X-Ray Certification Equipment Operation and Maintenance 3 — Questions and Answers
Question 1: Which type of X-ray generator provides the most consistent and efficient X-ray production?
- Single-phase, half-wave rectified
- Single-phase, full-wave rectified
- Three-phase, six-pulse
- High-frequency generator (Correct answer)
Correct answer: High-frequency generator
High-frequency generators produce near-constant potential with less than 1% ripple, resulting in the most consistent and efficient X-ray production of all generator types.
Question 2: A collimator light field should match the X-ray field to within what tolerance according to quality control standards?
- Within 5% of the SID in each direction (Correct answer)
- Within 2% of the SID in total
- Within 3% of the SID in each direction
- Within 10mm at any SID
Correct answer: Within 5% of the SID in each direction
The light field/X-ray field congruence must be within 2% of the SID in each direction (not to exceed ±1% of SID per side) per ACR/NCRP guidelines.
Question 3: What is the function of the autotransformer in an X-ray circuit?
- Rectifies alternating current to direct current
- Provides the high voltage necessary for X-ray production
- Allows selection of kVp by varying voltage supplied to the step-up transformer (Correct answer)
- Controls the mA by regulating filament current
Correct answer: Allows selection of kVp by varying voltage supplied to the step-up transformer
The autotransformer acts as a voltage selector that supplies variable voltage to the primary of the step-up transformer, allowing the radiographer to select the desired kVp.
Question 4: During fluoroscopy, the image intensifier converts X-rays to a visible image through which sequence?
- X-rays → light → electrons → light (Correct answer)
- X-rays → electrons → light → electrons
- X-rays → light → heat → electrons
- X-rays → electrons → heat → light
Correct answer: X-rays → light → electrons → light
The image intensifier converts X-rays to light (input phosphor), then to electrons (photocathode), then accelerates and focuses electrons, and finally converts back to light at the output phosphor.
Question 5: Which factor directly controls the quantity (number) of X-rays produced in an X-ray tube?
- kVp
- mAs (Correct answer)
- Added filtration
- Field size
Correct answer: mAs
mAs (milliampere-seconds) directly controls the quantity of X-rays produced by determining the number of electrons flowing from cathode to anode per unit time multiplied by exposure time.
Question 6: What type of preventive maintenance should be performed on a portable X-ray unit's wheels and casters?
- Replacement every 6 months regardless of condition
- Regular cleaning, lubrication, and inspection for wear or damage (Correct answer)
- Application of high-voltage grease monthly
- Daily calibration with a dosimeter
Correct answer: Regular cleaning, lubrication, and inspection for wear or damage
Portable X-ray unit wheels and casters require regular cleaning, lubrication, and inspection to ensure safe transport and prevent mechanical failures that could endanger patients or staff.
Question 7: What is the purpose of the beam-limiting device (collimator) in addition to reducing patient dose?
- It increases the mA delivered to the patient
- It reduces scattered radiation reaching the image receptor, improving contrast (Correct answer)
- It filters out high-energy photons
- It measures the patient's absorbed dose
Correct answer: It reduces scattered radiation reaching the image receptor, improving contrast
Collimation reduces the volume of tissue irradiated, which decreases scatter radiation production, thereby improving radiographic contrast and image quality.
X-Ray Certification Equipment Operation and Maintenance 3
Which type of X-ray generator provides the most consistent and efficient X-ray production?