ARRT Radiation Therapy Exam Prep
Your test date decides what you study: the 2022 ARRT radiation therapy outline applies through January 31, 2027, and the new outline applies from February 1, 2027. Start with the 26 original, unofficial practice questions below; these are study exercises, not instructions for patient treatment.
26 original practice questions
Patient Care: questions 1–6
Question 1 · Patient Interactions and Management · RT-001
A patient arrives for the first fraction of a course of treatment. Before the patient is set up, which action best confirms that the right patient is being treated?
Show answer and explanation for Question 1 (RT-001)
Answer: A. Ask the patient to state two identifiers, such as full name and date of birth, and match them to the treatment record
Joint Commission's 2026 hospital standard NPG.01.01.01 calls for at least two patient identifiers when providing care, treatment, and services. Neither identifier can be the patient's room number or physical location.
Why the other choices are wrong
- B. A setup photo helps, but on its own it does not meet the two-identifier standard.
- C. One identifier, offered by the staff member, invites a yes from the wrong person.
- D. A location or appointment slot is not a patient identifier; the wrong patient can be in the right slot.
Source: Joint Commission, 2026 Hospital National Performance Goals, NPG.01.01.01, EP 1, p. 1; Two Patient Identifiers — Understanding the Requirements
Before you open an answer, say why your pick is right and why each other choice is wrong. If you can't explain a choice, log it as a miss even if you guessed right. Keep a basic scientific calculator handy, since the real exam gives you one on screen.
Question 2 · Patient Interactions and Management · RT-002
An inpatient with Clostridioides difficile (C. diff) infection is brought down for treatment. Which precautions apply, in addition to the standard precautions used with every patient?
Show answer and explanation for Question 2 (RT-002)
Answer: B. Contact precautions
CDC's isolation guideline (Appendix A) lists Clostridioides difficile under Contact + Standard precautions. It is spread by touching the patient or contaminated surfaces and equipment, so the couch, immobilization devices, and other shared surfaces need cleaning and disinfection under the department's C. difficile protocol.
Why the other choices are wrong
- A. Airborne precautions are for diseases spread by small airborne particles, like tuberculosis or measles, not C. difficile.
- C. Starting antibiotics does not end contact precautions. CDC's acute-care guidance recommends maintaining them for at least 48 hours after diarrhea resolves, and sometimes through the rest of the hospitalization.
- D. Droplet precautions are for organisms spread by respiratory droplets, like influenza.
Source: CDC, Isolation Precautions Appendix A, C. difficile row; CDC, Clinical Guidance for C. diff Infection Prevention in Acute Care Facilities
Question 3 · Patient Interactions and Management · RT-003
A patient getting external beam photon treatment asks if it is safe to hug a grandchild after today's session. What is the most accurate answer?
Show answer and explanation for Question 3 (RT-003)
Answer: D. Yes. External beam radiation does not make the patient radioactive
NCI says external beam radiation therapy will not make you radioactive, and that patients may safely be around other people, including babies and young children. EPA's RadTown makes the same point. Restrictions on close contact after radiation are tied to some internal sources, such as certain implants or radiopharmaceuticals, and follow the instructions for that specific treatment.
Why the other choices are wrong
- A. Shielding isn't needed; external beam treatment does not make the patient radioactive.
- B. That kind of restriction can apply after some internal sources, not after external beam treatment.
- C. No waiting period is needed after external beam treatment, because nothing radioactive stays in the body.
Source: NCI, External Beam Radiation Therapy; EPA RadTown, Radiation Therapy
Question 4 · Patient Interactions and Management · RT-004
During week 3 of treatment to the oropharynx, a patient says their mouth feels dry and their saliva has gotten thick. The symptoms are mild, and the patient can eat and drink normally. What is the best response?
Show answer and explanation for Question 4 (RT-004)
Answer: A. Explain that this is an expected side effect of radiation to the mouth and neck, record it, and report it to the nurse or physician for mouth-care management
MedlinePlus lists dry mouth and thick saliva among the expected effects of radiation to the mouth and neck. The therapist's job is to acknowledge the symptom, document it, and route it to the care team.
Why the other choices are wrong
- B. Dry mouth and thick saliva are well-known effects of radiation to the mouth and neck.
- C. Alcohol-based rinses dry and irritate the mouth; mouth care should follow the care team's instructions.
- D. Gentle mouth care should continue according to the care team's instructions. Stopping brushing and rinsing increases the risk of oral problems.
Source: MedlinePlus, Mouth and neck radiation – discharge; ASRT Practice Standards, Standard Five — Evaluation and Standard Eight — Documentation
Question 5 · Patient Interactions and Management · RT-005
Which skin-care instruction for the treated area matches standard patient guidance during radiation therapy?
Show answer and explanation for Question 5 (RT-005)
Answer: B. Wash gently with lukewarm water and a mild soap, then pat the skin dry
MedlinePlus tells patients to wash the treatment area gently with lukewarm water, use a mild soap that doesn't dry the skin, pat dry instead of rubbing, and not to put heating pads or ice bags on the area.
Why the other choices are wrong
- A. Scrubbing injures skin that is already irritated. Patients are told to pat the skin dry, not rub it.
- C. Heat on treated skin is something patients are told to avoid.
