Castleport Test Prep

Free ARRT CT Practice Test

60 original questions mapped to the ARRT Computed Tomography content specifications effective September 1, 2026, with the answer and a full explanation under each one. These are unofficial practice questions written by Castleport Test Prep, not ARRT exam items.

Question 1 · Procedures — Neck and Chest A CT pulmonary angiogram is set up with bolus tracking. Where should the monitoring region of interest (ROI) be placed?
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Answer: C. For a PE study you want peak opacification of the pulmonary arteries, so you trigger off the vessel you're trying to fill — the pulmonary trunk. The SVC (D) enhances first and would trigger the scan too early, before the pulmonary arteries peak, and dense undiluted contrast there can cause streak artifact. The left ventricle (A) and ascending aorta (B) peak after the pulmonary circulation; triggering there times the scan for systemic arteries (a coronary CTA or aortic study), so the pulmonary arteries may already be washing out.

Source: Fleischner Society position paper on CT pulmonary angiography

Source context: The Fleischner position paper linked above addresses pulmonary hypertension. For the pulmonary-trunk bolus-tracking technique in this question, see the published CTPA study's key points, which explicitly describe pulmonary-trunk monitoring as a widely used bolus-tracking approach.

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Question 2 · Safety — Radiation Safety and Dose A helical scan has a weighted CTDI (CTDIw) of 12 mGy and a pitch of 1.5. What is the CTDIvol?
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Answer: A. For helical scanning, CTDIvol = CTDIw ÷ pitch, so 12 ÷ 1.5 = 8 mGy. A pitch above 1 spreads the same exposure over more table travel, lowering the average dose in the scanned volume. Multiplying instead of dividing gives 18 mGy (D). C ignores pitch entirely, and B is a distractor with no basis in the formula.

Source: AAPM CT Dose Summit (2011), Assessing Radiation Dose: CTDIvol, DLP and AAPM Report 96 k-factors

Question 3 · Patient Care — Patient Interactions and Management An outpatient who takes metformin is scheduled for a contrast-enhanced CT. Her eGFR is 52 mL/min/1.73 m², and she has no signs of acute kidney injury. What does current ACR guidance say about her metformin?
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Answer: C. The ACR Manual on Contrast Media says patients with eGFR ≥30 and no AKI don't need to discontinue metformin before or after IV iodinated contrast, and don't need routine follow-up renal testing. Holding metformin is reserved for patients with AKI or eGFR below 30. Options A and B describe older, more conservative practice. D withholds a diagnostic test with no indication to do so. Always follow your facility's written policy, which should be built on this guidance.

Source: ACR Manual on Contrast Media, Metformin chapter, p. 48

Question 4 · Image Production — Image Formation A 64-row scanner uses a detector configuration of 64 × 0.625 mm, and the table travels 52 mm per gantry rotation. What is the pitch?
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Answer: C. Pitch = table travel per rotation ÷ total beam collimation. Total collimation is 64 × 0.625 mm = 40 mm, so 52 ÷ 40 = 1.3. Choice A comes from dividing the wrong way (40 ÷ 52). A pitch of 1.0 (B) would mean the table moved exactly 40 mm per rotation. Always calculate total collimation first — not the single-row width.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 5 · Procedures — Abdomen and Pelvis A dual-phase pancreas protocol is ordered to evaluate a suspected pancreatic adenocarcinoma. Which phase gives the best conspicuity of the tumor?
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Answer: B. Adenocarcinoma usually enhances less than normal pancreas. Imaging during the pancreatic parenchymal phase maximizes the attenuation difference between enhancing normal pancreas and the typically hypoenhancing tumor. The portal venous phase that follows is useful for liver metastases, nodes and venous anatomy. A noncontrast phase (A) cannot show differential enhancement; excretory imaging (C) is a urinary-tract phase; and delayed equilibrium imaging (D) is not the phase optimized for primary tumor conspicuity.

Source: AJR: pancreatic-phase versus portal-vein-phase CT of the pancreas

Question 6 · Image Production — Image Evaluation and Archiving An abdomen is displayed with a window level of 40 HU and a window width of 400 HU. Which range of CT numbers is displayed as shades of gray?
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Answer: D. The window is centered on the level and extends half the width in each direction: 40 − 200 = −160 and 40 + 200 = +240. Anything above +240 HU displays white and anything below −160 HU displays black. C forgets to center on the level of 40. A starts at zero, and B adds the full width to each side instead of half.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 7 · Procedures — Head, Spine, and Musculoskeletal On a noncontrast head CT, how does an acute intraparenchymal hemorrhage typically appear compared with normal brain?
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Answer: A. Fresh clotted blood is denser than brain parenchyma and appears bright on noncontrast CT, which is why noncontrast head CT is the first study when hemorrhage is suspected. Blood becomes isoattenuating (C) and then hypoattenuating (B) as it ages over days to weeks, so timing matters. Fat density (D) doesn't describe hemorrhage. Giving IV contrast first can confuse the picture — enhancing structures can mimic or hide blood.

Source: ACR Appropriateness Criteria — Head Trauma

Question 8 · Patient Care — Patient Interactions and Management Shortly after contrast injection, a patient becomes pale and sweaty. Blood pressure is 78/40 mm Hg and heart rate is 46 bpm. There are no hives and no wheezing. After calling for help, which management fits this presentation?
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Answer: B. Hypotension with bradycardia points to a vasovagal reaction. The ACR adult reaction card manages it with oxygen, leg elevation, and a wide-open normal saline bolus, adding atropine if hypotension is refractory. Anaphylaxis typically produces hypotension with tachycardia — that is when epinephrine (A) is indicated. Diphenhydramine (C) can worsen hypotension, and an inhaler (D) treats bronchospasm, which this patient doesn't have.

