ARRT Computed Tomography

Case 001 (Patient Screening): A 58-year-old male presents for a contrast-enhanced abdominal CT. His medical history includes type 2 diabetes managed with metformin. His most recent eGFR is 28 mL/min/1.73 m². What is the most appropriate course of action?

• AProceed with iodinated contrast as planned since metformin can be resumed immediately aft…
• BWithhold the contrast and consult the ordering physician before proceeding.
• CAdminister half the normal contrast dose to reduce kidney risk.
• DReplace iodinated contrast with gadolinium-based contrast for the CT scan.

Case 002 (Contrast Allergy): A 45-year-old female is scheduled for a CT pulmonary angiography (CTPA) to rule out pulmonary embolism. She reports a prior moderate allergic reaction (hives and facial swelling) to iodinated contrast during a previous CT. What is the recommended pre-medication protocol?

• AAdminister 50 mg oral prednisone at 13 hours, 7 hours, and 1 hour before contrast injecti…
• BGive 25 mg IV diphenhydramine immediately before injection without corticosteroids.
• CUse a different brand of iodinated contrast without pre-medication since the allergy is b…
• DCancel the CTPA entirely and order a ventilation-perfusion scan instead.

Case 003 (Informed Consent): A technologist is preparing to administer IV iodinated contrast for a CT of the abdomen and pelvis. Which element is NOT typically required as part of informed consent for contrast administration?

• ADescription of the purpose of the contrast injection.
• BPossible risks including allergic reaction and contrast-induced nephropathy.
• CA guarantee that no adverse reaction will occur.
• DThe patient's right to refuse the contrast injection.

Case 004 (NPO Guidelines): A 72-year-old patient is scheduled for a contrast-enhanced CT of the chest at 10:00 AM. The patient ate breakfast at 7:30 AM. According to current ACR guidelines regarding fasting before IV contrast, what should the technologist do?

• AReschedule the exam for later in the day to ensure a full 8-hour fast.
• BProceed with the exam since current ACR guidelines do not mandate routine fasting before…
• CAdminister an antiemetic before the contrast injection to prevent aspiration.
• DConvert the study to a non-contrast CT to avoid aspiration risk.

Case 005 (Emergency Response): During a contrast-enhanced CT scan, a 50-year-old patient develops stridor, facial edema, and a drop in blood pressure to 70/40 mmHg within 2 minutes of injection. What is the FIRST medication that should be administered?

• AIV diphenhydramine 50 mg.
• BIntramuscular epinephrine 0.3 mg (1:1,000 concentration) in the anterolateral thigh.
• CIV methylprednisolone 125 mg.
• DSublingual nitroglycerin 0.4 mg.

Case 006 (Patient Positioning): A technologist is positioning a patient for a non-contrast head CT to evaluate for acute hemorrhagic stroke. What is the correct patient positioning to minimize radiation to the lens of the eye?

• ASupine with the head tilted chin-down so the scan plane is parallel to the orbitomeatal l…
• BSupine with the head hyperextended so the scan plane is angled above the orbits.
• CProne with the forehead resting on the table.
• DLateral decubitus to reduce motion artifact.

Case 007 (Contrast Extravasation): While injecting 100 mL of iodinated contrast at 4 mL/s through a 20-gauge antecubital IV, the technologist notices swelling at the injection site on the contrast injector pressure waveform. What is the FIRST action?

• AContinue the injection at a slower rate to complete the study.
• BStop the injection immediately, disconnect the tubing, and aspirate residual contrast if…
• CApply a warm compress to the site and continue the injection.
• DIncrease the injection rate to push past the obstruction.

Case 008 (CTDIvol): A routine adult head CT is performed with a CTDIvol of 75 mGy displayed on the scanner console. The ACR CT Dose Index Registry median for this exam type is approximately 57 mGy. What should the technologist do?

