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Question 1. Which laboratory value is most important to review before administering iodinated contrast to assess renal function? A) Serum calcium B) Blood urea nitrogen (BUN) C) Serum creatinine D) Hemoglobin Answer: C Explanation: Serum creatinine is used to calculate eGFR, which determines the risk of contrast-induced nephropathy. Question 2. A patient reports a metallic taste during contrast injection. This sensation is most commonly associated with which type of contrast media? A) Non-ionic low-osmolar agents B) Ionic high-osmolar agents C) Barium sulfate D) Gadolinium-based agents Answer: A Explanation: Non-ionic low-osmolar iodinated agents frequently cause a transient metallic taste due to their high iodine content. Question 3. Which of the following is the correct order of steps when obtaining informed consent for a CT exam? A) Explain risks → Obtain signature → Verify identity → Perform scan B) Verify identity → Explain procedure and risks → Answer questions → Obtain consent C) Perform scan → Explain risks → Obtain consent → Document D) Verify identity → Perform scan → Explain risks → Obtain consent Answer: B
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Explanation: Consent must be obtained after patient identification and a full explanation of the procedure and its risks. Question 4. During a CT scan, the technologist notices the patient’s heart rate is 95 bpm. Which cardiac CT protocol adjustment is most appropriate? A) Increase tube current (mAs) to improve image quality B) Administer beta-blocker to lower heart rate below 65 bpm C) Switch to a higher kVp setting D) Perform a non-ECG-gated scan Answer: B Explanation: Lowering the heart rate improves temporal resolution for coronary CTA; beta-blockers are commonly used for this purpose. Question 5. Which dose-modulation technique automatically adjusts the tube current based on patient attenuation? A) Fixed mAs B) Automatic exposure control (AEC) C) Pitch increase D) High-kVp technique Answer: B Explanation: AEC (e.g., CARE Dose) modulates mAs in real time according to the patient’s size and attenuation. Question 6. The CTDIvol for a routine chest scan is 8 mGy and the scan length is 30 cm. What is the DLP? A) 240 mGy·cm B) 8 mGy·cm C) 30 mGy·cm D) 2400 mGy·cm
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Answer: B Explanation: IR models the imaging physics and noise statistics, allowing dose reduction without compromising diagnostic quality. Question 10. A 4-year-old child requires an abdominal CT. Which of the following strategies best reduces radiation exposure? A) Use a higher kVp (140) and lower mAs B) Apply a pediatric-specific protocol with lower mAs and automated exposure control C) Increase slice thickness to 5 mm D) Perform a scout scan twice for better localization Answer: B Explanation: Pediatric protocols tailor kVp, mAs, and use AEC to achieve the ALARA principle while maintaining image quality. Question 11. Which of the following is a contraindication for iodinated IV contrast administration? A) Controlled asthma B) Prior contrast reaction of mild hives C) Pregnancy in the first trimester D) Diabetes mellitus type 2 Answer: C Explanation: Iodinated contrast is generally avoided in early pregnancy due to unknown fetal risk. Question 12. During a CT angiography of the pulmonary arteries, the technologist must time the contrast bolus using which technique? A) Fixed delay of 30 seconds B) Bolus tracking with ROI in the main pulmonary artery C) Test bolus with 5 ml contrast
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D) No timing needed; contrast is continuous Answer: B Explanation: Bolus tracking monitors contrast arrival in the target vessel and triggers the scan at optimal enhancement. Question 13. Which of the following best describes the function of the gantry tilt in cardiac CT? A) Reduces patient dose by shortening scan length B) Aligns the imaging plane with the long axis of the heart to avoid beam-hardening from the diaphragm C) Improves spatial resolution in the axial plane D) Allows imaging of the pelvis without moving the patient table Answer: B Explanation: Gantry tilt aligns the scan plane with the heart’s orientation, minimizing artifacts from the diaphragm and improving coronary visualization. Question 14. The term “partial volume averaging” refers to: A) Loss of detail when a voxel contains multiple tissue types B) Streaks caused by high-density objects C) Noise reduction by increasing mAs D) Motion artifact from patient breathing Answer: A Explanation: Partial volume averaging occurs when a voxel includes more than one tissue, resulting in an averaged attenuation value. Question 15. In CT dose reporting, which metric is most directly related to the risk of stochastic effects? A) CTDIvol B) DLP
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B) Urticaria limited to the arm C) Hypotension with altered mental status D) Transient flushing Answer: C Explanation: Severe reactions (anaphylaxis) present with hypotension, bronchospasm, and altered consciousness, requiring epinephrine and advanced life support. Question 19. In a CT brain without contrast, what Hounsfield unit (HU) range is typical for normal gray matter? A) –100 to –30 HU B) 0 to 20 HU C) 30 to 45 HU D) 60 to 80 HU Answer: C Explanation: Normal cerebral gray matter attenuates around 30- 45 HU, while white matter is slightly lower. Question 20. Which of the following best explains why a higher kVp reduces patient dose? A) Higher kVp increases photon energy, allowing fewer photons to achieve the same image contrast B) Higher kVp reduces the number of detector rows needed C) Higher kVp shortens scan time, thus lowering dose D) Higher kVp automatically triggers dose-modulation software Answer: A Explanation: Higher photon energy penetrates tissue more efficiently, requiring fewer photons for adequate image quality, thereby reducing dose.
