ARRT Computed Tomography: Free Preparation Guide and Learning Test Study Guide

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A patient reports shellfish allergy and an earlier episode of wheezing after contrast-enhanced CT. Clarify the contrast episode and communicate its severity before injection; that respiratory reaction directly changes planning and emergency preparedness.

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A septic patient develops oliguria and rising creatinine despite a previously normal value. Recognize possible acute kidney injury and communicate the change before contrast planning, even if the calculated eGFR appears reassuring.

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For stable eGFR 58 before intravenous contrast, ACR permits continuation. The cited product labeling requires withholding, reassessing eGFR after 48 hours, and restarting only when renal function is stable.

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During venipuncture, a patient becomes pale and hypotensive with pulse 44, without rash or wheezing. Assess airway and vital signs, summon assistance, and recognize a vasovagal pattern rather than assigning an unsupported contrast allergy.

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Immediately after injection, a patient develops hoarseness, stridor, falling oxygen saturation, and hypotension. Activate emergency response and prepare reaction equipment while airway and circulatory treatment begin. The respiratory and hemodynamic findings establish urgency without requiring a rash.

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A CTA patient has a PICC with unknown pressure rating. Verify the device information and permitted lumen before use or establish suitable alternative access, then assess patency and the site before the planned injection.

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After a small estimated extravasation, fingers become numb and capillary refill worsens. Escalate urgently despite the modest volume estimate, document neurovascular findings, and ensure reassessment rather than routine discharge after a compress.

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After helping a patient with a draining wound, remove gloves, perform hand hygiene, and disinfect contacted equipment before handling clean IV supplies for the next patient. Select fresh protection for the new task.

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A protocol doubles mAs while keeping kVp, geometry, pitch, and reconstruction unchanged. Predict approximately doubled scanner output and lower quantum noise. If kVp or automatic current control also changes, reassess the actual delivered technique.

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A caregiver wants to stand beside the gantry during scanning. Determine whether their presence is necessary and use the designated protected position and protective measures if it is required. Do not assume beam filtration protects everyone nearby.

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A report lists CTDIvol 9 mGy and DLP 270 mGy·cm. Identify the scanner index and the length-related indicator separately. Neither value directly states the patient's effective dose or an individual organ dose.

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A series uses CTDIvol 8 mGy over 35 cm, yielding 280 mGy·cm. Two identical acquisitions total 560 mGy·cm. Creating coronal or sagittal images from either acquisition does not add another acquisition DLP.

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Two reports show the same CTDIvol, but one uses a 16 cm reference phantom and the other a 32 cm phantom. Establish each reference before selecting size factors and comparing estimates.

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For a justified pediatric abdominal examination, check prior imaging and select an appropriate size-based protocol with necessary coverage and phases. Explain the procedure to the child and caregiver to improve cooperation and reduce motion-related repeats.

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An AP localizer was acquired below isocenter. Correct table height, acquire an appropriate new localizer, and verify recalculated technique. For the described GE systems, an existing lateral localizer may remain usable after correction followed by an orthogonal AP localizer.

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Pitch rises from 1.0 to 1.5 while mAs per rotation rises from 120 to 180. Effective mAs remains 120, so the pitch change alone does not establish proportional exposure reduction.

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A circular artifact persists in unrelated patients and a water phantom. Investigate detector calibration and the acquisition chain instead of attributing it to patient anatomy or contrast timing.

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Cerebral perfusion requires repeated measurements during contrast passage. Dynamic acquisition supplies a time series. One routine helical pass supplies spatial coverage but does not provide equivalent repeated measurements at every sampled location.

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With 40 mm total nominal beam width and 60 mm table travel per rotation, pitch is 60 divided by 40, or 1.5. The calculation describes acquisition geometry regardless of a later 1 mm reconstruction.

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At 240 mA and 0.5 seconds per rotation, mAs per rotation is 120. With pitch 1.5, effective mAs is 80. A displayed effective mAs of 80 does not mean the tube current is 80 mA.

