X-ray Interactions: Photoelectric Effect and Compton Scatter

Photoelectric Effect

Photon energy transfers to eject inner shell electron.

Compton Scatter

results in the removal of an outer shell electron leading to the photon becoming scattered.

this electron with move in a different direction than the beam

Attenuation

in relation to x-rays it reduces x-ray beam intensity.

affected by absorption and scatter

X-ray Absorption

Process where X-rays are absorbed by tissue.

Inverse Square Law

Intensity decreases with distance squared from source.

Electron Binding Energy

Minimum energy to remove an electron from atom.

Atomic Number (Z)

Number of protons in an atom's nucleus.

High Atomic Number

Higher Z leads to greater photoelectric absorption.

Soft Tissue Absorption

Soft tissue has average atomic number of 7.4.

Bone Absorption

Bone has average atomic number of 13.8.

Radiation Dose

Amount of radiation energy absorbed by tissue.

photoelectron effect increases skin exposure

Compton scatter increases patient exposure

Image Quality

Clarity and detail of X-ray images.

Scattered Photon

Photon that changes direction after interaction.

Forward Scatter

Higher energy scatter that may reach receptor, this will lead reduced image quality

Side Scatter

has lower energy levels but can create a dose for anyone else in the room

Air Gap Technique

Space between patient and receptor to reduce scatter.

Grids

used to stop scattered x-rays from reaching receptor.

made of lead strips with gaps between.

placed between patient and receptor.

scattered x-rays are absorbed by the lead

Radiation Protection

Measures to safeguard against excessive radiation exposure.

Occupational Dose

Radiation exposure to healthcare workers.

Image Contrast

Difference in brightness between areas in an image.

Tissue Thickness

Greater thickness increases likelihood of scatter.

Density of Matter

Higher density leads to increased attenuation.

Vacuum Attenuation

Attenuation is zero in a vacuum.

K-shell Electron

Inner shell electron with high binding energy.

L-shell Electron

Outer shell electron with lower binding energy.

Mathematical Algorithms

Technology to reduce scatter post-exposure.

can remove scatter post procedure and improve contrast.

Radiographic Techniques

Methods to optimize X-ray imaging quality.