RAD 105 Exam: Digital Radiography Concepts and Techniques,
Exams of Nursing - 191 Questions
Comprehensive examination on RAD 105 Exam: Digital Radiography Concepts and Techniques, Exams of
Nursing. It contains 191 multiple-choice questions, each with four distractors and a fully worked rationale that
explains why the keyed answer is correct. Content is organized into 8 focused sections: Principles of Digital
Radiography, Image Acquisition and Processing, Image Display and Post-Processing, PACS and Image
Archiving, Exposure Techniques and Dose Optimization, Quality Control and Artifact Identification, Radiation
Safety and Regulations, Digital Imaging Anatomy and Positioning. Targeted learning outcomes include:
Demonstrate mastery of core concepts. Every item has been reviewed for clinical accuracy, current guidelines,
and clarity so that students can study with confidence and self-correct as they work through the bank. Use it as a
high-yield review immediately before the exam, or as a structured practice tool during the unit - the rationales
double as concise teaching notes. The recommended writing time is 3 hours, with a passing score of 70%. Aligned
with Aligned with US university standards. standards and reflects the question style commonly seen on accredited
program examinations. Students consistently achieving above the cut score on this bank have historically gone on
to earn A+ on the corresponding course exam. Read every stem carefully - distractors are written to look
plausible, and the best answer is sometimes the one that addresses the patient's most immediate physiological or
safety need. Where multiple options appear correct, prioritize airway, breathing, circulation, safety, and Maslow's
Section 1: Principles of Digital Radiography (Questions 1-22)
1 In digital radiography, the detective quantum efficiency (DQE) of a system is
defined as the:
A) Ratio of the output signal-to-noise ratio squared to the input
signal-to-noise ratio squared
B) Product of the modulation transfer function and the noise power spectrum
C) Ratio of the absorbed dose to the incident dose
D) Inverse of the noise equivalent quanta
Answer: A
Rationale: DQE measures how efficiently a detector converts incident X-ray
quanta into a useful image signal, defined as (SNR_out)^2/(SNR_in)^2. Option
B describes the noise-equivalent transfer function. Option C is the absorption
efficiency. Option D is the reciprocal of NEQ, not DQE.
2 A digital radiography system with a pixel pitch of 140 m and a fill factor of
80% is used. The theoretical Nyquist frequency (in cycles/mm) is
approximately:
A) 3.57
B) 7.14
C) 1.79
D) 2.86
,Answer: A
Rationale: Nyquist frequency = 1 / (2 * pixel pitch in mm). Pitch = 140 ¼m =
0.14 mm, so Nyquist = 1/(2*0.14) 3.57 cycles/mm. Options B, C, D are
incorrect calculations.
3 In a computed radiography (CR) system, the stimulated emission from the
photostimulable phosphor is inversely proportional to:
A) The intensity of the laser stimulation
B) The time delay between exposure and readout
C) The logarithm of the incident exposure
D) The square of the phosphor layer thickness
Answer: B
Rationale: The PSP exhibits fading; the signal decreases exponentially with
increasing time delay between exposure and readout. Option A: stimulated
emission increases with laser intensity up to saturation. Option C: CR response
is linear to exposure, not log. Option D: thickness affects sensitivity and
scatter, but not inverse proportionality.
4 In a direct conversion flat-panel detector using amorphous selenium, the
latent image is formed by:
A) Trapping of electron-hole pairs in the selenium layer
B) Conversion of X-rays to light by a scintillator
C) Storage of electrons in deep traps in the phosphor
D) Ionization of gas atoms in a chamber
Answer: A
Rationale: Direct conversion uses a photoconductor (a-Se) that directly converts
X-rays to electron-hole pairs, which are then collected by an applied electric
field to form the latent image. Option B describes indirect conversion. Option
C describes CR. Option D describes gas ionization detectors, not flat-panel.
5 An image quality factor that incorporates both noise and resolution, and is
often used to compare digital detector performance, is the:
A) Contrast-to-noise ratio (CNR)
B) Signal-to-noise ratio (SNR)
C) Detective quantum efficiency (DQE)
D) Noise equivalent quanta (NEQ)
,Answer: D
Rationale: NEQ combines the effects of noise and resolution (via MTF and
NPS) to give the number of quanta that would produce the same SNR if the
system were ideal. DQE is the ratio of NEQ to incident quanta. CNR and SNR
are simpler measures that do not fully incorporate resolution.
6 A digital radiography system with a matrix size of 2000 × 2000 pixels and a
field of view (FOV) of 40 × 40 cm is used. The spatial resolution in line pairs
per millimeter (lp/mm) limited by pixel size is:
A) 2.5
B) 5.0
C) 1.25
D) 0.25
Answer: A
Rationale: Pixel size = FOV / matrix size = 400 mm / 2000 = 0.2 mm. The
limiting resolution (Nyquist) is 1/(2 * 0.2) = 2.5 lp/mm. Option B doubles that,
option C halves, option D is off by factor 10.
