Free ARRT Radiation Therapy Practice Test
Here are 50 original, unofficial practice questions with answers and full explanations, approximately weighted to ARRT's Radiation Therapy outline for exams through January 31, 2027. If you're testing on or after February 1, 2027, the same eight sections continue, but check what the new outline adds.
Practice questions
Patient Interactions and Management (Questions 1–7)
Question 1
Patient Care · Patient identification RT-001
Before a treatment fraction, a patient states a full name that matches the open treatment record, but the date of birth she gives doesn't match the record. What should the radiation therapist do?
Show answer and explanation for Question 1
Answer: A. Hold treatment and resolve the mismatch through the department's identification process before treating.
Two identifiers exist so that a single coincidence (two patients with the same name, a wrong record left open) can't slip through. When the second identifier disagrees, the patient hasn't been identified yet. Stop and sort it out using your department's process before any beam goes on.
Why the others don't fit:
- B: One matching identifier doesn't cancel a conflicting one. Same-name patients are exactly the case two identifiers are meant to catch.
- C: Editing the record assumes you already know which version is wrong. That could put a different patient's plan on this person.
- D: Schedule slots and treatment sites aren't person-specific identifiers. The Joint Commission specifically rules out location (such as room number) as an identifier.
Source: The Joint Commission, Two Patient Identifiers—Understanding the Requirements, acceptable person-specific identifiers and matching the person to the intended care. · ID RT-001
Question 2
Patient Care · Informed consent RT-002
At CT simulation, a patient says, "I'm honestly not sure I want this. Nobody explained the side effects to me." His signed consent form is in the chart. What should the therapist do?
Show answer and explanation for Question 2
Answer: A. Pause and notify the radiation oncologist so his questions are answered before continuing.
Consent is an informed agreement, not just a signature. A patient saying he doesn't understand his treatment, and isn't sure he wants it, means that agreement is in doubt. The physician responsible for the consent discussion needs to address it before simulation goes ahead.
Why the others don't fit:
- B: A signature doesn't override a patient who now says he wasn't informed and may not want to proceed.
- C: Therapists educate patients about procedures, but a new signature alone does not resolve his unanswered questions or uncertainty about proceeding.
- D: Uncertainty isn't refusal. He's asking for information, not declining care.
Source: ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standard One (consent), Standard Two—Radiation Therapy (patient questions and withholding treatment), and Standard Three (education and referral). · ID RT-002
Question 3
Patient Care · Patient education (teach-back) RT-003
You've just explained a full-bladder preparation for prostate treatment. Which question best checks whether the patient understood?
Show answer and explanation for Question 3
Answer: D. "So I know I explained it clearly, can you tell me what you'll do before your appointment tomorrow?"
That's the teach-back method: the patient explains the instruction in their own words, which shows what they actually understood. If they miss something, explain it a different way and check again. Framing it as a check on your explanation keeps it from feeling like a quiz.
Why the others don't fit:
- A: Yes/no questions don't show understanding. AHRQ notes that patients tend to say yes whether they understand or not.
- B: Same problem: AHRQ specifically lists "Does that make sense?" as not a teach-back question.
- C: Inviting questions is good practice, but it doesn't show what the patient understood. Many patients don't know what to ask.
Source: AHRQ Health Literacy Universal Precautions Toolkit, Tool 5: Use the Teach-Back Method, Tool 5, overview and how-to. · ID RT-003
Question 4
Patient Care · Infection control: C. diff RT-004
A patient with confirmed Clostridioides difficile (C. diff) infection is on today's schedule. Which precautions apply in addition to Standard Precautions?
Show answer and explanation for Question 4
Answer: A. Contact Precautions: gown and gloves, with dedicated equipment or shared equipment cleaned and disinfected before reuse
C. diff spreads by contact: hands touching the patient, the couch, or an immobilization device. Contact Precautions mean gown and gloves for contact with the patient or their surroundings, plus dedicated equipment or shared equipment cleaned and disinfected before use on another patient. Contaminated treatment-room surfaces should be cleaned and disinfected with a C. difficile sporicidal agent.
Why the others don't fit:
- B: Droplet Precautions are for organisms spread by respiratory droplets. That's not how C. diff spreads.
- C: Airborne Precautions are for organisms like TB that stay suspended in the air.
- D: Neutropenic precautions protect a patient with weak immune defenses from others. They don't contain this patient's infection.
Worth knowing: CDC's current hand hygiene page still prefers alcohol-based hand sanitizer in most situations, even for C. diff, unless hands are visibly soiled. It encourages soap and water during C. diff outbreaks and treats correct glove and gown use as the priority.
Sources: CDC, Transmission-Based Precautions, Contact Precautions; CDC, Clinical Safety: Hand Hygiene for Healthcare Workers, hand hygiene and C. diff; CDC, Clinical Guidance for C. diff Infection Prevention in Acute Care Facilities, contact precautions and environmental cleaning. · ID RT-004
Question 5
Patient Care · Infection control: tuberculosis RT-005
A patient with suspected active pulmonary tuberculosis needs palliative treatment. While positioning the patient in the treatment room, what respiratory protection should the therapist wear?
Show answer and explanation for Question 5
Answer: D. A fit-tested N95 or higher-level respirator
TB spreads through the air, so Airborne Precautions apply: a fit-tested, NIOSH-approved N95 or higher-level respirator for staff providing direct care. CDC recommends an airborne infection isolation room; arrange the treatment visit with the infection-control team rather than assuming the treatment room provides airborne isolation.
Why the others don't fit:
- A: A surgical mask doesn't seal well enough to protect the wearer from airborne particles. It's used on the patient for source control, for example during transport.
- B: Masking the patient reduces what they release, but it doesn't replace staff respiratory protection.
- C: A face shield protects against splashes, not inhaled particles.
Source: CDC, Transmission-Based Precautions, Airborne Precautions. · ID RT-005
Question 6
Patient Care · Medical emergencies: seizure RT-006
During beam-on, the room monitor shows your patient having a generalized seizure on the treatment couch. About 20 MU remain in the field. What should you do?
Show answer and explanation for Question 6
Answer: A. Interrupt the beam, enter the room, protect the patient from falling or hitting equipment, and call for help.
The patient's safety comes first, and treating someone who's moving means the dose isn't going where it was planned. Stop the beam, get in, keep the patient from falling off a raised couch, clear nearby hazards, time the seizure, and get help.
Why the others don't fit:
- B: Finishing the field leaves the patient alone during an emergency and irradiates an unknown position.
- C: CDC first-aid guidance says not to hold a person down during a seizure. It can cause injury.
- D: CDC says never to put anything in a seizing person's mouth.