- D. Patients are told not to put ice bags or heating pads on the treated skin.
Source: MedlinePlus, Mouth and neck radiation – discharge, skin care
Question 6 · Patient and Medical Record Management · RT-006
When reviewing a new patient's history for cervical cancer treatment, which infection is most closely linked to almost all cervical cancers?
Show answer and explanation for Question 6 (RT-006)
Answer: C. Human papillomavirus (HPV)
CDC states that almost all cervical cancers are caused by human papillomavirus (HPV).
Why the other choices are wrong
- A. Hepatitis B is a major risk factor for liver cancer.
- B. H. pylori is linked to stomach cancer and gastric MALT lymphoma.
- D. EBV is linked to nasopharyngeal carcinoma and some lymphomas, not most cervical cancers.
Source: CDC, Cervical Cancer Risk Factors; NCI, Infectious Agents
Safety: questions 7–12
Question 7 · Radiation Protection, Equipment Operation, and Quality Assurance · RT-007
Under U.S. NRC regulations, excluding planned special exposures, what is the annual occupational dose limit for an adult radiation worker, expressed as total effective dose equivalent (TEDE)?
Show answer and explanation for Question 7 (RT-007)
Answer: B. 50 mSv (5 rem)
10 CFR 20.1201 sets the adult occupational limit at 50 mSv (5 rem) TEDE per year, with separate limits of 150 mSv for the lens of the eye and 500 mSv shallow dose for the skin or any extremity.
Why the other choices are wrong
- A. 1 mSv per year is the usual limit on a member of the public's TEDE from an NRC-licensed operation, with specified exclusions (10 CFR 20.1301).
- C. 150 mSv is the annual lens-of-the-eye dose equivalent limit, not the whole-body TEDE limit.
- D. 5 mSv is the usual limit for occupational dose to the embryo/fetus of a declared pregnant worker over the entire pregnancy (10 CFR 20.1208), not the annual adult TEDE limit.
Source: 10 CFR 20.1201; 20.1208; 20.1301
Question 8 · Radiation Protection, Equipment Operation, and Quality Assurance · RT-008
A radiation therapist working under an NRC license voluntarily declares her pregnancy in writing to the licensee, including the estimated date of conception. The embryo/fetus occupational dose so far is 0.2 mSv. What limit applies over the entire pregnancy?
Show answer and explanation for Question 8 (RT-008)
Answer: C. 5 mSv (0.5 rem) over the entire pregnancy
For this scenario, 10 CFR 20.1208 limits the embryo/fetus dose from occupational exposure to 5 mSv (0.5 rem) over the entire pregnancy. The licensee must also make efforts to avoid substantial variation above a uniform monthly exposure rate.
If the dose has already exceeded 5 mSv, or is within 0.5 mSv of it when pregnancy is declared, §20.1208(d) instead permits no more than 0.5 mSv additional dose during the rest of the pregnancy.
Why the other choices are wrong
- A. 50 mSv is the annual adult TEDE limit; the embryo/fetus has its own, much lower limit.
- B. The public limit is 1 mSv per year; the declared-pregnancy limit is 5 mSv over the whole pregnancy.
- D. 10 CFR 20.1208 sets a separate limit once pregnancy is declared.
Source: 10 CFR 20.1208; 10 CFR 20.1003, definition of declared pregnant woman
Question 9 · Radiation Protection, Equipment Operation, and Quality Assurance · RT-009
During the morning warm-up, the daily output check on a photon beam reads 3.8% above baseline. Your department uses the AAPM TG-142 daily output tolerance of 3%. What should the therapist do next?
Show answer and explanation for Question 9 (RT-009)
Answer: B. Stop and notify the qualified medical physicist, then follow the department's written procedure before treating with that beam
TG-142 lists a 3% daily tolerance for x-ray output constancy. AAPM's 2023 MPPG 8.b also specifies a 3% daily output action limit and says readings outside it must be reported to the qualified medical physicist. The physicist resolves the discrepancy and determines the appropriate course of action under the clinic's procedures. So the therapist's correct move is to report and follow procedure, not to decide on their own.
Why the other choices are wrong
- A. Re-measuring until you get a passing value hides a possible fault instead of reporting it.
- C. A daily result outside tolerance needs a same-day response; it is not simply logged for later.
- D. Therapists do not independently change a patient's monitor units to compensate for an unexplained machine-output discrepancy.
Source: AAPM TG-142, Klein et al., Med Phys 2009, Table I (daily output) and Sec. II.C.3 (action levels); AAPM MPPG 8.b, Krauss et al., 2023, Photon and electron output constancy (D1)
Question 10 · Radiation Physics and Radiobiology · RT-010
Which radiation effect is classified as deterministic (has a threshold, and severity increases with dose)?
Show answer and explanation for Question 10 (RT-010)
Answer: D. Cataract formation
NRC defines a nonstochastic (deterministic) effect as one whose severity varies with dose and that has a believed threshold, and names radiation-induced cataract as the example. Stochastic effects, like cancer and hereditary effects, are the ones where the probability rises with dose, not the severity.
Why the other choices are wrong
- A. Leukemia induction is a stochastic, cancer-type effect.
- B. Cancer induction is a stochastic effect. The probability rises with dose, but severity does not.
