Radiation Interactions with Matter

These flashcards cover key concepts related to the interaction of radiation with matter, specifically focusing on processes such as attenuation, absorption, scattering, and their implications in diagnostic imaging.

What is attenuation in the context of X-ray imaging?

Attenuation is the loss of primary photons due to absorption or scatter as the X-ray beam travels through matter.

How does absorption differ from attenuation?

Absorption occurs when a photon is completely absorbed by matter, while attenuation is the loss of photons that may occur through both absorption and scattering.

What is remnant radiation?

Remnant radiation refers to the photons that exit the patient and hit the image receptor.

What primary interactions with matter are important in X-ray imaging?

The primary interactions are photoelectric absorption and Compton scattering.

What happens during photoelectric absorption?

During photoelectric absorption, an incident photon interacts with an inner shell electron, ejecting it and ionizing the atom.

How does Compton scattering differ from photoelectric absorption?

Compton scattering involves the incident photon interacting with an outer shell electron, which results in a scattered photon and a recoil electron, whereas photoelectric absorption involves an inner shell electron.

What determines the likelihood of photoelectric absorption occurring?

The likelihood of photoelectric absorption is greater when the incident photon energy is slightly greater than the binding energy of the inner shell electron.

Why do higher atomic number elements increase the probability of photoelectric absorption?

Higher atomic number elements have more electrons, resulting in higher binding energies and thus a greater likelihood of interaction.

What is the role of scatter in X-ray imaging?

Scatter does not contribute to the diagnostic image and can lead to radiation fog, reducing image quality.

What is meant by 'radiation fog'?

Radiation fog is unwanted exposure on a radiographic image due to scatter radiation.

Why is it important to use grids in X-ray imaging?

Grids are used to absorb scatter and improve the image quality by reducing unwanted exposure.

How does kinetic energy relate to an ejected photoelectron?

The kinetic energy of the ejected photoelectron is equal to the difference between the energy of the incident photon and the binding energy of the electron.