Sources: CDC, First Aid for Seizures, injury prevention and actions to avoid; ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standard Four (patient monitoring, first aid, safety, and changes in clinical condition); eviQ, Brain cancer radiation therapy—patient information, What happens during radiation therapy?. · ID RT-006
Question 7
Patient Care · Neutropenic precautions RT-007
A patient on chemoradiation has a very low neutrophil count, and the physician orders neutropenic precautions. What are these precautions for?
Show answer and explanation for Question 7
Answer: D. Protecting the patient from germs carried by staff, visitors, and other patients
Neutropenia means too few neutrophils, the white blood cells that fight infection, so the patient picks up infections more easily. Neutropenic precautions turn the usual direction of protection around: they shield the patient from others.
Why the others don't fit:
- A: That's what transmission-based precautions do for a patient who has an infection.
- B: That describes Airborne Precautions.
- C: Infection precautions have nothing to do with radiation dose.
Source: NCI, Infection and Neutropenia during Cancer Treatment, neutropenia and infection risk. · ID RT-007
Patient and Medical Record Management (Questions 8–12)
Question 8
Patient Care · Medical event reporting RT-008
At an NRC-licensed facility using byproduct material (for example, an HDR brachytherapy unit), an error meets the NRC definition of a medical event. When must the licensee notify the NRC Operations Center by telephone?
Show answer and explanation for Question 8
Answer: A. No later than the next calendar day after discovering the event
Under 10 CFR 35.3045, the telephone report to the NRC Operations Center is due no later than the next calendar day after the medical event is discovered.
Why the others don't fit:
- B: 15 days is the deadline for the written report.
- C: 30 days isn't a deadline in this rule.
- D: Reporting can't wait for an inspection.
Scope: this question applies to an NRC licensee using byproduct material, such as HDR sources or cobalt-60. Check the applicable regulator's rules for Agreement State licensees and linear accelerator events.
Source: 10 CFR 35.3045, Report and notification of a medical event, paragraphs (c) and (d). · ID RT-008
Question 9
Patient Care · Treatment record: accumulated dose RT-009
The prescription is 50.4 Gy in 1.8 Gy fractions. After the 15th fraction, which treatment-record entries are correct?
Show answer and explanation for Question 9
Answer: A. 27.0 Gy delivered; 13 fractions remaining
Total fractions: 50.4 ÷ 1.8 = 28. Dose so far: 15 × 1.8 = 27.0 Gy. Fractions left: 28 − 15 = 13.
Why the others don't fit:
- B: The dose is right, but 28 − 15 is 13, not 14.
- C: 25.2 Gy is the dose after 14 fractions.
- D: 28.8 Gy is the dose after 16 fractions.
Calculation: Derived from the prescription and completed fractions supplied in the question. Topic alignment: ARRT Radiation Therapy content specifications (through Jan. 31, 2027), Patient Care 2.C.1.c and 2.C.1.g: daily and accumulated dose, and fractions. · ID RT-009
Question 10
Patient Care · Lab values: platelets RT-010
A patient's weekly blood count shows a low platelet count. Which new symptom is most directly related and should be reported?
Show answer and explanation for Question 10
Answer: D. New bruising, bleeding gums, or tiny red or purple spots on the skin
Platelets help blood clot. When they're low (thrombocytopenia), patients bruise and bleed more easily, and may get tiny red or purple spots on the skin.
Why the others don't fit:
- A: Fever and chills can signal infection and also need prompt reporting, but they aren't the symptom pattern most directly linked to low platelets.
- B: Hair loss in the field is a local radiation effect, not a platelet problem.
- C: Fatigue is common and has many causes. It isn't the specific sign of low platelets.
Sources: NCI, Bleeding and Bruising (Thrombocytopenia) and Cancer Treatment, what thrombocytopenia is and its signs; NCI, Infection and Neutropenia during Cancer Treatment, signs of infection and when to contact the care team. · ID RT-010
Question 11
Patient Care · Skin care education RT-011
In week 3 of breast treatment, a patient asks if she can put a heating pad on her treated chest wall for muscle soreness. What's the best response?
Show answer and explanation for Question 11
Answer: A. Don't use heating pads or ice packs on the treatment area. Ask the care team about pain relief.
NCI's guidance for people getting radiation is to avoid heating pads and ice packs on the treated skin, and to check with the care team before using products or dressings there. Irradiated skin is already stressed, and heat or cold can make the reaction worse.
Why the others don't fit:
- B: Heat on irradiated skin is specifically discouraged.
- C: Ice packs are on the same avoid list.
- D: A low setting is still heat on the treatment area.
Source: NCI, Skin and Nail Changes during Cancer Treatment, skin changes from radiation therapy. · ID RT-011
Question 12
Patient Care · Documenting a treatment variance RT-012
After treating a patient, you realize the prescribed bolus wasn't placed for today's fraction. What should happen next?
Show answer and explanation for Question 12
Answer: C. Record the omission accurately as a variance and notify the physicist and radiation oncologist according to department policy.
A missed bolus changes the dose the skin received. The record has to show what actually happened, and the physician and physicist need to know so they can judge the effect and decide whether anything should change.
Why the others don't fit:
- A: Changing the next fraction changes the prescription, which isn't the therapist's call.
- B: An informal note and an assumption that one fraction won't matter do not replace formal documentation and review.
- D: That falsifies the record, which is a serious ethics violation on top of the original error.
Sources: ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standard Six—Radiation Therapy (reporting deviations and authorized changes) and Standard Eight (accurate documentation and unintended outcomes); IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.5.3, Bolus, printed p. 244. · ID RT-012
Radiation Physics and Radiobiology (Questions 13–17)
Question 13
Safety · Photon interactions RT-013
Which photon interaction predominates in soft tissue in a typical 6 MV external beam treatment?
Show answer and explanation for Question 13
Answer: D. Compton scattering
Compton scattering dominates in soft tissue in a typical 6 MV treatment beam. Because it depends on electron density rather than atomic number, bone and soft tissue look much more alike on MV portal images than on diagnostic films.
Why the others don't fit:
- A: The photoelectric effect is more important at lower photon energies and in higher-atomic-number materials; it does not predominate in soft tissue in a typical 6 MV treatment beam.
- B: Pair production needs photons above 1.02 MeV and grows at higher energies, but it isn't the main interaction in soft tissue for this beam.
- C: Coherent scattering deposits essentially no energy and is minor at these energies.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §§1.4.4–1.4.10, printed pp. 28–37; Compton scattering in §1.4.6. · ID RT-013
Question 14
Safety · Inverse square law RT-014
A source's dose rate is 2.0 Gy/min at 100 cm. What is the dose rate at 120 cm, using a point-source approximation with unchanged output and ignoring attenuation and scatter?
Show answer and explanation for Question 14
Answer: B. 1.39 Gy/min
Inverse square law: I₂ = I₁ × (d₁ ÷ d₂)² = 2.0 × (100 ÷ 120)² = 2.0 × 0.694 = 1.39 Gy/min.
