Radiographic Image Production

Flashcards covering key concepts in radiographic image production, including attenuation, absorption, scattering, and digital imaging principles.

Attenuation

Reduction in the energy or number of photons in the primary x-ray beam as it passes through anatomic tissue.

Absorption (Photoelectric effect)

Total photon absorption that depends on the energy of the incoming x-ray photon and the atomic number of anatomic tissue; involves the removal of an inner-shell electron.

Scattering (Compton effect)

Photon interacts with an outer orbital electron, imparting some of its energy to the electron, ejecting it from orbit. The photon continues on an altered path with less energy.

Coherent Scattering

An interaction that occurs with low-energy x-rays, typically below the diagnostic range.

Transmission

X-ray photons that pass through the body without any interaction with the atomic structures.

Tissue Thickness & Beam Attenuation

Increasing tissue thickness increases beam attenuation (absorption or scattering); X-rays are attenuated exponentially and reduced by ~50% for each 4 to 5 cm of tissue thickness.

Tissue Atomic Number & Beam Attenuation

Tissue with a higher atomic number (bone) attenuates the x-ray beam more than tissue with a lower atomic number (fat). Attenuation order: Bone, Muscle, Fat, Air (BMFA).

Tissue Density & Beam Attenuation

More dense (compact) tissue attenuates the x-ray beam more. Tissue density is defined as matter per unit volume.

X-ray Beam Quality (kVp) & Beam Attenuation

Higher-penetrating x-rays (shorter wavelength, higher frequency) are more likely to be transmitted, resulting in decreased attenuation. Lower-penetrating x-rays are more likely to be absorbed, resulting in increased attenuation.

Exit/Remnant Radiation

The remaining radiation of the x-ray beam after it leaves the patient, composed of both transmitted and scattered radiation.

Fog in Radiography

Unwanted exposure on the image caused by scatter radiation.

Latent Image

The invisible image that exists on the exposed film before it is chemically processed.

Manifest Image

The visible image on the exposed film after processing.

Digital Image Receptor Dynamic Range

Digital image receptors can respond to a wider range of x-ray exposures. Anatomic areas of widely different attenuation can be more easily visualized.

Matrix (Digital Imaging)

Image composed of numeric data combined in rows and columns.

Pixel (Digital Imaging)

Each pixel is recorded as a single numeric value.