- C. Hereditary effects are stochastic.
Source: 10 CFR 20.1003, definitions of nonstochastic and stochastic effects
Question 11 · Radiation Physics and Radiobiology · RT-011
For x-rays and other low linear energy transfer (LET) radiation, about how much more dose is needed to produce the same biological effect in hypoxic cells as in well-oxygenated cells?
Show answer and explanation for Question 11 (RT-011)
Answer: C. About 3 times
The oxygen enhancement ratio (OER) for x-rays is about 3, and it falls toward 1 as LET increases (ICRP Publication 127, summarized in ICRPaedia).
Why the other choices are wrong
- A. An OER near 1 describes very high-LET radiation, where oxygen matters little.
- B. Ten is much higher than the approximate x-ray OER of 3 given in the cited reference.
- D. Hypoxic cells are more radioresistant, so they need more dose, not less.
Question 12 · Radiation Physics and Radiobiology · RT-012
QUANTEC dose-response data for a first course of treatment at 2 Gy per day to the full spinal-cord cross-section estimate about what risk of myelopathy at a total cord dose of 50 Gy?
Show answer and explanation for Question 12 (RT-012)
Answer: B. About 0.2%
QUANTEC estimates the risk of myelopathy at about 0.2%, 6%, and 50% for cord doses of 50, 60, and 69 Gy in 2 Gy daily fractions. These estimates apply to the stated fractionation and cord exposure. Reirradiation and stereotactic schedules require their own constraints.
Why the other choices are wrong
- A. Roughly 6% is the estimate at about 60 Gy.
- C. 5% is not the QUANTEC estimate at 50 Gy; the estimate at 50 Gy is far lower.
- D. Roughly 50% is the estimate at about 69 Gy.
Source: Kirkpatrick JP, van der Kogel AJ, Schultheiss TE. Radiation dose–volume effects in the spinal cord. IJROBP. 2010;76(3 Suppl):S42–S49, p. S47, Recommended Dose–Volume Limits; full text PDF
Procedures: questions 13–26
Question 13 · Treatment Sites and Tumors · RT-013
Using the general G1–G4 differentiation grading scheme, a pathology report describes a tumor as Grade 1 (G1). What does that mean?
Show answer and explanation for Question 13 (RT-013)
Answer: D. The cells are well differentiated and look most like normal cells (low grade)
The NCI explains that tumor grade describes how abnormal the cells look under a microscope. G1 means well differentiated, or low grade. Grade is not the same thing as stage.
Why the other choices are wrong
- A. That describes a high grade (G3), not G1.
- B. Lymph node spread is staging (the N category), not grade.
- C. Tumor size is part of staging (the T category), not grade.
Source: NCI, Tumor Grade
Question 14 · Treatment Sites and Tumors · RT-014
A patient is staged T2 N1 M0. Which statement is correct?
Show answer and explanation for Question 14 (RT-014)
Answer: D. The cancer has spread to nearby lymph nodes, and there is no distant metastasis
In the TNM system, T describes the primary tumor, N describes regional lymph node involvement, and M describes distant metastasis. N1 means nodes are involved, and M0 means no distant metastasis.
Why the other choices are wrong
- A. M0 means no distant metastasis, and N1 means nodal spread is present.
- B. Nodes that cannot be assessed are coded NX, not N1.
- C. T2 refers to the size/extent of the primary tumor, not grade, and M0 means no distant spread.
Source: NCI, Cancer Staging
Question 15 · Treatment Sites and Tumors · RT-015
Which site is the most common distant destination when prostate cancer spreads through the bloodstream?
Show answer and explanation for Question 15 (RT-015)
Answer: C. Bone
NCI identifies bone as the most common site of distant prostate-cancer spread. Osteoblastic (bone-forming) lesions are associated with prostate cancer.
Why the other choices are wrong
- A. The brain is an occasional site, not the typical one.
- B. Skin is not a characteristic site of blood-borne spread from prostate cancer.
- D. The spleen is not a characteristic metastatic site for prostate cancer.
Source: NCI, Prostate Cancer Treatment PDQ, Staging Tests; NCI, Cancer of Unknown Primary Treatment PDQ, Bone Metastases if Blastic
Question 16 · Treatment Volume Localization · RT-016
On a CT simulation scan, what is the Hounsfield unit (HU) value of water by definition?
Show answer and explanation for Question 16 (RT-016)
Answer: C. 0 HU
The Hounsfield scale is defined so that water is 0 HU and air is −1000 HU.
Why the other choices are wrong
- A. −1000 HU is air.
- B. +1000 HU is not the defined value for water.
- D. +100 HU is not the defined value for water.
Source: ICRP, ICRPaedia Hounsfield unit, adapted from ICRP Publication 129
Question 17 · Treatment Volume Localization · RT-017
For a lung tumor that moves with breathing, which volume is built by adding an internal margin to the CTV to account for that motion?
Show answer and explanation for Question 17 (RT-017)
Answer: A. Internal target volume (ITV)
ICRU Report 62 defines the ITV as the CTV plus an internal margin for physiologic motion such as breathing. The PTV then adds the setup margin.
Why the other choices are wrong
- B. The GTV is the visible or palpable tumor; it has no motion margin.