Why the others don't fit:
- A: This scales by 100/120 once instead of squaring the ratio.
- C: This multiplies by the distance ratio. Dose rate falls with distance.
- D: This squares the ratio but upside down.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §6.4, printed pp. 167–169, inverse-square dose-rate relation. · ID RT-014
Question 15
Safety · Cell cycle radiosensitivity RT-015
For typical proliferating mammalian cells exposed to low-LET radiation, which cell-cycle phases are most and least sensitive?
Show answer and explanation for Question 15
Answer: A. Most sensitive in M (and G2); least sensitive in late S
Cells are most sensitive at or near mitosis (G2/M) and most resistant in late S phase. This is behind redistribution, one of the four Rs: after a fraction kills sensitive cells, survivors can move into more sensitive phases before the next fraction.
Why the others don't fit:
- B: This reverses the pattern.
- C: G2 is near the sensitive end, not the resistant end.
- D: Sensitivity varies a lot through the cycle.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §14.3, cell cycle and cell death, and §14.12, dose rate and fractionation. · ID RT-015
Question 16
Safety · Oxygen effect RT-016
For low-LET x-rays, the maximum oxygen enhancement ratio (OER) under otherwise comparable experimental conditions is about:
Show answer and explanation for Question 16
Answer: C. 2.5 to 3
OER compares the dose needed to cause an effect without oxygen to the dose needed with oxygen. For the same biological endpoint in anoxic and well-oxygenated cells, the maximum effect for low-LET x-rays is about 2.5 to 3. It is not a multiplier for a patient’s prescribed dose.
Why the others don't fit:
- A: An OER of 1 would mean oxygen makes no difference, which is closer to very high-LET radiation.
- B: Below the usual maximum under these conditions.
- D: Not the usual maximum for low-LET x-rays.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §14.10, printed pp. 498–499, oxygen effect and OER. · ID RT-016
Question 17
Safety · Normal tissue tolerance RT-017
In the historical tolerance-dose notation, TD5/5 for an organ is best defined as the dose that:
Show answer and explanation for Question 17
Answer: B. Is expected to cause severe complications in 5% of patients within 5 years
TD5/5 is the dose expected to cause severe complications in 5% of patients within 5 years for a specified complication endpoint, irradiated organ volume, and fractionation schedule.
Why the others don't fit:
- A: That's TD50/5, which uses a 50% complication risk rather than 5%.
- C: The numbers describe a complication rate and a time frame, not a fractionation scheme.
- D: TD values describe normal-tissue complications, not tumor control.
Source: AAPM-hosted Lawrence B. Marks lecture, Predicting Normal Tissue Injury in the Modern Era: A Review of QUANTEC, slides 3–4 and 13: historical TD5/5 and TD50/5 definitions and volume dependence. · ID RT-017
Radiation Protection, Equipment Operation, and Quality Assurance (Questions 18–24)
Question 18
Safety · Daily QA: output out of tolerance RT-018
During morning QA on a conventional (non-IMRT) linac, the 6 MV output constancy reads +3.8% from baseline. AAPM MPPG 8.b gives a 3% daily output-constancy action limit. What should the therapist do?
Show answer and explanation for Question 18
Answer: C. Report it to the qualified medical physicist and follow the department's out-of-tolerance procedure before treating with that beam.
MPPG 8.b sets a 3% daily output-constancy action limit and says readings outside it must be reported to the qualified medical physicist (QMP). The QMP evaluates the result and determines the required response before that beam is used.
Why the others don't fit:
- A: 5% isn't the MPPG 8.b daily output-constancy action limit.
- B: Calibration adjustments require the qualified medical physicist's direction and verification; don't make an independent adjustment.
- D: Repeating until it passes hides a real result.
Source: AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests, §8.2.1, D1 (daily photon and electron output constancy), and §10 (action limits). · ID RT-018
Question 19
Safety · Daily QA: laser localization RT-019
Under AAPM MPPG 8.b, when lasers provide final positioning for non-SRS/SBRT treatment, the daily laser localization action limit is:
Show answer and explanation for Question 19
Answer: C. 2 mm
MPPG 8.b gives a 2 mm daily localization action limit for non-SRS/SBRT treatments. When lasers provide final positioning, they must be checked to 2 mm each day; the monthly localization check uses 1 mm.
Why the others don't fit:
- A: 1 mm is the monthly localization action limit in this guideline.
- B: 1.5 mm is not the daily action limit specified for this scenario.
- D: 5 mm exceeds the daily action limit for this scenario.
Source: AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests, §8.2.2, M1 (daily and monthly localization device check). · ID RT-019
Question 20
Safety · Occupational dose limit RT-020
What annual effective dose limit for occupational exposure is recommended in NCRP Report 116, the report named in ARRT’s current outline?
Show answer and explanation for Question 20
Answer: C. 50 mSv
NCRP Report 116 recommends 50 mSv per year, with lifetime cumulative effective dose not exceeding 10 mSv × age in years. The NRC's adult occupational limit is also 0.05 Sv (5 rem) total effective dose equivalent per year.
Why the others don't fit:
- A: 1 mSv per year is the usual NRC limit for individual members of the public under 10 CFR 20.1301, subject to that rule’s exceptions.
- B: 5 mSv is the NRC limit for an embryo or fetus over an entire declared pregnancy.
- D: 150 mSv is the NRC's annual limit for the lens of the eye.
Sources: NCRP Report 116, Limitation of Exposure to Ionizing Radiation, §8, printed pp. 33–35; 10 CFR 20.1201, Occupational dose limits for adults, paragraph (a), adult annual and lens dose limits; 10 CFR 20.1208, Dose equivalent to an embryo/fetus, paragraph (a), embryo/fetus dose; 10 CFR 20.1301, Dose limits for individual members of the public, paragraphs (a), (c), and (d), public-dose limit and specified exceptions. · ID RT-020
Question 21
Safety · Declared pregnancy RT-021
A therapist declares her pregnancy. What monthly equivalent dose limit to the embryo or fetus does NCRP Report 116 recommend?
Show answer and explanation for Question 21
Answer: B. 0.5 mSv
NCRP Report 116 recommends 0.5 mSv per month to the embryo or fetus once pregnancy is declared. The NRC's regulation sets a 5 mSv whole-pregnancy limit and requires efforts to avoid substantial monthly variation. If the dose is already at least 4.5 mSv when pregnancy is declared, no more than 0.5 mSv additional dose is permitted during the remainder of the pregnancy.
Why the others don't fit:
- A: Ten times lower than the recommendation.
- C: 5 mSv is the NRC total for the entire pregnancy, not a monthly figure.
