ARRT CT Exam Flashcards

Q: How many questions are on the ARRT CT exam?

ARRT's Computed Tomography content specifications (board approved July 2025, effective September 1, 2026) list 195 total questions: 165 scored items plus 30 unscored pilot items. Candidates are not told which items are pilot questions, so every item should be answered as if it counts.

Q: How long is the ARRT CT exam appointment?

ARRT lists 180 minutes of test time within a 210-minute (3.5-hour) appointment window for CT candidates. The extra time covers the tutorial, nondisclosure agreement, and other administrative steps before and after testing.

Q: What score do I need to pass ARRT CT?

ARRT requires a total scaled score of 75 (on a 1-99 scale) to pass CT, the same cut score used across all ARRT certification exams. A scaled score of 75 does not mean 75% correct — ARRT's 2024 data shows CT candidates needed approximately 66% correct to reach the passing standard.

Q: How is the ARRT CT exam content weighted?

ARRT's CT content specifications assign 165 scored questions across four categories: Patient Care (21 questions, 12.7%), Safety (21 questions, 12.7%), Image Production (52 questions, 31.5%), and Procedures (71 questions, 43.0%). Procedures alone make up nearly half the scored exam.

Q: How much does the ARRT CT exam cost?

ARRT's postprimary fee schedule lists CT at a $225 application fee under the standard ARRT-supported pathway. Each new attempt after a failure requires a new application and fee, so confirm current pricing in your ARRT account before applying.

Q: What is the ARRT CT pass rate?

ARRT's 2024 Annual Exam Report lists a 73.9% pass rate for Computed Tomography, with a mean scaled score of 79.2. This is lower than Radiography's 85.2% pass rate, so budgeting real study time for CT-specific content matters.

Q: What happens if I fail the ARRT CT exam?

ARRT's postprimary pathway allows a maximum of three attempts to pass CT within three years of your first exam window opening. Each attempt requires a brand-new application and fee — there is no unlimited-retake option, so structured review between attempts matters.

Question 1

Metformin and Reduced Renal Function Before Contrast

Accepted Answer

Iodinated contrast can transiently worsen renal function; in a patient taking metformin with reduced renal function, impaired metformin clearance raises the risk of lactic acidosis. Protocol is to check renal function (eGFR/creatinine) first and involve the ordering physician about holding metformin — not to withhold contrast from every metformin patient automatically.

Question 2

eGFR Threshold That Triggers Contrast Caution

Accepted Answer

An eGFR below roughly 30 mL/min/1.73m² (severe renal impairment) is the key threshold prompting physician consultation before iodinated contrast. Between 30-45 the decision is more individualized based on risk/benefit; above 45, contrast is generally given without extra renal precautions.

Question 3

Contrast Reaction Severity Levels

Accepted Answer

Mild (hives, itching, mild nausea) is monitored and treated symptomatically. Moderate (bronchospasm, facial/laryngeal edema, hypotension) needs medication and close observation. Severe (anaphylactoid shock, cardiopulmonary arrest) requires an emergency response with epinephrine and the code team. The severity level — not just the presence of a reaction — determines the treatment pathway.

Question 4

Premedication for a Prior Contrast Reaction

Accepted Answer

A common regimen gives an oral corticosteroid (e.g., prednisone) at roughly 13, 7, and 1 hour before contrast, plus an antihistamine about 1 hour before. Premedication reduces recurrence risk but does not eliminate it, so the patient still requires full monitoring during and after the injection.

Question 5

Managing a Contrast Extravasation

Accepted Answer

Stop the injection immediately, elevate the affected limb, apply a warm or cold compress per department protocol, and document the estimated extravasated volume. Most cases are managed conservatively; a surgical consult is reserved for large volumes, skin blistering, or signs of vascular/nerve compromise.

Question 6

NPO Status Before a Contrast CT

Accepted Answer

Many departments have moved away from strict fasting orders for contrast-enhanced CT, since nausea/vomiting risk with modern low- and iso-osmolar iodinated contrast is low — clear liquids are often permitted until shortly before the scan. Actual practice still varies by department, so confirm local protocol rather than assuming a blanket NPO rule.

Question 7

ALARA Principle

Accepted Answer

As Low As Reasonably Achievable — minimize radiation dose to patients and staff while still obtaining diagnostic image quality. It means optimizing technique for the clinical question, not simply lowering technique factors until an image becomes non-diagnostic.