- C. The PTV adds the setup margin on top of the internal margin, so it is a larger, later step.
- D. A PRV adds a margin around a normal structure, not around the target.
Source: Balter, target volumes and margins (ICRU 62 concepts), AAPM 2003
Question 18 · Prescription and Dose Calculation · RT-018
A machine is calibrated to 1.000 cGy/MU at dmax (1.5 cm) at 100 cm SSD. Using inverse square only, what is the dose per MU at dmax when the patient is treated at 120 cm SSD?
Show answer and explanation for Question 18 (RT-018)
Answer: B. 0.698 cGy/MU
Factor = ((SSD₀ + dmax)/(SSD + dmax))² = (101.5/121.5)² = 0.698. So the dose per MU at dmax is 1.000 × 0.698 = 0.698 cGy/MU.
Why the other choices are wrong
- A. This uses the simple ratio 100/120 without squaring it.
- C. This uses (100/120)², leaving dmax out of both distances. The calibration point sits at SSD + dmax: 101.5 cm and 121.5 cm.
- D. This inverts the ratio. Moving the source farther away lowers the dose per MU, so the factor must be less than 1.
Source: AAPM TG-71, Gibbons et al., Med Phys 2014, Eq. 3 inverse-square term
Question 19 · Prescription and Dose Calculation · RT-019
What is the equivalent square of an 8 cm × 20 cm rectangular field, using the 4A/P method?
Show answer and explanation for Question 19 (RT-019)
Answer: A. 11.4 cm
Equivalent square = 4A/P = 4(8 × 20)/(2(8 + 20)) = 640/56 = 11.4 cm.
Why the other choices are wrong
- B. This is the average of the two sides, which overstates the equivalent square.
- C. This is double the short side and has no basis as an equivalent-square method.
- D. This is the square root of the area (√160). That is a different method, and it overestimates for elongated fields.
Source: AAPM TG-71, equivalent-square discussion
Question 20 · Prescription and Dose Calculation · RT-020
An SSD setup at 100 cm prescribes 200 cGy to a depth where the PDD is 86.0%. The machine delivers 1.000 cGy/MU at dmax at 100 cm SSD, and all other factors equal 1.000. How many MU are needed?
Show answer and explanation for Question 20 (RT-020)
Answer: B. 233 MU
MU = Dose / (output × PDD) = 200 / (1.000 × 0.860) = 232.6, which rounds to 233 MU.
Why the other choices are wrong
- A. This multiplies the dose by the PDD instead of dividing. Dose at depth is less than dose at dmax, so you need more MU, not fewer.
- C. 240 MU would deliver 240 × 0.860 = 206.4 cGy under the stated conditions, exceeding 200 cGy.
- D. This ignores the PDD and delivers 200 cGy at dmax, which underdoses the prescription depth.
Source: AAPM TG-71, Eq. 3 (SSD setup)
Question 21 · Prescription and Dose Calculation · RT-021
An isocentric (SAD 100 cm) treatment prescribes 180 cGy at isocenter. The TMR at depth is 0.780. The machine is calibrated to 1.000 cGy/MU at dmax 1.5 cm at 100 cm SSD, so the inverse-square correction is (101.5/100)². Sc × Sp = 1.000. Assume all other correction factors are 1.000. How many MU are needed?
Show answer and explanation for Question 21 (RT-021)
Answer: D. 224 MU
(101.5/100)² = 1.030. MU = 180 / (1.000 × 1.000 × 0.780 × 1.030) = 224.0, which rounds to 224 MU.
Why the other choices are wrong
- A. This applies the inverse-square factor upside down (dividing the TMR by it).
- B. This leaves out the inverse-square correction from the calibration distance (101.5 cm) to isocenter (100 cm).
- C. This multiplies the dose by the factors instead of dividing by them.
Source: AAPM TG-71, Eq. 2 (SAD setup)
Question 22 · Prescription and Dose Calculation · RT-022
An open field needs 200 MU. A wedge with a transmission (wedge) factor of 0.70 is added, and nothing else changes. How many MU are needed now?
Show answer and explanation for Question 22 (RT-022)
Answer: C. 286 MU
The wedge factor goes in the denominator of the MU equation: 200 / 0.70 = 285.7, which rounds to 286 MU. The supplied wedge factor of 0.70 means that dose per MU is 70% of the open-field value.
Why the other choices are wrong
- A. This ignores the wedge factor entirely, so the patient would be underdosed by 30%.
- B. This multiplies by the wedge factor. A wedge attenuates the beam, so you need more MU, not fewer.
- D. This adds 70 MU, treating 0.70 as a fixed increment instead of a divisor.
Source: AAPM TG-71, wedge factor definition
Question 23 · Treatments · RT-023
For a narrow monoenergetic photon beam, a shielding block is 5 half-value layers thick. Neglect scatter. About what percentage of the primary beam is transmitted through it?
Show answer and explanation for Question 23 (RT-023)
Answer: A. 3.1%
Each HVL halves the remaining intensity, so 5 HVL transmits (½)⁵ = 1/32 = 3.1%.
Why the other choices are wrong
- B. 20% comes from dividing 100% by 5; transmission through successive HVLs is multiplicative, not 100% divided by the number of layers.
