Is CTA performed with or without contrast?

CTA is Performed WITH Contrast

CTA (CT Angiography) is always performed with intravenous contrast—this is the defining characteristic that distinguishes it from standard CT imaging. 1, 2

Critical Distinction: CTA vs Standard CT

• CTA is fundamentally a contrast-enhanced examination that requires IV contrast administration to visualize vascular structures, detect active bleeding, and evaluate arterial anatomy 2
• The ACR explicitly states that "CTA is a separate procedure distinct from CT abdomen and pelvis with IV contrast"—CTA involves optimized contrast timing, arterial phase acquisition, and 3D vascular reconstructions that standard CT with contrast does not provide 1
• Standard CT with IV contrast alone is rated "usually not appropriate" for vascular evaluation and bleeding detection, whereas CTA without and with IV contrast is the recommended protocol 1, 2

Standard CTA Protocol Components

Multiphasic Acquisition (Without AND With Contrast)

• The recommended CTA protocol includes BOTH non-contrast and contrast-enhanced phases (termed "CTA without and with IV contrast") 1, 2
• The non-contrast phase is essential for identifying baseline high-attenuation materials that could mimic active bleeding or contrast extravasation on post-contrast images 1, 2
• The Society of Abdominal Radiology Gastrointestinal Bleeding Disease-Focused Panel achieved 100% consensus recommending non-contrast images for CTA performed on single-energy CT 1
• Multiphasic protocols (unenhanced + arterial + portal venous phase) achieve 92% sensitivity for detecting GI bleeding compared to 83% for single-phase protocols 1

Technical Requirements

• Thin collimation (≤1 mm) enables high-quality multiplanar reformations that are required elements of CTA 2
• Optimized contrast timing targets the arterial phase for vascular visualization 1, 2
• 3D reconstructions including multiplanar reformatted and maximum-intensity projection images create an arterial roadmap 1

Clinical Applications Requiring Contrast

Hemoptysis and Bleeding Evaluation

• CTA identifies bronchial and nonbronchial arteries for pre-procedural embolization planning with 86-97% concordance with conventional arteriography 1
• CTA detects bleeding rates as slow as 0.3 mL/min, more sensitive than conventional angiography (0.5-1.0 mL/min) 1, 2
• Sensitivity of 85% and specificity of 92% for detecting active GI bleeding 1, 2

Peripheral Arterial Disease

• CTA achieves 90-100% sensitivity and specificity for detecting stenoses >50% diameter compared to catheter angiography 1
• Volumetric acquisition enables visualization of collaterals and arteries distal to occlusions that may not appear on planar catheter angiography 1

When Non-Contrast CT May Be Considered

• CT chest without IV contrast is only warranted for massive hemoptysis in patients with poor renal function or life-threatening contrast allergy 1
• For routine vascular evaluation, bleeding detection, or pre-procedural planning, contrast administration is mandatory 1, 2

Contrast Volume Considerations

• Modern protocols using tube potential selection and weight-based methods can reduce iodine contrast volume by 63% (from 138 mL to 49 mL) while maintaining diagnostic quality 3
• In patients with renal insufficiency, CTA with prophylactic oral hydration shows low risk of contrast nephropathy (only 2/50 patients in one study) 4, 5
• The risk of contrast nephropathy from CTA is not significantly higher than intraarterial DSA despite greater contrast volumes 5