Source: ACR adult contrast reaction card (updated Sept. 2026)

Question 9 · Image Production — Image Formation A chest was acquired with a 16 × 1.25 mm detector configuration. The radiologist now wants 0.625 mm images for a small nodule. What is true?
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Answer: D. In multidetector CT, the acquired detector width sets the minimum reconstructed slice thickness. Data collected in 1.25 mm channels can be reconstructed at 1.25 mm or thicker, never thinner. Raw data (A) lets you change the kernel, field of view and thickness only within that limit. A sharper kernel (C) changes edge sharpening, not slice thickness, and reformatting (B) can't create z-axis detail that wasn't acquired. Choose thin collimation up front when thin images may be needed.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 10 · Procedures — Neck and Chest A patient arriving for coronary CTA has a heart rate of 58 bpm after oral metoprolol. During screening he mentions he took sildenafil 12 hours ago. Which planned medication should be withheld?
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Answer: A. Sublingual nitroglycerin is used to dilate the coronary arteries for coronary CTA, but it is contraindicated after a recent phosphodiesterase-5 inhibitor such as sildenafil because the combination can cause severe hypotension. The contrast (B) is still needed. The heart rate is already at the usual goal of 60 bpm or less, so no more beta-blocker is needed, but metoprolol itself isn't the interacting drug (C). Proceeding unchanged (D) ignores a dangerous interaction. Notify the supervising physician and document.

Source: Abbara et al., SCCT guidelines for the performance and acquisition of coronary CT angiography, JCCT (2016)

Question 11 · Image Production — Image Evaluation and Archiving A concentric circular artifact appears at the same location on every axial image, centered on the isocenter. What is the most likely cause?
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Answer: A. Rings are an equipment artifact of rotate-rotate (third-generation) scanners: one detector element reading incorrectly traces a circle as the gantry rotates. Recalibration (an air calibration) or service is the fix. Motion (B) makes streaks, blurring or doubled edges. Beam hardening (C) causes dark streaks between dense structures and cupping. Partial volume averaging (D) blurs small structures and alters their CT numbers. None of those produce perfect circles.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 12 · Procedures — Abdomen and Pelvis A patient in the ED has acute flank pain and suspected ureteral stone. Which protocol is most appropriate?
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Answer: A. Stones are easiest to see without contrast, and a low-dose technique is usually adequate because stones are very high-contrast against surrounding tissue. Excreted contrast in the collecting system (C) can hide a stone that's just as dense. Portal venous imaging (B) and renal CTA (D) answer other questions. A urogram or added phases may follow if the radiologist needs them.

Source: ACR Appropriateness Criteria — Acute Onset Flank Pain, Suspicion of Stone Disease

Question 13 · Safety — Radiation Safety and Dose At diagnostic CT energies, which photon interaction accounts for most of the attenuation in soft tissue?
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Answer: C. In soft tissue at the effective energies of a CT beam, Compton scattering dominates. The photoelectric effect (A) is more important at lower energies and in high-atomic-number materials like iodine, calcium and bone, which is why they look so bright. Coherent scattering (B) is a small contributor. Pair production (D) requires photon energies above 1.02 MeV, far beyond diagnostic CT.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 14 · Procedures — Head, Spine, and Musculoskeletal A trauma patient arrives on a backboard in a cervical collar for CT of the cervical spine. How should sagittal and coronal images be obtained?
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Answer: D. Until the spine is cleared, the neck must not be moved. A thin-section helical acquisition with immobilization in place produces high-quality sagittal and coronal reformats, without repositioning the patient. Removing the collar or flexing the neck (A) risks spinal cord injury. Thick 5 mm data (C) produces poor reformats that can miss nondisplaced fractures. Gantry tilt (B) can't produce a true coronal plane, and it doesn't replace reformats.

Source: ACR CT Accreditation — Adult Spine technique parameters

Question 15 · Image Production — Image Formation A completed abdomen scan was reconstructed with a soft-tissue algorithm. The radiologist asks for a bone-algorithm set of the lumbar spine from the same scan. What must be available?
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Answer: D. Changing the reconstruction kernel, the display field of view, or the reconstructed slice thickness requires the raw projection data, a process called retrospective reconstruction. Images already on PACS (A) are finished image data; you can window or reformat them, but you can't change their kernel. A new scout (C) does nothing here, and as long as raw data is still stored on the scanner, rescanning the patient (B) adds unnecessary dose.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 16 · Patient Care — Patient Interactions and Management During a power injection, about 50 mL of contrast extravasates into the forearm. The arm is mildly swollen and tender, with normal sensation, capillary refill and finger motion. What is the best management?
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Answer: C. The ACR recommends elevating the affected extremity and permits either warm or cold compresses; a health care provider should examine the limb, the event should be documented, and outpatients need clear instructions about when to seek care because severe injury can evolve after discharge. Surgical consultation is driven by concerning signs such as increasing pain, altered perfusion or sensation, reduced range of motion, or blistering—not by an extravasated volume alone (A). Routine aspiration through the IV catheter (B) and hyaluronidase injection (D) are not recommended.

Source: ACR Manual on Contrast Media — Extravasation of Contrast Media

Question 17 · Procedures — Neck and Chest A cardiologist wants to assess valve motion and ejection fraction across the entire cardiac cycle from a cardiac CT. Which acquisition supports this?
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Answer: D. Retrospective gating acquires data continuously while the ECG is recorded, so images can be reconstructed at any point in the R-R interval — necessary for functional analysis across the cycle. The tradeoff is higher dose (which ECG-based tube current modulation can reduce). Prospective triggering (A) exposes only a chosen phase window, lowering dose but limiting functional data. Non-gated scans (C) suffer cardiac motion, and calcium scoring (B) is a single noncontrast phase.