- D: 50 mSv is the annual occupational limit for adults.
Sources: NCRP Report 116, Limitation of Exposure to Ionizing Radiation, §10, printed p. 38; 10 CFR 20.1208, Dose equivalent to an embryo/fetus, paragraphs (a), (b), and (d). · ID RT-021
Question 22
Safety · Area classification RT-022
Under NRC definitions, a high radiation area is an area accessible to individuals where a person could receive a dose equivalent exceeding:
Show answer and explanation for Question 22
Answer: B. 1 mSv in 1 hour at 30 cm
A high radiation area is accessible to individuals and has radiation levels that could result in a dose equivalent above 1 mSv (100 mrem) in one hour at 30 cm from the source or from any surface the radiation penetrates.
Why the others don't fit:
- A: A dose equivalent exceeding 0.05 mSv (5 mrem) in an hour at 30 cm is the threshold for a radiation area.
- C: An absorbed dose exceeding 5 Gy (500 rad) in an hour at 1 m defines a very high radiation area.
- D: That's an annual personal dose limit, not an area classification.
Source: 10 CFR 20.1003, Definitions, definitions of radiation area, high radiation area, and very high radiation area. · ID RT-022
Question 23
Safety · QA instrumentation RT-023
Which instrument is used with a phantom for daily linac output constancy checks?
Show answer and explanation for Question 23
Answer: D. Ionization chamber
Output checks need a dosimeter that measures high dose rates accurately and reproducibly. An ionization chamber in a phantom, or a daily QA device built around ion chambers, is an appropriate tool. MPPG 8.b also permits other suitable detector arrays when validated by the qualified medical physicist.
Why the others don't fit:
- A: A GM meter is a sensitive survey instrument for finding low levels of radiation, not for measuring a therapy beam's output.
- B: OSL badges record a worker's accumulated dose over weeks.
- C: Neutron detectors measure neutrons, not photon output.
Sources: AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests, §8.2.1, D1 (daily output-constancy equipment and QMP validation); IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §3.3, ionization chamber dosimetry systems, and §4.3, area survey meters. · ID RT-023
Question 24
Safety · Daily safety checks RT-024
Select all that apply. Which of these are daily safety checks specified in AAPM MPPG 8.b?
Show answer and explanation for Question 24
Answer: A, B and D.
MPPG 8.b requires daily checks of the door interlock, audiovisual monitoring, and beam-on indicators at the console and room entrance.
Why the others aren't daily safety checks:
- C: Full TG-51 output calibration is an annual test. Daily output checks establish constancy.
- E: MLC transmission is a dosimetric measurement, not one of the daily safety-function checks listed here.
Source: AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests, §8.2.4, S1 (door interlock), S3 (audiovisual monitoring), and S4 (beam-on indicators); §8.2.1, D1 (annual reference dosimetry). · ID RT-024
Treatment Sites and Tumors (Questions 25–30)
Question 25
Procedures · TNM staging RT-025
In the TNM staging system, what does N describe?
Show answer and explanation for Question 25
Answer: A. Whether nearby lymph nodes contain cancer, and how many or where
T describes the size and extent of the primary tumor, N describes regional lymph nodes with cancer, and M describes whether the cancer has spread to distant sites.
Why the others don't fit:
- B: Mitotic count isn't a TNM component.
- C: Grade is reported separately from stage.
- D: Distant spread is M.
Source: NCI, Cancer Staging, The TNM staging system. · ID RT-025
Question 26
Procedures · Tumor grade RT-026
A pathology report uses the general GX/G1–G4 grading scheme and describes a tumor as G1. What does that mean?
Show answer and explanation for Question 26
Answer: B. Well differentiated (low grade)
In the common grading scheme, G1 is well differentiated (low grade), G2 moderately differentiated, G3 poorly differentiated (high grade), and G4 undifferentiated. Grade describes how abnormal the cells look under a microscope.
Why the others don't fit:
- A: Poorly differentiated is G3.
- C: A grade that can't be assessed is GX.
- D: Grade and stage are different. Stage describes size and spread.
Source: NCI, Tumor Grade, grading categories. · ID RT-026
Question 27
Procedures · Oncologic emergency: SVC syndrome RT-027
A patient with a right upper lobe lung mass arrives for simulation with swelling of the face and neck that gets worse when he bends forward, swollen veins on his chest wall, and shortness of breath. Which oncologic emergency is most likely?
Show answer and explanation for Question 27
Answer: C. Superior vena cava syndrome
When the superior vena cava is blocked, blood backs up from the head, neck, and arms. That causes facial and upper-body swelling (often worse bending over), swollen chest veins, and shortness of breath. Lung cancer is the leading cancer cause, followed by non-Hodgkin lymphoma. These patients may not tolerate lying flat, which matters for simulation positioning.
Why the others don't fit:
- A: Cord compression causes back pain and neurologic changes, not swelling of the face and veins.
- B: Brain metastases cause neurologic symptoms, not venous congestion.
- D: Radiation pneumonitis develops after irradiation of lung tissue. The facial swelling and distended chest veins here point to SVC obstruction.
Sources: Oncology Nursing Society, STAT: Superior Vena Cava Syndrome, causes, signs, and nursing considerations; eviQ, Radiation-induced lung injury (pneumonitis and pulmonary fibrosis), definition and signs and symptoms. · ID RT-027
Question 28
Procedures · Oncologic emergency: spinal cord compression RT-028
In a patient with cancer, which symptom is most often the first sign of malignant spinal cord compression?
Show answer and explanation for Question 28
Answer: D. Back pain
Back pain shows up in about 90% of patients and is often the first symptom. New or worsening back pain in a cancer patient should be reported promptly.
Why the others don't fit:
- A: Bladder problems tend to be later signs.
- B: Weakness such as foot drop is usually later, and waiting for it risks permanent damage.
- C: Bowel problems are also generally later signs.
Source: UNC Lineberger Cancer Network, Oncologic Emergencies (2024), PDF p. 14, slide 27, Symptoms of SCC. · ID RT-028
Question 29
Procedures · Lung anatomy RT-029
A CT report describes a nodule in the lingula. Which lobe is that part of?
Show answer and explanation for Question 29
Answer: A. Left upper lobe
The left lung has only two lobes, upper and lower. The lingula projects from the lower part of the left upper lobe, so a lingular lesion is in the left upper lobe.
Why the others don't fit:
- B: The right middle lobe sits in a similar front-lower position, but on the right. The lingula is roughly its left-sided counterpart.
- C: The lingula belongs to the upper lobe, not the lower.
- D: The lingula is on the left side.
Source: NCI SEER Training, Anatomy of the Lungs, lobes and lingula. · ID RT-029
Question 30
Procedures · Stage at diagnosis RT-030
A patient was staged IIIA at diagnosis two years ago and now has new bone metastases. Under standard staging convention, how is the cancer's stage described?
