ARRT Equipment Operation and QA 3

Question 1

A radiograph displays increased quantum mottle. Which of the following changes would most directly reduce this artifact?

Accepted Answer

Increase mAs

Answer

Quantum mottle results from insufficient photon flux reaching the detector; increasing mAs produces more photons and reduces statistical noise (mottle).

Question 2

Which digital detector type uses a direct conversion process where x-rays are converted directly into electrical charge?

Accepted Answer

Direct flat-panel detector using amorphous selenium

Answer

Direct flat-panel detectors use amorphous selenium (a-Se), which converts x-ray photons directly into electrical charge without an intermediate light conversion step.

Question 3

What is the primary function of a grid in radiography?

Accepted Answer

To absorb scattered radiation before it reaches the image receptor

Answer

Grids are composed of alternating radiopaque lead strips and radiolucent interspacing material that absorb obliquely traveling scattered photons while transmitting the primary beam.

Question 4

On a sensitometric curve (H&D curve), the region where the curve is steepest represents:

Accepted Answer

The straight-line portion — optimal diagnostic range

Answer

The steepest portion (straight-line region) represents the optimal exposure range where small changes in exposure produce proportional and maximum changes in density, yielding best contrast.

Question 5

A timer accuracy test reveals that the actual exposure time is 20% longer than the set time. This most likely indicates:

Accepted Answer

A malfunctioning timer circuit requiring calibration

Answer

Timer inaccuracy — where actual exposure time deviates more than ±5% from the set value — indicates the timer circuit is out of calibration and needs servicing.

ARRT - American Registry of Radiologic Technologists Practice Test

ARRT - American Registry of Radiologic Technologists Practice Test

ARRT Equipment Operation and QA 3