Question 8

CTDIvol vs. DLP

Accepted Answer

CTDIvol (in mGy) reflects the dose intensity at a given scan location, based on a standard phantom. DLP (in mGy·cm) reflects total exam dose — essentially CTDIvol multiplied by scan length. A short scan with a high CTDIvol can still produce a lower DLP than a long scan with a lower CTDIvol.

Question 9

Size-Specific Dose Estimate (SSDE)

Accepted Answer

SSDE adjusts CTDIvol using the patient's actual effective diameter, giving a more accurate individual dose estimate than CTDIvol alone, which is based on a fixed 32 cm or 16 cm reference phantom regardless of the patient's true body size.

Question 10

Automatic Tube Current Modulation

Accepted Answer

Adjusts mA in real time along the z-axis and/or angularly around the patient based on attenuation, lowering dose through thinner regions (e.g., chest) while raising current through thicker or denser regions (e.g., shoulders, pelvis) to keep noise consistent across the scan.

Question 11

Iterative Reconstruction vs. Filtered Back Projection

Accepted Answer

Iterative reconstruction reduces image noise at a given dose — or allows a lower dose at equivalent noise — compared with traditional filtered back projection, at the cost of greater computational processing time per image.

Question 12

Occupational Radiation Monitoring

Accepted Answer

CT technologists wear a personal dosimeter (commonly at the collar) to track cumulative occupational exposure against regulatory annual limits. This monitors staff dose over time — it has no bearing on an individual patient's exam dose, which is tracked separately through CTDIvol/DLP.

Question 13

Overranging in Helical CT

Accepted Answer

Extra dose delivered just beyond the prescribed scan range, needed because helical reconstruction requires raw data from slightly before and after the requested anatomy to complete the first and last image slices. Overranging dose grows with wider collimation and lower pitch, making it a larger factor on wide-detector scanners.

Question 14

Pitch Formula

Accepted Answer

Pitch = table feed per gantry rotation ÷ total beam collimation width. Pitch of 1 gives contiguous coverage; pitch below 1 overlaps data per rotation (higher dose, better resolution); pitch above 1 leaves wider spacing between helical sweeps per rotation (generally lower dose, faster coverage).

Question 15

kVp vs. mAs — Different Jobs

Accepted Answer

kVp controls the energy and penetration of the x-ray beam, affecting contrast and beam hardening; mAs controls the quantity of photons, primarily affecting image noise. Raising kVp helps penetrate a large patient, while raising mAs mainly reduces noise rather than improving penetration.

Question 16

Slice Thickness Trade-off

Accepted Answer

Thinner slices improve z-axis spatial resolution and reduce partial-volume averaging, which helps detect small lesions or fine fractures, but they increase image noise per slice. Thicker slices lower noise but blur small structures through greater partial-volume averaging.

Question 17

Isotropic Voxels

Accepted Answer

Voxels with equal dimensions along x, y, and z axes, which enable high-quality coronal and sagittal reformats without loss of detail compared with the original axial images. Non-isotropic (elongated) voxels degrade reformatted image quality even if the original axial images look sharp.

Question 18

Reconstruction Interval vs. Acquired Slice Thickness

Accepted Answer

Reconstruction interval is the spacing between reconstructed image planes and can be set smaller than the acquired slice thickness to create overlapping images — improving 3D reformats and small-lesion detection — without any additional patient dose, since the raw helical data was already acquired.

Question 19

Bolus Tracking vs. Test Bolus

Accepted Answer

Bolus tracking monitors attenuation in a region of interest (e.g., the aorta) during the actual diagnostic injection and auto-triggers the scan at a set HU threshold. Test bolus instead uses a small preliminary injection to measure time-to-peak enhancement before the full diagnostic bolus is given — both time image acquisition to peak enhancement, but by different methods.

Question 20

Window Width vs. Window Level

Accepted Answer

Window width sets the range of Hounsfield Units displayed across the full gray scale (controls image contrast); window level sets the center HU value of that range (controls overall brightness). A wide lung window reveals subtle density differences in aerated lung; a narrower soft-tissue window boosts contrast between similar-density abdominal structures.

Question 21

Dual-Energy CT Advantage

Accepted Answer

Acquires data at two different x-ray energy spectra, enabling material decomposition — such as distinguishing iodine from calcium or hemorrhage — and generation of virtual monochromatic and virtual non-contrast images, a capability standard single-energy CT cannot provide.