Show answer and explanation for Question 30
Answer: B. It keeps its original stage, and the new spread is recorded as added information.
NCI explains that a cancer keeps the stage it was given at diagnosis, even if it spreads later. New information about how it changed is added to the original stage.
Why the others don't fit:
- A: The diagnosis stage isn't thrown out.
- C: Growth of the primary doesn't trigger a new stage under this convention.
- D: The diagnosis stage stays part of the record.
Source: NCI, Cancer Staging, stage after diagnosis. · ID RT-030
Treatment Volume Localization (Questions 31–35)
Question 31
Procedures · Target volumes RT-031
For an intact target in a simplified nested-margin model with nonzero microscopic-disease, internal-motion, and setup margins, put these target volumes in order from smallest to largest.
Show answer and explanation for Question 31
Answer: GTV → CTV → ITV → PTV (C, D, A, B)
GTV is the tumor you can see or feel. CTV adds a margin for microscopic spread you can't see. ITV adds an internal margin for the CTV's movement and shape changes, such as breathing. PTV adds a setup margin for day-to-day positioning and machine uncertainty.
Watch for: Placing the PTV before the ITV. The ITV covers internal motion, and the PTV adds the setup margin on top of it.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §§7.2.1–7.2.4, printed pp. 219–221, GTV, CTV, ITV, and PTV. · ID RT-031
Question 32
Procedures · Internal target volume RT-032
The internal margin added to the CTV to form the internal target volume (ITV) accounts for:
Show answer and explanation for Question 32
Answer: C. Movement and shape changes of the CTV inside the patient, such as breathing motion
ITV = CTV + internal margin. The internal margin covers changes in the target's position, size, and shape inside the body, for example a lung tumor moving as the patient breathes. A 4D CT scan is often used to see that motion.
Why the others don't fit:
- A: Setup uncertainty is the setup margin, added to make the PTV.
- B: Organ-at-risk dose is a separate planning concept.
- D: Microscopic disease is included in the CTV, rather than being the purpose of the ITV margin.
Sources: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.2.3, printed p. 221, internal target volume; AAPM Task Group 76, The management of respiratory motion in radiation oncology, §VI.A.4, printed p. 3884, respiration-correlated CT. · ID RT-032
Question 33
Procedures · CT image values RT-033
On the Hounsfield scale used for CT simulation images, what is the nominal CT number of water?
Show answer and explanation for Question 33
Answer: B. 0 HU
The Hounsfield scale defines water as 0 HU. Planning systems use CT numbers to estimate tissue density for dose calculation. A measured water-phantom result is assessed against the scanner's specified quality-control tolerance, not a requirement for exactly 0 on every measurement.
Why the others don't fit:
- A: −1000 HU is air.
- C: +100 HU isn't a reference value for water.
- D: +1000 HU is in the range of dense bone, not water.
Sources: IAEA, Quality Assurance for PET and PET/CT Systems, glossary, Hounsfield unit, printed p. 140; IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §11.4.3 (CT-based density information), printed p. 400, and §12.3.6 (CT simulator quality control), printed p. 429. · ID RT-033
Question 34
Procedures · Immobilization RT-034
A head and neck patient asks why she has to wear the mask made at her simulation for every treatment. What's the best explanation?
Show answer and explanation for Question 34
Answer: D. It keeps her head in the same position each day, matching the position her plan was built on.
The plan is built on images taken in the simulation position. A custom mask holds the head still and lets the therapist reproduce that position every day, so the dose goes where it was planned.
Why the others don't fit:
- A: A thermoplastic mask isn't shielding. It's for positioning.
- B: Reproducibility matters for every fraction, not just the first few.
- C: Immobilization reduces movement, but it doesn't replace image guidance or setup checks.
Sources: NCI, External Beam Radiation Therapy for Cancer, simulation and masks; IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.4.4, patient treatment position and immobilization devices. · ID RT-034
Question 35
Procedures · Reference marks RT-035
What is the main purpose of the small permanent tattoos placed at simulation?
Show answer and explanation for Question 35
Answer: A. To give reproducible reference points that line up with the room lasers, so the simulation position can be rebuilt each day
Reference marks let therapists rebuild the simulation position every day: lining the patient up to the lasers and leveling them to prevent rotation, before image guidance fine-tunes the setup. Not every patient gets permanent tattoos; some centers use ink marks or other methods.
Why the others don't fit:
- B: A few dots can't trace a tumor's outline. They're reference points.
- C: Field edges are defined by the plan and machine, not skin marks.
- D: Skin marks sit on the surface. They aren't internal soft-tissue markers.
Sources: NCI, External Beam Radiation Therapy for Cancer, simulation: tattoos and ink marks; IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.4.8.5, printed pp. 235–236, laser positioning of fiducial marks and tattoos. · ID RT-035
Prescription and Dose Calculation (Questions 36–41)
In ARRT's 2025 exam report, this section had the lowest average section score among first-time radiation therapy candidates. Work these on scratch paper, the way you will on exam day.
Question 36
Procedures · Equivalent square RT-036
What is the approximate equivalent square of an 8 cm × 18 cm open rectangular photon field, using the area-to-perimeter approximation?
Show answer and explanation for Question 36
Answer: B. 11.1 cm
Equivalent square = 4 × area ÷ perimeter = 4(8 × 18) ÷ 2(8 + 18) = 576 ÷ 52 = 11.1 cm.
Why the others don't fit:
- A: This just takes the short side.
- C: This is the square root of the area (√144), not the area-to-perimeter method.
- D: This is the simple average of the two sides.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §6.6.1, printed p. 173, Eq. 6.25. · ID RT-036
Question 37
Procedures · MU calculation: SSD setup RT-037
A single 6 MV field at 100 cm SSD is to deliver 180 cGy at 10 cm depth. The PDD at that depth is 67.0%, and the output for this field size is 1.000 cGy/MU at dmax at 100 cm SSD. There are no beam modifiers. How many MU are needed?
Show answer and explanation for Question 37
Answer: C. 269 MU
For an SSD setup, MU = dose at depth ÷ (output × PDD) = 180 ÷ (1.000 × 0.670) = 268.7, which rounds to 269 MU.
Why the others don't fit:
- A: This multiplies by the PDD instead of dividing.
- B: This ignores the PDD and treats the depth dose as the dmax dose.
- D: This doesn't follow from the given values.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §6.7.1, printed pp. 179–180, and §6.14, printed pp. 212–213. · ID RT-037
Question 38
Procedures · MU calculation: SAD setup RT-038
An isocentric field (SAD 100 cm) delivers 200 cGy at isocenter, 8 cm deep. The reference-field output is 1.000 cGy/MU at dmax with a 100 cm source-to-measurement-point distance, the TMR is 0.850, and the combined field-size factor (Sc × Sp) is 0.990. No other corrections apply. How many MU? Round to the nearest whole MU.