- C. 10% is one tenth-value layer, about 3.3 HVL, not 5 HVL.
- D. 50% is the transmission through a single HVL.
Question 24 · Treatments · RT-024
A patient is set up isocentrically on a 100 cm SAD machine with the isocenter 9 cm deep along the central axis. What SSD should the optical distance indicator read on the skin?
Show answer and explanation for Question 24 (RT-024)
Answer: D. 91 cm
SSD = SAD − depth to isocenter along the central axis = 100 − 9 = 91 cm.
Why the other choices are wrong
- A. This adds the depth instead of subtracting it.
- B. This subtracts half the depth, which has no basis.
- C. 100 cm is the SAD. The skin is closer to the source than the isocenter.
Source: AAPM TG-71, SSD and SAD setup definitions
Question 25 · Treatments · RT-025
Why is tissue-equivalent bolus placed on the skin over a superficial target during megavoltage photon treatment?
Show answer and explanation for Question 25 (RT-025)
Answer: A. To bring the dose buildup region to the skin, overcoming the beam's skin-sparing effect
Megavoltage beams have a skin-sparing buildup region. Placing bolus material on the skin shifts dose buildup into the bolus and increases the surface dose.
Why the other choices are wrong
- B. Tissue-equivalent bolus is not a shield; lung protection comes from field design, blocks, or MLC.
- C. Bolus increases the dose at the skin surface; reducing skin dose is the opposite of its purpose.
- D. Bolus moves dmax toward the skin surface, not deeper.
Source: IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students, §7.5.3, p. 244
Question 26 · Treatments · RT-026
A prostate patient's setup is being verified against the planned soft-tissue anatomy, not just bony landmarks. Which imaging method gives volumetric soft-tissue information?
Show answer and explanation for Question 26 (RT-026)
Answer: A. Cone-beam CT (CBCT)
TG-179 notes that CBCT provides volumetric and soft-tissue information, while 2D kV imaging is mainly useful for bony anatomy and fiducial markers.
Why the other choices are wrong
- B. MV portal images have low soft-tissue contrast and are two-dimensional.
- C. Planar kV images are good for bone and implanted markers, but they do not give volumetric soft-tissue detail.
- D. The ODI measures distance to the skin surface; it does not image internal anatomy.
Source: AAPM TG-179, Secs. II.B and III.B (volumetric imaging and soft-tissue localization)
We wrote these questions from public references: NRC regulations, AAPM task group reports, CDC, NCI, and others. Each one links to its source. They are original and unofficial, not real, recalled, or leaked ARRT questions. Each topic fits both the 2022 and 2027 outlines. The mix roughly follows the exam (6 Patient Care, 6 Safety, 14 Procedures), with extra dose-calc practice.
All 26 answers are open. Return to the normal view
Use your results
Count your misses by subsection. Twenty-six questions is a starting check, not a measure of your readiness or a predicted ARRT score. A percentage on this set only describes these 26 items.
| Subsection | Questions | Missed |
|---|---|---|
| Patient Interactions and Management | 1–5 | |
| Patient and Medical Record Management | 6 | |
| Radiation Protection, Equipment Operation, and QA | 7–9 | |
| Radiation Physics and Radiobiology | 10–12 | |
| Treatment Sites and Tumors | 13–15 | |
| Treatment Volume Localization | 16–17 | |
| Prescription and Dose Calculation | 18–22 | |
| Treatments | 23–26 |
Then copy this error log and fill in one row per miss, or per lucky guess:
| Question | What I thought | The correct rule | What to review | Review again on |
|---|---|---|---|---|
| Q21 (example) | I flipped the inverse-square factor | Factor = (calibration distance ÷ calculation distance)² = (101.5 ÷ 100)² = 1.030, and it goes in the denominator with TMR | TG-71 SAD equation; traps 1–2 below | 3 days from now |
The "review again" date matters. Come back to each corrected rule a few days later with a new problem, not the same one. Rereading a question you've already seen mostly tests whether you remember the answer.
What the exam covers on your test date
| Section and subsection | Through Jan 31, 2027 | From Feb 1, 2027 |
|---|---|---|
| Patient Care | 46 (23%) | 47 (23.5%) |
| Patient Interactions and Management | 29 | 28 |
| Patient and Medical Record Management | 17 | 19 |
| Safety | 51 (25.5%) | 51 (25.5%) |
| Radiation Physics and Radiobiology | 21 | 23 |
| Radiation Protection, Equipment Operation, and Quality Assurance | 30 | 28 |
| Procedures | 103 (51.5%) | 102 (51%) |
| Treatment Sites and Tumors | 26 | 23 |
| Treatment Volume Localization | 18 | 20 |
| Prescription and Dose Calculation | 24 | 21 |
| Treatments | 35 | 38 |
| Total scored questions | 200 | 200 |
Counts are scored questions from ARRT's 2022 content specifications and 2027 content specifications. Percentages are our math (count ÷ 200). Every form also carries 30 unscored pilot questions you can't tell apart from the rest. Go by your actual exam date, not your graduation date or the year printed on a review book.
Procedures is just over half the scored exam, so give it a substantial share of your review time. Adjust those hours to your own gaps. Inside Procedures, dose calculation is where first-time candidates scored lowest in 2025, so it gets its own section below.