7 In a digital radiographic image, the appearance of quantum mottle will be
most pronounced when the:
A) Detector dose is low and the detector has high DQE
B) Detector dose is high and the detector has low DQE
C) Detector dose is low and the detector has low DQE
D) Detector dose is high and the detector has high DQE
Answer: C
Rationale: Quantum mottle (noise) increases when fewer X-ray quanta are used
(low dose) and when the detector is inefficient (low DQE), so more noise per
quantum. High DQE reduces noise for a given dose.
8 Which of the following post-processing operations is most likely to increase
the contrast of subtle, low-contrast lesions in a digital radiograph?
A) Adaptive histogram equalization
B) Edge enhancement using an unsharp mask
C) Smoothing with a Gaussian filter
D) Global linear contrast stretching
Answer: A
, Rationale: Adaptive histogram equalization locally redistributes pixel values to
enhance contrast in regions with similar gray levels, improving visibility of
subtle features. Edge enhancement (B) increases sharpness but may increase
noise. Smoothing (C) reduces contrast. Global stretching (D) improves overall
contrast but may not help in low-contrast areas.
9 In a flat-panel detector based on amorphous silicon (a-Si) with a cesium
iodide (CsI) scintillator, the conversion of X-rays to light occurs primarily
via:
A) Photoelectric effect in CsI
B) Compton scattering in CsI
C) Bremsstrahlung in Si
D) Pair production in CsI
Answer: A
Rationale: CsI is a scintillator that absorbs X-rays mainly through the
photoelectric effect (due to high atomic number), producing visible light
photons. Compton scattering (B) is less probable at diagnostic energies and
does not efficiently produce light. Bremsstrahlung (C) is not the primary
conversion mechanism. Pair production (D) requires >1.022 MeV.
10 For each image processing technique, select whether it primarily affects
spatial resolution, contrast, or noise. (Indicate the effect for each.)
A) All rows correctly assigned
B) One row incorrectly assigned
C) Two rows incorrectly assigned
D) Three or more rows incorrectly assigned
Answer: A
Rationale: Unsharp mask and edge enhancement affect spatial resolution
(sharpness). Histogram equalization and window level affect contrast. Median
filtering and adaptive noise reduction reduce noise. All rows are correctly
assigned.
11 A digital radiography system's detective quantum efficiency (DQE) is
measured at 0.65 at 0.5 cycles/mm. Which statement best interprets the
clinical impact of this DQE value compared to a system with DQE 0.80 at
the same frequency?
Exams of Nursing - 191 Questions
Comprehensive examination on RAD 105 Exam: Digital Radiography Concepts and Techniques, Exams of
Nursing. It contains 191 multiple-choice questions, each with four distractors and a fully worked rationale that
explains why the keyed answer is correct. Content is organized into 8 focused sections: Principles of Digital
Radiography, Image Acquisition and Processing, Image Display and Post-Processing, PACS and Image
Archiving, Exposure Techniques and Dose Optimization, Quality Control and Artifact Identification, Radiation
Safety and Regulations, Digital Imaging Anatomy and Positioning. Targeted learning outcomes include:
Demonstrate mastery of core concepts. Every item has been reviewed for clinical accuracy, current guidelines,
and clarity so that students can study with confidence and self-correct as they work through the bank. Use it as a
high-yield review immediately before the exam, or as a structured practice tool during the unit - the rationales
double as concise teaching notes. The recommended writing time is 3 hours, with a passing score of 70%. Aligned
with Aligned with US university standards. standards and reflects the question style commonly seen on accredited
program examinations. Students consistently achieving above the cut score on this bank have historically gone on
to earn A+ on the corresponding course exam. Read every stem carefully - distractors are written to look
plausible, and the best answer is sometimes the one that addresses the patient's most immediate physiological or
safety need. Where multiple options appear correct, prioritize airway, breathing, circulation, safety, and Maslow's
Section 1: Principles of Digital Radiography (Questions 1-22)
1 In digital radiography, the detective quantum efficiency (DQE) of a system is
defined as the:
A) Ratio of the output signal-to-noise ratio squared to the input
signal-to-noise ratio squared
B) Product of the modulation transfer function and the noise power spectrum
C) Ratio of the absorbed dose to the incident dose
D) Inverse of the noise equivalent quanta
Answer: A
Rationale: DQE measures how efficiently a detector converts incident X-ray
quanta into a useful image signal, defined as (SNR_out)^2/(SNR_in)^2. Option
B describes the noise-equivalent transfer function. Option C is the absorption
efficiency. Option D is the reciprocal of NEQ, not DQE.
2 A digital radiography system with a pixel pitch of 140 m and a fill factor of
80% is used. The theoretical Nyquist frequency (in cycles/mm) is
approximately:
A) 3.57
B) 7.14
C) 1.79
D) 2.86
,Answer: A
Rationale: Nyquist frequency = 1 / (2 * pixel pitch in mm). Pitch = 140 ¼m =
0.14 mm, so Nyquist = 1/(2*0.14) 3.57 cycles/mm. Options B, C, D are
incorrect calculations.