Show answer and explanation for Question 38
Answer: D. 238 MU
MU = dose ÷ (output × TMR × Sc·Sp) = 200 ÷ (1.000 × 0.850 × 0.990) = 200 ÷ 0.8415 = 237.7, which rounds to 238 MU.
Why the others don't fit:
- A: This multiplies by the factors instead of dividing (200 × 0.850 × 0.990 = 168.3).
- B: This uses only the field-size factor and leaves out the TMR (200 ÷ 0.990 = 202.0).
- C: This leaves out the field-size factor (200 ÷ 0.850 = 235.3).
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §6.8.5 (TMR) and §7.7.2, printed pp. 267–269 (isocentric MU calculation). · ID RT-038
Question 39
Procedures · Gap calculation RT-039
Two adjacent fields with parallel central axes perpendicular to a flat surface both use 100 cm SSD. Their field lengths at the surface, measured perpendicular to the shared junction, are 20 cm and 30 cm. For their diverging edges to meet at 5 cm depth, what skin gap is needed?
Show answer and explanation for Question 39
Answer: C. 1.25 cm
Each field contributes (L ÷ 2) × (d ÷ SSD). Field 1: 10 × (5 ÷ 100) = 0.50 cm. Field 2: 15 × (5 ÷ 100) = 0.75 cm. Total gap = 1.25 cm.
Why the others don't fit:
- A: This counts only the 20 cm field.
- B: This counts only the 30 cm field.
- D: This forgets to halve the field lengths. Divergence spreads out from the central axis, so you use half of each length.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.5.7.7, printed pp. 255–256, Eq. 7.5 and Fig. 7.24. · ID RT-039
Question 40
Procedures · Wedge factor RT-040
An open field needs 150 MU. A wedge with a wedge factor of 0.70 is added, and nothing else changes. How many MU are now needed?
Show answer and explanation for Question 40
Answer: C. 214 MU
A wedge factor below 1 means the wedge reduces output, so you need more MU: 150 ÷ 0.70 = 214.3, which rounds to 214 MU.
Why the others don't fit:
- A: This multiplies by the wedge factor, which would underdose.
- B: This ignores the wedge.
- D: This adds 70% instead of dividing by 0.70.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.5.2, printed pp. 242–244, wedge transmission factor. · ID RT-040
Question 41
Procedures · Isodose prescription RT-041
A plan's isodose lines are normalized so that 100% is the maximum dose. The physician prescribes 180 cGy per fraction to the 90% isodose line. What dose does the 100% point receive per fraction?
Show answer and explanation for Question 41
Answer: D. 200 cGy
If 90% of the maximum equals 180 cGy, the maximum is 180 ÷ 0.90 = 200 cGy.
Why the others don't fit:
- A: This takes 90% of the prescription (180 × 0.90), reversing the relationship.
- B: 180 cGy is the dose at the 90% line, not at the 100% point.
- C: This adds 10% of 180 instead of dividing by 0.90.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.7.3, printed p. 270, dose normalization; arithmetic uses the stated 90% prescription. · ID RT-041
Treatments (Questions 42–50)
Question 42
Procedures · Image guidance: shift above action level RT-042
Daily cone-beam CT registration calls for a 1.4 cm vertical shift. Your department's policy requires review before treatment for shifts above 1.0 cm at this site. What should you do?
Show answer and explanation for Question 42
Answer: B. Hold treatment and get the review your department's policy requires (for example, from the physician or physicist) before going ahead.
Action levels exist so that unusually large shifts get looked at before treatment. A big shift can mean a setup error, weight loss, anatomy changes, or the wrong reference image, and the people who own those decisions need to see it.
Why the others don't fit:
- A: Applying a shift the policy says needs review skips the check.
- C: Throwing away the imaging ignores a real discrepancy.
- D: Half a shift has no basis and is wrong whichever position is correct.
Source: ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standard Two—Radiation Therapy (verification, consultation, and withholding treatment), Standard Five (comparison with expected results), and Standard Six (authorized changes). · ID RT-042
Question 43
Procedures · Respiratory gating RT-043
In respiratory-gated treatment, the beam is:
Show answer and explanation for Question 43
Answer: C. On only during a selected phase or amplitude window of the breathing cycle
Gating synchronizes the beam with breathing, so dose is delivered only in a chosen part of the cycle, such as near the end of exhale. TG-142 includes QA tests for gated beam control and gating interlocks.
Why the others don't fit:
- A: Following the tumor continuously is tracking, a different technique.
- B: Simply asking the patient to breathe faster does not provide a gating window or verify target position.
- D: Gating is widely used with photon treatments.
Sources: AAPM Task Group 76, The management of respiratory motion in radiation oncology, §VI.B.1, printed pp. 3884–3885, phase- and displacement-based gating; AAPM Task Group 142 report, Quality assurance of medical accelerators (2009), respiratory gating QA. · ID RT-043
Question 44
Procedures · Patient movement during treatment RT-044
Partway through a field, the patient lifts his head off the headrest. What should you do first?
Show answer and explanation for Question 44
Answer: D. Interrupt the beam right away, then reposition and verify before continuing.
Once the patient moves, the beam may miss the target and hit healthy tissue. Stop the beam, then reposition and recheck the setup (including any repeat imaging your policy calls for) before resuming, and document the interruption.
Why the others don't fit:
- A: Finishing irradiates an unknown position.
- B: The beam stays on while the position is wrong.
- C: Changing future fractions isn't the therapist's decision, and the dose is still landing in the wrong place now.
Source: ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standards Four, Five, Six, and Eight: patient monitoring, setup verification, authorized changes, and documentation. · ID RT-044
Question 45
Procedures · Equipment malfunction RT-045
During treatment, the linac faults and the beam is terminated by the backup monitor unit counter. The primary MU display is lost. What's the correct response?
Show answer and explanation for Question 45
Answer: A. Record the available backup reading and fault information, keep treatment on hold, and notify the qualified medical physicist according to department policy.
The backup reading is evidence to preserve, not a sufficient basis by itself for resuming treatment after a fault. Record the available readings and preserve the delivery record. The physicist must assess the fault and determine what dose was delivered before the team decides how to complete the fraction.
Why the others don't fit:
- B: Delivering the full field again risks an overdose.
- C: Elapsed time alone is unreliable during a fault; completion requires verified delivery information.
- D: This resumes on a machine that just faulted before the fault and delivered dose have been assessed.
Sources: ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standards Four, Five, Six, and Eight: malfunctions, delivery verification, collaboration, and documentation; IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §5.5.15, printed pp. 149–150, independent dose-monitoring systems. · ID RT-045
Question 46
Procedures · Record and verify systems RT-046
What does a record and verify (R&V) system do?
