Bushong’s Radiologic Science for Technologists Test Bank
13th Edition EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Radiologic Physics and Electromagnetism
2. The X-ray Imaging System and Tube Dynamics
3. X-ray Production, Emission, and Filtration
4. X-ray Interaction with Matter
5. Radiographic Image Quality and Artifacts
6. Digital Radiography and Image Processing
7. Computed Tomography Physics
8. Radiobiology at the Molecular and Cellular Level
9. Early and Late Radiation Effects
10. Health Physics and Radiation Protection
1. During a routine fluoroscopic procedure, the operator notices that the image brightness suddenly
drops when panning over a thicker anatomical part, but then quickly recovers. Which component
of the fluoroscopic system is primarily responsible for compensating for this change, and what
specific parameter is being dynamically adjusted?
A. The input phosphor; altering the conversion efficiency of x-rays to light photons based on
tissue density.
, B. The Automatic Brightness Control (ABC); modulating the mA and/or kVp of the x-ray
tube.
C. The flux gain mechanism; increasing the kinetic energy of the photoelectrons traveling across
the intensifying tube.
D. The minification gain; adjusting the electrostatic focusing lenses to compress the electron
beam tighter.
CORRECT ANSWER : B
Rationale: The Automatic Brightness Control (ABC) circuit continuously monitors the light
output or video signal of the image intensifier and automatically adjusts the x-ray tube's mA
and/or kVp to maintain optimal image brightness as tissue thickness changes. The input
phosphor, flux gain, and minification gain represent physical properties or inherent operational
physics of the image intensifier tube that cannot be dynamically adjusted on the fly to
compensate for patient variations.
2. A radiologic technologist is evaluating an image of a lateral lumbar spine that exhibits significant
quantum mottle despite using an optimal kVp. If the technologist wishes to reduce the image
noise by half in the repeat exposure, what precise adjustment must be made to the technical
factors?
A. Increase the mAs by a factor of 2.
B. Decrease the kVp by 15% to increase photoelectric absorption.
C. Increase the mAs by a factor of 4.
D. Increase the source-to-image distance (SID) to reduce scatter reaching the receptor.
CORRECT ANSWER : C
Rationale: Quantum mottle is a statistical fluctuation in the number of x-ray photons interacting
with the image receptor, governed by Poisson statistics. Because the signal-to-noise ratio (SNR)
is proportional to the square root of the number of photons, decreasing the noise by half requires
increasing the number of photons (the mAs) by a factor of four. Doubling the mAs would only
improve the SNR by a factor of 1.41, while altering kVp or SID addresses contrast and intensity
respectively, but not the fundamental statistical requirement for halving noise.
3. In analyzing the continuous x-ray emission spectrum, a shift of the peak amplitude to the right
(higher energy) accompanied by an increase in the total area under the curve is observed on a
graph. Which operator adjustment most accurately accounts for this specific spectral change?
A. Increasing the mAs from 10 to 20.
, B. Increasing the kVp from 70 to 85.
C. Adding 2 mm Al equivalent of added filtration.
D. Changing the target material from molybdenum to tungsten.
CORRECT ANSWER : B
Rationale: Increasing the kVp increases both the maximum energy (shifting the spectrum to the
right) and the total number of x-rays produced (increasing the amplitude/area under the curve).
Increasing mAs only increases the amplitude without shifting the energy peak, whereas adding
filtration reduces amplitude while shifting the peak to the right. Changing the target material
alters the discrete characteristic emission spectrum, not just the continuous bremsstrahlung
peak.
4. A patient undergoing a chest CT scan has metallic orthopedic hardware in their thoracic spine.
The resulting images demonstrate prominent streak artifacts obscuring the mediastinal anatomy.
Which physical interaction of x-rays with matter is fundamentally responsible for this specific
artifact in computed tomography?
A. Photoelectric absorption completely attenuating the primary beam.
B. Compton scattering deflecting high-energy photons into adjacent detectors.
C. Coherent scattering creating secondary, low-energy scatter rays.
D. Pair production creating localized annihilation radiation events.
CORRECT ANSWER : A
Rationale: Metallic streak artifacts in CT (photon starvation) occur because dense materials
with high atomic numbers completely absorb the x-ray beam via photoelectric effect, resulting in
zero or near-zero photons reaching the detectors behind the metal. The reconstruction algorithm
cannot compute tissue densities without transmission data, causing streaks. Compton and
coherent scatter degrade contrast but do not cause total signal dropout, and pair production
requires energies over 1.02 MeV, which are not used in diagnostic CT.
5. When assessing the linear energy transfer (LET) and relative biological effectiveness (RBE) of
various ionizing radiations, a health physicist notes that 5 MeV alpha particles cause
significantly more double-strand DNA breaks than 5 MeV x-rays. Which principle best explains
this observation?
