Computed Tomography
Computed Tomography is a trademark of its owner, which is not affiliated with and does not endorse Test Treasure Publication or TTP Prep.
Computed Tomography is a trademark of its owner, which is not affiliated with and does not endorse Test Treasure Publication or TTP Prep.
10 sample questions for the Computed Tomography, with the correct answer and an explanation for each. No account needed. Try each one before you open the answer.
Sections covered on the exam: Patient Interactions And Management, Patientmonitoringandsafety, Patient Interactions and Management, Radiation Safety And Dose, Photoninteractionsandattenuation, Minimizingpatientexposure, Specialpatientsandpersonnelprotection, Image Formation, Imagingparameters, Methodsofdataacquisition, Imagereconstruction, Postprocessing, Image Evaluation And Archiving, Imagedisplay, Imagequality, Qualitycontrolandaccreditation, Image Evaluation and Archiving, Informatics, Head, Spine, And Musculoskeletal, Head, Spine, and Musculoskeletal, Abdomen and Pelvis, Temporalbones,Orbits,Sinuses,Andfacialbones, Spineandpostmyelogramct, Musculoskeletalandpostarthrogramct, Neck And Chest, Neckandairway, Neck and Chest, Thoracicvascularandtraumaimaging, Abdomen And Pelvis, Multiphaseliver,Pancreas,Spleen,Andadrenals, Kidneys,Urography,Andrenalstones, Pelvis,Bladder,Andcolon, Vascular,Trauma,Andinterventionalprocedures, X-Rayproductionandthex-Raybeam, Radiation Safety and Dose.
Question 1 · Patient Interactions And Management
A 64-year-old patient with type 2 diabetes is scheduled for a contrast-enhanced CT of the abdomen and pelvis. He takes metformin twice daily. His eGFR measured yesterday is 42 mL/min/1.73 m2, and there is no evidence of acute kidney injury. Which instruction regarding metformin is MOST appropriate?
Answer: B. Continue metformin as usual; there is no need to withhold it
Current ACR guidance states that patients with an eGFR of 30 or higher and no acute kidney injury do not need to stop metformin before or after IV iodinated contrast. Withholding the drug for 48 hours and rechecking renal function is reserved for eGFR below 30, AKI, or arterial studies with first-pass renal exposure. Holding metformin for two days before the exam is an outdated practice.
Question 2 · Photoninteractionsandattenuation
Before scanning, the console displays a Dose Notification because the planned CTDIvol for an adult head exam exceeds the Notification Value set for that protocol. What should the technologist do?
Answer: D. Verify the scan parameters and document the justification if proceeding
A Notification Value (AAPM dose check; for example, adult head CTDIvol 80 mGy) flags a planned series that exceeds the expected level for the protocol. The technologist confirms that mAs, kVp, pitch, and scan range are correct and, if the higher dose is justified (such as a large patient), proceeds and records the reason. Arbitrarily lowering tube current can make the study nondiagnostic, and cumulative dose at one location is the purpose of the separate Alert Value.
Question 3 · Imagereconstruction
A pediatric abdomen protocol is revised to reduce dose by 40%. With filtered backprojection the new images are judged too noisy. Which change will BEST restore acceptable image quality without increasing dose?
Answer: D. Reconstruct with an iterative reconstruction algorithm
Iterative reconstruction models noise statistics and system geometry, lowering noise at a given dose far more effectively than filtered backprojection. A sharper kernel, thinner slices, and a smaller display field of view each increase noise, which would worsen the problem.
Question 4 · Abdomen and Pelvis
On an axial CTA image through the suprasellar cistern, the radiologist traces a small vessel running posteriorly from the supraclinoid internal carotid artery to join the proximal posterior cerebral artery. Which vessel is being described?
Answer: C. Posterior communicating artery
The posterior communicating artery links the internal carotid (anterior) circulation with the posterior cerebral artery (vertebrobasilar circulation) on each side of the circle of Willis. The anterior communicating artery instead joins the two anterior cerebral arteries across the midline. The superior cerebellar artery arises from the basilar artery just below the PCA, and the anterior choroidal artery arises from the ICA but courses posterolaterally toward the choroidal fissure rather than joining the PCA.