Source: Abbara et al., SCCT guidelines for the performance and acquisition of coronary CT angiography, JCCT (2016)

Question 18 · Image Production — Image Evaluation and Archiving An image is reconstructed with a 250 mm display field of view and a 512 × 512 matrix. What is the approximate pixel size?
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Answer: A. Pixel size = DFOV ÷ matrix size = 250 mm ÷ 512 ≈ 0.49 mm. Shrinking the DFOV or enlarging the matrix makes pixels smaller and can improve displayed spatial resolution, up to the limits set by the acquisition. D is what you'd get with a 500 mm DFOV; B and C come from misplaced decimals or dividing the wrong way.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 19 · Procedures — Abdomen and Pelvis An adrenal protocol shows an adrenal nodule measuring 20 HU unenhanced, 100 HU in the portal venous phase, and 40 HU on a 15-minute delayed image. What is the absolute washout, and what does it suggest?
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Answer: C. Absolute washout = (enhanced − delayed) ÷ (enhanced − unenhanced) × 100 = (100 − 40) ÷ (100 − 20) = 60 ÷ 80 = 75%. An absolute washout of 60% or more is the commonly used threshold supporting an adenoma. (Relative washout here — (100 − 40) ÷ 100 = 60% — also exceeds its usual 40% threshold.) B uses the relative-washout figure and mislabels it. A and D come from arithmetic errors, and washout alone doesn't diagnose pheochromocytoma.

Source: Mayo-Smith et al., Management of Incidental Adrenal Masses: ACR Incidental Findings Committee white paper, JACR (2017)

Question 20 · Safety — Radiation Safety and Dose An adult chest CT has a CTDIvol of 10 mGy over a 35 cm scan length. Using a chest conversion coefficient (k) of 0.014 mSv/(mGy·cm), what is the estimated effective dose?
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Answer: C. First DLP = CTDIvol × scan length = 10 mGy × 35 cm = 350 mGy·cm. Then effective dose ≈ DLP × k = 350 × 0.014 = 4.9 mSv. D confuses DLP with effective dose (and uses the wrong unit); A multiplies only CTDIvol by k; B skips a step. Remember effective dose is a population-level estimate for comparing exams, not a precise dose to the individual patient.

Source: AAPM CT Dose Summit (2011), Assessing Radiation Dose: CTDIvol, DLP and AAPM Report 96 k-factors

Question 21 · Procedures — Head, Spine, and Musculoskeletal Which reconstruction approach is standard for CT of the temporal bones?
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Answer: C. Current ACR adult temporal-bone accreditation technique calls for axial and coronal images no thicker than 2 mm, a sharp/high-spatial-frequency reconstruction, and a small display field of view. Those choices preserve fine bony detail in structures such as the ossicles and otic capsule. Thick, smooth or soft-tissue reconstructions (A, B) sacrifice spatial resolution. Contrast-enhanced brain-algorithm images (D) are not a substitute for the dedicated high-resolution bony reconstruction.

Source: ACR CT Accreditation — Adult Head and Neck technique parameters

Question 22 · Image Production — Image Formation Compared with filtered back projection, what is the main practical advantage of iterative reconstruction?
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Answer: D. Iterative (and model-based) reconstruction repeatedly compares and corrects estimated images against the measured data and models noise, producing less noise than filtered back projection at the same dose. Protocols can then use lower mAs or kVp. It is a reconstruction method, so it doesn't change rotation time (A) or detector hardware (B), and it still needs raw data (C). Heavy strength settings can change image texture, which is why radiologists set the levels.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 23 · Patient Care — Patient Interactions and Management An outpatient scheduled for contrast-enhanced CT of the abdomen has an eGFR of 24 mL/min/1.73 m². She isn't on dialysis. What should the technologist do?
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Answer: B. The ACR treats eGFR below 30 (in patients not on dialysis) as the group at potential risk for contrast-induced kidney injury from IV iodinated contrast, so a radiologist should weigh the indication and alternatives before contrast is given. For these patients, ACR–National Kidney Foundation consensus statements recommend IV normal saline prophylaxis unless it's contraindicated, such as in heart failure. A ignores that threshold. Changing dose or rate on your own (C) or switching agents without an order (D) are outside the technologist's role, and they don't resolve the risk decision.

Source: ACR–NKF consensus statements on IV iodinated contrast in kidney disease, Radiology (2020)

Source: ACR Manual on Contrast Media, Post-Contrast AKI chapter, p. 39

Question 24 · Procedures — Neck and Chest Under the USPSTF recommendation for lung cancer screening with low-dose CT, which person is eligible?
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Answer: C. The USPSTF recommends annual low-dose CT for adults aged 50 to 80 with at least a 20 pack-year history who currently smoke or quit within the past 15 years. Only C meets all three criteria. A is under 50, B quit more than 15 years ago, and D is over 80. Insurer and program criteria can differ, so screening programs verify eligibility for each patient.

Source: USPSTF, Lung Cancer: Screening (2021)

Question 25 · Image Production — Image Evaluation and Archiving On a head CT, dark streaks run horizontally between the petrous portions of the temporal bones, obscuring the posterior fossa. What is the artifact?
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Answer: A. As the polychromatic beam passes through dense bone, low-energy photons are preferentially absorbed. The beam becomes harder, the scanner underestimates attenuation, and dark streaks appear between dense structures — classically between the petrous ridges. Thin slices, bone-correction software and good positioning reduce it. Rings (B) are circular, out-of-field artifacts (C) occur at the edge when anatomy extends beyond the scan field, and tube arcing (D) is an equipment fault producing streaks across the image.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 26 · Procedures — Abdomen and Pelvis A multiphase liver CT is ordered in a patient with cirrhosis to evaluate for hepatocellular carcinoma. Which phase best shows a lesion's arterial-phase hyperenhancement?
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Answer: A. HCC gets its blood supply mainly from the hepatic artery, so it enhances avidly when hepatic arterial enhancement peaks, before the background liver (supplied mostly by the portal vein) has fully enhanced. Portal venous (B) and delayed (D) phases show the "washout" and capsule features. The noncontrast phase (C) is a baseline for judging enhancement. Imaging too early (early arterial) can miss hyperenhancement, which is why bolus tracking is used for timing.

