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NRSB RRS practice questions

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Question 1Radiation Protection and Safety

Under the ALARA principle, what is the primary obligation of a radiation worker when a task can be completed at different dose levels?

  1. Achieve zero occupational dose for every worker regardless of cost
  2. Prioritize collective dose over any individual's exposure
  3. Keep individual and collective doses as low as reasonably achievable, economic and social factors considered Correct answer.
  4. Reduce dose only until it falls below the annual regulatory limit

Explanation

ALARA requires that all exposures be kept as low as reasonably achievable, taking economic and social factors into account. It is a continuous optimization process, not a threshold that ends once a legal limit is met. Individual dose control remains the first priority.

Question 2Radiation Protection and Safety

A sealed source is to be moved between two shielded positions. Which combination of controls best reflects the three basic principles of external dose reduction?

  1. Rely on administrative permits alone, since paperwork limits exposure
  2. Increase time near the source to finish quickly, reduce shielding, and work at close range
  3. Maximize distance, minimize time near the source, and use appropriate shielding Correct answer.
  4. Use only personal dosimeters, since monitoring replaces time, distance, and shielding controls

Explanation

External exposure is controlled by reducing time, increasing distance, and adding shielding. Distance is especially powerful because dose rate falls with the inverse square of distance for a point source. Monitoring and permits support these controls but do not replace them.

Question 3Radiation Protection and Safety

Which statement correctly describes the difference between equivalent dose and effective dose?

  1. Equivalent dose applies only to internal exposures, while effective dose applies only to external exposures
  2. Effective dose is measured in becquerels, while equivalent dose is measured in gray
  3. Equivalent dose applies radiation weighting factors to organ absorbed dose, while effective dose additionally applies tissue weighting factors Correct answer.
  4. Equivalent dose is weighted by tissue sensitivity, while effective dose uses radiation weighting factors

Explanation

Equivalent dose equals absorbed dose multiplied by the radiation weighting factor for the type of radiation. Effective dose then sums equivalent doses across organs using tissue weighting factors to express overall stochastic risk. Both are expressed in sieverts.

Question 4Radiation Protection and Safety

What is the main purpose of a controlled area in a radiation protection program?

  1. To provide a rest area for workers during long shifts
  2. To store administrative records away from radiation sources
  3. To allow unrestricted public access near the source
  4. To designate a region where exposure conditions require specific protection measures and access control Correct answer.

Explanation

A controlled area is defined by expected dose rates or contamination levels that require engineered and administrative controls, including restricted access. It separates areas needing protection measures from supervised or unrestricted areas. Its purpose is dose control, not convenience or storage.

Question 5Radiation Protection and Safety

Which instrument is designed to detect and measure surface contamination rather than to assess external dose rate?

  1. A pressurized ionization chamber survey meter
  2. An electronic personal dosimeter
  3. A Geiger-Mueller survey meter fitted with a thin window probe Correct answer.
  4. A personal thermoluminescent dosimeter

Explanation

Thin-window Geiger-Mueller probes detect alpha and beta emissions from contamination on surfaces, making them suitable for contamination surveys. Personal dosimeters record dose to the wearer and are not used to scan surfaces. Ionization chambers are typically used for external dose-rate measurement.

Question 6Radiation Protection and Safety

What is the appropriate immediate response when a worker's personal dosimeter reading approaches the investigation level?

  1. Ignore the reading until the annual limit is exceeded
  2. Immediately revoke the worker's authorization permanently
  3. Recalibrate the dosimeter without reviewing work practices
  4. Conduct an investigation of the cause and consider corrective actions Correct answer.

Explanation

An investigation level is a trigger for reviewing the cause of elevated dose, not a legal limit. The review should examine work practices, shielding, and procedures and lead to corrective action where warranted. Permanent removal or simple recalibration does not address the underlying cause.

Question 7Radiation Protection and Safety

Which of the following is a characteristic of high-level radioactive waste that most influences its handling and disposal strategy?

  1. It can be safely disposed of by ordinary landfill burial
  2. It is always in gaseous form
  3. It decays to background levels within a few days
  4. It generates significant heat and requires long-term isolation from the biosphere Correct answer.

