Respiratory Therapy Comprehensive Review
Respiratory Therapy Comprehensive Review
Comprehensive Review | Questions 1–200
Question 1
Which principle is most directly responsible for reducing a patient’s radiation exposure during an X-ray
examination?
Options
A. Increasing exposure time
B. Using the highest reasonable kVp and lowest appropriate mAs
C. Increasing the source-to-image distance
D. Using a larger focal spot
Correct Answer: B. Using the highest reasonable kVp and lowest appropriate mAs
Detailed Rationale:
Using an appropriate higher kVp with the lowest mAs that produces a diagnostically acceptable image can reduce
patient radiation exposure. mAs primarily controls the quantity of X-rays produced, while kVp controls beam energy
and penetration. Technique selection must always maintain adequate diagnostic image quality.
Why the Other Options Are Incorrect:
A. Increasing exposure time: Longer exposure time can increase radiation exposure if mA remains unchanged.
C. Increasing SID: Increasing SID can reduce radiation intensity at the image receptor according to the inverse square
law, but it is not the primary technique described here.
D. Using a larger focal spot: Focal-spot size primarily affects spatial resolution rather than directly minimizing patient
dose.
Question 2
Which interaction between an X-ray photon and an atom results in complete absorption of the photon?
Options
A. Coherent scattering
B. Compton scattering
C. Photoelectric absorption
D. Pair production
Correct Answer: C. Photoelectric absorption
Detailed Rationale:
During photoelectric absorption, the incoming X-ray photon transfers all of its energy to an inner-shell electron and is
completely absorbed. The electron is ejected, leaving an ionized atom. Photoelectric absorption contributes
significantly to subject contrast because tissues with different atomic numbers demonstrate different probabilities of
photoelectric interactions.
Why the Other Options Are Incorrect:
A. Coherent scattering: The photon changes direction without significant energy loss or ionization.
B. Compton scattering: The photon transfers part of its energy to an outer-shell electron and continues in a different
direction.
D. Pair production: This requires photon energy of at least 1.022 MeV and is not the typical interaction in diagnostic
radiography.
Question 3
What is the primary purpose of collimation in diagnostic radiography?
Respiratory Therapy Comprehensive Review | Practice Resource • Page 1
, Respiratory Therapy Comprehensive Review
Options
A. Increase scatter radiation
B. Increase patient dose
C. Restrict the X-ray beam to the area of clinical interest
D. Increase exposure time
Correct Answer: C. Restrict the X-ray beam to the area of clinical interest
Detailed Rationale:
Collimation restricts the X-ray beam to the anatomical region being examined. This reduces the volume of tissue
irradiated and decreases scatter radiation reaching the image receptor. Proper collimation can therefore improve
image contrast while helping reduce unnecessary radiation exposure.
Why the Other Options Are Incorrect:
A. Increase scatter radiation: Collimation decreases scatter production.
B. Increase patient dose: Proper collimation generally decreases unnecessary radiation exposure.
D. Increase exposure time: Exposure time is controlled separately by the radiographic technique.
Question 4
Which radiographic factor primarily controls the quantity of X-rays produced?
Options
A. kVp
B. mAs
C. SID
D. OID
Correct Answer: B. mAs
Detailed Rationale:
Milliampere-seconds (mAs) represent tube current multiplied by exposure time. mAs primarily determines the
quantity of X-ray photons produced. Increasing mAs generally increases receptor exposure and patient radiation
dose.
Why the Other Options Are Incorrect:
A. kVp: Primarily controls photon energy and beam penetration and also influences receptor exposure.
C. SID: Source-to-image distance affects beam intensity at the receptor.
D. OID: Object-to-image distance affects magnification and spatial relationships.
Question 5
A radiographer increases the kVp while keeping mAs constant. What is the most likely effect?
Options
A. Decreased beam penetration
B. Increased beam penetration
C. Complete elimination of scatter
D. No change in photon energy
Correct Answer: B. Increased beam penetration
Detailed Rationale:
Increasing kVp increases the maximum and average energy of photons in the X-ray beam. This produces a more
penetrating beam. Changes in kVp also affect image receptor exposure and radiographic contrast, so technique
adjustments should be made carefully.