Source: ACR LI-RADS support: technique (late arterial phase)

Question 27 · Image Production — Image Formation A CTA runoff of the lower extremities needs a single image that shows the contrast-filled arteries along their full length, similar to a conventional angiogram. Which postprocessing technique is most commonly used?
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Answer: B. A MIP projects the highest-attenuation voxel along each ray, so dense contrast-filled vessels stand out from surrounding tissue in an angiogram-like image. Dense calcification and bone are also bright on MIP, which can hide the lumen, so they're often reviewed along with curved reformats or volume rendering. MinIP (A) highlights low-attenuation structures like airways. A single thin MPR (C) can't show a tortuous vessel's full course, and skin-surface display (D) doesn't show vessels.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 28 · Safety — Radiation Safety and Dose Why does lowering the tube potential from 120 kVp to 100 kVp help a CT angiogram in a small adult?
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Answer: A. Iodine's attenuation rises sharply just above its K-edge at 33.2 keV. A lower-kVp beam has more photons near that energy, so iodine enhancement increases. That lets the protocol keep vascular contrast-to-noise at a lower dose, or reduce contrast volume. The tradeoff is more noise, because fewer photons penetrate (B is backward), so it fits smaller patients best. Lower kVp doesn't eliminate beam hardening (C) — it can worsen it — and it has nothing to do with temporal resolution (D).

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 29 · Procedures — Head, Spine, and Musculoskeletal A patient is scanned for a suspected orbital floor (blowout) fracture. Which plane best demonstrates the orbital floor?
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Answer: C. The orbital floor runs roughly horizontally, so axial slices (A) cut parallel to it and can miss a depressed fragment or herniated orbital fat or muscle. Coronal images — usually reformatted from thin axial data — cut across the floor and show depression directly. A midline sagittal plane (B) misses both orbits; a parasagittal reformat through each orbit can help. An oblique optic-nerve plane (D) is for the nerve, not the floor.

Source: ACR Appropriateness Criteria — Orbital Imaging and Vision Loss

Question 30 · Patient Care — Patient Interactions and Management An outpatient with a prior moderate allergic-like reaction to iodinated contrast is scheduled for an elective contrast CT tomorrow. Which is an ACR-listed elective premedication regimen?
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Answer: A. The ACR Manual lists a 13-hour oral regimen: prednisone 50 mg at 13, 7 and 1 hour before contrast, with diphenhydramine 50 mg 1 hour before (the antihistamine is considered optional). Another listed option is methylprednisolone 32 mg at 12 and 2 hours before. The ACR notes that regimens under 4–5 hours haven't been shown to work, which rules out B and D, and an antihistamine alone (C) isn't a corticosteroid premedication regimen. Breakthrough reactions can still occur, so reaction readiness stays in place.

Source: ACR Manual on Contrast Media, Patient Selection chapter, premedication regimens, pp. 9–10

Question 31 · Image Production — Image Evaluation and Archiving A 4 mm lung nodule measures soft-tissue density on 1 mm images but appears faint, with a lower CT number, on 5 mm images. What explains the difference?
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Answer: A. Each voxel shows the average attenuation of everything inside it. A 4 mm nodule in a 5 mm thick voxel is averaged with surrounding air-filled lung, lowering its CT number and making it faint. Thinner slices reduce partial volume averaging. Beam hardening (B) creates dark streaks near dense objects; noise (C) makes graininess rather than a consistent lower value; out-of-field (D) affects the image edges.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 32 · Procedures — Neck and Chest Which coverage is standard for a CT angiography evaluation before transcatheter aortic valve replacement (TAVR)?
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Answer: A. TAVR planning needs precise annulus and aortic-root measurements (ECG-gated, to freeze motion) and an assessment of the access route — the aorta and iliofemoral arteries — for size, tortuosity and calcification. Noncontrast chest (B) can't measure lumens. Intracranial CTA (C) and a venous-phase abdomen (D) don't answer the valve or access questions.

Source: SCCT expert consensus on CT imaging before TAVI/TAVR, JCCT (2019)

Question 33 · Image Production — Image Formation What does the slip ring allow a CT scanner to do?
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Answer: D. Slip rings transfer power and data across the rotating gantry through sliding contacts, so the gantry can spin continuously in one direction. That made helical (spiral) scanning possible. Analog-to-digital conversion (A) happens in the data acquisition system. Filtration (C) and beam shaping (B) are done by filters, including the bowtie filter, and collimators.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 34 · Procedures — Abdomen and Pelvis In a trauma patient with a pelvic fracture and suspected bladder injury, why is a CT cystogram performed by retrograde filling through a Foley catheter rather than relying on contrast excreted from an IV injection?
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Answer: B. A bladder tear can stay hidden if the bladder isn't under distending pressure. Retrograde filling with dilute iodinated contrast through a catheter fills the bladder adequately, so leakage into the perivesical space (extraperitoneal) or around bowel loops (intraperitoneal) becomes visible. A is the reverse of the truth. C is wrong because contrast is diluted for CT to avoid streak artifact. D is wrong because retrograde filling requires a catheter.