Explanation

High-level waste contains long-lived radionuclides and produces substantial decay heat, so it requires shielding, cooling, and long-term isolation. Ordinary landfill disposal would not provide adequate containment or isolation. Physical form varies and is not always gaseous.

Question 8Radiation Protection and Safety

What does the term 'justification' mean in the context of radiation protection?

  1. No practice should be adopted unless it produces sufficient benefit to offset the detriment it causes Correct answer.
  2. Every exposure must be below the annual limit
  3. Every worker must receive the same dose as colleagues doing similar work
  4. All radiation sources must be shielded to the maximum extent possible

Explanation

Justification is a principle of radiological protection requiring that a practice produce more benefit than harm. It is distinct from optimization and dose limitation. It applies to the decision to undertake an activity, not to individual dose levels.

Question 9Radiation Protection and Safety

A worker spends 30 minutes at a location where the dose rate is 40 microsieverts per hour. What is the estimated dose received during that period?

  1. 1,200 microsieverts
  2. 120 microsieverts
  3. 2 microsieverts
  4. 20 microsieverts Correct answer.

Explanation

Dose equals dose rate multiplied by time, with time expressed in hours. Thirty minutes is 0.5 hours, so 40 microsieverts per hour times 0.5 hours equals 20 microsieverts. Converting minutes incorrectly to 0.05 or 3 hours produces the other values.

Question 10Radiation Protection and Safety

The dose rate from a point source is 100 microsieverts per hour at 2 meters. What is the approximate dose rate at 4 meters, ignoring attenuation?

  1. 50 microsieverts per hour
  2. 10 microsieverts per hour
  3. 200 microsieverts per hour
  4. 25 microsieverts per hour Correct answer.

Explanation

For a point source, dose rate falls with the inverse square of distance. Doubling distance from 2 to 4 meters reduces the rate by a factor of four, giving 25 microsieverts per hour. Linear halving would incorrectly give 50.

Question 11Radiation Protection and Safety

Which practice best minimizes internal contamination when handling unsealed radioactive material in a laboratory?

  1. Eating and drinking at the bench to reduce interruptions
  2. Working without gloves to preserve manual dexterity
  3. Storing personal items next to the source to keep them supervised
  4. Using fume hoods, gloves, and strict no-eating rules with frequent hand monitoring Correct answer.

Explanation

Internal contamination is prevented by containment, personal protective equipment, and prohibiting eating or drinking in the work area. Hand and surface monitoring detects spread before it leads to intake. Removing gloves or eating at the bench creates direct ingestion pathways.

Question 12Radiation Protection and Safety

A survey meter is calibrated for gamma radiation but is used to assess beta dose rate from a source. What is the main concern with this approach?

  1. The meter's response may not be appropriate for beta energies, so the reading may be inaccurate Correct answer.
  2. The calibration certificate automatically covers all radiation types
  3. Beta radiation cannot be detected by any survey instrument
  4. The meter will overestimate beta dose because beta particles are heavier

Explanation

Instrument response depends on radiation type and energy, and a gamma calibration does not guarantee accurate beta measurement. Beta particles may be shielded by the detector housing or produce a different efficiency. A beta-appropriate detector and calibration are needed for reliable readings.

Question 13Radiation Protection and Safety

What is the purpose of a dosimetry badge being worn at the collar over a lead apron during fluoroscopy?

  1. To estimate dose to the lens of the eye and unprotected head Correct answer.
  2. To measure the dose to the hands during procedures
  3. To replace the need for a whole-body dosimeter
  4. To measure the dose to the feet

Explanation

A collar badge placed outside the apron estimates dose to the head and lens of the eye, which are not shielded by the apron. It is used with a badge under the apron to estimate effective dose. Hand and foot doses require separate extremity dosimeters.

Question 14Radiation Protection and Safety

Which of the following correctly describes the relationship between absorbed dose and equivalent dose for alpha radiation?

  1. Equivalent dose equals absorbed dose because weighting factors are only for photons
  2. Equivalent dose cannot be calculated for alpha radiation
  3. Equivalent dose is lower than absorbed dose because alpha particles are stopped by skin
  4. Equivalent dose is higher than absorbed dose because the radiation weighting factor for alpha particles is 20 Correct answer.

