CRI Image Quality & Artifacts 3 — Questions and Answers
Question 1: What is the effect of increasing kilovoltage (kV) on radiographic contrast?
- Contrast increases due to greater photon energy differences
- Contrast decreases because higher kV produces more uniform beam penetration (Correct answer)
- Contrast is unaffected by kV changes
- Contrast increases only in thin specimens
Correct answer: Contrast decreases because higher kV produces more uniform beam penetration
Higher kV increases beam penetrating power and reduces differential absorption between materials, resulting in lower (flatter) radiographic contrast.
Question 2: A circular, dark spot with a light halo on a film radiograph is most characteristic of which artifact?
- Water drop artifact during processing (Correct answer)
- Static electricity discharge
- Pressure mark from handling
- Chemical contamination
Correct answer: Water drop artifact during processing
Water drops on film before or during processing cause localized developer concentration changes, producing a dark center with a surrounding lighter halo pattern.
Question 3: In industrial radiography, what does the term 'equivalent penetrameter sensitivity' (EPS) measure?
- The optical density of the film background
- The smallest detectable hole in an IQI expressed as a percentage of specimen thickness (Correct answer)
- The ratio of subject contrast to noise
- The minimum source-to-film distance required
Correct answer: The smallest detectable hole in an IQI expressed as a percentage of specimen thickness
EPS expresses the smallest visible IQI hole diameter as a percentage of specimen thickness, serving as a standard measure of radiographic technique sensitivity.
Question 4: Which processing artifact results from film being fed unevenly through an automatic processor, causing alternating light and dark bands perpendicular to the film transport direction?
- Dichroic stain
- Roller marks / hesitation marks (Correct answer)
- Reticulation
- Curtaining
Correct answer: Roller marks / hesitation marks
Roller marks or hesitation marks appear as periodic light or dark bands when film transport is intermittent or rollers are dirty, causing uneven developer contact.
Question 5: What is the primary advantage of using a higher film-to-source distance (FSD) in industrial radiography?
- Shorter exposure times
- Reduced geometric unsharpness and improved image sharpness (Correct answer)
- Higher film density
- Greater scatter radiation
Correct answer: Reduced geometric unsharpness and improved image sharpness
Greater FSD reduces the geometric unsharpness by increasing the source-to-object distance relative to object-to-film distance, producing sharper images.
Question 6: In digital radiography, 'fixed-pattern noise' is best corrected by which image processing technique?
- Spatial filtering
- Dark-field and gain correction (offset/gain calibration) (Correct answer)
- Edge enhancement
- Histogram equalization
Correct answer: Dark-field and gain correction (offset/gain calibration)
Dark-field (offset) correction removes detector dark current noise, and gain correction normalizes each pixel's sensitivity, together eliminating fixed-pattern noise.
Question 7: A wire-type IQI is placed on the SOURCE side of a test specimen. Why is this the preferred placement?
- It reduces the required exposure time
- It represents the worst-case geometric unsharpness condition, ensuring the technique meets sensitivity requirements (Correct answer)
- It prevents scatter radiation from reaching the film
- It allows the IQI to be visible at higher densities
Correct answer: It represents the worst-case geometric unsharpness condition, ensuring the technique meets sensitivity requirements
Placing the IQI on the source side subjects it to maximum geometric unsharpness; if the IQI wires are visible under this worst-case condition, the technique is demonstrated to be sensitive enough.
CRI Image Quality & Artifacts 3
What is the effect of increasing kilovoltage (kV) on radiographic contrast?