Dose calculation: the lowest-scoring section
ARRT's 2025 Annual Exam Report (p. 12) gives mean section scores for 958 first-time radiation therapy candidates, all tested on the 2022 outline. Section scores run 0.1–9.9.
| Section | Scored items | 2025 mean section score |
|---|---|---|
| Patient Interactions and Management | 29 | 8.4 |
| Treatment Sites and Tumors | 26 | 8.2 |
| Treatment Volume Localization | 18 | 8.1 |
| Radiation Protection, Equipment Operation, and QA | 30 | 8.0 |
| Patient and Medical Record Management | 17 | 7.9 |
| Radiation Physics and Radiobiology | 21 | 7.9 |
| Treatments | 35 | 7.9 |
| Prescription and Dose Calculation | 24 | 7.4 |
These are group averages, not your score. The report does not break that section down by MU calculation or by error type. Use the worked problems in questions 18–22 to find and correct your own setup, factor, and unit errors.
The two MU equations
These central-axis photon equations are simplified from AAPM Task Group 71 for the dmax-normalized examples used here. Output is the reference dose per MU at dmax and calibration SSD₀; the PDD, TMR, and scatter factors must match the stated geometry and field:
- Isocentric (SAD) setup: MU = dose ÷ (output × Sc × Sp × TMR × wedge factor × tray factor × inverse-square factor)
- SSD setup: MU = dose ÷ (output × Sc × Sp × PDD × wedge factor × tray factor × inverse-square factor)
A few definitions:
- Output is the calibrated dose per MU at dmax and SSD₀.
- Sc and Sp are the collimator and phantom scatter factors.
- PDD is percent depth dose, written as a decimal.
- TMR is the tissue-maximum ratio.
- Inverse-square factor: for the SAD equation, use ((SSD₀ + dmax)/SAD)². For the SSD equation, use ((SSD₀ + dmax)/(SSD + dmax))². The SSD equation uses PDD for the treatment SSD; do not add a second correction from dmax to the prescription depth.
Four traps to drill
- Inverse-square distances. In the SAD equation, compare the source-to-calibration-point distance with SAD. In the SSD equation, compare the source-to-dmax distances at calibration and treatment. Increasing the denominator distance lowers the factor (questions 18 and 21).
- Which way the factors go. Divide the prescribed dose in cGy by the calculated dose per MU in cGy/MU. A smaller dose per MU requires more MU for the same prescribed dose. The numerical MU value is not always greater than the dose in cGy; that comparison depends on the output and all correction factors (questions 20–22).
- Equivalent square. Use 4A/P. The average of the sides and √area both run high for long, narrow fields (question 19).
- Geometry and attenuation. For an isocentric setup, SSD = SAD − depth along the central axis. For a narrow monoenergetic photon beam with negligible scatter, n HVLs transmit (½)ⁿ (questions 23 and 24).
One useful check: before you touch the calculator, identify the units and decide whether each correction factor should increase or decrease the result.
8-week study plan
This plan assumes you've finished, or nearly finished, an ARRT-recognized radiation therapy program. It runs about 8–10 hours a week, in six sessions of 80–100 minutes. It's an editorial plan, not an official requirement or a guarantee.
Every session follows the same pattern:
- 10 minutes of closed-book recall
- 15 minutes of dose calculation with new numbers
- The rest on the week's focus
- 5 minutes updating your error log
| Week | Focus | Practice tasks | Done when |
|---|---|---|---|
| 1 | Baseline | Confirm your outline by test date. Work all 26 questions untimed, explain every choice, and start the error log. Read the subsection list for your outline. | You have chosen two subsections to review first from your missed concepts and course feedback |
| 2 | Prescription and Dose Calculation | SSD and SAD MU problems; PDD vs TMR; inverse square at extended distance; equivalent square; wedge and tray factors. Ten new problems a day. | You can set up both MU equations from memory and estimate the answer before calculating |
| 3 | Radiation Physics and Radiobiology | Photon interactions; beam quality and HVL; LET, OER, and cell survival; deterministic vs stochastic effects; tissue tolerance. | You can explain each concept in two sentences without notes |
| 4 | Protection, Equipment Operation, and QA | NRC dose limits; time, distance, and shielding; TG-142 and MPPG 8.b daily and monthly checks; interlocks; what to do when a check fails. First timed mixed set at 1 minute per question. | You can state the main tolerances and the correct response to an out-of-tolerance result |
| 5 | Treatment Sites and Tumors | Grade vs stage; TNM; for major sites, lymph drainage, spread pattern, and the dose-limiting organs. Build one worksheet per site. | You have a worksheet for each site your program emphasized |
| 6 | Localization and Treatments | CT simulation and immobilization; GTV/CTV/ITV/PTV/PRV; HU and image registration; IGRT choices; SSD/SAD geometry; bolus; electrons; brachytherapy basics. If you test on or after Feb 1, 2027, include the expanded simulation coverage, TBI, and TSE in the 2027 outline. | You can pick the right volume and imaging method for a scenario |
| 7 | Patient Care and records | Identification; infection control; assessment and side-effect management; communication; documentation and record management; medical emergencies; treatment-monitoring emergency situations (2022) or urgent-situation responses (2027); the expanded systemic-therapy coverage if testing on or after Feb 1, 2027. | Every subsection has had at least one focused session |
| 8 | Full rehearsal | One full timed session using 230 authorized course or practice questions in 230 minutes, following the standard 2026 timing. Review every miss and every guess. Last two days are light recall only. Confirm your appointment, ID, and arrival time from your ARRT and Pearson VUE instructions. | Error log reviewed; exam-day logistics set |
Use your program's authorized practice problems for new calculation drills and the full rehearsal. This page supplies 26 questions, not a 230-question mock exam. In Week 8, combine normal study blocks into one uninterrupted 230-minute rehearsal, then review it separately.