Explanation

Equivalent dose is the product of absorbed dose and the radiation weighting factor. Alpha particles have a weighting factor of 20, so equivalent dose is 20 times the absorbed dose for the same energy deposition. This reflects their high relative biological effectiveness.

Question 15Radiation Protection and Safety

A facility must decide whether to introduce a new radiographic procedure. Which principle requires an assessment that the overall benefit outweighs the radiation detriment?

  1. Justification Correct answer.
  2. Dose limitation
  3. Containment
  4. Optimization

Explanation

Justification requires that a new practice produce sufficient benefit to offset the detriment it causes. Optimization then seeks to keep doses as low as reasonably achievable once the practice is justified. Dose limitation sets individual bounds, and containment is an engineering control.

Question 16Radiation Protection and Safety

Why is a lead apron effective at reducing dose to the trunk during fluoroscopy but less effective at protecting the lens of the eye?

  1. Lead aprons absorb all radiation regardless of geometry, so eye dose is always zero
  2. The lens is insensitive to radiation and requires no protection
  3. The apron attenuates scattered photons reaching the trunk, while the eye is often outside the shielded area and closer to the source Correct answer.
  4. Scattered radiation cannot reach the head during fluoroscopy

Explanation

Aprons attenuate scattered photons that would otherwise reach the trunk, but the head and eyes may be outside the apron and closer to the patient, which is the main scatter source. Eye dose therefore often requires ceiling-suspended shields, leaded glasses, or collar dosimetry. Geometry and proximity, not lens insensitivity, explain the difference.

Question 17Radiation Protection and Safety

What is the primary reason for using a personal air sampler in a workplace where radioactive aerosols may be present?

  1. To estimate the intake of airborne radioactivity by the worker and support internal dose assessment Correct answer.
  2. To detect surface contamination on floors
  3. To calibrate the worker's dosimeter
  4. To measure external gamma dose rate in the room

Explanation

A personal air sampler draws air from the worker's breathing zone to estimate airborne activity and support intake and internal dose assessment. It does not measure external dose rate or surface contamination. Calibration of dosimeters is a separate function.

Question 18Radiation Protection and Safety

A worker's annual effective dose is 18 millisieverts. What percentage of a 20 millisievert annual dose limit does this represent?

  1. 18 percent
  2. 90 percent Correct answer.
  3. 180 percent
  4. 45 percent

Explanation

The percentage is calculated by dividing the dose by the limit and multiplying by 100. Eighteen divided by twenty equals 0.9, which is 90 percent. This shows the worker is close to the limit and should trigger review.

Question 19Radiation Protection and Safety

Which detection method is most appropriate for identifying an unknown radionuclide emitting gamma rays in a sample?

  1. A personal dosimeter
  2. A wipe test with a liquid scintillation counter
  3. A Geiger-Mueller counter with a rate meter only
  4. A gamma spectrometer with a scintillation or semiconductor detector Correct answer.

Explanation

Gamma spectrometry identifies radionuclides by measuring the energies of emitted gamma rays. A rate meter gives only a count rate without energy information. Wipe tests assess removable contamination, and personal dosimeters measure dose, not nuclide identity.

Question 20Radiation Protection and Safety

A sealed source is found to have a damaged weld and a smear test shows removable contamination. What is the most appropriate immediate action?

  1. Discard the source in ordinary waste
  2. Restrict access, contain the contamination, and arrange for source repair or replacement Correct answer.
  3. Continue using the source while monitoring the area weekly
  4. Increase the workload to use the source before it decays

Explanation

A damaged sealed source with removable contamination indicates a loss of containment and requires immediate access control and decontamination. The source should be repaired, replaced, or disposed of through authorized channels. Continuing use or ordinary disposal would spread contamination and violate safety requirements.

Question 21Radiation Protection and Safety

Which statement best explains why the dose limit for the lens of the eye is lower than the limit for the skin?

  1. The skin is not radiosensitive and requires no limit
  2. The skin limit applies only to internal exposures
  3. The lens receives less radiation than the skin in all exposures
  4. The lens is more sensitive to deterministic effects such as cataract formation at lower doses than skin erythema Correct answer.

