OPPapers.com

X-Ray Fundamentals

Basic physics of X-ray imaging
Carl A Carlsson and Gudrun Alm Carlsson
Department of Radiation Physics
Faculty of Health Sciences
Linköping university
Sweden
REPORT
LiH-RAD-R-008
Second edition 1996

TABLE OF CONTENTS
1. Introduction .........3
2. The physics of the X-ray source: the X-ray tube .........3
3. The energy spectrum of X-rays .........7
4. The interactions of X-rays with matter .........12
5. Contrast .........19
6. Energy absorption of X-rays .........22
7. Stochastics in the X-ray image .........27
8. Appendix .........28
9. References .........29

Basic physics of X-ray imaging
1. INTRODUCTION
In X-ray diagnostics, radiation that is partly transmitted through and partly absorbed in
the irradiated object is utilised. An X-ray image shows the variations in transmission
caused by structures in the object of varying thickness, density or atomic composition. In
Figure 1, the necessary attributes for X-ray imaging are shown: X-ray source, object
(patient) and a radiation detector (image receptor).
Figure 1. The necessary attributes for X-ray imaging: X ray source, object (patient) and
radiation detector
After an introductory description of the nature of   X-rays, the most important processes in
the X-ray source, the object (patient) and radiation detector for the generation of an X-ray
image will be described.
2. THE PHYSICS OF THE X-RAY SOURCE: THE X-RAY TUBE
a. The nature of X-rays
X-rays are like radio waves and visible light electromagnetic radiation. X-rays, however,
have higher frequency, ν, and shorter wavelength, λ, than light and radio waves. The
radiation can be considered as emitted in quanta, photons, each quantum having a well
defined energy, hν, where h is a physical constant, Plancks constant, and ν is the
frequency. The energy of X-ray photons are considerably higher than those of light.
A number of the phenomena, which are observed with...