Source: ACR Practice Parameter for Imaging of the Urinary Tract in Adults

Question 35 · Safety — Radiation Safety and Dose With tube current held constant and automatic exposure control turned off, the pitch is increased from 1.0 to 1.375 while all other settings stay the same. What happens to CTDIvol?
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Answer: C. CTDIvol is inversely proportional to pitch: 1 ÷ 1.375 ≈ 0.73, a drop of about 27%. A reverses the relationship. Note that some scanners use an "effective mAs" setting that automatically raises tube current as pitch increases to keep CTDIvol constant, which is why the stem specifies constant tube current. Higher pitch also slightly reduces z-axis resolution.

Source: AAPM CT Dose Summit (2011), Assessing Radiation Dose: CTDIvol, DLP and AAPM Report 96 k-factors

Question 36 · Procedures — Head, Spine, and Musculoskeletal Which contrast agent is appropriate for intrathecal injection before a postmyelogram CT?
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Answer: B. Only nonionic iodinated agents approved and labeled for intrathecal use, at labeled concentrations and doses, are used for myelography. Inadvertent intrathecal injection of an ionic agent (A) can cause severe, potentially fatal neurotoxic reactions — which is why intrathecal contrast is verified before injection. Barium (C) is never injected into the thecal sac. Gadolinium (D) isn't a routine intrathecal agent.

Source: DailyMed — iohexol injection prescribing information

Question 37 · Patient Care — Patient Interactions and Management During a power injection a patient suddenly develops dyspnea, chest pain and hypotension, and the images show air in the main pulmonary artery. Besides calling for help, which immediate measures are recommended?
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Answer: D. For clinically significant venous air embolism, the ACR describes giving 100% oxygen and placing the patient left side down, which helps keep air in the right side of the heart away from the pulmonary outflow tract. Hyperbaric oxygen may be considered, and CPR started if arrest occurs. A puts the wrong side down without oxygen. C treats an allergic reaction, not air. B continues the source of the problem. Purging air from the syringe and tubing before every injection is the prevention.

Source: ACR Manual on Contrast Media, Safe Injection chapter, pp. 14–15

Question 38 · Image Production — Image Formation Which statement about coronary artery calcium scoring using the Agatston method is correct?
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Answer: B. Agatston scoring uses a noncontrast, ECG-synchronized scan. Calcified lesions at or above the 130 HU threshold are measured, and each lesion's area is weighted by a density factor based on its peak attenuation. Iodinated contrast (A) would be indistinguishable from calcium. A 0 HU threshold (C) would count water-density tissue. DLP (D) is a dose metric, not a calcium measurement.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 39 · Image Production — Image Evaluation and Archiving During morning QC, an ROI placed in the water section of the manufacturer's phantom measures a mean of +22 HU. What is the appropriate response?
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Answer: C. By definition water is 0 HU (air is −1000 HU), so a water reading this far from 0 is a calibration problem that will shift every CT number, affecting things like lesion characterization. Follow the facility's QC procedure, which typically calls for recalibration and retesting, then service if it fails, before scanning patients. A and B accept an out-of-tolerance result. Changing the display window (D) doesn't change measured CT numbers.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 40 · Procedures — Neck and Chest Why are prone images often added to a high-resolution chest CT (HRCT) for interstitial lung disease?
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Answer: D. In the supine position, gravity-dependent density in the posterior lungs can mimic early fibrosis. If it disappears when the patient is prone, it was dependent atelectasis; if it persists, it's real disease. Prone images add dose rather than reduce it (A), HRCT is typically noncontrast (C), and thin, sharp-kernel sections remain essential (B). Expiratory images are another common add-on, used to assess air trapping.

Source: ACR Appropriateness Criteria — Diffuse Lung Disease

Question 41 · Procedures — Abdomen and Pelvis An incidental adrenal nodule measures 6 HU on noncontrast CT. What does this most suggest?
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Answer: A. An unenhanced attenuation of 10 HU or less is the widely used threshold for a lipid-rich adenoma: intracellular fat lowers the CT number. Acute hemorrhage (C) is typically higher density. Pheochromocytoma (B) and metastases (D) usually measure above 10 HU unenhanced, so a nodule above that threshold may need washout imaging or other evaluation.

Source: Mayo-Smith et al., Management of Incidental Adrenal Masses: ACR Incidental Findings Committee white paper, JACR (2017)

Question 42 · Safety — Radiation Safety and Dose What is "over-ranging" in helical CT?
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Answer: B. Helical reconstruction interpolates data from either side of each image location, so the scanner must expose a bit beyond the planned range at both ends. Over-ranging matters most for short scan lengths and wide beams. Adaptive (dynamic) collimation that blocks the unused part of the beam at the start and end reduces it. Patient motion (A), dose alerts (C) and field-of-view choices (D) are different issues.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 43 · Procedures — Head, Spine, and Musculoskeletal In acute ischemic stroke, what is CT brain perfusion mainly used for?
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Answer: D. Perfusion maps (cerebral blood flow, cerebral blood volume, and transit-time measures such as MTT or Tmax) estimate how much tissue is already infarcted (core) versus at risk but salvageable (penumbra), which informs treatment decisions. Hemorrhage (A) is excluded on noncontrast CT, which still comes first (B). Perfusion CT doesn't measure CSF flow (C).