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A shoulder extends outside the measurement field and creates truncation streaks. Viewer zoom cannot recover missing projections. For a properly acquired wrist, a smaller reconstruction field can improve pixel sampling of the included anatomy.

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A 256 mm field on a 512 by 512 matrix gives 0.5 mm pixels. With 2 mm thickness, nominal voxel dimensions are 0.5 by 0.5 by 2 mm.

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A series with 3 mm thickness and 1.5 mm interval contains overlapping 3 mm images. To reduce averaging of a small structure, use a supported thinner reconstruction rather than simply creating more overlapping positions.

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One chest acquisition must support lung and mediastinal review. Produce a suitable sharper lung reconstruction and smoother soft-tissue reconstruction, then select appropriate display windows for their respective anatomical tasks.

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Only thick soft-tissue images remain after raw-data deletion. A workstation can create reformations, but cannot reproduce the same fine-detail result as a supported thin sharp reconstruction from original projections.

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A lesion measures higher after contrast than before it. Assess whether the same viable tissue was sampled with comparable images and whether the ROI avoids adjacent vessels, calcification, and boundary averaging.

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Two matched water-phantom images average 0 HU, but standard deviations are 4 and 8 HU. The second is noisier despite equal means; water calibration and noise represent different performance characteristics.

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Nearby soft-tissue values look similar on a broad window. Narrow width while retaining an appropriate center, then review additional settings for structures with substantially different attenuation, such as bone or aerated lung.

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A tiny dense focus is faint on 5 mm images but distinct on supported 1 mm reconstructions. Compare adjacent thin sections to confirm its position and recognize reduced averaging rather than a biological change.

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A dark band lies between dense bones across an expected anatomical region. Compare adjacent images and alternative reconstructions before interpreting it as a discrete low-attenuation lesion based on one section.

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A ring appears in an abdominal scan and a water phantom at the same radius. Document it, arrange calibration or service assessment, and verify correction with suitable quality-control images.

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Images show doubled diaphragm contours and separate streaks from spinal hardware. Address breathing cooperation for the first pattern and metal-related reconstruction options for the second rather than assigning one cause to both.

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A fracture's relationship to a joint is unclear axially. Generate coronal and oblique reformations from the thin volume and correlate with source sections before considering any additional acquisition.

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A vascular MIP suggests narrowing beside dense calcification. Review thin cross-sectional images and targeted reformations to determine whether the projection exaggerates obstruction. Use rendering to communicate relationships while retaining source review.

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The scanner reports transfer completion, but PACS contains only thick axial images. Verify study association and resolve transfer of the required thin and reformatted series before marking imaging complete for interpretation.

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An adult develops worsening neurological symptoms after a fall and needs initial traumatic intracranial assessment. Prepare the noncontrast head study and distinguish it from any additional request for arterial injury evaluation.

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The team suspects a neck arterial injury after trauma. Confirm CTA coverage and injection timing instead of substituting an already completed noncontrast brain series simply because it images part of the same region.

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A perfusion abnormality lies beside aneurysm clips and source images show streaking. Assess the source time series and processing quality, communicate the limitation, and avoid interpreting the color map alone as proof of deficient perfusion.

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A fracture interrupts the carotid canal wall. Communicate the vascular concern because head-and-neck CTA addresses suspected arterial injury. Suspected CSF leakage instead makes dedicated noncontrast temporal bone or maxillofacial assessment relevant; coronal thin bone images help assess tegmen defects.

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A trauma examination needs intracranial and skull assessment. Review suitable brain and bone presentations, ensuring the soft-tissue window emphasizes relevant attenuation differences and the bone images retain adequate boundary detail.

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A patient with suspected disc-related neural compression cannot undergo MRI. Myelography followed by CT can delineate the contrast-filled subarachnoid space around the cord and roots. Match coverage to the symptomatic region rather than assuming the lumbar puncture level defines the CT target.

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After fluoroscopic lumbar puncture, contrast outlines nerve roots in the CSF-containing space. Identify the subarachnoid compartment, confirm requested spinal coverage, and use contrast suitable for intrathecal administration.

