CRI Contrast & Exposure Parameters 2 — Questions and Answers
Question 1: Which radiographic parameter most directly controls the energy of X-rays and thus penetrating power?
- Milliamperage (mA)
- Kilovoltage peak (kVp) (Correct answer)
- Exposure time
- Source-to-film distance
Correct answer: Kilovoltage peak (kVp)
kVp controls the maximum energy of X-ray photons, directly affecting their ability to penetrate the material being examined.
Question 2: In radiographic interpretation, subject contrast is primarily affected by:
- Film processing temperature
- Differences in material thickness and density (Correct answer)
- Darkroom illumination
- Film base + fog density
Correct answer: Differences in material thickness and density
Subject contrast arises from differences in thickness, density, and atomic number of the material being radiographed.
Question 3: When evaluating a radiograph, increasing kVp while keeping mAs constant will generally:
- Increase image contrast and decrease density
- Decrease image contrast and increase density (Correct answer)
- Increase both contrast and density equally
- Have no effect on film density
Correct answer: Decrease image contrast and increase density
Higher kVp produces more penetrating radiation, reducing differential absorption and lowering subject contrast while increasing overall film density.
Question 4: The term 'radiographic sensitivity' in industrial RT refers to:
- The ability of the detector to record images quickly
- The smallest detectable discontinuity size relative to specimen thickness (Correct answer)
- The speed class of the radiographic film used
- The ISO rating of the digital detector
Correct answer: The smallest detectable discontinuity size relative to specimen thickness
Radiographic sensitivity is expressed as the smallest detectable discontinuity as a percentage of the total material thickness.
Question 5: Which exposure parameter, when doubled, requires halving the exposure time to maintain equivalent film density?
- kVp
- Milliamperage (mA) (Correct answer)
- Source-to-film distance
- Film speed class
Correct answer: Milliamperage (mA)
mA and exposure time are reciprocally related; doubling mA allows the time to be halved while maintaining the same mAs and equivalent density.
Question 6: A longer source-to-film distance (SFD) in radiography primarily results in:
- Increased geometric unsharpness
- Decreased geometric unsharpness (Correct answer)
- Higher radiation dose to the film
- Increased scatter radiation reaching the film
Correct answer: Decreased geometric unsharpness
Increasing SFD reduces the penumbra (geometric unsharpness) because the radiation source subtends a smaller angle at the object.
Question 7: When comparing Class 1 and Class 4 industrial radiographic films, which statement is correct?
- Class 4 has finer grain and higher contrast than Class 1
- Class 1 has finer grain and higher contrast but requires more exposure than Class 4 (Correct answer)
- Class 1 and Class 4 have similar grain sizes but different speed
- Class 4 requires more exposure but produces higher resolution images
Correct answer: Class 1 has finer grain and higher contrast but requires more exposure than Class 4
Class 1 films are fine-grain, high-contrast films that require significantly more exposure than the faster Class 4 films.
CRI Contrast & Exposure Parameters 2
Which radiographic parameter most directly controls the energy of X-rays and thus penetrating power?