ARRT exam prep
ARRT QA & Safety Practice Questions: Free 20-Question Set
QA and safety questions are high-yield for boards and for the job: these 20 cover daily and periodic linac QA, machine safety and malfunctions, personnel dosimetry, ALARA and NRC regulations, and first-fraction image verification — each with a full explanation. Working therapists use the same set as a refresher.
Want adaptive quizzes that drill your weakest safety topics automatically? Rad Therapy Guru packs mock exams, question banks, flashcards, and mastery tracking into one free trial, and it was built by a working therapist and instructor you can read about here.
Section A — Daily & Periodic QA
Questions 1–4 · answers and explanations included
Daily linear accelerator QA performed by the radiation therapist includes:
- A.A full TG-51 absorbed dose calibration in a water phantom
- B.Output constancy checks plus safety checks such as the door interlock, audiovisual monitoring, and lasersCorrect
- C.CT number calibration of the simulator
- D.Brachytherapy source strength verification
Answer: B
Morning QA pairs output constancy (dose per MU against baseline) with the safety suite: door interlock, audiovisual monitoring, lasers, and emergency stops. TG-51 calibration is the physicist's annual task, not a daily check.
Light field and radiation field coincidence is checked periodically with a typical tolerance of:
- A.2 mm of alignment or 2% of the field sizeCorrect
- B.5 cm of alignment at any field size
- C.1% of the prescribed dose
- D.10 mm of alignment regardless of field size
Answer: A
The classic tolerance for light/radiation field agreement is about 2 mm or 2% of the field dimension — small, because the light field defines where the therapist believes the beam is aimed.
The annual formal linear accelerator calibration determines absorbed dose to water according to:
- A.The AAPM TG-51 protocolCorrect
- B.10 CFR Part 20
- C.ICRU Report 50 on target volumes
- D.The NCRP Report 160 population survey
Answer: A
TG-51 is the AAPM protocol for absorbed dose to water calibration of megavoltage photon and electron beams with a calibrated ionization chamber in a water phantom — the physicist's annual standard.
The difference between a tolerance and an action level in a QA program is:
- A.A tolerance is the pass/fail bound; an action level is the value that triggers investigation or recalibrationCorrect
- B.The two terms are interchangeable
- C.A tolerance shuts the machine down while an action level is advisory only
- D.An action level applies only to imaging QA
Answer: A
Readings within tolerance pass; readings beyond tolerance fail. The action level sits as the trigger for investigation or recalibration before the situation worsens — the two thresholds structure every QA response.
Section B — Machine Safety & Malfunctions
Questions 5–8 · answers and explanations included
If the door interlock test fails during morning QA, the correct response is:
- A.The beam must terminate and the machine is tagged out of service until repaired and verifiedCorrect
- B.Continue treating with a staff member posted at the door
- C.Re-test at the end of the treatment day
- D.Double the daily QA checks instead of repairing the interlock
Answer: A
A failed interlock is a failed safety system: no beam, machine out of service, and no treatments until the repair is verified. Posting a person at the door or deferring the fix is never acceptable.
After a cobalt-60 source change, a radiation survey of the treatment room and source head is performed to:
- A.Measure the new isocenter location
- B.Confirm there is no radiation leakage above regulatory limitsCorrect
- C.Calibrate the optical distance indicator
- D.Reset the treatment timer
Answer: B
A new source is surveyed for leakage around the source head and through the room barriers, confirming exposures stay within regulatory limits before the unit returns to clinical use.
The monitor unit (timer) linearity check exceeds tolerance during monthly QA. The physicist should:
- A.Adjust the prescribed dose instead
- B.Be notified, and no treatments are delivered until linearity is corrected and verifiedCorrect
- C.Average the error into next month's check
- D.Continue treatment and defer correction to the annual calibration
Answer: B
A linearity failure means delivered dose cannot be trusted across the MU range, so treatments stop until the physicist corrects and verifies it. Averaging or deferring hides a dosimetric fault.