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Two days after myelography, a patient reports headache on standing with substantial relief supine. Recognize the positional pattern and ask about severity, persistence, fever, and neurological changes while arranging clinical assessment.

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An adult has lipohemarthrosis on a lateral knee radiograph without a clearly characterized fracture. Dedicated noncontrast CT can assess intra-articular injury. If a tibial plateau fracture is present, identify surface depression and posterior involvement rather than describing only a cortical break.

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A neck series shows duplicated soft-tissue boundaries despite adequate contrast enhancement. Identify possible motion, review whether it obscures the target, and use clear swallowing instructions for any clinically necessary repeat.

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Strong aortic enhancement accompanies poor pulmonary arterial opacification in a suspected embolism examination. Recognize the target mismatch and communicate the limitation before regarding the study as an adequate pulmonary angiogram.

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A known dissection requires assessment of abdominal extension and renal arterial involvement. Include the requested abdominal aorta and renal arteries, assess their enhancement and continuity on thin source images, and correlate with reformations. A bright thoracic segment alone cannot answer the branch-involvement question.

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A patient asks whether zero calcium proves there is no coronary plaque. Explain that the examination detects calcified plaque and can miss noncalcified disease; its result does not provide a complete anatomical exclusion.

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A request seeks coronary lumen assessment, but the scheduled protocol is calcium scoring. Resolve the mismatch before scanning because the completed score would not supply the requested contrast-enhanced anatomical information.

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One task requires anatomy at a selected phase, while another needs multiple phases. Choose a timing approach that supplies the necessary data, recognizing that a narrowly triggered acquisition may lack other desired phases.

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Before a multiphase abdominal study, connect each proposed acquisition to a specific question. After scanning, verify the target distribution rather than assuming that every labeled phase achieved its purpose.

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Contrast surrounds bowel loops in one trauma cystogram, supporting intraperitoneal leakage. Another shows irregular contrast in tissues around the bladder, supporting an extraperitoneal pattern. Describe both distributions if both appear.

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A liver CT series labeled arterial shows fully enhanced hepatic arteries, a portal vein less enhanced than liver, and no hepatic venous enhancement by antegrade flow. These findings indicate early arterial timing. If the examination lacks another acquisition showing portal vein enhancement greater than liver while meeting the other arterial-phase criteria, the preferred late arterial information is missing. A tumor without conspicuous enhancement on that early acquisition may still enhance during the late arterial phase. Coronal or sagittal reconstructions change the viewing plane but preserve the original acquisition time; they cannot supply the missing enhancement phase.

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A treated liver tumor contains dense oil and the question is residual enhancement. Identify this limitation and communicate why another imaging approach may better address response, rather than interpreting all intralesional density as viable tumor.

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A nonpregnant adult has new colicky flank pain and suspected ureteral stone. Prepare the ordered noncontrast stone examination rather than converting it to contrast urography. Recognize that pregnancy requires a different initial imaging decision.

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A hematuria examination shows enhanced kidneys but excludes distal ureters and bladder. Identify missing tract segments and assess whether the required collecting-system distribution is demonstrated before regarding the urographic task as complete.

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A renal laceration raises concern for urinary leakage. Check the delayed assessment and actual collecting-system opacification, particularly in hypovolemia, rather than accepting a fixed elapsed time as evidence that excretion was adequate.

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Delayed intravenous images show only a partly filled bladder after adult pelvic trauma. Once catheter suitability is established, perform the requested active retrograde cystographic filling rather than accepting partial passive filling as equivalent.

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A postoperative patient needs enteric leak assessment and has impaired swallowing. Select suitable water-soluble low- or iso-osmolality contrast and a route addressing the suspected segment, considering both leakage and aspiration risks.

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A small-bowel examination targets mural enhancement, but dense positive oral contrast is proposed. Clarify the enterography preparation so luminal material does not conceal the wall abnormalities the examination is intended to assess.