• AAccept the dose because it is below the regulatory limit of 100 mGy.
• BDocument the dose and notify the supervising radiologist or physicist, as the CTDIvol exc…
• CRepeat the scan at lower dose to bring the average down.
• DDelete the dose report to avoid regulatory documentation of the higher dose.

Case 009 (ALARA Principle): A CT technologist is scanning a thin 55 kg adult female for an abdominal CT. The default protocol is set for an 80 kg reference patient. Applying the ALARA principle, what is the most appropriate adjustment?

• AUse the default 80 kg protocol since it produces diagnostic images for all body habitus.
• BReduce the tube current (mA) to account for the smaller body habitus while maintaining di…
• CIncrease the kVp by 20% to ensure adequate penetration.
• DDouble the pitch to compensate for the smaller patient size.

Case 010 (DLP and Effective Dose): A CT chest-abdomen-pelvis scan records a DLP of 1,200 mGy·cm. To estimate the effective dose in millisieverts (mSv), the DLP is multiplied by an appropriate conversion factor (k-factor). For a chest-abdomen-pelvis scan, using an approximate k-factor of 0.015 mSv/(mGy·cm), what is the estimated effective dose?

• A8 mSv.
• B12 mSv.
• C18 mSv.
• D24 mSv.

Case 011 (Pediatric Dose Reduction): A 5-year-old child (20 kg) is scheduled for a CT of the abdomen and pelvis to evaluate suspected appendicitis. Compared to the standard adult protocol, which combination of parameter adjustments best reduces dose while maintaining diagnostic quality?

• AReduce kVp to 80-100, reduce mA by 40-60%, and use iterative reconstruction.
• BKeep adult kVp and mA settings but reduce scan length only.
• CUse adult parameters with a smaller FOV to automatically lower dose.
• DIncrease kVp to 140 and reduce mA to maintain the same dose.

Case 012 (SSDE): A CT scan of the abdomen is performed on a patient with an effective diameter of 22 cm. The displayed CTDIvol is 10 mGy. The size-specific dose estimate (SSDE) conversion factor for a 22 cm effective diameter using the 32 cm phantom is approximately 1.52. What is the SSDE?

• A6.6 mGy.
• B10.0 mGy.
• C15.2 mGy.
• D22.0 mGy.

Case 013 (Shielding in CT): A technologist is preparing to scan a 30-year-old female patient for a CT of the chest. Should a bismuth breast shield be placed over the breasts during the scan?

• AYes, bismuth shields should always be used for female chest CT to reduce breast dose.
• BNo, bismuth shields are no longer recommended by the AAPM because they cause artifacts an…
• CYes, but only for patients under age 40 who have dense breast tissue.
• DNo, because bismuth shields only reduce dose by less than 1% and are not worth the effort.

Case 014 (Regulatory Compliance): According to federal and state regulatory requirements, what is the purpose of the CT dose notification included in the patient's imaging record (dose report)?

• ATo serve as a billing code for the exam.
• BTo provide a permanent record of CTDIvol and DLP for quality assurance, accreditation, an…
• CTo calculate the patient's cumulative lifetime dose for insurance purposes.
• DTo replace the need for annual CT scanner quality control testing.

Case 015 (kVp Selection): A 110 kg patient is being scanned for a contrast-enhanced CT of the abdomen. The technologist is considering whether to use 120 kVp or 140 kVp. What is the primary reason to increase kVp to 140 for this large patient?

• ATo increase the contrast enhancement of iodinated contrast material.
• BTo ensure adequate x-ray penetration through the larger body habitus and reduce photon st…
• CTo decrease the radiation dose to the patient.
• DTo improve spatial resolution of the reconstructed images.

Case 016 (Tube Current and Noise): If the tube current (mA) for a CT scan is reduced by half while all other parameters remain constant, what happens to image noise?

• AImage noise decreases by half.
• BImage noise increases by approximately 41% (factor of √2).
• CImage noise doubles.
• DImage noise is unchanged because noise depends only on kVp.