A. Alpha particles have a higher velocity, allowing them to penetrate deeper into the cell
nucleus.
B. X-rays are electromagnetic waves that bypass the cytoplasm without transferring energy.
, C. Alpha particles possess a higher mass and charge, causing dense ionization tracks and
higher energy deposition per micrometer of tissue.
D. The oxygen enhancement ratio (OER) is maximized when cells are exposed to high-LET
radiations like alpha particles.
CORRECT ANSWER : C
Rationale: Alpha particles have a +2 charge and significant mass, causing them to interact
heavily with atomic electrons, yielding a high LET and dense ionization tracks that are highly
effective at causing irreparable double-strand DNA breaks. X-rays have no mass or charge,
resulting in sparse, low-LET ionization events. Furthermore, the oxygen enhancement ratio
(OER) is actually lower (closer to 1) for high-LET radiations, making option D factually
incorrect.
6. During quality control testing of a digital radiography system, the physicist evaluates the
modulation transfer function (MTF). A spatial frequency test reveals an MTF of 0.1 at 4 line
pairs per millimeter (lp/mm). How should this measurement be interpreted regarding the system's
performance?
A. The system perfectly reproduces the anatomical details at this spatial frequency with zero
noise.
B. The system accurately reproduces only 10% of the object's original contrast at this
specific spatial frequency.
C. The image receptor requires 10% more exposure to resolve structures at 4 lp/mm.
D. The system is operating optimally, as an MTF of 0.1 is the maximum theoretical limit for
digital receptors.
CORRECT ANSWER : B
Rationale: Modulation Transfer Function (MTF) is a ratio of image contrast to object contrast at
a given spatial frequency. An MTF of 0.1 indicates that only 10% of the original subject contrast
is preserved in the image at 4 lp/mm, meaning small details are severely blurred. A perfect
system would have an MTF of 1.0 (100% preservation). Options A, C, and D misinterpret the
mathematical definition and practical application of MTF in imaging physics.
7. A radiographer is positioning a patient for an AP projection of the abdomen. To manage patient
dose, the radiographer considers the application of the inverse square law and air gap technique.
If the source-to-image distance (SID) is increased from 100 cm to 150 cm, what happens to the
intensity of the unattenuated x-ray beam at the image receptor if technical factors remain
unchanged?
A. The intensity is reduced to 66% of its original value.
13th Edition EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Radiologic Physics and Electromagnetism
2. The X-ray Imaging System and Tube Dynamics
3. X-ray Production, Emission, and Filtration
4. X-ray Interaction with Matter
5. Radiographic Image Quality and Artifacts
6. Digital Radiography and Image Processing
7. Computed Tomography Physics
8. Radiobiology at the Molecular and Cellular Level
9. Early and Late Radiation Effects
10. Health Physics and Radiation Protection
1. During a routine fluoroscopic procedure, the operator notices that the image brightness suddenly
drops when panning over a thicker anatomical part, but then quickly recovers. Which component
of the fluoroscopic system is primarily responsible for compensating for this change, and what
specific parameter is being dynamically adjusted?
A. The input phosphor; altering the conversion efficiency of x-rays to light photons based on
tissue density.
, B. The Automatic Brightness Control (ABC); modulating the mA and/or kVp of the x-ray
tube.
C. The flux gain mechanism; increasing the kinetic energy of the photoelectrons traveling across
the intensifying tube.
D. The minification gain; adjusting the electrostatic focusing lenses to compress the electron
beam tighter.
CORRECT ANSWER : B
Rationale: The Automatic Brightness Control (ABC) circuit continuously monitors the light
output or video signal of the image intensifier and automatically adjusts the x-ray tube's mA
and/or kVp to maintain optimal image brightness as tissue thickness changes. The input
phosphor, flux gain, and minification gain represent physical properties or inherent operational
physics of the image intensifier tube that cannot be dynamically adjusted on the fly to
compensate for patient variations.
2. A radiologic technologist is evaluating an image of a lateral lumbar spine that exhibits significant
quantum mottle despite using an optimal kVp. If the technologist wishes to reduce the image
noise by half in the repeat exposure, what precise adjustment must be made to the technical
factors?
A. Increase the mAs by a factor of 2.
B. Decrease the kVp by 15% to increase photoelectric absorption.
C. Increase the mAs by a factor of 4.
D. Increase the source-to-image distance (SID) to reduce scatter reaching the receptor.
CORRECT ANSWER : C
Rationale: Quantum mottle is a statistical fluctuation in the number of x-ray photons interacting
with the image receptor, governed by Poisson statistics. Because the signal-to-noise ratio (SNR)
is proportional to the square root of the number of photons, decreasing the noise by half requires
increasing the number of photons (the mAs) by a factor of four. Doubling the mAs would only
improve the SNR by a factor of 1.41, while altering kVp or SID addresses contrast and intensity
respectively, but not the fundamental statistical requirement for halving noise.