Question 5 · Thoracicvascularandtraumaimaging
A patient with severe tearing chest pain is imaged for suspected acute aortic syndrome. The protocol begins with a noncontrast acquisition of the chest before the CT angiogram. Which finding is this noncontrast acquisition primarily intended to detect?
Answer: C. A crescent of high-attenuation thickening within the aortic wall
Acute intramural hematoma appears as a crescentic hyperattenuating aortic wall thickening that is best seen before contrast, because enhancing lumen can mask it. An intimal flap and differential lumen enhancement are shown on the CTA phase, which is the tempting mix-up. Active extravasation, by definition, requires IV contrast.
Question 6 · Patient Interactions And Management
A patient is scheduled on the same day for a fluoroscopic barium enema and a CT of the abdomen and pelvis with IV contrast. Which scheduling sequence is MOST appropriate?
Answer: C. CT first, followed by the barium enema
Residual barium in the colon produces dense streak artifact that can make the CT nondiagnostic, so the CT is performed before the barium study. Evacuation and hydration do not reliably clear barium within hours. IV contrast given for the CT does not meaningfully interfere with a subsequent barium enema.
Question 7 · Minimizingpatientexposure
A helical chest protocol at a pitch of 1.0 produces a CTDIvol of 18 mGy. If the pitch is increased to 1.5 while tube current and rotation time are held constant, what is the new CTDIvol?
Answer: D. 12 mGy
CTDIvol = CTDIw / pitch, so at a fixed mA and rotation time dose is inversely proportional to pitch: 18 × (1.0/1.5) = 12 mGy. Multiplying by the new pitch (27 mGy) reverses the relationship. On scanners that hold effective mAs constant, the system raises mA as pitch increases and CTDIvol would not fall, which is why the tube current is specified as constant here.
Question 8 · Postprocessing
On a thick-slab maximum intensity projection of a lower- extremity CTA, a heavily calcified superficial femoral artery appears to have a severe stenosis that is not confirmed on source images. What explains this pitfall?
Answer: B. Dense calcium is projected over the lumen along each ray
Maximum intensity projection displays only the highest value encountered along each ray, so dense calcified plaque can overlie and obscure the contrast column, overstating stenosis. Hiding structures by displaying the lowest values describes minimum intensity projection, which is not used for CTA.
Question 9 · Radiation Safety and Dose
On an axial noncontrast head CT at the level of the frontal horns of the lateral ventricles, a gray-matter structure bulges into and forms the lateral wall of each frontal horn. Which structure is this?
Answer: C. Head of the caudate nucleus
The head of the caudate nucleus indents the lateral wall of the frontal horn, which is why caudate atrophy (as in Huntington disease) enlarges the frontal horns. The thalamus lies more posteriorly, bordering the third ventricle. The putamen is lateral to the internal capsule, and the genu of the corpus callosum forms the anterior roof of the frontal horns rather than their lateral wall.
Question 10 · Thoracicvascularandtraumaimaging
After a CT pulmonary angiogram, the radiologist requests indirect CT venography of the pelvis and lower extremities to look for deep vein thrombosis without giving more contrast. When should the venous acquisition be started, measured from the start of the contrast injection?
Answer: A. About 3 to 3.5 minutes after the start of injection
Leg and pelvic veins opacify late because contrast must pass through the systemic arterial and capillary beds of the lower extremities, so indirect CT venography is performed roughly 3 to 3.5 minutes after injection begins. The 60 to 70 second delay is the tempting choice because it is the familiar portal venous phase, but the lower extremity veins are not yet adequately enhanced then. By 10 minutes the contrast has redistributed and venous enhancement has faded.
TTP Prep has 200 Computed Tomography practice questions with explanations, timed and mock-exam modes, 86 flashcards, interactive lessons, a printable cheat sheet and a readiness score. Start free, no card needed.
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