Respiratory Therapy Comprehensive Review | Practice Resource • Page 2
, Respiratory Therapy Comprehensive Review
Why the Other Options Are Incorrect:
A. Decreased beam penetration: The opposite occurs when kVp increases.
C. Complete elimination of scatter: Scatter cannot be completely eliminated by increasing kVp.
D. No change in photon energy: kVp directly affects photon energy.
Question 6
Which device is primarily used to restrict the size and shape of the X-ray beam?
Options
A. Grid
B. Collimator
C. Cassette
D. Ionization chamber
Correct Answer: B. Collimator
Detailed Rationale:
The collimator contains adjustable shutters that restrict the X-ray beam to the desired field size. Limiting the field
reduces irradiated tissue volume and scatter production.
Why the Other Options Are Incorrect:
A. Grid: A grid absorbs scatter radiation before it reaches the image receptor.
C. Cassette: A cassette houses an image receptor in systems that use cassette-based imaging.
D. Ionization chamber: It measures radiation exposure and may be used in automatic exposure control systems.
Question 7
What is the primary purpose of an anti-scatter grid?
Options
A. Increase patient motion
B. Absorb scatter radiation before it reaches the image receptor
C. Reduce beam energy
D. Increase the size of the radiation field
Correct Answer: B. Absorb scatter radiation before it reaches the image receptor
Detailed Rationale:
A grid consists of alternating radiopaque and radiolucent strips designed to preferentially allow primary radiation to
reach the detector while absorbing much of the scattered radiation. This improves image contrast. Because grids
absorb some primary radiation as well, technique adjustments may be required.
Why the Other Options Are Incorrect:
A. Increase patient motion: Motion is unrelated to the purpose of a grid.
C. Reduce beam energy: Grid operation does not primarily alter photon energy.
D. Increase radiation field size: Field size is controlled primarily through collimation.
Question 8
Which positioning principle is most important when obtaining a diagnostic radiograph?
Options
A. Position the patient randomly as long as the anatomy is included
B. Follow the required anatomical and positioning criteria for the projection
Respiratory Therapy Comprehensive Review | Practice Resource • Page 3
, Respiratory Therapy Comprehensive Review
C. Always use the largest possible field size
D. Always use the shortest SID available
Correct Answer: B. Follow the required anatomical and positioning criteria for the projection
Detailed Rationale:
Accurate positioning is essential for demonstrating anatomy in the intended projection and minimizing distortion. The
radiographer must follow established positioning criteria, identify the correct side, center accurately, and ensure the
required anatomy is included.
Why the Other Options Are Incorrect:
A. Random positioning: Incorrect positioning can obscure anatomy or create misleading appearances.
C. Largest possible field: Excessive field size increases unnecessary radiation and scatter.
D. Shortest SID: SID should be selected according to the examination and projection requirements.
Question 9
Which projection is commonly used to demonstrate the heart and lungs while minimizing cardiac
magnification?
Options
A. AP supine
B. PA upright
C. AP prone
D. Lateral decubitus only
Correct Answer: B. PA upright
Detailed Rationale:
A PA chest radiograph is commonly obtained with the patient upright and the anterior chest against the image
receptor. The heart is closer to the receptor, which helps minimize magnification compared with an AP projection.
Why the Other Options Are Incorrect:
A. AP supine: Often produces greater cardiac magnification and is frequently used for patients who cannot stand.
C. AP prone: Not the standard routine chest projection.
D. Lateral decubitus only: Decubitus imaging is used for specific clinical indications rather than as the standard chest
examination.
Question 10
Which breathing instruction is commonly used for a routine chest radiograph?
Options
A. Suspend respiration after full expiration
B. Suspend respiration after the second full inspiration
C. Breathe rapidly throughout the exposure
D. Hold the breath only after coughing
Correct Answer: B. Suspend respiration after the second full inspiration
Detailed Rationale:
A routine PA chest radiograph is generally obtained after the patient takes a deep inspiration and holds the breath.
Adequate inspiration helps maximize lung expansion and improves visualization of the pulmonary fields.
Why the Other Options Are Incorrect:
A. Full expiration: Expiratory images may be obtained for specific indications but are not the routine standard.
C. Breathe rapidly: Motion from respiration would degrade the image.
Respiratory Therapy Comprehensive Review | Practice Resource • Page 4
Respiratory Therapy Comprehensive Review
Comprehensive Review | Questions 1–200
Question 1
Which principle is most directly responsible for reducing a patient’s radiation exposure during an X-ray
examination?
