Podgorsak Radiation Physics for Medical Physicists

2006
ISBN: 978-3-540-29471-9
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 438 Seiten, eBook

Reihe: Biological and Medical Physics, Biomedical Engineering

This book is intended as a textbook for a course in radiation physics in a- demic medical physics graduate programs. The book may also be of interest to the large number of professionals, not only physicists, who in their daily occupations deal with various aspects of medical physics and have a need to improve their understanding of radiation physics. Medical physics is a rapidly growing specialty of physics, concerned with the application of physics to medicine mainly, but not exclusively, in the - plication of ionizing radiation to diagnosis and treatment of human disease. In contrast to other physics specialties, such as nuclear physics, solid-state physics, and high-energy physics, studies of modern medical physics attract a much broader base of professionals including graduate students in me- cal physics, medical residents and technology students in radiation oncology and diagnostic imaging, students in biomedical engineering, and students in radiationsafetyandradiationdosimetryeducationalprograms.Theseprof- sionals have diverse background knowledge of physics and mathematics, but they all have a common desire to improve their knowledge of the physics that underlies the application of ionizing radiation in diagnosis and treatment of disease.

Zielgruppe

Research

Autoren/Hrsg.

Podgorsak, Ervin B.

Inhaltsverzeichnis

to Modern Physics.- Rutherford—Bohr Atomic Model.- Production of X Rays.- Two—Particle Collisions.- Interactions of Charged Particles with Matter.- Interactions of Neutrons with Matter.- Interactions of Photons with Matter.- Radioactivity.

Leseproben

3 Production of X Rays ( p. 87)

This chapter is devoted to a study of the production of the two known types of x rays: characteristic radiation and bremsstrahlung. Both types of x rays are important in medical physics, since both are used extensively in diagnostic imaging and in external beam radiotherapy. Characteristic x-rays are produced by electronic transitions in atoms triggered by vacancies in inner electronic shells of the absorber atom.

Bremsstrahlung, on the other hand, is produced by Coulomb interactions between an energetic light charged particle and the nucleus of the absorber atom. Vacancies in electronic shells of atoms can be produced by various means such as Coulomb interactions, photon interactions, nuclear decay, positron annihilation and Auger effect, however, x-rays used in medicine are produced only through Coulomb interactions of energetic electrons with orbital electrons and nuclei of an x-ray target.

This chapter provides a discussion of theoretical and practical aspects of x-ray production, briefy introduces Cerenkov radiation and synchrotron radiation, both of some interest in nuclear and medical physics, and concludes with a brief discussion of various accelerators of interest in medicine.

3.1 X-Ray Line Spectra (Characteristic Radiation)
A vacancy in an atomic shell plays an important role in physics and chemistry. De.ned as an electron missing from the normal complement of electrons in a given atomic shell, a vacancy can be produced by eight different effects or interactions ranging from various photon-atom interactions through charge particle-atom interactions to nuclear effects.

Depending on the nature and energy of the interaction, the vacancy may occur in the outer shell or in one of the inner shells of the atom. The list of the 8 effects for production of shell vacancy in an atom is as follows:

1. Photoelectric effect (see Sect. 7.5)
2. Compton scattering (see Sect. 7.3)
3. Triplet production (see Sect. 7.6.1)
4. Charged particle Coulomb interaction with an atom (see Sect. 5.3.1)
5. Internal conversion (see Sect. 8.9.3)
6. Electron capture (see Sect. 8.8.4)
7. Positron annihilation (see Sect. 7.6.7)
8. Auger effect (see Sect. 3.1.2)

An atom with a vacancy in its inner shell is in a highly excited state and returns to its ground state through a series of electronic transitions. Electrons from higher atomic shells will fill the shell vacancies and the energy difference in binding energies between the initial and final shell or sub-shell will be emitted from the atom in one of two ways:

1. Radiatively in the form of characteristic (fluorescent) radiation.

2. Non-radiatively in the form of Auger electrons, Coster-Kronig electrons or super Coster-Kronig electrons.

3.1.1 Characteristic Radiation

Radiative transitions result in emission of photons that are called characteristic radiation, since the wavelength ? and energy h? of the emitted photon are characteristic of the atom in which the photon originated.

Über Autor(innen)

Ervin B. Podgorsak was born in Vienna, Austria and grew up in Ljubljana, Slovenia where he completed his undergraduate studies in technical physics at the University of Ljubljana in 1968. He then studied at the University of Wisconsin in Madison, Wisconsin, USA and obtained M.Sc. and Ph.D. degrees in physics. He completed his post-doctoral studies in medical physics at the University of Toronto in 1974 and moved to McGill University in Montreal, where he currently holds positions of Professor of Medical Physics and Director of the Medical Physics department.