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Question 21. During a CT colonography, the patient is asked to hold their breath for 15 seconds. What is the primary reason for this instruction? A) To reduce motion artifact in the abdomen B) To improve lung visualization C) To increase contrast enhancement of the colon D) To prevent aspiration of oral contrast Answer: A Explanation: Breath-holding minimizes respiratory motion, which can blur abdominal and pelvic images. Question 22. Which of the following is the most appropriate method for verifying patient identity before a scan? A) Checking the patient’s wristband against the order in the RIS B) Asking the patient to state their name only C) Looking at the patient’s face and assuming correct identity D) Verifying the patient’s insurance card Answer: A Explanation: Matching the wristband to the Radiology Information System (RIS) order ensures correct patient identification. Question 23. In CT perfusion imaging for acute stroke, which parameter reflects the time it takes for contrast to reach a region of interest? A) Cerebral blood volume (CBV) B) Mean transit time (MTT) C) Cerebral blood flow (CBF) D) Time-to-peak (TTP) Answer: D Explanation: TTP measures the delay from contrast injection to peak enhancement, indicating perfusion delay.
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Explanation: Wide WW (≈1500) and high WL (≈300) display the high attenuation of bone. Question 27. In a CT angiography of the carotid arteries, the technologist must use a “bolus tracking” technique. Where is the region of interest (ROI) most appropriately placed? A) Left ventricle of the heart B) Ascending aorta C) Common carotid artery at the bifurcation D) Superior vena cava Answer: C Explanation: Placing the ROI in the carotid artery ensures the scan starts when the contrast reaches the target vessels. Question 28. Which of the following statements about the CT number (HU) is correct? A) Water has a value of –1000 HU B) Air has a value of 0 HU C) Fat typically measures around –100 HU D) Bone always measures less than 500 HU Answer: C Explanation: Fat attenuates less than water, giving negative values around –100 HU. Question 29. When performing a CT scan of the abdomen with oral contrast, which substance is most commonly used? A) Barium sulfate suspension B) Iodinated water-soluble contrast C) Gadolinium chelate D) Air
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Answer: B Explanation: Water-soluble iodinated agents are preferred for gastrointestinal lumen opacification because they are safe if aspirated. Question 30. Which of the following is the primary purpose of a “scout” or “localizer” image? A) To calculate radiation dose B) To determine patient positioning and planning the scan range C) To replace the diagnostic scan in emergencies D) To assess contrast timing Answer: B Explanation: Scout images provide a low-dose overview used for planning the scan limits and patient alignment. Question 31. A radiology technologist observes that the CT scanner’s tube temperature exceeds the manufacturer’s limit during a long scan. What is the most appropriate action? A) Increase the kVp to compensate B) Continue the scan; temperature is not critical C) Pause the scan and allow the tube to cool before proceeding D) Decrease the pitch to finish the scan faster Answer: C Explanation: Overheating can damage the tube; the scan must be stopped to prevent hardware failure. Question 32. Which of the following best describes the principle of “ALARA” in radiology? A) As Low As Reasonably Achievable—minimize radiation dose while maintaining diagnostic quality B) As Long As Radiation Allows—extend scan time for better images
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B) Turn off the pacemaker during the scan C) Verify that the device is MRI-compatible and monitor ECG leads for interference D) Use only non-contrast imaging Answer: C Explanation: Modern pacemakers may be safe for CT, but interference should be monitored, and the device’s specifications verified. Question 36. Which reconstruction parameter directly influences the visual thickness of displayed slices? A) Pitch B) Slice thickness C) kVp D) mAs Answer: B Explanation: Slice thickness determines the anatomical depth represented in each reconstructed image. Question 37. During a high-resolution CT (HRCT) of the lung, why are thin slices (≤ 1 mm) and a high spatial frequency reconstruction algorithm used? A) To reduce radiation dose B) To improve visualization of fine parenchymal detail such as interstitial disease C) To speed up acquisition time D) To increase contrast between blood vessels and airway walls Answer: B Explanation: Thin slices and high-frequency kernels enhance spatial resolution, which is essential for detecting subtle interstitial changes. Question 38. Which of the following best describes “bolus tracking” in CT angiography?