4-week version
For about 15–18 hours a week: six sessions of 150–180 minutes, broken into shorter blocks. Keep the daily dose-calc block. If your first pass through the questions went badly, use more weeks if your exam window allows.
| Week | Focus |
|---|---|
| 1 | Baseline set and error log; Prescription and Dose Calculation |
| 2 | Radiation Physics and Radiobiology; Protection, Equipment, and QA; first timed mixed set |
| 3 | Treatment Sites and Tumors; Treatment Volume Localization; Treatments |
| 4 | Patient Care and records; full timed rehearsal; review misses; light final two days |
Retake plan
- Rank your sections. Your ARRT score report gives a score for each section. List them lowest first. Our ARRT exam results guide explains how to read them.
- Check your outline and passing standard. A retake on or after February 1, 2027 uses the new content outline and ARRT's updated passing standard. The reported passing score is still 75.
- Split your time. As an editorial starting point, put about 60% on your two lowest sections, including daily dose calc if Prescription and Dose Calculation is one of them, and 40% on mixed timed practice.
- Confirm your attempts and deadlines. ARRT allows three attempts within three years of your first exam window opening, and each attempt needs a new application and fee. Our ARRT exam retake policy guide covers the clock and fees.
What changes on February 1, 2027
Two things change for radiation therapy candidates who test on or after that date.
The content outline. Per ARRT's April 2026 notice and the 2027 specifications:
- Added: reviewing the patient's medical history; communication during the procedure; CT simulation compliance; 3D/4D simulation; electronic medical devices; total body irradiation (TBI) and total skin electron treatment.
- Reworded: chemotherapy expands to systemic therapy; in the Treatments section, emergency situations becomes urgent situation responses; the rotation check becomes a mechanical safety check.
- Removed: fusion with outside diagnostic studies. That's one bullet. Image registration itself is still covered.
- Re-weighted: Treatments goes up (35 → 38) and Treatment Volume Localization goes up (18 → 20). Sites and Tumors (26 → 23) and Prescription and Dose Calculation (24 → 21) go down.
The passing standard. On October 19, 2026, ARRT announced an updated passing standard for the Radiation Therapy exam, effective for candidates testing on or after February 1, 2027. The reported passing score stays 75. ARRT says the change isn't meant to make the exam easier or harder.
If you test before February 1, 2027, use the 2022 outline as your coverage checklist. Some 2027 additions make existing topics more explicit, so the change list is not a list of concepts to skip.
Exam format, scoring, and rules
| Item | Rule | Source |
|---|---|---|
| Questions | 230 total: 200 scored and 30 unscored pilot. Mostly single-best-answer multiple choice, with some multi-select, sorting, and image or video items. Random order. | 2026 Primary Handbook, pp. 37, 44 |
| Time | Standard timing in the 2026 handbook: 230 minutes of test time in a 250-minute appointment. The appointment includes a tutorial with a few practice questions, a nondisclosure agreement, and a survey. | Handbook p. 44; Preparing for Your Exam |
| Calculator | On-screen basic/scientific calculator. Pearson VUE can provide a four-function handheld. You can't bring your own. | Handbook pp. 40–41 |
| Strategy | Answer every question; you're never penalized for guessing. Flag uncertain items and come back if time allows. | Handbook p. 43 |
| Score scale | Scaled 1–99; 75 passes. Section scores run 0.1–9.9. | ARRT Exam Scoring; Handbook pp. 53–54 |
| Results | You see a preliminary score at the test center, but it isn't final. ARRT emails you within about 10 business days when official results are ready. | ARRT Exam Scoring |
| Passing standard | Raised February 1, 2025 (about seven more correct answers needed). It updates again for tests on or after February 1, 2027. Both are still reported as 75. | ARRT, Aug 2023; ARRT, Oct 2026 |
| 2025 results | 958 first-time candidates; 77% passed; mean scaled score 79.8 | 2025 Annual Exam Report, p. 3 |
| Attempts | Three within three years of your first exam window opening; each one needs a new application and fee | Handbook pp. 7, 14 |
| Exam window | Normally 365 calendar days, subject to your remaining three-year exam eligibility period and the handbook's early-closure rules. Follow the dates on your Candidate Status Report. | Handbook pp. 14, 29–30 |
| Application fee | $225 for a primary application | ARRT fees |
| Eligibility | Complete an ARRT-verified radiation therapy program, earn an associate degree or higher from an appropriately accredited institution, and meet ethics requirements. Establish ARRT eligibility within three years of program completion. Online application may begin up to 90 days before the later of program completion or degree completion; both must be complete before testing. | Handbook pp. 6–7, 22–23; ARRT three-year rule |
A scaled 75 is not 75% correct. ARRT converts your number of correct answers to a 1–99 scale so forms of different difficulty are judged fairly. ARRT's illustrative example, not a radiation-therapy cutoff: on one form you might need 131 of 200 correct, and on a slightly harder form, 130. On the 2025 radiation therapy forms, the passing point worked out to about 68% correct (2025 Annual Exam Report, p. 3). That figure describes 2025 forms only. It doesn't carry over to tests under the February 2027 standard.
