Radiology Key

Interactions of Ionizing Radiation When an x- or γ-ray beam passes through a medium, interaction between photons and matter can take place with the result that energy is transferred to…

Quality Assurance The term quality assurance (QA) describes a program that is designed to control and maintain the standard of quality set for that program. For radiation oncology, a quality…

Measurement of Ionizing Radiation 6.1. Introduction In the early days of x-ray usage for diagnosis and therapy, attempts were made to measure ionizing radiation on the basis of chemical and…

Nuclear Transformations 2.1. Radioactivity Radioactivity, first discovered by Antonio Henri Becquerel (1852–1908) in 1896, is a phenomenon in which radiation is given off by the nuclei of the elements. This…

Clinical Radiation Generators 4.1. Kilovoltage Units Up to about 1950, most of the external beam radiotherapy was carried out with x-rays generated at voltages up to 300 kVp. Subsequent development…

Quality of X-ray Beams In Chapter 5, we described x-ray beam in terms of photon fluence and energy fluence. Such a description requires the knowledge of the number and energy…

Production of X-rays X-rays were discovered by Roentgen in 1895 while studying cathode rays (stream of electrons) in a gas discharge tube. He observed that another type of radiation was…

Structure of Matter 1.1. The Atom All matter is composed of individual entities called elements. Each element is distinguishable from the others by the physical and chemical properties of its…