Radiation Therapy Board Practice Exam 2025 - Free Radiation Therapy Practice Questions and Study Guide

The interaction of x-rays with matter is fundamental to understanding radiation therapy and imaging techniques. The basic types of interactions include Compton scatter, photoelectric absorption, and pair production, all of which describe the various mechanisms by which x-rays lose energy and transfer it to matter.

Compton scatter involves the interaction of x-rays with electrons, resulting in a scattered photon and a recoil electron. This process is significant at diagnostic energies and contributes to image contrast and dose distribution in radiation therapy.

Photoelectric absorption describes the complete absorption of an x-ray photon by an atom, resulting in the ejection of an inner-shell electron and the subsequent emission of characteristic radiation as the atom returns to stability. This process is highly energy-dependent and is more pronounced in high atomic number materials.

Pair production occurs when a photon with sufficient energy (>1.022 MeV) interacts with the atomic nucleus to create a particle-antiparticle pair (an electron and a positron). This interaction is significant at high energies, particularly in therapeutic radiation.

On the other hand, radiative bremsstrahlung production, while a significant concept in radiation physics, does not represent a basic type of interaction between x-rays and matter. Instead, bremsstrahlung refers to the radiation produced when charged particles