Emergency stop buttons on a linear accelerator:
- A.Are optional on machines manufactured after 2010
- B.Must be known by location to all staff and are tested as part of daily QACorrect
- C.Terminate only the couch motion, not the beam
- D.Are tested only by the service engineer once a year
Answer: B
Staff must know where every emergency stop is and verify function in daily QA — these buttons terminate beam and motion immediately when a patient or staff member is at risk.
Section C — Personnel Monitoring & Protection
Questions 9–12 · answers and explanations included
A personal radiation dosimeter (badge) should be worn:
- A.Under the lead apron at the waist
- B.At the collar, outside any lead apronCorrect
- C.On the treatment console while the therapist is in the room
- D.Only during brachytherapy procedures
Answer: B
The badge reads whole-body exposure and is worn at the collar outside protective aprons — an apron would block the reading. Leaving it on the console defeats its purpose entirely.
OSL and TLD occupational badge readings are typically exchanged:
- A.Annually
- B.Monthly or quarterly depending on the facility, and a lost badge must be reported so the dose can be reconstructedCorrect
- C.Only after a suspected exposure
- D.Every five years per NRC requirement
Answer: B
Badges are exchanged on a monthly or quarterly cycle set by the facility. A lost badge is reported, not ignored, because an estimated dose must be reconstructed for the record.
The NRC declared-pregnancy fetal dose limit is:
- A.50 mSv (5 rem) for the gestation
- B.5 mSv (0.5 rem) over the gestation once pregnancy is declaredCorrect
- C.1 mSv per month with no gestation cap
- D.The same as the adult occupational limit
Answer: B
Once a worker voluntarily declares pregnancy, the fetal dose limit is 5 mSv (0.5 rem) for the entire gestation, with monthly monitoring typically applied. The 50 mSv adult annual limit is the standard distractor.
Gonadal shielding for a patient whose gonads lie near, but outside, the treatment field should be placed:
- A.Before the field is set up, wherever it seems reasonable
- B.After confirming the field position, so the shield does not interfere with the treatment fieldCorrect
- C.Only if the patient requests it
- D.Never in radiation therapy
Answer: B
Shields are placed after the field is verified so they protect the gonads without blocking or scattering the treatment beam. Placement before field definition risks shielding part of the target.
Section D — ALARA, Regulations & Documentation
Questions 13–16 · answers and explanations included
ALARA stands for:
- A.As Low As Reasonably Achievable, pursued through time, distance, and shieldingCorrect
- B.As Large As Reasonably Achievable
- C.Annual Limits For All Radiation Areas
- D.Always Log And Report Accurately
Answer: A
ALARA — as low as reasonably achievable — is the governing radiation protection principle, implemented through minimizing exposure time, maximizing distance, and using shielding.
Body fluids spill from a patient during an HDR brachytherapy procedure, for example from a gynecologic applicator. The correct response is to:
- A.Clean it up with paper towels and continue
- B.Contain the spill, notify the RSO, and follow the facility's spill-kit procedureCorrect
- C.Flood the room with water before cleaning
- D.Ask the patient to clean it up
Answer: B
A spill during a radioactive source procedure follows the radiological spill procedure: contain it, notify the RSO, and use the spill kit per protocol. Improvised cleanup risks spreading contamination.
Regarding byproduct material regulation in the United States:
- A.All states are regulated directly by the NRC
- B.Most states are Agreement States that regulate byproduct material directly under agreement with the NRCCorrect
- C.States have no role in radiation regulation
- D.Byproduct material is regulated by the Joint Commission
Answer: B
Most U.S. states are Agreement States: they have assumed regulatory authority over byproduct material under agreement with the NRC, which retains authority in the remaining states. The Joint Commission accredits, it does not license sources.
The cardinal rule for treatment documentation is to:
- A.Chart what was actually done, contemporaneously — never in advanceCorrect
- B.Batch-chart all treatments at the end of the week
- C.Chart the planned values whether or not they were delivered
- D.Avoid documenting deviations to protect the record
Answer: A
Documentation records what actually happened, when it happened. Charting in advance or batch-charting creates false records, and hiding deviations defeats incident learning — all classic wrong answers.
