X-Ray Certification Exposure Factors 2 — Questions and Answers
Question 1: A radiograph appears too light (underexposed). Which adjustment would most directly increase radiographic density?
- Decrease kVp by 15%
- Increase mAs by 50% (Correct answer)
- Increase SID by 10 cm
- Decrease OID by 5 cm
Correct answer: Increase mAs by 50%
mAs directly controls the quantity of x-rays produced, so increasing it raises radiographic density.
Question 2: Which of the following best describes the effect of increasing kVp on radiographic contrast?
- Contrast increases because more photons are produced
- Contrast decreases because more scattered radiation is produced (Correct answer)
- Contrast is unaffected because kVp only changes density
- Contrast increases because subject contrast improves
Correct answer: Contrast decreases because more scattered radiation is produced
Higher kVp produces more Compton scatter, which adds noise and reduces radiographic contrast.
Question 3: When doubling the SID, how must mAs be adjusted to maintain the same receptor exposure?
- Halve the mAs
- Double the mAs
- Quadruple the mAs (Correct answer)
- No adjustment needed
Correct answer: Quadruple the mAs
The inverse square law requires mAs to be quadrupled when SID doubles to compensate for the fourfold reduction in intensity.
Question 4: A patient's arm is imaged at 60 kVp / 5 mAs. To apply the 15% kVp rule and maintain density, what should the new technique be?
- 69 kVp / 2.5 mAs (Correct answer)
- 69 kVp / 5 mAs
- 51 kVp / 10 mAs
- 69 kVp / 10 mAs
Correct answer: 69 kVp / 2.5 mAs
Adding 15% to kVp (≈69 kVp) doubles receptor exposure, so mAs must be halved to 2.5 mAs to maintain density.
Question 5: Which exposure factor primarily determines the quality (penetrating power) of the x-ray beam?
- mA
- Exposure time
- kVp (Correct answer)
- mAs
Correct answer: kVp
kVp sets the peak energy of the x-ray beam, which determines its penetrating power.
Question 6: A grid with a ratio of 12:1 is used instead of an 8:1 grid. What is the expected effect on patient dose?
- Dose decreases because the higher ratio removes more scatter
- Dose increases because higher mAs is required to compensate for greater scatter cleanup (Correct answer)
- Dose is unchanged because grid ratio does not affect technique
- Dose decreases because fewer primary photons are absorbed
Correct answer: Dose increases because higher mAs is required to compensate for greater scatter cleanup
A higher grid ratio requires increased mAs to maintain exposure at the receptor, raising patient dose.
Question 7: If OID increases significantly without changing SID, what happens to image magnification and sharpness?
- Magnification decreases; sharpness improves
- Magnification increases; sharpness decreases (Correct answer)
- Magnification is unchanged; sharpness decreases
- Magnification increases; sharpness improves
Correct answer: Magnification increases; sharpness decreases
Greater OID increases geometric magnification and penumbra (blur), degrading both size accuracy and sharpness.
X-Ray Certification Exposure Factors 2
A radiograph appears too light (underexposed).
Which adjustment would most directly increase radiographic density?