Quiz III Review - X-ray Interactions and Attenuation

Vocabulary flashcards covering core radiological physics topics including attenuation, transmission, differential absorption, HVL, x-ray interaction types, and PE conditions for Quiz III review.

Transmission

The process by which x-ray photons pass through tissue without interacting or losing energy, reaching the image receptor directly.

Attenuation

The total reduction in the intensity of the primary x-ray beam resulting from both absorption and scattering as it passes through a material or tissue.

Differential Absorption

The difference between x-ray photons that are absorbed photoelectrically and those that are transmitted through the patient to the image receptor.

Subject Contrast

The degree of differential absorption among different anatomical tissues due to variations in tissue thickness, mass density, and atomic number ($Z$).

Half-Value Layer (HVL)

The thickness of absorbing material required to reduce the x-ray beam intensity to half of its original value, serving as a measure of beam quality and penetrability.

X-ray Interaction Target Levels

Low-energy x-rays interact with the whole atom, moderate-energy x-rays interact with orbital electrons, and high-energy x-rays interact directly with the atomic nucleus.

Five Fundamental X-ray Interactions

The five ways x-ray photons interact with matter: Coherent scattering, Compton scattering, Photoelectric effect, Pair production, and Photodisintegration.

Ionizing vs. Non-Ionizing Interactions

Compton scattering, Photoelectric effect, and Pair production cause ionization of target atoms, whereas Coherent scattering is a non-ionizing interaction.

Three Conditions for Photoelectric (PE) Interactions

1) Incoming photon energy must equal or exceed the binding energy of the inner-shell electron; 2) Photon energy and electron binding energy should be close; 3) The target electron must be tightly bound in an inner shell.

Effect of Increasing kVp on Attenuation

As kVp increases, overall attenuation decreases due to higher beam penetrability, and within the attenuated beam, Compton scattering increases relative to Photoelectric absorption.

Atomic Number ($Z$) and kVp Dependence of Photoelectric Effect

Photoelectric interactions are directly proportional to the cube of the atomic number ($Z^3$) and inversely proportional to the cube of the photon energy or peak kilovoltage ($1/\text{kVp}^3$).

Effect of Mass Density on Attenuation

Attenuation is directly proportional to the mass density of the tissue; doubling the mass density doubles the probability of x-ray interactions.

Total Differential Absorption Relationship

The total differential absorption represents the contrast formed by the ratio of photoelectric absorption to photon transmission through adjacent body structures.