Show answer and explanation for Question 46
Answer: B. It compares machine settings with the approved plan and blocks or flags mismatches, while the therapist still verifies the setup.
An R&V system checks settings such as energy, MU, gantry and collimator angles, and MLC files against the plan and can stop delivery when they don't match. It does not replace the therapist's verification of patient identity and setup.
Why the others don't fit:
- A: An electronic match does not replace patient identification and setup checks.
- C: It flags mismatches. It doesn't fix the plan.
- D: Recording is part of its job, but interlocking against the plan is the safety function.
Sources: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §12.4.4, printed pp. 443–445, record and verify systems; ASRT, Practice Standards for Medical Imaging and Radiation Therapy, Standards One and Two—Radiation Therapy: patient identity and treatment-plan verification. · ID RT-046
Question 47
Procedures · Total body irradiation RT-047
Which is a standard use of total body irradiation (TBI)?
Show answer and explanation for Question 47
Answer: C. As part of conditioning before a bone marrow (stem cell) transplant
TBI treats the whole body and is typically part of the conditioning regimen before a bone marrow or stem cell transplant. ARRT's 2027 outline lists TBI with the example "pre-bone marrow transplant," and the current outline lists bone marrow transplant among treatment sites.
Why the others don't fit:
- A: A field directed at a single bone metastasis is local treatment, not total body irradiation.
- B: A small skin cancer gets local treatment.
- D: Breast adjuvant radiation is local or regional, not whole-body.
Sources: NCI Dictionary of Cancer Terms, Total-body irradiation, definition and use before stem cell transplantation; ARRT Radiation Therapy content specifications (from Feb. 1, 2027), Procedures: treatments (TBI, pre-bone marrow transplant); ARRT Radiation Therapy content specifications (through Jan. 31, 2027), Procedures: treatment sites (bone marrow transplant). · ID RT-047
Question 48
Procedures · Radiation recall RT-048
Months after finishing chest wall radiation, a patient starts a new chemotherapy drug and develops redness and peeling only inside her old treatment field. Which reaction best fits this pattern?
Show answer and explanation for Question 48
Answer: D. Radiation recall
NCI describes radiation recall as skin in a previously treated area turning red, blistering, peeling, or becoming painful after certain chemotherapy drugs. The giveaway is that the reaction follows the old field's borders.
Why the others don't fit:
- A: She isn't getting radiation now.
- B: No new skin-contact exposure is described; the chemotherapy timing and old-field pattern favor radiation recall.
- C: No current pressure exposure from a positioning device is described; the chemotherapy timing and old-field pattern favor radiation recall.
Source: NCI, Skin and Nail Changes during Cancer Treatment, radiation recall. · ID RT-048
Question 49
Procedures · Beam modifiers: blocks and HVL RT-049
A shielding block is 5 half-value layers (HVL) thick for the beam in use. Using a constant-HVL, narrow-beam attenuation model and ignoring scatter, about what percentage of the primary beam gets through?
Show answer and explanation for Question 49
Answer: B. 3.1%
Each HVL cuts transmission in half: (½)⁵ = 1/32 = 3.125%, or about 3.1%.
Why the others don't fit:
- A: About 1.6% is 6 HVLs (1.5625%).
- C: 6.25% is 4 HVLs.
- D: 10% is what one tenth-value layer transmits, a different measure.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §1.4.2, printed pp. 26–27, exponential attenuation and HVL. · ID RT-049
Question 50
Procedures · Machine setup: SSD check RT-050
An isocentric plan (SAD 100 cm) places isocenter 8.0 cm deep along the beam's central axis from the entrance skin surface. At that setup, what should the optical distance indicator (ODI) read on the skin at the central axis?
Show answer and explanation for Question 50
Answer: B. 92.0 cm
For an isocentric setup, SSD = SAD − depth = 100 − 8.0 = 92.0 cm. Checking the ODI against the expected SSD is a quick cross-check of the source-to-skin distance.
Why the others don't fit:
- A: 88.0 cm would correspond to a depth of 12.0 cm, not the stated 8.0 cm.
- C: 100 cm is the SAD, at isocenter, not the skin.
- D: This adds the depth instead of subtracting it.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.7.2, printed p. 269, SAD/SSD/depth geometry. · ID RT-050
Score your results
Give yourself one point per question. Question 24 (select all) and Question 31 (put in order) count only if your whole answer is right, with no partial credit. If you skipped a question, count it as unanswered, not wrong, and keep it on your review list. Use your first answer, not a second try after reading the explanation. An answer revealed before you try the question stays unanswered. For your percentage, divide your number correct by 50 and multiply by 100; unanswered questions stay in the 50-question total.
| ARRT section | Questions | Your score | Real exam items (current → Feb. 2027) |
|---|---|---|---|
| Patient Interactions and Management | 1–7 | ___ / 7 | 29 → 28 |
| Patient and Medical Record Management | 8–12 | ___ / 5 | 17 → 19 |
| Radiation Physics and Radiobiology | 13–17 | ___ / 5 | 21 → 23 |
| Radiation Protection, Equipment Operation, and Quality Assurance | 18–24 | ___ / 7 | 30 → 28 |
| Treatment Sites and Tumors | 25–30 | ___ / 6 | 26 → 23 |
| Treatment Volume Localization | 31–35 | ___ / 5 | 18 → 20 |
| Prescription and Dose Calculation | 36–41 | ___ / 6 | 24 → 21 |
| Treatments | 42–50 | ___ / 9 | 35 → 38 |
| Total | 1–50 | ___ / 50 | 200 scored |
Real exam item counts come from ARRT's current and February 2027 content specifications.
With five to nine questions per section, one miss moves a section score a lot, so look for patterns rather than exact percentages. Two or more misses in a section is a good reason to work through that part of ARRT's outline line by line. Procedures accounts for 103 of the 200 scored questions in the current outline, so give that domain a substantial place in your review plan.
Review the reason, not the letter
For each miss, write one sentence naming the rule you got wrong, such as "PDD goes in the denominator of an SSD MU calculation" or "a laser out of tolerance goes to the physicist." Then come back in a few days and redo the miss from a blank page. Redoing the calculations without looking is what makes the formulas stick. On the real exam you'll have about a minute per question, so time your second pass.
A practice percentage isn't an ARRT score
Your percentage here is how you did on these 50 questions. It doesn't predict your ARRT score or whether you'll pass.
ARRT reports a scaled score from 1 to 99, and 75 passes. A scaled 75 doesn't mean 75% correct. The number of correct answers needed can vary slightly between exam forms because forms differ a little in difficulty. ARRT has approved an updated passing standard for Radiation Therapy for exams on or after February 1, 2027. The reported passing score stays 75, and ARRT says the update isn't meant to make the exam easier or harder.