3. In analyzing the continuous x-ray emission spectrum, a shift of the peak amplitude to the right
(higher energy) accompanied by an increase in the total area under the curve is observed on a
graph. Which operator adjustment most accurately accounts for this specific spectral change?
A. Increasing the mAs from 10 to 20.
, B. Increasing the kVp from 70 to 85.
C. Adding 2 mm Al equivalent of added filtration.
D. Changing the target material from molybdenum to tungsten.
CORRECT ANSWER : B
Rationale: Increasing the kVp increases both the maximum energy (shifting the spectrum to the
right) and the total number of x-rays produced (increasing the amplitude/area under the curve).
Increasing mAs only increases the amplitude without shifting the energy peak, whereas adding
filtration reduces amplitude while shifting the peak to the right. Changing the target material
alters the discrete characteristic emission spectrum, not just the continuous bremsstrahlung
peak.
4. A patient undergoing a chest CT scan has metallic orthopedic hardware in their thoracic spine.
The resulting images demonstrate prominent streak artifacts obscuring the mediastinal anatomy.
Which physical interaction of x-rays with matter is fundamentally responsible for this specific
artifact in computed tomography?
A. Photoelectric absorption completely attenuating the primary beam.
B. Compton scattering deflecting high-energy photons into adjacent detectors.
C. Coherent scattering creating secondary, low-energy scatter rays.
D. Pair production creating localized annihilation radiation events.
CORRECT ANSWER : A
Rationale: Metallic streak artifacts in CT (photon starvation) occur because dense materials
with high atomic numbers completely absorb the x-ray beam via photoelectric effect, resulting in
zero or near-zero photons reaching the detectors behind the metal. The reconstruction algorithm
cannot compute tissue densities without transmission data, causing streaks. Compton and
coherent scatter degrade contrast but do not cause total signal dropout, and pair production
requires energies over 1.02 MeV, which are not used in diagnostic CT.
5. When assessing the linear energy transfer (LET) and relative biological effectiveness (RBE) of
various ionizing radiations, a health physicist notes that 5 MeV alpha particles cause
significantly more double-strand DNA breaks than 5 MeV x-rays. Which principle best explains
this observation?
A. Alpha particles have a higher velocity, allowing them to penetrate deeper into the cell
nucleus.
B. X-rays are electromagnetic waves that bypass the cytoplasm without transferring energy.
, C. Alpha particles possess a higher mass and charge, causing dense ionization tracks and
higher energy deposition per micrometer of tissue.
D. The oxygen enhancement ratio (OER) is maximized when cells are exposed to high-LET
radiations like alpha particles.
CORRECT ANSWER : C
Rationale: Alpha particles have a +2 charge and significant mass, causing them to interact
heavily with atomic electrons, yielding a high LET and dense ionization tracks that are highly
effective at causing irreparable double-strand DNA breaks. X-rays have no mass or charge,
resulting in sparse, low-LET ionization events. Furthermore, the oxygen enhancement ratio
(OER) is actually lower (closer to 1) for high-LET radiations, making option D factually
incorrect.
6. During quality control testing of a digital radiography system, the physicist evaluates the
modulation transfer function (MTF). A spatial frequency test reveals an MTF of 0.1 at 4 line
pairs per millimeter (lp/mm). How should this measurement be interpreted regarding the system's
performance?
A. The system perfectly reproduces the anatomical details at this spatial frequency with zero
noise.
B. The system accurately reproduces only 10% of the object's original contrast at this
specific spatial frequency.
C. The image receptor requires 10% more exposure to resolve structures at 4 lp/mm.
D. The system is operating optimally, as an MTF of 0.1 is the maximum theoretical limit for
digital receptors.
CORRECT ANSWER : B
Rationale: Modulation Transfer Function (MTF) is a ratio of image contrast to object contrast at
a given spatial frequency. An MTF of 0.1 indicates that only 10% of the original subject contrast
is preserved in the image at 4 lp/mm, meaning small details are severely blurred. A perfect
system would have an MTF of 1.0 (100% preservation). Options A, C, and D misinterpret the
mathematical definition and practical application of MTF in imaging physics.
7. A radiographer is positioning a patient for an AP projection of the abdomen. To manage patient
dose, the radiographer considers the application of the inverse square law and air gap technique.
If the source-to-image distance (SID) is increased from 100 cm to 150 cm, what happens to the
intensity of the unattenuated x-ray beam at the image receptor if technical factors remain
unchanged?
A. The intensity is reduced to 66% of its original value.