Source: ACR Appropriateness Criteria — Cerebrovascular Diseases: Stroke and Stroke-Related Conditions

Question 44 · Image Production — Image Formation A chest is acquired with 0.625 mm collimation. Images are reconstructed at 1.0 mm thickness every 0.5 mm. What does this overlap accomplish?
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Answer: A. A reconstruction interval smaller than the slice thickness produces overlapping images. That better samples small structures along the z-axis and gives smoother, more accurate MPR and 3D images. Overlap is a reconstruction choice made after the exposure, so it doesn't change dose (B), temporal resolution (C) or scan time (D) — it does create more images to store.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 45 · Patient Care — Patient Interactions and Management Five minutes after contrast injection, a patient develops a few scattered hives on the chest with mild itching. Vital signs are normal and there is no respiratory distress. What is the appropriate initial management?
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Answer: B. A few scattered hives with normal vital signs and no respiratory symptoms are a mild allergic-like reaction. Current ACR guidance allows observation alone for limited urticaria; an antihistamine may be considered if symptoms are bothersome or progress. Epinephrine (A) is reserved for a more severe reaction such as anaphylaxis with respiratory compromise or hypotension. Immediate discharge (C) without observation is inappropriate, and a wide-open fluid bolus (D) is not indicated when blood pressure is normal.

Source: ACR adult contrast reaction card (updated Sept. 2026)

Question 46 · Image Production — Image Evaluation and Archiving Which change most directly improves temporal resolution in CT?
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Answer: C. Temporal resolution is how well a scanner freezes motion, and it depends mainly on how quickly the projection data for one image is acquired. Faster rotation — plus techniques such as dual-source acquisition and partial-scan or multisegment reconstruction — improves it, which matters for cardiac imaging. Matrix size (A) and slice thickness (B) affect spatial resolution; kVp (D) affects penetration, contrast and noise.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 47 · Procedures — Neck and Chest A CT esophagram is ordered to evaluate a suspected esophageal perforation after endoscopy. Which oral contrast is appropriate?
Show answer and explanation

Answer: D. When perforation is suspected, water-soluble iodinated contrast is used first because barium (A) that leaks into the mediastinum can cause serious inflammation and persists in the tissues. Gadolinium (C) isn't an oral CT agent. Air alone (B) can't show a leak tract the way positive contrast can. Aspiration risk is also part of contrast selection, so follow the radiologist's protocol.

Source: ACR Practice Parameter for Esophagrams and Upper GI Examinations in Adults (2024), Sections II.A and IV.C.5

Question 48 · Procedures — Abdomen and Pelvis In a CT urogram, what is the main purpose of the excretory (delayed) phase?
Show answer and explanation

Answer: B. The excretory phase is timed for contrast to fill the collecting systems, ureters and bladder, so filling defects such as urothelial tumors and other abnormalities stand out against dense urine. Some protocols use a split-bolus technique to combine phases. Stones (C) are assessed on the noncontrast phase. Arterial or nephrographic phases (A) characterize renal masses. An extra phase adds dose rather than reducing it (D).

Source: ACR Appropriateness Criteria — Hematuria

Question 49 · Image Production — Image Formation What is the primary function of the data acquisition system (DAS)?
Show answer and explanation

Answer: D. The DAS sits between the detectors and the computer. It samples and amplifies detector output, digitizes it with analog-to-digital converters, and transmits the raw data for reconstruction. The generator (A) supplies tube voltage, PACS (C) stores finished images, and the table (B) is controlled separately.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 50 · Safety — Radiation Safety and Dose What is the difference between a CT dose notification and a dose alert?
Show answer and explanation

Answer: B. Dose-check features compare planned exposure with facility-set values before scanning. A notification is a per-series prompt to double-check the protocol. An alert looks at the accumulated dose at any location across the whole exam and calls for stricter review: per AAPM guidance, the operator enters their name and confirms or changes the settings, and a facility may also require a password. C and D describe things these tools don't do, and A ignores the distinction.

Source: AAPM, Recommendations Regarding Notification and Alert Values for CT Scanners (NEMA XR 25), 2011

Question 51 · Procedures — Head, Spine, and Musculoskeletal For surgical planning of a complex acetabular fracture, which postprocessing presentation do orthopedic surgeons commonly request in addition to the axial and multiplanar images?
Show answer and explanation

Answer: B. 3D volume-rendered images let the surgeon see the fracture pattern and fragment displacement as a whole, and digitally removing the femoral head exposes the acetabular articular surface. MinIP (A) is for airways and low-density structures, curved vascular reformats (C) are for vessels, and perfusion maps (D) are for blood flow.

Source: ACR Appropriateness Criteria — Acute Hip Pain

Question 52 · Patient Care — Patient Interactions and Management A patient has a PICC line, and the protocol calls for power injection at 4 mL/s. Neither the catheter nor the chart identifies it as power-injectable. What should the technologist do?
Show answer and explanation

Answer: C. The ACR advises power injecting into a central venous catheter or PICC only when it is certified for power injection, and then within the manufacturer's flow-rate limit. An unverified line risks catheter rupture or tip migration. A and B assume a rating you haven't confirmed. Forceful hand injection (D) can also generate high pressure in a small-bore catheter.

Source: ACR Manual on Contrast Media, Safe Injection chapter, pp. 14–15

Source: ACR Manual on Contrast Media, Extravasation chapter, pp. 17–24

Question 53 · Image Production — Image Formation Which capability depends on dual-energy (spectral) CT?
Show answer and explanation

Answer: D. Acquiring data at two energy spectra lets software separate materials by how their attenuation changes with energy. It can then subtract iodine to create virtual noncontrast images, or create iodine maps and virtual monoenergetic images. MPR (A), retrospective kernel changes (C) and bolus tracking (B) are available on single-energy scanners.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 54 · Procedures — Neck and Chest A soft-tissue neck CT is ordered for a suspected peritonsillar abscess and enlarged cervical lymph nodes. Why is IV contrast routinely given for this exam?
Show answer and explanation

Answer: B. IV contrast helps distinguish enhancing vessels from lymph nodes and improves depiction of inflammatory collections and masses, including peripheral enhancement around an abscess. Current ACR guidance rates contrast-enhanced CT neck as appropriate for common neck-mass/infectious evaluations, and ARRT's current clinical-experience documents include contrast-enhanced soft-tissue neck CT. Contrast does not lower radiation dose (A), it is not given to opacify the esophagus (C), and the airway is visible without IV contrast (D).