Explanation

The lens can develop cataracts at relatively low doses, so its dose limit is set to prevent deterministic effects. Skin effects such as erythema generally require higher thresholds. Dose limits reflect tissue-specific sensitivity, not the amount of radiation received.

Question 22Radiation Protection and Safety

A point source produces 400 microsieverts per hour at 1 meter. A worker must remain at 2 meters for 15 minutes. What is the estimated dose?

  1. 100 microsieverts
  2. 50 microsieverts Correct answer.
  3. 200 microsieverts
  4. 25 microsieverts

Explanation

At 2 meters the inverse square law reduces the rate to 400 divided by four, or 100 microsieverts per hour. Fifteen minutes is 0.25 hours, so the dose is 100 times 0.25, which is 25 microsieverts. The other values arise from omitting the distance correction or misapplying the time conversion.

Question 23Radiation Protection and Safety

Two workers perform the same task. Worker A receives 2 millisieverts to the whole body. Worker B receives 2 millisieverts to the thyroid only. Which statement about effective dose is most accurate?

  1. Both workers have the same effective dose because the equivalent dose is equal
  2. Effective dose cannot be compared between partial and whole-body exposures
  3. Worker B's effective dose is lower because the thyroid has a lower tissue weighting factor than the whole-body weighting Correct answer.
  4. Worker A's effective dose is always zero because whole-body exposure is not weighted

Explanation

Effective dose applies tissue weighting factors that reflect the relative radiosensitivity of irradiated organs. A thyroid-only exposure is weighted by the thyroid factor, which is much lower than the sum of factors for whole-body irradiation. Equal equivalent dose therefore does not mean equal effective dose.

Question 24Radiation Protection and Safety

A facility wants to reduce collective dose from a repetitive task. Which approach best reflects the ALARA optimization process?

  1. Compare shielding, distance, and time options, evaluate their costs and dose savings, and select a reasonably achievable improvement Correct answer.
  2. Rotate workers so that no individual exceeds the limit
  3. Assign the highest doses to the most experienced workers
  4. Set a single dose limit for the team and stop monitoring once it is met

Explanation

Optimization compares available options for their dose savings and their economic and social costs, then selects an improvement that is reasonably achievable. It is a structured evaluation, not merely meeting a limit. Assigning or rotating dose does not reduce collective dose or optimize protection.

Question 25Radiation Protection and Safety

A worker is exposed internally to a radionuclide that concentrates in bone. Which factor most strongly influences the resulting effective dose?

  1. The calibration date of the survey meter
  2. The worker's height alone
  3. The radionuclide's biokinetics, emitted radiation type, and the tissue weighting of bone Correct answer.
  4. The color of the container used to store the material

Explanation

Internal dose depends on how the radionuclide is taken up, retained, and cleared, on the radiation it emits, and on the weighting of the irradiated tissue. Bone-seeking nuclides deliver dose to bone and marrow, which carry specific tissue weights. Container color and meter calibration do not determine internal dose.

Question 26Radiation Protection and Safety

Under the ALARA principle, which of the following best describes the required approach to radiation protection?

  1. Doses must be kept below the annual limits at all times, with no further reduction required.
  2. Doses should be minimized only for workers who are pregnant.
  3. Doses should be kept as low as reasonably achievable, taking economic and social factors into account. Correct answer.
  4. Doses should be reduced only when they exceed the investigation level.

Explanation

ALARA requires that all exposures be kept as low as reasonably achievable, considering economic and social factors, not merely compliance with dose limits. It applies to all workers and the public, and is a proactive optimization principle rather than a reactive one triggered by investigation levels.

Question 27Radiation Protection and Safety

Which of the following is the primary function of a personal dosimeter in a radiation protection program?

  1. To measure the activity concentration of radioactive material in the air.
  2. To measure and record the accumulated dose received by an individual over a monitoring period. Correct answer.
  3. To determine the energy spectrum of the radiation field.
  4. To provide an immediate alarm if the dose rate exceeds a preset level.

Explanation

A personal dosimeter is worn by an individual to measure cumulative dose over a monitoring period for legal and administrative recordkeeping. It is not designed for real-time alarming, air concentration measurement, or spectrometry.