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A) A fixed delay after contrast injection before scanning B) Real-time monitoring of contrast density in a predefined ROI to trigger the scan automatically C) A test bolus of 10 mL used to calculate scan delay D) Continuous infusion of contrast throughout the scan Answer: B Explanation: Bolus tracking uses an ROI to detect when contrast reaches a target attenuation, then initiates the scan. Question 39. In a CT scan of the lumbar spine, a patient’s body habitus is larger than average. Which adjustment will most effectively reduce image noise while maintaining dose? A) Increase pitch B) Increase mAs C) Decrease kVp D) Reduce scan length Answer: B Explanation: Raising mAs increases photon flux, reducing quantum noise without changing other parameters. Question 40. Which of the following is a typical sign of an allergic reaction to iodinated contrast on the patient’s skin? A) Petechiae B) Urticaria (hives) C) Ecchymosis D) Erythema migrans Answer: B Explanation: Hives (urticaria) are a common manifestation of an allergic contrast reaction.
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Question 44. Which of the following is the most accurate description of a “non-ionic” contrast agent? A) It contains no iodine atoms B) It does not dissociate into charged particles in solution, reducing osmolality and side-effects C) It is administered only orally D) It is always hyper-osmolar compared with blood Answer: B Explanation: Non-ionic agents remain electrically neutral in solution, resulting in lower osmolality and fewer adverse reactions. Question 45. In CT, the term “noise” refers to: A) Random variation in pixel values that degrades image quality B) Artifacts caused by patient motion C) Beam hardening from dense structures D) The visual appearance of contrast enhancement Answer: A Explanation: Noise is the statistical fluctuation of detected photons, appearing as graininess. Question 46. A technologist is preparing a patient for a CT brain perfusion study. Which intravenous line is most appropriate for rapid contrast injection? A) Peripheral IV in the hand B) Peripheral IV in the foot C) Central venous catheter D) PICC line in the arm Answer: C
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Explanation: Central venous catheters allow high-flow rates necessary for perfusion studies with minimal pressure concerns. Question 47. Which of the following best explains why a higher pitch reduces radiation dose? A) The table moves faster, decreasing the time the patient is exposed per rotation B) It increases the number of detector rows used C) It lowers the kVp automatically D) It improves detector efficiency Answer: A Explanation: A higher pitch means the table advances more per rotation, shortening exposure time and thus lowering dose. Question 48. In a CT scan of the thorax, the technologist notices streak artifacts arising from the heart. What is the most likely cause? A) Beam hardening from the high-density contrast in the heart B) Motion artifact due to cardiac pulsation C) Improper collimation D) Low kVp setting Answer: B Explanation: Cardiac motion causes streaking artifacts, especially in the mediastinum. Question 49. Which of the following is a primary indication for performing a non-contrast CT of the head in an adult? A) Evaluation of acute intracranial hemorrhage B) Assessment of contrast-enhancing tumors C) Detection of cerebral aneurysms D) Monitoring of postoperative surgical clips
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D) It eliminates the need for a test bolus Answer: A Explanation: The abdominal aorta is upstream of the lower extremity vessels, so detecting contrast there ensures optimal timing for the entire scan. Question 53. Which of the following is the most common cause of “metal artifact reduction” (MAR) algorithm failure? A) Low tube voltage B) Large metal implants causing severe photon starvation C) Excessive patient motion D) Incorrect reconstruction kernel selection Answer: B Explanation: Very dense metal can cause photon starvation that exceeds the capability of MAR algorithms. Question 54. A patient with a known severe asthma history requires contrast-enhanced CT. Which pre-procedure medication is most appropriate to minimize the risk of bronchospasm? A) Intravenous epinephrine B) Oral corticosteroid 12 hours before the exam C) Inhaled albuterol immediately before contrast injection D) No medication; asthma is unrelated to contrast reactions Answer: C Explanation: Inhaled bronchodilators (e.g., albuterol) are given prophylactically to prevent bronchospasm in high-risk asthmatic patients. Question 55. Which of the following scan parameters directly influences the temporal resolution of a cardiac CT? A) Pitch B) Gantry rotation time
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C) Slice thickness D) kVp Answer: B Explanation: Shorter gantry rotation times improve temporal resolution, critical for imaging a moving heart. Question 56. In a CT abdomen with oral contrast, the patient complains of nausea. Which of the following is the most appropriate immediate action? A) Stop the scan and discontinue oral contrast B) Increase the flow rate of the oral contrast C) Administer anti-emetic medication and continue if tolerated D) Switch to IV contrast only Answer: C Explanation: Anti-emetics can alleviate nausea; the scan can proceed if the patient feels better. Question 57. Which of the following best describes the function of a “power injector” in CT contrast administration? A) It manually pushes contrast through a peripheral line B) It delivers contrast at a precisely controlled flow rate and volume C) It monitors patient vital signs during injection D) It dilutes contrast with saline automatically Answer: B Explanation: Power injectors provide automated, reproducible injection parameters critical for timing and dose. Question 58. When performing a CT scan of the cervical spine, the technologist must avoid which of the following to reduce the risk of radiation to the thyroid gland? A) Using a low kVp setting