Source: ACR Appropriateness Criteria — Neck Mass/Adenopathy

Source: ARRT, Updated CT clinical experience requirements (May 29, 2026)

Question 55 · Image Production — Image Evaluation and Archiving A patient brings outside CT images on a CD to be loaded into your hospital's PACS. Which standard lets images from different vendors be stored, transferred and displayed together?
Show answer and explanation

Answer: A. DICOM (Digital Imaging and Communications in Medicine) defines the medical image format and the network protocols that let scanners, PACS and workstations from different vendors exchange images and their metadata. HL7 (B) carries text-based clinical messages such as orders and reports between information systems. JPEG (C) is a general image compression format that lacks DICOM's medical metadata. HIPAA (D) is a privacy law, not an image standard.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 56 · Procedures — Abdomen and Pelvis Why is CT colonography performed with the patient in both supine and prone positions?
Show answer and explanation

Answer: D. Changing position moves residual fluid and stool and shifts where the colon distends best. A polyp hidden under fluid supine, or a segment collapsed in one position, is often seen in the other. Distension is achieved with insufflated gas, usually CO2. Screening CTC uses low-dose technique (A is backward), routine screening doesn't require IV contrast (C), and it doesn't measure perfusion (B).

Source: ACR Practice Parameter for CT Colonography

Question 57 · Procedures — Head, Spine, and Musculoskeletal For an adult hip CT, which image set matches the current ACR CT accreditation technique parameters?
Show answer and explanation

Answer: B. Current ACR adult hip CT technique requires axial images with sagittal, coronal, and long-oblique-axis reformations. Axial-only (A) or coronal-only (C) imaging omits required planes. Three-dimensional renderings (D) may be useful for selected problems, but they do not replace the diagnostic cross-sectional and multiplanar image set.

Source: ACR CT Accreditation — Adult MSK technique parameters

Question 58 · Safety — Radiation Safety and Dose A patient is positioned with the body center several centimeters below the gantry isocenter. What is a likely consequence?
Show answer and explanation

Answer: C. Bowtie filters are shaped to deliver more radiation to the center of the field than to the edges, assuming the patient is centered. When the patient is off-center, parts of the body receive the less-filtered, higher-intensity portion of the beam, raising surface dose, while other areas can be noisier. Off-center positioning also changes the patient's apparent size on the localizer, which can make automatic exposure control set inappropriate tube current. Centering at isocenter is a basic dose-optimization step.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 59 · Image Production — Image Formation Which acquisition method does CT brain perfusion use to image the same anatomic coverage repeatedly as the contrast bolus passes through?
Show answer and explanation

Answer: D. Perfusion needs time–attenuation curves, so the same tissue is scanned many times over roughly a minute. Cine mode keeps the table stationary while the gantry repeatedly images one volume; shuttle (toggling table) mode moves back and forth to cover more length. A single helical pass (A) or one pass of contiguous slabs (C) gives one time point. A scout (B) isn't a cross-sectional acquisition.

Source: AAPM Diagnostic Radiology Residents Physics Curriculum, Module 11: Computed Tomography

Question 60 · Procedures — Head, Spine, and Musculoskeletal For an adult knee CT, which primary image set matches the current ACR CT accreditation technique parameters?
Show answer and explanation

Answer: B. Current ACR adult knee CT technique requires axial images with sagittal and coronal reformations. Coronal-only (A) or sagittal-only (C) imaging is incomplete. Three-dimensional rendering (D) can supplement selected studies but does not replace the required diagnostic cross-sectional and multiplanar images.

Source: ACR CT Accreditation — Adult MSK technique parameters

Answer key

Answer key
# Answer # Answer # Answer # Answer
1 C 16 C 31 A 46 C
2 A 17 D 32 A 47 D
3 C 18 A 33 D 48 B
4 C 19 C 34 B 49 D
5 B 20 C 35 C 50 B
6 D 21 C 36 B 51 B
7 A 22 D 37 D 52 C
8 B 23 B 38 B 53 D
9 D 24 C 39 C 54 B
10 A 25 A 40 D 55 A
11 A 26 A 41 A 56 D
12 A 27 B 42 B 57 B
13 C 28 A 43 D 58 C
14 D 29 C 44 A 59 D
15 D 30 A 45 B 60 B

Review your misses by section

Compare your accuracy within each row rather than using raw miss counts alone, because this practice set has different numbers of questions in each section. Start with your lowest section percentage; if two sections are close, use the last column as a secondary priority because it shows how many scored questions ARRT assigns to that section.

Review your misses by section
Section Question numbers In this set Scored on the real exam
Patient Care — Patient Interactions and Management 3, 8, 16, 23, 30, 37, 45, 52 8 21
Safety — Radiation Safety and Dose 2, 13, 20, 28, 35, 42, 50, 58 8 21
Image Production — Image Formation 4, 9, 15, 22, 27, 33, 38, 44, 49, 53, 59 11 30
Image Production — Image Evaluation and Archiving 6, 11, 18, 25, 31, 39, 46, 55 8 22
Procedures — Head, Spine, and Musculoskeletal 7, 14, 21, 29, 36, 43, 51, 57, 60 9 25
Procedures — Neck and Chest 1, 10, 17, 24, 32, 40, 47, 54 8 22
Procedures — Abdomen and Pelvis 5, 12, 19, 26, 34, 41, 48, 56 8 24
Total 60 165

What your score means

Your result here is the share of these 60 questions you got right, nothing more. If you answer 45 of 60 correctly, that's 75% on this set. It is not an ARRT scaled score of 75, and it doesn't predict whether you'll pass.