Quick answers
Are these real ARRT questions? No. Every question here is original and unofficial. ARRT doesn't endorse any study materials and warns against anything claiming to contain actual exam questions (Handbook p. 38).
Should I reschedule because of the February 2027 change? That's your call, but ARRT says the update does not require rescheduling. ARRT says the updated standard isn't meant to make the exam easier or harder. What matters is studying the outline that matches the date you actually test.
Does passing make me licensed? Passing meets the examination requirement; you must also meet ARRT's education and ethics requirements. Permission to practice is set by each state, so check your state's licensing rules separately. See the 2026 Primary Handbook, pp. 15 and 54.
Official ARRT resources and related guides
From ARRT
- Radiation Therapy credential page: links both outlines, task inventories, and clinical requirements
- Content specifications through Jan 31, 2027 (PDF)
- Content specifications from Feb 1, 2027 (PDF)
- 2026 Primary Eligibility Pathway Handbook (PDF)
From Castleport Test Prep
- Apply for and schedule your ARRT exam
- Understand your ARRT score report
- ARRT exam retake policy
- ARRT continuing education requirements, for after you pass
Sources
Exam rules and data (ARRT)
- Radiation Therapy Content Specifications, effective Jan 1, 2022, through Jan 31, 2027, p. 1 and topic outline
- Radiation Therapy Content Specifications, effective Feb 1, 2027 (version 2026.03.27), p. 1 and topic outline
- Updated Radiation Therapy Documents, Apr 1, 2026
- Updated Passing Standard for Radiation Therapy, Oct 19, 2026
- Radiation Therapy Cut Score Change Effective Feb 1, 2025, Aug 30, 2023
- 2026 Primary Eligibility Pathway Handbook
- Exam Scoring and Preparing for Your Exam
- 2025 Annual Exam Report, pp. 3, 12
- Application Fees
Teaching references
- U.S. NRC regulations, 10 CFR Part 20: §20.1003, §20.1201, §20.1208, §20.1301
- Klein EE et al. AAPM TG-142: Quality assurance of medical accelerators. Med Phys. 2009;36(9):4197–4212
- Gibbons JP et al. AAPM TG-71: Monitor unit calculations for external photon and electron beams. Med Phys. 2014;41(3):031501; full text PDF
- Joint Commission, 2026 Hospital National Performance Goals, p. 1, NPG.01.01.01, EP 1
- CDC, Isolation Precautions Appendix A; Clinical Guidance for C. diff Infection Prevention in Acute Care Facilities
- NCI, External Beam Radiation Therapy; EPA RadTown, Radiation Therapy
- MedlinePlus, Mouth and neck radiation – discharge
- CDC, Cervical Cancer Risk Factors; NCI, Infectious Agents
- ICRPaedia, Oxygen enhancement ratio
- Kirkpatrick JP, van der Kogel AJ, Schultheiss TE. Radiation dose–volume effects in the spinal cord. IJROBP. 2010;76(3 Suppl):S42–S49, especially p. S47; full text PDF
- NCI, Tumor Grade; NCI, Cancer Staging
- NCI, Prostate Cancer Treatment PDQ, Staging Tests; NCI, Cancer of Unknown Primary Treatment PDQ, Bone Metastases if Blastic
- ICRP, ICRPaedia Hounsfield unit, adapted from ICRP Publication 129 (2015)
- Balter JM, Target volumes and margins, AAPM Summer School 2003
- IAEA, Radiation Oncology Physics: A Handbook for Teachers and Students (2005), §1.7.2, pp. 26–27; §6.3, p. 167; §7.5.3, p. 244
- ASRT Practice Standards, Standard Five — Evaluation and Standard Eight — Documentation
- AAPM MPPG 8.b: Linear accelerator performance tests. J Appl Clin Med Phys. 2023;24:e14160, Photon and electron output constancy (D1)
- Bissonnette JP et al. AAPM TG-179: Quality assurance for image-guided radiation therapy utilizing CT-based technologies. Med Phys. 2012;39(4):1946–1963, Secs. II.B and III.B
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) or Pearson VUE. Exam and credential names are used only to identify the exam, and trademarks belong to their respective owners. Exam rules change, so confirm current requirements with ARRT.
How we built this page. AI-assisted tools helped develop and check this page under our methodology. We checked each exam rule and number on this page against the ARRT document linked beside it. We wrote every practice question from the public references listed and recomputed every calculation. A credentialed radiation therapist or medical physicist has not reviewed this page. Exam-style scenarios are simplified, so in the clinic, follow your department's policies and your physicist's and physician's direction. If you spot an error, tell us and we'll fix it.