Question 28Radiation Protection and Safety

Which of the following best defines the term 'absorbed dose'?

  1. The number of ion pairs produced per unit volume of air.
  2. The activity of a radionuclide per unit mass.
  3. The amount of energy imparted per unit mass by ionizing radiation. Correct answer.
  4. The biological effect of radiation on human tissue.

Explanation

Absorbed dose is the fundamental physical quantity representing energy deposited per unit mass, measured in grays (joules per kilogram). It does not directly describe biological effect, ionization density in air, or activity concentration.

Question 29Radiation Protection and Safety

What is the primary purpose of placing a radiation warning sign at the entrance to a controlled area?

  1. To identify the radionuclide used within the area.
  2. To satisfy documentation requirements for the facility's license.
  3. To warn individuals of the presence of radiation hazards and restrict access to authorized persons. Correct answer.
  4. To indicate the exact dose rate at the location of the sign.

Explanation

Warning signs at controlled area entrances serve to alert people to the radiation hazard and to limit entry to those authorized and adequately informed. They are not intended to provide precise dose rates or radionuclide identification.

Question 30Radiation Protection and Safety

A radiographer must remain near a sealed source for 20 minutes. The measured dose rate at the working position is 250 microsieverts per hour. What is the estimated effective dose received during this task?

  1. 250 microsieverts
  2. 50 microsieverts
  3. 83 microsieverts Correct answer.
  4. 125 microsieverts

Explanation

Dose equals dose rate multiplied by time. Twenty minutes is one-third of an hour, so 250 microsieverts per hour times 0.333 hours equals approximately 83 microsieverts. This calculation assumes the dose rate is constant and the whole-body dose is uniform.

Question 31Radiation Protection and Safety

A worker is exposed to a mixture of radionuclides. The committed effective dose from inhalation is estimated to be 5 millisieverts, and the external effective dose is 3 millisieverts. What is the total effective dose?

  1. 2 millisieverts
  2. 8 millisieverts Correct answer.
  3. 5 millisieverts
  4. 15 millisieverts

Explanation

Total effective dose is the sum of the committed effective dose from internal intake and the effective dose from external exposure. Adding 5 millisieverts and 3 millisieverts gives 8 millisieverts. Internal and external doses are additive for the purpose of demonstrating compliance with dose limits.

Question 32Radiation Protection and Safety

Which of the following is the most appropriate action when a sealed source is found to have a damaged outer capsule but no detectable removable contamination?

  1. Attempt to repair the capsule with epoxy to prevent further damage.
  2. Place the source in a sealed container, restrict access, and arrange for leak testing and assessment by a qualified person. Correct answer.
  3. Continue using the source normally because no contamination was detected.
  4. Return the source to its storage shield and document the finding in the next annual report.

Explanation

Any physical damage to a sealed source capsule compromises its integrity and requires immediate isolation, restricted access, and formal leak testing and assessment. Continuing use, deferring action, or attempting unauthorized repair could lead to uncontrolled contamination or exposure.

Question 33Radiation Protection and Safety

Which of the following best explains why the dose limit for the lens of the eye is lower than the limit for the skin?

  1. The lens is located closer to the radiation source in most geometries.
  2. The lens receives higher doses than skin during most external exposures.
  3. The lens is more radiosensitive than skin because lens cells do not repair radiation damage efficiently. Correct answer.
  4. The skin is shielded by clothing, whereas the lens is not.

Explanation

The lens of the eye is recognized as a radiosensitive tissue with a high risk of cataract formation at relatively low doses, and lens cells have limited repair capacity. This biological sensitivity, not geometry or shielding, is why the lens dose limit is lower than the skin limit.

Question 34Radiation Protection and Safety

A facility uses a gamma-emitting source. Which of the following shielding materials is most effective for reducing the dose rate from this source?

  1. Lead Correct answer.
  2. Water
  3. Plastic
  4. Concrete

Explanation

For gamma radiation, shielding effectiveness increases with material density and atomic number. Lead has high density and high atomic number, making it more effective per unit thickness than water, concrete, or plastic for typical gamma energies.

Question 35Radiation Protection and Safety

Which of the following is the correct unit for equivalent dose in the International System of Units (SI)?