Question 22

Beam Hardening Artifact

Accepted Answer

Appears as dark streaks or cupping between two dense structures (e.g., between the petrous bones, or across a thick pelvis) because lower-energy photons are preferentially absorbed passing through dense tissue, shifting the remaining beam to a higher mean energy. Partly corrected with beam-hardening correction algorithms or, in some cases, higher kVp.

Question 23

Metal Artifact

Accepted Answer

Bright and dark streaking radiating from high-density metal (implants, dental hardware) caused by photon starvation and beam hardening. Metal artifact reduction (MAR) algorithms and dual-energy virtual monochromatic reconstructions reduce, but do not fully eliminate, this artifact.

Question 24

Motion Artifact

Accepted Answer

Causes blurring or streaking from patient movement — voluntary or involuntary (cardiac/respiratory) — during acquisition. Mitigated by shorter scan times and patient instruction, and for cardiac motion, by ECG gating — not by adjusting kVp or mA, which affect noise, not motion.

Question 25

Ring Artifact

Accepted Answer

A complete circular artifact centered on the axis of rotation, caused by a miscalibrated or malfunctioning detector element. Fixed through detector recalibration and routine QC, not by adjusting an individual patient's scan parameters.

Question 26

Partial Volume Averaging

Accepted Answer

Occurs when a voxel contains a mixture of tissue types with different attenuation, producing an averaged CT number that doesn't represent any single tissue accurately. Most problematic with thick slices and small structures oriented obliquely to the scan plane.

Question 27

Hounsfield Unit Reference Points

Accepted Answer

Water is fixed at 0 HU and air at -1000 HU on the Hounsfield scale, with dense cortical bone near +1000 HU or higher and fat in the negative range (roughly -50 to -100 HU). These fixed reference points anchor daily CT number accuracy quality control.

Question 28

Daily CT Number Accuracy QC

Accepted Answer

A water phantom is scanned each day to confirm the CT number for water reads within an accepted tolerance and that noise/uniformity meet specification. This catches scanner calibration drift before it affects patient studies, distinct from periodic dosimetry or accreditation testing.

Question 29

Noncontrast Head CT for Acute Stroke

Accepted Answer

The first imaging study for suspected acute stroke, used to rapidly rule out hemorrhage before thrombolytic therapy is considered. It does not reliably show early ischemic infarct — excluding bleeding is the deciding factor for tPA eligibility, not detecting the infarct itself.

Question 30

High-Resolution Temporal Bone CT

Accepted Answer

Requires very thin (submillimeter) slices and a high-spatial-frequency bone reconstruction kernel to resolve fine structures like the ossicles and semicircular canals. A standard soft-tissue kernel and routine slice thickness will not adequately depict these small structures.

Question 31

Cervical Spine Trauma Protocol

Accepted Answer

Uses thin-slice acquisition with sagittal and coronal reformats to assess alignment and fracture, typically without contrast — unless vascular injury such as vertebral artery dissection is suspected, which adds a CT angiogram component to the study.

Question 32

Soft-Tissue Neck CT Contrast Timing

Accepted Answer

Typically timed to peak venous/parenchymal enhancement — a later phase than arterial timing — to best evaluate lymph nodes and soft-tissue masses. A neck CT angiogram instead uses earlier arterial-phase timing, so the clinical question determines which delay is used.

Question 33

CT Myelography Indication

Accepted Answer

Used to evaluate the spinal canal and nerve roots when MRI is contraindicated, such as with certain implanted hardware. Contrast is injected intrathecally via lumbar puncture before scanning — not given intravenously as with most other CT studies.

Question 34

Dedicated Sinus CT Technique

Accepted Answer

Typically thin-slice, noncontrast images reformatted in coronal and axial planes to evaluate the osteomeatal complex before functional endoscopic sinus surgery. Contrast is reserved for suspected infection complications or tumor — not part of the routine anatomic protocol.

Question 35

CT Pulmonary Angiography Timing

Accepted Answer

Requires precise bolus timing — usually bolus tracking on the main pulmonary artery — so peak contrast enhancement coincides with acquisition. Mistimed injection is a leading cause of a nondiagnostic PE study, unlike routine chest CT where timing is less critical.

