X-Ray Certification Equipment Operation and Maintenance 2 — Questions and Answers
Question 1: Which component in an X-ray tube is responsible for focusing the electron beam onto the focal spot?
- Rotating anode
- Focusing cup (Correct answer)
- Glass envelope
- Stator
Correct answer: Focusing cup
The focusing cup (cathode cup) surrounds the filament and uses a negative charge to electrostatically focus electrons toward the focal spot on the anode.
Question 2: What is the primary purpose of the heel effect in X-ray imaging?
- It increases tube current on the anode side
- It creates a variation in beam intensity across the field, with less intensity on the anode side (Correct answer)
- It reduces off-focus radiation
- It improves contrast resolution on the cathode side
Correct answer: It creates a variation in beam intensity across the field, with less intensity on the anode side
The heel effect causes beam intensity to be lower on the anode side because X-rays produced deeper in the anode are attenuated by the anode material itself.
Question 3: A radiographer notices the X-ray tube makes a loud grinding noise during rotation. What is the most likely cause?
- Excessive kVp setting
- Worn or damaged rotor bearings (Correct answer)
- Overloaded filament
- Low line voltage
Correct answer: Worn or damaged rotor bearings
Grinding noises during tube rotation indicate worn or damaged rotor bearings, which requires immediate tube replacement to prevent rotor failure.
Question 4: What does the term 'effective focal spot size' refer to in X-ray equipment?
- The actual surface area on the anode where electrons strike
- The projected focal spot size as seen from the image receptor (Correct answer)
- The total heat capacity of the anode
- The distance between the focal spot and image receptor
Correct answer: The projected focal spot size as seen from the image receptor
The effective (projected) focal spot is the size of the focal spot as seen from the image receptor, which is smaller than the actual focal spot due to the anode angle.
Question 5: Which quality control test is used to evaluate the accuracy of timer settings on an X-ray unit?
- Spinning top test or digital timer tester (Correct answer)
- Step wedge test
- Half-value layer measurement
- Focal spot measurement
Correct answer: Spinning top test or digital timer tester
The spinning top test (for single-phase units) or a digital timer tester (for high-frequency units) is used to evaluate the accuracy of exposure timer settings.
Question 6: In a three-phase, 12-pulse X-ray generator, what is the approximate voltage ripple?
- 100%
- 13-25%
- 4% (Correct answer)
- Less than 1%
Correct answer: 4%
A three-phase, 12-pulse generator produces approximately 4% voltage ripple, resulting in a nearly constant potential that improves X-ray beam quality and efficiency.
Question 7: What happens to radiographic density if the source-to-image distance (SID) is doubled while all other factors remain constant?
- Density doubles
- Density quadruples
- Density decreases to one-quarter (Correct answer)
- Density decreases by half
Correct answer: Density decreases to one-quarter
Per the inverse square law, doubling the SID reduces intensity (and thus density) to one-quarter of the original value (1/2² = 1/4).
X-Ray Certification Equipment Operation and Maintenance 2
Which component in an X-ray tube is responsible for focusing the electron beam onto the focal spot?