  1. Sievert (Sv) Correct answer.
  2. Gray (Gy)
  3. Coulomb per kilogram (C/kg)
  4. Becquerel (Bq)

Explanation

Equivalent dose is expressed in sieverts, which account for the radiation weighting factor applied to absorbed dose. The gray is the unit of absorbed dose, the becquerel is activity, and coulomb per kilogram is exposure.

Question 36Radiation Protection and Safety

A worker's annual effective dose is 12 millisieverts. What percentage of the 20 millisievert annual dose limit for occupational exposure does this represent?

  1. 120%
  2. 40%
  3. 80%
  4. 60% Correct answer.

Explanation

The percentage is calculated as (12 / 20) × 100, which equals 60%. This indicates the worker has received 60% of the annual effective dose limit, which may trigger additional monitoring or ALARA review depending on facility procedures.

Question 37Radiation Protection and Safety

Which of the following best describes the purpose of a controlled area in a radiation facility?

  1. To house the facility's administrative offices away from radiation sources.
  2. To provide a space where dose rates are always below public dose limits.
  3. To designate an area where access is controlled and radiation protection measures are applied to limit occupational exposure. Correct answer.
  4. To store all radioactive waste generated by the facility.

Explanation

A controlled area is a defined area where access is restricted and specific radiation protection procedures are implemented to control occupational exposure. It is not defined by being below public limits, nor is it specifically for waste storage or administration.

Question 38Radiation Protection and Safety

A point source emits gamma radiation. The dose rate at 1 meter is 600 microsieverts per hour. What is the approximate dose rate at 3 meters?

  1. 300 microsieverts per hour
  2. 1800 microsieverts per hour
  3. 67 microsieverts per hour Correct answer.
  4. 200 microsieverts per hour

Explanation

For a point source, dose rate follows the inverse square law: dose rate is inversely proportional to the square of the distance. Tripling the distance reduces the dose rate by a factor of nine, so 600 / 9 ≈ 67 microsieverts per hour.

Question 39Radiation Protection and Safety

Which of the following best explains why a dosimeter worn under a lead apron may underestimate the effective dose to the whole body during fluoroscopy?

  1. The dosimeter's calibration is invalid when placed under a lead apron.
  2. The dosimeter is less sensitive when worn under a lead apron due to temperature effects.
  3. The dosimeter only measures beta radiation, which is blocked by the apron.
  4. The lead apron attenuates the radiation reaching the dosimeter, so it does not record the dose to unshielded tissues. Correct answer.

Explanation

A dosimeter under a lead apron measures only the attenuated dose behind the apron, while tissues outside the apron (such as the head and neck) may receive higher doses. For this reason, a second dosimeter is often worn at the collar to estimate effective dose more accurately.

Question 40Radiation Protection and Safety

A facility is reviewing its radiation protection program. Which of the following best reflects the principle of optimization as applied to occupational exposure?

  1. Providing dosimeters only to workers who are likely to exceed 10 millisieverts per year.
  2. Keeping individual and collective doses as low as reasonably achievable, considering economic and social factors. Correct answer.
  3. Reducing dose rates only in areas where the public has access.
  4. Ensuring that no worker exceeds the annual dose limit.

Explanation

Optimization requires that doses be kept as low as reasonably achievable, taking into account economic and social factors, and applies to both individual and collective doses. It goes beyond mere compliance with limits and applies to all exposed individuals, not just the public.

Question 41Radiographic Equipment and Image Production

Which component of a rotating anode X-ray tube is responsible for emitting electrons that strike the target?

  1. The anode disc focal track
  2. The stator winding
  3. The beryllium exit window
  4. The filament in the cathode assembly Correct answer.

Explanation

Thermionic emission occurs at the filament housed in the cathode assembly, which supplies the electron beam directed toward the anode. The focal track is the target area, the window transmits the beam, and the stator drives anode rotation.

Question 42Radiographic Equipment and Image Production

What is the primary purpose of adding filtration to the X-ray beam?

