GXMO GXMO Quality Control and Maintenance 1 — Questions and Answers
Question 1: Which quality control test is used to verify that the light field of the collimator accurately corresponds to the X-ray field?
- Beam alignment (light/radiation field congruence) test (Correct answer)
- Half-value layer (HVL) test
- Sensitometric strip test
- Focal spot size test
Correct answer: Beam alignment (light/radiation field congruence) test
The beam alignment test verifies that the visible light field from the collimator matches the actual radiation field within accepted tolerances (typically ±2% of SID).
Question 2: The half-value layer (HVL) of an X-ray beam is a measure of:
- Beam quality (penetrating ability) (Correct answer)
- Beam quantity (number of photons)
- Focal spot size
- Detector sensitivity
Correct answer: Beam quality (penetrating ability)
HVL is the thickness of a specified material (usually aluminum) required to reduce beam intensity by 50%, indicating the beam's penetrating quality.
Question 3: A sensitometer is used in radiographic quality control to:
- Expose film/CR plates to a standardized series of light steps for processing evaluation (Correct answer)
- Measure radiation output from the X-ray tube
- Check collimator accuracy
- Evaluate focal spot size
Correct answer: Expose film/CR plates to a standardized series of light steps for processing evaluation
A sensitometer exposes imaging media to controlled light increments, and the resulting density steps are measured with a densitometer to assess processor consistency.
Question 4: Acceptable tolerance for kVp accuracy in a quality control program is generally:
- ±5% of the indicated kVp (Correct answer)
- ±10% of the indicated kVp
- ±1% of the indicated kVp
- ±15% of the indicated kVp
Correct answer: ±5% of the indicated kVp
Quality control standards (NCRP, ACR) generally accept kVp accuracy within ±5% of the set value to ensure consistent image contrast and patient dose.
Question 5: The purpose of collimator shutters in an X-ray unit is to:
- Restrict the primary beam to the area of clinical interest (Correct answer)
- Filter low-energy photons from the beam
- Support the image receptor
- Cool the X-ray tube anode
Correct answer: Restrict the primary beam to the area of clinical interest
Collimator shutters are adjustable lead blades that restrict the X-ray beam to the area being examined, reducing patient dose and scatter.
Question 6: Which QC test evaluates whether the X-ray tube's focal spot has enlarged beyond acceptable limits?
- Star resolution pattern or pinhole camera test (Correct answer)
- Step wedge exposure test
- Sensitometric strip test
- Beam alignment test
Correct answer: Star resolution pattern or pinhole camera test
The star resolution pattern or pinhole camera test measures actual focal spot size; an enlarged focal spot reduces spatial resolution.
GXMO GXMO Quality Control and Maintenance 1
Which quality control test is used to verify that the light field of the collimator accurately corresponds to the X-ray field?