What considerations should be taken for a patient undergoing a CT (Computed Tomography) aortogram?

Key Considerations for CT Aortogram

For patients undergoing CT aortogram, proper patient preparation, contrast administration protocols, and monitoring for complications are essential to minimize risks and maximize diagnostic accuracy.

Patient Assessment Before CT Aortogram

• Renal function evaluation is mandatory before administering iodinated contrast media 1, 2

  • Check serum creatinine levels (avoid contrast if >1.8-2.0 mg/dL)
  • Ensure adequate hydration before and after the procedure to reduce risk of contrast-induced nephropathy
  • Consider alternative imaging modalities (MRA) for patients with significant renal dysfunction

• Allergy screening is critical 2

  • Document history of previous reactions to contrast media
  • Identify patients with known iodine sensitivity
  • Screen for clinical hypersensitivity (bronchial asthma, hay fever, food allergies)
  • Consider premedication with antihistamines or corticosteroids for high-risk patients

• Medication review 2

  • Note patients on beta-blockers as they may mask signs of anaphylactoid reactions
  • Document all current medications including non-prescription drugs

Technical Considerations for Optimal Imaging

• CT scanner specifications 1

  • Use multidetector CT scanners with 16 or more detector rows for isotropic resolution
  • Recommended parameters: slice thickness ≤3mm, reconstruction interval ≤50% of slice thickness, tube rotation ≤1 second, 120-140 kVp

• Contrast administration protocol 1

  • Intravenous contrast delivered at 3-5 mL/s via power injector
  • Total contrast volume should be minimized (≤150 mL)
  • Consider ECG-gating for ascending aortic imaging to eliminate motion artifact

• Image acquisition technique 1

  • Scan coverage should start above the aortic arch and extend at least to the aortoiliac bifurcation
  • Use centerline of flow measurements to reduce error from tangential measurements
  • Report external aortic diameter measurements (not just luminal diameter)

Essential Elements in CT Aortogram Reports

The report should include 1:

1. Location of any aortic abnormality
2. Maximum diameter of any dilatation, measured perpendicular to the axis of flow
3. Presence of internal filling defects (thrombus, atheroma)
4. Presence of intramural hematoma, penetrating atherosclerotic ulcer, or calcification
5. Extension of abnormality into branch vessels
6. Evidence of rupture (periaortic/mediastinal hematoma, contrast extravasation)
7. Comparison with prior studies to determine changes in diameter

Post-Procedure Monitoring

• Observe patients for at least 30-60 minutes after contrast administration 2
• Monitor for delayed contrast reactions
• Ensure continued hydration post-procedure
• Assess for signs of contrast-induced nephropathy (rising creatinine 24-72 hours post-procedure)

Special Considerations

• Radiation exposure minimization 1

  • Use techniques to minimize episodic and cumulative radiation exposure
  • Consider MRI for follow-up studies in younger patients requiring repeated imaging

• Alternative imaging modalities 1

  • MRA may be substituted if CT cannot be performed (contrast allergy)
  • MRA without gadolinium for patients with severe renal insufficiency
  • Catheter arteriography has limited utility, reserved for specific cases with contraindications to both CTA and MRA

Pitfalls to Avoid

• Inadequate contrast timing leading to poor vessel opacification
• Failure to use ECG-gating for ascending aorta, which can simulate aortic dissection due to motion artifact 1
• Relying on a single measurement plane in tortuous aneurysms
• Underestimating aneurysm size by measuring only the contrast-filled lumen and not the external diameter 1
• Overlooking branch vessel involvement in aortic pathology 1

By following these guidelines, clinicians can ensure optimal diagnostic quality of CT aortograms while minimizing risks to patients.