Question 36

High-Resolution CT (HRCT) for Interstitial Lung Disease

Accepted Answer

Uses thin slices with a sharp reconstruction kernel and often adds prone imaging to distinguish fixed fibrosis from dependent atelectasis. Prone positioning is the key added step that separates an HRCT protocol from a standard chest CT.

Question 37

Low-Dose CT Lung Cancer Screening

Accepted Answer

A noncontrast, reduced-dose technique for eligible high-risk smokers, with findings classified using the Lung-RADS system. This differs from a standard diagnostic chest CT, which uses full-dose technique to work up an already-identified abnormality.

Question 38

Triple-Phase (Multiphase) Liver CT

Accepted Answer

Acquires unenhanced, arterial (~25-35 seconds post-injection), and portal venous (~60-70 seconds) phases to characterize hypervascular liver lesions such as hepatocellular carcinoma, which enhance in the arterial phase and washout on later imaging. A single-phase study would miss that washout pattern entirely.

Question 39

Renal Stone (Renal Colic) Protocol

Accepted Answer

Performed as a noncontrast, low-dose CT because contrast can obscure small calcifications and mimic or hide stones. Giving contrast for this indication is a protocol error, not a dose-optimization choice.

Question 40

Appendicitis CT Contrast Approach

Accepted Answer

IV contrast is standard for adult appendicitis CT to evaluate bowel wall enhancement and detect complications like abscess or perforation. Oral contrast use varies by institution and patient body habitus rather than being universally required with modern scanners.

Question 41

CT Colonography Distension Requirement

Accepted Answer

Requires colonic insufflation (room air or CO2) plus both supine and prone (or decubitus) positioning to fully distend the colon and distinguish fixed polyps from mobile stool. Inadequate distension, not scan technique, is the most common cause of a nondiagnostic exam.

Question 42

Split-Bolus Contrast Technique

Accepted Answer

Divides the contrast dose into two separate injections — for example, an earlier portal-venous-timed dose and a later excretory-timed dose — to combine two enhancement phases into a single acquisition, reducing total dose compared with running two separate full scans.

Question 43

3D Volume Rendering for Fracture Assessment

Accepted Answer

Gives a spatial, surgeon-friendly overview of fracture fragment displacement, but it is a post-processing display technique. Diagnosis and detailed fracture characterization still rely on the underlying thin-slice axial and multiplanar reformatted images, not the 3D rendering alone.

Question 44

Metal Artifact Reduction for Orthopedic Hardware

Accepted Answer

Dedicated MAR algorithms, together with adjusted kVp/mAs technique, reduce streak artifact around joint prostheses and fixation hardware, improving visualization of adjacent bone and soft tissue. Standard reconstruction alone often leaves the region near the hardware non-diagnostic.

Question 45

CT-Guided Musculoskeletal Biopsy

Accepted Answer

CT provides precise real-time needle localization for bone and soft-tissue lesions, particularly valuable for deep or complex targets such as the pelvis or spine, where ultrasound cannot adequately visualize the lesion.

Question 46

Extremity Trauma: CT vs. Radiography

Accepted Answer

CT is reserved for complex intra-articular fractures, surgical planning, or equivocal radiographs — it is not a routine first-line study for simple extremity trauma, where plain radiography remains the initial modality.

Question 47

CT Angiography of the Aorta for Dissection

Accepted Answer

Requires arterial-phase timing and full coverage from the aortic root through the femoral arteries to identify the intimal flap and distinguish the true lumen from the false lumen. Incomplete coverage can miss distal extension of the dissection.

Question 48

Runoff CT Angiography

Accepted Answer

Images the arterial tree from the abdominal aorta to the feet in a single contrast bolus, with table speed matched to the bolus's travel down the legs to evaluate peripheral arterial disease. Timing is calibrated to bolus transit rather than a single fixed delay used in most other CTA studies.

Question 49

CT-Guided Abscess Drainage

Accepted Answer

Uses CT to plan and confirm a safe percutaneous needle or catheter trajectory to a fluid collection while avoiding bowel, vessels, and other critical structures — the image guidance during needle advancement is what distinguishes this from a purely diagnostic scan.

Question 50

CT Fluoroscopy During Interventional Procedures

Accepted Answer

Provides near real-time image updates during needle advancement for biopsy or drainage, improving procedural speed and accuracy compared with conventional step-and-shoot CT guidance. It delivers continuous dose to both patient and operator, which requires careful ALARA management, including using pulsed technique and keeping hands out of the beam.

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