RT Practice Test

Candidates who complete an ARRT-recognized Radiation Therapy program, hold an associate degree or higher, and satisfy ARRT ethics requirements take the Radiation Therapy exam to earn ARRT credentialing. This page offers practice question sets, step-by-step sample solutions, and an outline of the test structure across Patient Care, Procedures, and Safety to support your independent study before you sit for the exam.

RT Exam at a Glance

What the RT is and how it works

According to The American Registry of Radiologic Technologists, “RADIATION THERAPY Scored Items 200 Tutorial 8 minutes Pilot Items 30 NDA 2 minutes Total Items 230 Survey 10 minutes”^[1]

The Radiation Therapy exam administered by The American Registry of Radiologic Technologists (ARRT) certifies individuals seeking credentialing as radiation therapists. Candidates must complete an ARRT-recognized Radiation Therapy program, hold an associate degree or higher, and meet ARRT ethics requirements before applying. The application fee is $225. Note that state licensing requirements vary by state, so candidates should confirm local rules directly with their state licensing board or ARRT.

Testing is computer-based at Pearson VUE test centers. The session includes a 250-minute appointment with 230 minutes of test time. The examination consists of 230 questions, including 200 scored items and 30 unscored pilot items. Scoring uses a scale from 1 to 99, and candidates need a scaled score of 75 to pass. Test takers receive a preliminary score at the test center, and official results appear in their ARRT online account in about 10 business days.

Candidates are permitted 3 attempts within 3 years to pass, with the window starting on the start date of the initial exam window. Once earned, the credential is valid 1 year at a time and renewed annually.

RT content outline and where to practise each area

The content areas below are copied from the official RT content outline published by The American Registry of Radiologic Technologists. The right-hand column shows which of our practice sets covers it.

Worked examples: how to reason through RT questions

These are practice questions written for this site, not questions from the real exam. Each explanation shows why the right answer is right and why the others are wrong.

Example 1

Question: For heterogeneity corrections, the treatment planning system converts CT numbers to:

1. Atomic number
2. Relative electron density
3. Mass attenuation coefficient of lead
4. Physical tissue temperature

Answer: B. Relative electron density

Explanation:

Option B is correct because radiation treatment planning systems use a scanner calibration curve that translates CT numbers, also known as Hounsfield units, into relative electron density. Dose calculation algorithms require electron density to account for differences in photon attenuation and scatter across varied tissues such as lung, soft tissue, and bone. Option A is incorrect because atomic number alone does not convey the electron concentration needed for dose deposition modeling. Option C is incorrect because lead is a shielding material, not a tissue density reference in patient scans. Option D is incorrect because physical tissue temperature does not govern photon beam attenuation. Remember the rule: dose calculation algorithms correct for tissue inhomogeneities by converting CT numbers directly into relative electron density.

Example 2

Question: For an electron beam of energy E (in MeV), the approximate depth of the 80% isodose in cm is:

1. E/2
2. E/4
3. E/3
4. E/5

Answer: C. E/3

Explanation:

Option C is correct because the therapeutic depth, represented by the 80% isodose line for an electron beam of energy E in MeV, is estimated clinically using the rule of thumb E/3 in cm. Option A is incorrect because E/2 in cm estimates the practical range of the electrons, which is the depth where the beam ceases to deliver useful dose. Option B is incorrect because E/4 in cm underestimates penetration depth and does not correlate with standard clinical electron range benchmarks. Option D is incorrect because E/5 in cm also significantly underestimates depth and represents a fraction with no standard role in electron dosimetry. Remember this rule: for an electron beam of energy E in MeV, the depth of the 80% isodose line is approximately E/3 in cm, whereas the practical range is approximately E/2 in cm.

Example 3

Question: What is the primary purpose of the linear-quadratic (LQ) model in radiation therapy?

1. Calculating tumor volume from imaging
2. Predicting cell survival and comparing fractionation schedules
3. Measuring radiation output from a linac
4. Determining beam energy selection

Answer: B. Predicting cell survival and comparing fractionation schedules

Explanation:

Option B is correct because the linear-quadratic model describes cell survival following radiation exposure and provides the mathematical basis for comparing the biological effectiveness of different fractionation schedules. Option A is incorrect because tumor volume calculations rely on anatomical imaging and segmentation tools rather than radiobiological survival models. Option C is incorrect because radiation output from a linac is measured physically using calibrated ionization chambers and electrometers. Option D is incorrect because clinical beam energy selection depends on target depth, patient anatomy, and tumor location rather than cellular response formulas. Remember this rule: the linear-quadratic model is used to predict cell survival and evaluate equivalent doses across altered fractionation schedules in radiation therapy.

How to use these practice tests

Begin by reviewing the official ARRT content specifications covering Patient Care, Procedures, and Safety. Pair each content area with targeted practice tests to assess your current knowledge and locate subject areas that require deeper review.

Work through foundational topics using RT Clinical Assessment Methods and RT Patient Safety Protocols. Review technical subjects with RT Radiation Physics and Dosimetry and RT Treatment Planning. Read every explanation thoroughly to understand why the correct choice works and why alternate options fail.

Prior to your exam date, complete mixed practice sets under timed conditions to prepare for answering 230 questions within the 230 minutes of test time during the 250-minute appointment. Track areas where your accuracy falls below the scaled score of 75 benchmark, and revisit those specific practice sets until your performance stabilizes before exam day.

Sources & last verified

1. assets-us-01.kc-usercontent.com — number of questions, time limit, eligibility (official source). “RADIATION THERAPY Scored Items 200 Tutorial 8 minutes Pilot Items 30 NDA 2 minutes Total Items 230 Survey 10 minutes” Verified Oct 21, 2026.
2. The American Registry of Radiologic Technologists — exam fee (official source). “Primary (R, N, T, MR, S, VS): $225” Verified Oct 21, 2026 · source checked Oct 18, 2026.
3. The American Registry of Radiologic Technologists — passing score, score release (official source). “Our exam scoring scale ranges from 1 to 99, and you’ll need a total score of 75 to pass the exam.” Verified Oct 21, 2026 · source checked Oct 18, 2026.
4. The American Registry of Radiologic Technologists — retake policy (official source). “You may make three attempts within three years to pass a certification and registration exam. The three-year period begins with the starting date of your…” Verified Oct 23, 2026 · source checked Oct 23, 2026.
5. The American Registry of Radiologic Technologists — validity (official source). “You’ll renew your certification and registration every year.” Verified Oct 23, 2026 · source checked Oct 23, 2026.
6. The American Registry of Radiologic Technologists — delivery (official source). “Pearson provides computer-based testing services for ARRT. The company has more than 200 professional test centers in the U.S. and abroad.” Verified Oct 23, 2026 · source checked Oct 23, 2026.
7. assets-us-01.kc-usercontent.com — other (official source). “patient care” Verified Oct 21, 2026.

How we verify: editorial & fact-checking policy. Report an error: contact us.