Options
A. Increasing exposure time
B. Using the highest reasonable kVp and lowest appropriate mAs
C. Increasing the source-to-image distance
D. Using a larger focal spot
Correct Answer: B. Using the highest reasonable kVp and lowest appropriate mAs
Detailed Rationale:
Using an appropriate higher kVp with the lowest mAs that produces a diagnostically acceptable image can reduce
patient radiation exposure. mAs primarily controls the quantity of X-rays produced, while kVp controls beam energy
and penetration. Technique selection must always maintain adequate diagnostic image quality.
Why the Other Options Are Incorrect:
A. Increasing exposure time: Longer exposure time can increase radiation exposure if mA remains unchanged.
C. Increasing SID: Increasing SID can reduce radiation intensity at the image receptor according to the inverse square
law, but it is not the primary technique described here.
D. Using a larger focal spot: Focal-spot size primarily affects spatial resolution rather than directly minimizing patient
dose.
Question 2
Which interaction between an X-ray photon and an atom results in complete absorption of the photon?
Options
A. Coherent scattering
B. Compton scattering
C. Photoelectric absorption
D. Pair production
Correct Answer: C. Photoelectric absorption
Detailed Rationale:
During photoelectric absorption, the incoming X-ray photon transfers all of its energy to an inner-shell electron and is
completely absorbed. The electron is ejected, leaving an ionized atom. Photoelectric absorption contributes
significantly to subject contrast because tissues with different atomic numbers demonstrate different probabilities of
photoelectric interactions.
Why the Other Options Are Incorrect:
A. Coherent scattering: The photon changes direction without significant energy loss or ionization.
B. Compton scattering: The photon transfers part of its energy to an outer-shell electron and continues in a different
direction.
D. Pair production: This requires photon energy of at least 1.022 MeV and is not the typical interaction in diagnostic
radiography.
Question 3
What is the primary purpose of collimation in diagnostic radiography?
Respiratory Therapy Comprehensive Review | Practice Resource • Page 1
, Respiratory Therapy Comprehensive Review
Options
A. Increase scatter radiation
B. Increase patient dose
C. Restrict the X-ray beam to the area of clinical interest
D. Increase exposure time
Correct Answer: C. Restrict the X-ray beam to the area of clinical interest
Detailed Rationale:
Collimation restricts the X-ray beam to the anatomical region being examined. This reduces the volume of tissue
irradiated and decreases scatter radiation reaching the image receptor. Proper collimation can therefore improve
image contrast while helping reduce unnecessary radiation exposure.
Why the Other Options Are Incorrect:
A. Increase scatter radiation: Collimation decreases scatter production.
B. Increase patient dose: Proper collimation generally decreases unnecessary radiation exposure.
D. Increase exposure time: Exposure time is controlled separately by the radiographic technique.
Question 4
Which radiographic factor primarily controls the quantity of X-rays produced?
Options
A. kVp
B. mAs
C. SID
D. OID
Correct Answer: B. mAs
Detailed Rationale:
Milliampere-seconds (mAs) represent tube current multiplied by exposure time. mAs primarily determines the
quantity of X-ray photons produced. Increasing mAs generally increases receptor exposure and patient radiation
dose.
Why the Other Options Are Incorrect:
A. kVp: Primarily controls photon energy and beam penetration and also influences receptor exposure.
C. SID: Source-to-image distance affects beam intensity at the receptor.
D. OID: Object-to-image distance affects magnification and spatial relationships.
Question 5
A radiographer increases the kVp while keeping mAs constant. What is the most likely effect?
Options
A. Decreased beam penetration
B. Increased beam penetration
C. Complete elimination of scatter
D. No change in photon energy
Correct Answer: B. Increased beam penetration
Detailed Rationale:
Increasing kVp increases the maximum and average energy of photons in the X-ray beam. This produces a more
penetrating beam. Changes in kVp also affect image receptor exposure and radiographic contrast, so technique
adjustments should be made carefully.
