GXMO Image Quality and Interpretation 5

Question 1

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

Accepted Answer

Beam alignment/collimator accuracy test

Answer

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.

Question 2

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

Accepted Answer

Histogram analysis and equalization

Answer

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.

Question 3

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?

Accepted Answer

Excessive internal or external rotation of the leg

Answer

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.

Question 4

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

Accepted Answer

The amount of radiation that reached the image detector

Answer

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

Question 5

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

Accepted Answer

Increasing mAs

Answer

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.

(GXMO) General X-Ray Machine Operator Practice Test

(GXMO) General X-Ray Machine Operator Practice Test

GXMO Image Quality and Interpretation 5