applica- tions of radiation in medicine will be highlighted. It would be impossible to embark on this project unless heavy support from my active colleagues at the “group of Biophysics and Medical physics” at The University of Oslo. The group is engaged in re- search with the aim to attain information about the physical processes taking place in cells and tissue when irradiated. This include the formation of radical ions and how they lead to the known biological endpoints. The group members (professors Eli Olaug Hole and Einar Sagstuen) are using magnetic resonance (ESR) to study radical formation, secondary processes and fate. Other members of the group (professor Erik Pettersen) are using mammalian cells in culture. The interests are the control mechanisms working in the cell cycle. Of particular interest is the effect of small radiation doses. These studies are of importance for environmental problems as well as within cancer treatment. The group have close cooperations with active radiation therapy (professor Dag Rune Olsen and Eirik Malinen) and diagnostic (associate professor Hilde Olerud.). Einar Sagstuen The group of Biophysics Eli Olaug Hole and Erik Pettersen Medical Physics Nina Jeppesen Edin Eirik Malinen I take this opportunity to thank all my coworkers with the previous books as well as the members of the biophysics group with the present book which is published on Internet. University of Oslo, 2009 Thormod Henriksen Contents Part I Radiation – doses Chapter 1. Radiation is discovered page 1 – 7 Chapter 2. What is radioactivity page 8 – 27 Chapter 3. Radioactive decay laws page 28 – 35 Chapter 4. Artificial radioactive isotopes page 36 – 45 Chapter 5. Activity and dose page 46 – 57 Chapter 6. The measurement of radiation page 58 – 74 Chapter 7. The Natural Radiation Sources and doses to the people page 75 – 99 Chapter 8. Nuclear weapons – Reactor accidents and pollution page 100 – 140 Chapter 9. Radiation used for diagnostic purposes page 141 – 179 PET 511 keV photon + – 511 keV photon Chapter 10. Radiation used for therapy – radiation therapy page 180 – 192 This chapter is so far unfinished. Chapter 1 Radiation is Discovered Introduction From the beginning of life on earth, all living things have been exposed to radiation. Life started and developed in spite of, or possibly because of, radiation. It is disquieting to people that they coexist with radiation yet it cannot be seen, heard or felt. Radiation, when broadly defined, includes the entire spectrum of electromagnetic waves: radio waves, microwaves, infrared, visible light, ultraviolet, x-rays­­ and atomic particles. In this book we are con- cerned with radiation having energies high enough to ionize matter. Examples are x-rays, cosmic rays, and the emissions from radioactive elements. Although the term “ionizing radiation” is in this case more precise, common usage often omits “ionizing” and that this is what is done here. In this book, “radiation” means “ionizing radiation.” Prior to the reactor accidents at Three Mile Island in the United States (1979) and at Chernobyl in the former Soviet Union (1986), radiation issues were addressed primarily by specialists. Now, however, radiation and biological effects are debated by the public and political leaders. They use expressions such as: radiation dose, becquerel, sievert, cesium and γ-radiation. Because people are easily confused by this technical language, all too often they are left with the perception that all uses of radiation are dangerous. This book is written for those who want to understand radiation in order to make informed decisions about it in their lives. This field of science, founded at the turn of the century, has provided dramatic insights into physics, chemistry, biology, and medicine. The work of the early investigators provided a strong foundation from which to understand radiation phenomena. We will meet a few of them in the following pages and gain insight into their work and lives. X-rays Radioactivity discovered November 1895 discovered March 1896 This radiation is man-made. We have devel- Both natural and man-made radioactivity ex- oped a variety of x-ray equipment. The radia- ist. The sources emit radiation all the time – tion exists only as long as the x-ray machine you can not turn them on and off. is turned on. The effect of x-rays and radioactivity on cells, animals and humans are equal. It is due to the fact that the radiation can ionize. Since the biological effect depends on the ionization density – it may be some differences between x- and γ-rays on one side and particle radiation on the other side. 1 X-rays X-rays was discovered by Wilhelm Conrad Roentgen at the University of Würtzburg in Germany. He, like many others in those days, was studying electric discharges in glass tubes filled with various gases at very low pressures. In experiments on November 8, 1895, Roentgen had covered the tube with some black paper and had darkened the room. He then discovered that a piece of paper painted with a fluorescent dye, at some distance from the tube, would glow when he turned on the high voltage between the electrodes in the tube. Realizing the importance of his discovery, Roentgen focused all his attention on the study of this new radiation that had the unusual property of passing through black paper. He found that the radiation not only could penetrate black paper but also thick blocks of wood, books and even his hand. In the dark room, he observed shadows of the bones in his own hand. This was the first x-ray image. The German anatomist von Koelliker (see his hand below) proposed that the new type of radiation be called Roentgen rays. Although this term is used in many countries, the most common name used is that coined by Roentgen himself, x-rays. The letter “x” is often used by physicists to indicate something “unknown.” Since the nature of these rays was unknown, Roentgen called them x-rays. All x-rays on earth are from man-made sources. There are x-rays from natural sources in outer space. They are, however, absorbed by the upper atmosphere and do not reach the earth’s surface. Roentgen discovered x-rays in the fall of 1895. He immedi- ately understood that the radiation from the x-ray tube had special properties, for example, it was possible to “see into” a human body. Within months this new radiation, called x- rays, was used in medical diagnostics. It was realized that x-rays also could kill living cells, and that the sensitivity for killing varied from one cell type to another. It was easier to kill cancer cells than normal cells. Consequently, x-rays could be used in cancer therapy. The unit R (roentgen) used for radiation exposure was named after Roentgen. An exposure of 1 R means that the radia- tion dose to ordinary tissue is approximately 9.3 mGy (see later). W. C. Roentgen (1845 - 1923) Nobel prize in Physics 1901 To Wilhelm Conrad Roentgen This x-ray picture was tak- “In recognition of the extraordinary en by Roentgen in January services he has rendered by the 1896. It is the hand of von discovery of the remarkable rays Koelliker who suggested the subsequently named after him”. name Roentgen rays. This was the very first Nobel Price. 2 What is X-rays? In order to produce x-rays you must have equipment like that shown in the 30 – 150 kV – drawing. It consists of an evacuated Cathode + glass tube with two electrodes and a Anode high voltage between the electrodes. Electrons The cathode is heated and electrons are emitted. They have a negative charge and is accelerated towards the posi- tive electrode (the anode).