Respiratory Therapy Comprehensive Review | Practice Resource • Page 2
, Respiratory Therapy Comprehensive Review
Why the Other Options Are Incorrect:
A. Decreased beam penetration: The opposite occurs when kVp increases.
C. Complete elimination of scatter: Scatter cannot be completely eliminated by increasing kVp.
D. No change in photon energy: kVp directly affects photon energy.
Question 6
Which device is primarily used to restrict the size and shape of the X-ray beam?
Options
A. Grid
B. Collimator
C. Cassette
D. Ionization chamber
Correct Answer: B. Collimator
Detailed Rationale:
The collimator contains adjustable shutters that restrict the X-ray beam to the desired field size. Limiting the field
reduces irradiated tissue volume and scatter production.
Why the Other Options Are Incorrect:
A. Grid: A grid absorbs scatter radiation before it reaches the image receptor.
C. Cassette: A cassette houses an image receptor in systems that use cassette-based imaging.
D. Ionization chamber: It measures radiation exposure and may be used in automatic exposure control systems.
Question 7
What is the primary purpose of an anti-scatter grid?
Options
A. Increase patient motion
B. Absorb scatter radiation before it reaches the image receptor
C. Reduce beam energy
D. Increase the size of the radiation field
Correct Answer: B. Absorb scatter radiation before it reaches the image receptor
Detailed Rationale:
A grid consists of alternating radiopaque and radiolucent strips designed to preferentially allow primary radiation to
reach the detector while absorbing much of the scattered radiation. This improves image contrast. Because grids
absorb some primary radiation as well, technique adjustments may be required.
Why the Other Options Are Incorrect:
A. Increase patient motion: Motion is unrelated to the purpose of a grid.
C. Reduce beam energy: Grid operation does not primarily alter photon energy.
D. Increase radiation field size: Field size is controlled primarily through collimation.
Question 8
Which positioning principle is most important when obtaining a diagnostic radiograph?
Options
A. Position the patient randomly as long as the anatomy is included
B. Follow the required anatomical and positioning criteria for the projection
Respiratory Therapy Comprehensive Review | Practice Resource • Page 3
, Respiratory Therapy Comprehensive Review
C. Always use the largest possible field size
D. Always use the shortest SID available
Correct Answer: B. Follow the required anatomical and positioning criteria for the projection
Detailed Rationale:
Accurate positioning is essential for demonstrating anatomy in the intended projection and minimizing distortion. The
radiographer must follow established positioning criteria, identify the correct side, center accurately, and ensure the
required anatomy is included.
Why the Other Options Are Incorrect:
A. Random positioning: Incorrect positioning can obscure anatomy or create misleading appearances.
C. Largest possible field: Excessive field size increases unnecessary radiation and scatter.
D. Shortest SID: SID should be selected according to the examination and projection requirements.
Question 9
Which projection is commonly used to demonstrate the heart and lungs while minimizing cardiac
magnification?
Options
A. AP supine
B. PA upright
C. AP prone
D. Lateral decubitus only
Correct Answer: B. PA upright
Detailed Rationale:
A PA chest radiograph is commonly obtained with the patient upright and the anterior chest against the image
receptor. The heart is closer to the receptor, which helps minimize magnification compared with an AP projection.
Why the Other Options Are Incorrect:
A. AP supine: Often produces greater cardiac magnification and is frequently used for patients who cannot stand.
C. AP prone: Not the standard routine chest projection.
D. Lateral decubitus only: Decubitus imaging is used for specific clinical indications rather than as the standard chest
examination.
Question 10
Which breathing instruction is commonly used for a routine chest radiograph?
Options
A. Suspend respiration after full expiration
B. Suspend respiration after the second full inspiration
C. Breathe rapidly throughout the exposure
D. Hold the breath only after coughing
Correct Answer: B. Suspend respiration after the second full inspiration
Detailed Rationale:
A routine PA chest radiograph is generally obtained after the patient takes a deep inspiration and holds the breath.
Adequate inspiration helps maximize lung expansion and improves visualization of the pulmonary fields.
Why the Other Options Are Incorrect:
A. Full expiration: Expiratory images may be obtained for specific indications but are not the routine standard.
C. Breathe rapidly: Motion from respiration would degrade the image.
Respiratory Therapy Comprehensive Review | Practice Resource • Page 4
