Image Quality and Interpretation Flashcards

Which quality control test is used to evaluate the accuracy of the X-ray beam collimator light field relative to the radiation field?

Answer: Beam alignment/collimator accuracy test

The beam alignment test uses a radio-opaque ruler or template to compare the light field to the actual radiation field, ensuring they coincide within tolerance limits.

Which digital image processing technique adjusts image brightness by analyzing the histogram of pixel values and remapping them to a standard output range?

Answer: Histogram analysis and equalization

Digital radiography systems perform histogram analysis to identify the exposure index and automatically adjust image brightness so that clinically relevant pixels map to the optimal display range.

On an AP knee radiograph, the tibial plateaus appear asymmetric and one compartment's joint space appears artificially narrowed. What is the most likely positioning error?

Answer: Excessive internal or external rotation of the leg

Rotation of the leg on an AP knee projection causes one condyle to project over the joint space, making one compartment appear narrower than it actually is.

What does the exposure index (EI) number reported by a digital radiography system indicate?

Answer: The amount of radiation that reached the image detector

The exposure index is a numeric value indicating the detector exposure level; it helps radiographers determine if the exposure was appropriate, underexposed, or overexposed.

Which of the following would MOST effectively reduce quantum mottle (noise) in a digital radiographic image?

Answer: Increasing mAs

Quantum mottle is caused by insufficient X-ray photons reaching the detector; increasing mAs delivers more photons, reducing the statistical noise (mottle) in the image.

A PA chest radiograph shows a sharp, well-defined opacity in the right lower lobe with an air bronchogram sign. What does the presence of the air bronchogram indicate?

Answer: The airways remain patent while the surrounding alveoli are filled with fluid or exudate

Air bronchograms appear when alveoli fill with fluid (consolidation) while the bronchi remain air-filled, making the air-containing bronchi visible against the opacified lung.

Which factor most directly controls the scale of contrast (long vs. short scale) on a radiographic image?

Answer: kVp

kVp determines the energy of the X-ray beam and therefore the range of tissues that can be penetrated; high kVp produces long-scale (low) contrast, while low kVp produces short-scale (high) contrast.