Which outline applies to your exam date
| Your exam date | ARRT outline to use | Scored items: Patient Care / Safety / Procedures |
|---|---|---|
| Through January 31, 2027 | Content specifications effective January 1, 2022 | 46 / 51 / 103 |
| February 1, 2027 or later | Content specifications effective February 1, 2027 | 47 / 51 / 102 |
ARRT lists both on its content specifications page. The exam stays at 200 scored questions, and the eight sections keep their names. What shifts is emphasis: Treatments grows from 35 to 38 items and Treatment Volume Localization from 18 to 20, while Treatment Sites and Tumors drops from 26 to 23 and Prescription and Dose Calculation from 24 to 21.
According to ARRT's summary of the changes, the 2027 outline adds or rewords topics including:
- reviewing pertinent medical history, communication during the procedure, and CT simulation compliance
- a mechanical safety check in place of the rotation check
- 3D and 4D CT simulation, and electronic medical devices
- systemic therapy in place of chemotherapy
- total body irradiation (TBI) and total skin or total body electrons (TSE/TBE)
- responses to urgent situations
It also removes fusion with outside diagnostic studies from Prescription and Dose Calculation.
The questions on this page are mapped to the outline for exams through January 31, 2027. If you're testing later, they still cover the same sections, but use the 2027 outline to find the added topics this set doesn't cover.
ARRT Radiation Therapy exam facts
| Item | Fact |
|---|---|
| Credential | R.T.(T)(ARRT), earned through ARRT's primary eligibility pathway |
| Questions | 230 total: 200 scored and 30 unscored pilot questions. Pilot questions aren't marked. |
| Time | 230 minutes of testing time, in a 250-minute appointment that includes a tutorial, nondisclosure agreement, and survey |
| Question formats | Mostly single-best-answer multiple choice. Some questions ask you to select multiple answers, sort items into order, select an image on the screen, or watch a video. |
| Scoring | Scaled score from 1 to 99; 75 passes. Total score is based on the number of questions you answer correctly. |
| Calculator | Don't bring one. Basic and scientific on-screen calculators are available, and the test center provides a basic four-function calculator on request. |
| Units | SI units are primary on this exam. |
| 2025 first attempts | 958 candidates; 77.1% passed; average scaled score 79.8 |
Sources: ARRT 2026 Primary Eligibility Pathway Handbook (pp. 5, 37, 40–44, 53–54); ARRT 2025 Annual Exam Report (p. 12); current Radiation Therapy content specifications (p. 1).
This practice set mirrors the main format and includes one select-all and one ordering question. It doesn't include image or video items.
If you're applying or scheduling, see how ARRT exam registration works. If you've already tested, see how to read your ARRT exam results or the ARRT retake policy.
FAQ
Are these real ARRT exam questions?
No. They're original practice questions written for this page. ARRT's handbook warns candidates about materials that claim to contain ARRT exam questions.
Is ARRT Radiation Therapy a primary or postprimary credential?
Primary. ARRT's 2026 Primary Eligibility Pathway Handbook lists Radiation Therapy among its primary-pathway credentials, and ARRT's Radiation Therapy credential page describes the requirements.
How hard is the radiation therapy registry exam?
In 2025, 77.1% of 958 first-time candidates passed, according to ARRT's annual exam report. Prescription and Dose Calculation had the lowest average section score that year.
Is brachytherapy on the exam?
Only basic concepts. ARRT's current outline says brachytherapy coverage is limited to basic concepts such as dose to surrounding tissue and radiation protection, not specific procedures or isotope characteristics.
Sources
Official ARRT documents
- Radiation Therapy content specifications, effective January 1, 2022 (exams through January 31, 2027)
- Radiation Therapy content specifications, effective February 1, 2027
- Examination content specifications index
- Updated Radiation Therapy documents (April 1, 2026)
- Updated passing standard for Radiation Therapy (October 19, 2026)
- 2026 Primary Eligibility Pathway Handbook
- Annual Exam Report, 2025
- Radiation Therapy credential page
Teaching references used in the explanations
- The Joint Commission, Two Patient Identifiers—Understanding the Requirements
- ASRT, Practice Standards for Medical Imaging and Radiation Therapy
- AHRQ Health Literacy Universal Precautions Toolkit, Tool 5: Use the Teach-Back Method
- CDC, Transmission-Based Precautions
- CDC, Clinical Safety: Hand Hygiene for Healthcare Workers
- CDC, Clinical Guidance for C. diff Infection Prevention in Acute Care Facilities
- CDC, First Aid for Seizures
- eviQ, Brain cancer radiation therapy—patient information
- NCI, Infection and Neutropenia during Cancer Treatment
- 10 CFR 35.3045, Report and notification of a medical event
- NCI, Bleeding and Bruising (Thrombocytopenia) and Cancer Treatment
- NCI, Skin and Nail Changes during Cancer Treatment
- IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students
- AAPM-hosted Lawrence B. Marks lecture, Predicting Normal Tissue Injury in the Modern Era: A Review of QUANTEC
- AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests
- NCRP Report 116, Limitation of Exposure to Ionizing Radiation
- 10 CFR 20.1201, Occupational dose limits for adults
- 10 CFR 20.1208, Dose equivalent to an embryo/fetus
- 10 CFR 20.1301, Dose limits for individual members of the public
- 10 CFR 20.1003, Definitions
- NCI, Cancer Staging
- NCI, Tumor Grade
- Oncology Nursing Society, STAT: Superior Vena Cava Syndrome
- eviQ, Radiation-induced lung injury (pneumonitis and pulmonary fibrosis)
- UNC Lineberger Cancer Network, Oncologic Emergencies (2024)
- NCI SEER Training, Anatomy of the Lungs
- AAPM Task Group 76, The management of respiratory motion in radiation oncology
- IAEA, Quality Assurance for PET and PET/CT Systems
- NCI, External Beam Radiation Therapy for Cancer
- AAPM Task Group 142 report, Quality assurance of medical accelerators (2009)
- NCI Dictionary of Cancer Terms, Total-body irradiation
About this page
Last verified October 27, 2026: ARRT exam length, timing, formats, scoring, calculator rules, both content outlines and the February 1, 2027 change, the updated passing standard announcement, 2025 exam statistics, and the teaching sources linked above.
Castleport Test Prep is an independent exam prep publisher. We are not affiliated with, endorsed by, or approved by the American Registry of Radiologic Technologists (ARRT). Exam and credential names are used only to identify them, and trademarks belong to their respective owners. These are original, unofficial practice questions, not ARRT exam questions and not instructions for any patient's treatment. Your results here don't predict an ARRT score, certification, licensure, or employment.