ARRT reports results on a scaled score from 1 to 99, and you need a 75 to pass (2026 Postprimary Handbook, pp. 56–57). A scaled score adjusts for differences in difficulty between exam versions, so it isn't a percentage. A section with only 8 questions here is a rough signal, not a precise measure — use it to decide what to study, not to grade yourself.

How to use this practice test

  1. Take it cold. Answer every question before reading the explanation, and don't look anything up.
  2. Read every explanation, including ones you got right by guessing. The wrong options teach as much as the right one.
  3. Study your weakest section using the explanations and the ARRT content specifications for that section.
  4. Retake only your misses after a few days of review, so you're testing what you learned rather than what you remember from an hour ago.

The set covers all seven ARRT subcategories roughly in proportion to the real exam, including topics new in September 2026: power injection and PICC lines (Q52), air embolism (Q37), dose alerts (Q50), cardiac CT and TAVR (Q10, Q17, Q32), esophagram (Q47), urogram (Q48), renal stone (Q12), retrograde cystogram (Q34), CT colonography (Q56) and surgical planning (Q51). All 60 are single-best-answer questions without images. ARRT's exam is mostly in that format, but it can also include multiple-answer, sorting, image-selection and short-video questions (Handbook, p. 39).

What's on the ARRT CT exam now

What's on the ARRT CT exam now
Current ARRT rule
Who takes it Technologists on ARRT's postprimary pathway who hold a supporting credential in Radiography (ARRT), Nuclear Medicine Technology (ARRT or NMTCB) or Radiation Therapy (ARRT), plus CT structured education and clinical experience (ARRT supporting categories)
Questions 195 total: 165 scored + 30 unscored pilot questions you can't identify (Handbook, p. 46)
Test time 195 minutes, within a 215-minute appointment that includes the tutorial, nondisclosure agreement and survey (Handbook, p. 46)
Passing Scaled score of 75 on a 1–99 scale (Handbook, pp. 56–57)
Application fee $225; $450 if NMTCB is your supporting credential (ARRT fees)
Exam window 365 days to schedule and test at a Pearson VUE center (Handbook, p. 32)
Attempts 3 attempts within 3 years of your first exam window opening; each needs a new application and fee (Handbook, p. 18)

Exam facts last verified October 27, 2026.

What changed on September 1, 2026

ARRT moved two scored questions into Image Formation and shifted one from Abdomen and Pelvis to Neck and Chest. The total stayed at 165 (content specifications, p. 1; prior counts from ARRT Annual Exam Report 2025, p. 23).

Scored questions by subcategory before and after September 1, 2026
Subcategory Through Aug. 31, 2026 From Sept. 1, 2026
Patient Interactions and Management 22 21
Radiation Safety and Dose 22 21
Image Formation 28 30
Image Evaluation and Archiving 22 22
Head, Spine, and Musculoskeletal 25 25
Neck and Chest 21 22
Abdomen and Pelvis 25 24
Total scored 165 165

ARRT also added time-out, power-injection options and scan-timing techniques to Patient Care, adverse event reporting to Safety, and external equipment to Image Production. In Procedures, it added esophagram, urogram/IVU, renal stone, retrograde cystogram and CT colonography, expanded cardiac CT, changed the pediatric focus to infants and young children, and added surgical planning (ARRT, Oct. 31, 2025). If you studied from an older outline or question bank, check these topics first.

Did the passing standard change too?

Yes. For anyone testing on or after September 1, 2026, ARRT applies an updated CT passing standard (ARRT, Aug. 27, 2026). You still need a scaled 75, but it takes more correct answers to get there. On the exam form ARRT used to set the new standard, 75 now equals 112 of 165 scored questions correct, up from about 110 on that same form. The exact number shifts from form to form, because forms differ in difficulty (Standard Setting Report, p. 6).

ARRT expects the first-time pass rate to settle around 69% under the new standard (Standard Setting Report, p. 6). In 2025, under the earlier standard, 74.7% of 4,966 first-time CT candidates passed (Annual Exam Report 2025, p. 23).

Frequently asked questions

Are these real ARRT CT exam questions?

No. All 60 are original questions we wrote from ARRT's published content outline, with the teaching points checked against the clinical and technical sources linked in the explanations. ARRT's exam questions are confidential, and ARRT tells candidates to be careful with study materials that claim to contain ARRT test questions (Handbook, p. 40).

Does ARRT offer an official CT practice test?

ARRT does not publish or endorse a CT mock practice test in the current handbook. It says it doesn't recommend or endorse review programs, mock registries or study guides, and it points candidates to the content specifications instead (Handbook, p. 40). At the test center, an optional tutorial lets you try the question screens and on-screen calculator before the exam starts.

What happens if I don't pass?

You have three attempts within three years, and each one needs a new application and fee. Before retesting, compare the current content specifications with the version you studied, because ARRT updates them (Handbook, pp. 18, 60). The ARRT exam retake policy page walks through the process.

Next steps

Sources

By the Castleport Test Prep Editorial Team. Exam facts last verified October 27, 2026.

Castleport Test Prep is an independent exam prep publisher. It is not affiliated with, endorsed by, or approved by The American Registry of Radiologic Technologists (ARRT). ARRT and other exam and credential names are used only to identify the exam this resource covers; trademarks belong to their respective owners. These are original, unofficial practice questions, not ARRT exam items. This page is a study resource and doesn't replace your facility's protocols, your supervising radiologist's direction, or ARRT's official requirements.

Free ARRT CT Practice Test: 60 Questions With Answers