Section E — Image Verification & Patient Safety
Questions 17–20 · answers and explanations included
Before the first treatment fraction, the setup is verified by:
- A.Comparing a port image or onboard image against the DRR to confirm the setupCorrect
- B.Trusting the simulation tattoos alone
- C.The patient's statement that the setup feels familiar
- D.Measuring the patient with a tape measure
Answer: A
First-fraction verification images the setup and compares it to the DRR reference before dose is delivered — the last checkpoint between planning geometry and the patient on the couch.
The frequency of image-guided verification (IGRT) is determined by:
- A.A single national schedule of one image per week
- B.The department protocol — more often for targets with motion or soft-tissue shiftsCorrect
- C.The patient's preference
- D.The total number of fractions only
Answer: B
IGRT frequency follows the department protocol, scaled to the uncertainty: mobile or soft-tissue targets get more frequent or daily imaging than rigid, bony-anchored targets.
A setup deviation beyond tolerance is discovered during a fraction. The correct response is to:
- A.Complete the fraction and report it at the weekly chart review
- B.Document the deviation, notify the physicist and physician, and correct the setup before continuing — feeding the event into incident learningCorrect
- C.Ignore the deviation unless the patient notices
- D.Remove the deviation from the record
Answer: B
Deviations are documented, reported to the physicist and physician, and corrected before treatment continues — with the event captured for incident learning (the RO-ILS mindset). Continuing on a bad setup compounds the error.
Hand hygiene and standard precautions in the radiation oncology treatment room:
- A.Do not apply, because treatments are non-invasive
- B.Apply to every patient contact, with extra precautions for immunosuppressed patientsCorrect
- C.Are required only during brachytherapy procedures
- D.Replace the need for cleaning the couch between patients
Answer: B
Standard precautions and hand hygiene govern every patient contact exactly as anywhere else in the clinic — with added vigilance for immunosuppressed patients, for whom routine organisms can be dangerous.
How Did You Do?
Score yourself one point per correct answer, then act on your band:
17–20 correct
You are in strong shape.
You are close to exam-ready. Identify your weakest category above and drill it until every explanation feels routine — then keep up timed practice sets.
12–16 correct
Solid foundation.
You know the fundamentals but have gaps. Rebuild the categories where you missed the most questions, then retake this set in a week and confirm the score holds.
Under 12
Study by category.
Map every miss to the ARRT content outline — daily and periodic QA, machine safety, personnel monitoring, ALARA and regulations, and image verification — and study one category at a time, starting with your weakest.
Get the printable Dosimetry Cheat Sheet (PDF)
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Ready for the full study suite?
These 20 questions are a taste of the practice materials inside Rad Therapy Guru: timed mock exams, adaptive quizzes, flashcards, and mastery tracking across every ARRT topic.
ARRT QA & Safety Practice Questions FAQ
What does daily linear accelerator QA include?
Therapists check output constancy plus the safety systems every morning: door interlock, audiovisual monitoring, lasers, emergency stops, and field-light indicators. Any failure takes the machine out of service until it is corrected and verified.
What is TG-51?
TG-51 is the AAPM protocol the medical physicist uses for the formal annual calibration — absorbed dose to water — of megavoltage photon and electron beams using a calibrated ionization chamber in a water phantom.
Who performs QA?
Therapists perform the daily morning checks; the medical physicist performs periodic (typically monthly and annual) calibrations and investigates any reading beyond tolerance. Radiation safety surveys are physicist and RSO responsibilities.
What happens if QA fails?
A tolerance failure takes the machine out of service: no patient treatments until the problem is found, corrected, and verified within tolerance. Action-level readings trigger investigation and recalibration before the next treatment day.
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Content reviewed by Kate, a working radiation therapist and instructor — see the full story on the about page.