  1. To raise the effective energy of the filament current
  2. To increase the number of photons reaching the image receptor
  3. To remove low-energy photons that would only contribute patient dose Correct answer.
  4. To sharpen the anode heel effect across the field

Explanation

Filtration attenuates low-energy photons that would be absorbed in tissue without contributing to the image, thereby reducing patient dose and hardening the beam. It does not increase photon count or alter filament current.

Question 43Radiographic Equipment and Image Production

A radiograph is produced using a 400 mA station, 0.1 s exposure, and 70 kVp. What is the mAs for this exposure?

  1. 70 mAs
  2. 4000 mAs
  3. 40 mAs Correct answer.
  4. 4 mAs

Explanation

mAs equals milliamperage multiplied by exposure time in seconds, so 400 mA × 0.1 s = 40 mAs. This product determines the total number of electrons crossing the tube during the exposure.

Question 44Radiographic Equipment and Image Production

Which interaction in the diagnostic energy range produces most of the photons in the X-ray beam?

  1. Coherent scattering in the target
  2. Pair production
  3. Bremsstrahlung Correct answer.
  4. Photoelectric absorption in the target

Explanation

Bremsstrahlung, or braking radiation, accounts for the majority of photons in a diagnostic beam as electrons decelerate in the target nucleus field. Characteristic radiation contributes a smaller fraction.

Question 45Radiographic Equipment and Image Production

Which unit expresses the absorbed dose received by a patient's tissue?

  1. Sievert
  2. Becquerel
  3. Gray Correct answer.
  4. Coulomb per kilogram

Explanation

The gray measures absorbed dose, defined as one joule per kilogram of tissue. Sievert expresses equivalent and effective dose, while coulomb per kilogram is exposure and becquerel is activity.

Question 46Radiographic Equipment and Image Production

What does the term spatial resolution describe in a radiographic image?

  1. The uniformity of brightness across the field
  2. The degree to which scatter reduces subject contrast
  3. The ability to distinguish two small objects that lie close together Correct answer.
  4. The range of tissue densities visible on the image

Explanation

Spatial resolution is the capacity to record fine detail, that is, to separate closely spaced structures. It is commonly measured in line pairs per millimeter and is limited by focal spot size, receptor pixel pitch, and motion.

Question 47Radiographic Equipment and Image Production

In a computed radiography system, what is the function of the photostimulable phosphor plate?

  1. It stores a latent image that is released as light when scanned by a laser Correct answer.
  2. It converts X-ray photons directly into electrical charge at each pixel
  3. It provides collimation of the primary beam
  4. It amplifies the X-ray beam before it reaches the patient

Explanation

The phosphor plate traps energy from X-ray exposure in metastable centers, forming a latent image. A scanning laser releases this energy as luminescence that is read by a photodetector.

Question 48Radiographic Equipment and Image Production

Which factor increases the anode heel effect across the image field?

  1. A large focal spot size
  2. A low mAs value
  3. A short source-to-image distance Correct answer.
  4. A high grid ratio

Explanation

The heel effect is the intensity variation along the anode-cathode axis caused by absorption in the anode. It becomes more pronounced at short source-to-image distances because the beam divergence angle across the field increases.

Question 49Radiographic Equipment and Image Production

A radiographer increases kVp from 70 to 80 while holding mAs constant. Which change is expected?

  1. No change in receptor exposure or contrast
  2. Decreased beam penetrability and higher patient dose
  3. A proportional increase in spatial resolution
  4. Increased beam penetrability and increased receptor exposure Correct answer.

Explanation

Raising kVp increases photon energy and beam penetrability. With mAs and other exposure conditions unchanged, receptor exposure and patient entrance dose generally increase, while subject contrast decreases. Using higher kVp to lower dose while maintaining receptor exposure requires a compensating mAs reduction.

Question 50Radiographic Equipment and Image Production

Which combination best reduces patient dose while preserving adequate image quality for a follow-up examination?

  1. Reducing source-to-image distance and increasing mAs
  2. Using a lower grid ratio and increasing mAs
  3. Increasing filtration and using the highest kVp consistent with required contrast Correct answer.
  4. Decreasing filtration and increasing mAs

Explanation

Additional filtration and higher kVp reduce the number of photons absorbed in tissue per unit receptor exposure. Both changes lower patient dose, provided contrast remains adequate for the clinical task.