What is a Computed Tomography Angiography (CTA) with run off?

What is a CTA with Runoff?

A CTA with runoff is a comprehensive computed tomography angiography examination that images the entire arterial system from the abdomen and pelvis through both lower extremities down to the feet, providing a complete vascular "road map" for diagnosing peripheral arterial disease and planning revascularization procedures. 1

Technical Definition

CTA with runoff uses multidetector CT scanners with helical and multistation axial acquisitions to rapidly scan the entire arterial system in a single examination. 1 The study specifically includes:

• Abdomen and pelvis imaging to evaluate the aorta and iliac arteries 1
• Bilateral lower extremity imaging extending from the femoral arteries through the tibial vessels to the pedal arteries 1
• Precise contrast timing to capture peak arterial enhancement throughout the entire vascular tree 2

Key Imaging Capabilities

The volumetric acquisition provides several critical advantages over traditional catheter angiography:

• Multiplanar reformatted and maximum-intensity projection images create a comprehensive arterial road map 1
• Visualization of collateral vessels and arteries distal to occlusions that may not appear on catheter angiography 1, 2
• Cross-sectional imaging that shows both vascular and nonvascular findings, including vessel wall characteristics and associated pathology like aneurysms 1

Diagnostic Performance

CTA with runoff demonstrates 90-100% sensitivity and specificity for detecting arterial stenoses greater than 50% diameter compared to catheter angiography. 1, 2 The examination achieves:

• 96% sensitivity and 96% specificity for hemodynamically significant arterial stenosis in multiple meta-analyses 1
• Superior accuracy for evaluating bypass grafts compared to duplex ultrasound 1
• Reference standard status for aortic imaging, having replaced catheter angiography 1

Clinical Applications

CTA with runoff serves as the primary noninvasive imaging modality for treatment planning in peripheral arterial disease, providing sufficient diagnostic confidence to derive treatment decisions in 97% of chronic PAD cases. 3 The examination is used for:

• Assessment of claudication to determine revascularization strategy 1
• Evaluation of acute limb ischemia with rapid diagnosis capability 1
• Pre-procedural planning before endovascular or surgical intervention 1
• Post-revascularization surveillance for graft patency and complications 1

Important Limitations

Heavily calcified atheromatous disease significantly limits interpretation, particularly in tibial arteries. 1, 2 Specific patient populations at risk for nondiagnostic studies include:

• Patients over 80 years of age 1
• Diabetic patients 1
• Patients on dialysis 1

Dual-energy CTA can reduce blooming and beam-hardening artifacts from calcium and metallic stents, improving diagnostic accuracy in these challenging cases. 1, 2

Practical Considerations

The examination requires iodinated contrast administration, which necessitates:

• Assessment of renal function before the procedure 4
• Hydration protocols for patients with baseline renal insufficiency 4
• Consideration of contrast allergy history and appropriate pretreatment 4

CTA with runoff provides faster acquisition times than MRA, with less susceptibility to motion artifact and better tolerance in patients with pacemakers, defibrillators, or claustrophobia. 1