3 In a computed radiography (CR) system, the stimulated emission from the
photostimulable phosphor is inversely proportional to:
A) The intensity of the laser stimulation
B) The time delay between exposure and readout
C) The logarithm of the incident exposure
D) The square of the phosphor layer thickness
Answer: B
Rationale: The PSP exhibits fading; the signal decreases exponentially with
increasing time delay between exposure and readout. Option A: stimulated
emission increases with laser intensity up to saturation. Option C: CR response
is linear to exposure, not log. Option D: thickness affects sensitivity and
scatter, but not inverse proportionality.
4 In a direct conversion flat-panel detector using amorphous selenium, the
latent image is formed by:
A) Trapping of electron-hole pairs in the selenium layer
B) Conversion of X-rays to light by a scintillator
C) Storage of electrons in deep traps in the phosphor
D) Ionization of gas atoms in a chamber
Answer: A
Rationale: Direct conversion uses a photoconductor (a-Se) that directly converts
X-rays to electron-hole pairs, which are then collected by an applied electric
field to form the latent image. Option B describes indirect conversion. Option
C describes CR. Option D describes gas ionization detectors, not flat-panel.
5 An image quality factor that incorporates both noise and resolution, and is
often used to compare digital detector performance, is the:
A) Contrast-to-noise ratio (CNR)
B) Signal-to-noise ratio (SNR)
C) Detective quantum efficiency (DQE)
D) Noise equivalent quanta (NEQ)
,Answer: D
Rationale: NEQ combines the effects of noise and resolution (via MTF and
NPS) to give the number of quanta that would produce the same SNR if the
system were ideal. DQE is the ratio of NEQ to incident quanta. CNR and SNR
are simpler measures that do not fully incorporate resolution.
6 A digital radiography system with a matrix size of 2000 × 2000 pixels and a
field of view (FOV) of 40 × 40 cm is used. The spatial resolution in line pairs
per millimeter (lp/mm) limited by pixel size is:
A) 2.5
B) 5.0
C) 1.25
D) 0.25
Answer: A
Rationale: Pixel size = FOV / matrix size = 400 mm / 2000 = 0.2 mm. The
limiting resolution (Nyquist) is 1/(2 * 0.2) = 2.5 lp/mm. Option B doubles that,
option C halves, option D is off by factor 10.
7 In a digital radiographic image, the appearance of quantum mottle will be
most pronounced when the:
A) Detector dose is low and the detector has high DQE
B) Detector dose is high and the detector has low DQE
C) Detector dose is low and the detector has low DQE
D) Detector dose is high and the detector has high DQE
Answer: C
Rationale: Quantum mottle (noise) increases when fewer X-ray quanta are used
(low dose) and when the detector is inefficient (low DQE), so more noise per
quantum. High DQE reduces noise for a given dose.
8 Which of the following post-processing operations is most likely to increase
the contrast of subtle, low-contrast lesions in a digital radiograph?
A) Adaptive histogram equalization
B) Edge enhancement using an unsharp mask
C) Smoothing with a Gaussian filter
D) Global linear contrast stretching
Answer: A
, Rationale: Adaptive histogram equalization locally redistributes pixel values to
enhance contrast in regions with similar gray levels, improving visibility of
subtle features. Edge enhancement (B) increases sharpness but may increase
noise. Smoothing (C) reduces contrast. Global stretching (D) improves overall
contrast but may not help in low-contrast areas.
9 In a flat-panel detector based on amorphous silicon (a-Si) with a cesium
iodide (CsI) scintillator, the conversion of X-rays to light occurs primarily
via:
A) Photoelectric effect in CsI
B) Compton scattering in CsI
C) Bremsstrahlung in Si
D) Pair production in CsI
Answer: A
Rationale: CsI is a scintillator that absorbs X-rays mainly through the
photoelectric effect (due to high atomic number), producing visible light
photons. Compton scattering (B) is less probable at diagnostic energies and
does not efficiently produce light. Bremsstrahlung (C) is not the primary
conversion mechanism. Pair production (D) requires >1.022 MeV.
10 For each image processing technique, select whether it primarily affects
spatial resolution, contrast, or noise. (Indicate the effect for each.)
A) All rows correctly assigned
B) One row incorrectly assigned
C) Two rows incorrectly assigned
D) Three or more rows incorrectly assigned
Answer: A
Rationale: Unsharp mask and edge enhancement affect spatial resolution
(sharpness). Histogram equalization and window level affect contrast. Median
filtering and adaptive noise reduction reduce noise. All rows are correctly
assigned.
11 A digital radiography system's detective quantum efficiency (DQE) is
measured at 0.65 at 0.5 cycles/mm. Which statement best interprets the
clinical impact of this DQE value compared to a system with DQE 0.80 at
the same frequency?
