CT angiography of extremity vessels

Evolution of vascular imaging modalities

Over the past three decades, the role of radiology in angiology has changed dramatically: it has evolved from purely diagnostic to therapeutic. Traditional invasive catheter angiography has given way to modern non-invasive techniques, which include multidetector CT angiography, MR angiography, and duplex ultrasound.

Today, direct catheter angiography is rarely used. It is employed primarily as an expert tool («gold standard» / «referee») to resolve complex clinical situations when the data from CT angiography and other non-invasive tests are contradictory.

CTA in the diagnosis of lower extremity venous pathology

The leading pathology of the venous system of the legs is deep vein thrombosis (DVT). Its causes include hypercoagulable states (dehydration, immobilization) and underlying iliac vein stenoses.

Even with anticoagulant therapy, 30–50% of patients with DVT develop post-thrombotic syndrome (post-thrombotic syndrome, PTS). It manifests as chronic pain, pronounced edema, intermittent claudication, and trophic ulcer formation.

In extensive thrombosis, interventional techniques are indicated: catheter-directed thrombolysis and mechanical thrombectomy. However, the large ATTRACT trial proved that when the thrombus is localized exclusively in the femoropopliteal segment, these procedures do not provide significant advantages in preventing post-thrombotic syndrome.

Imaging features of arteriovenous malformations

Arteriovenous malformations (AVMs) of the extremities have specific hemodynamics. Unlike the brain and lungs, where rapid blood shunting is observed (rapid arteriovenous shunting), blood flow through the AVM nidus in the extremities is often slowed. Because of this, feeding arteries and draining veins may be visualized simultaneously as early as the arterial phase.

For precise evaluation of AVM structure, multiphase imaging with high temporal resolution is required. Special techniques are used for rapid data acquisition:

• Keyhole imaging (key-hole / k-space sharing) involves frequent updating of the central zone of k-space, which is responsible for contrast.
• Non-Cartesian k-space sampling trajectories provide ultra-fast signal acquisition.

Planning endovascular treatment

In modern practice, the endovascular-first approach concept dominates. CT angiography serves as a vital navigator, allowing assessment of lesion anatomy and selection of the appropriate tool.

Main interventional procedures:

1. Percutaneous transluminal angioplasty (PTA): dilation of a narrowed or occluded blood vessel segment using balloon catheter inflation.
2. Stenting: implantation of a metal mesh framework. Stents are divided into balloon-expandable (deployed along with the balloon) and self-expanding (expand due to their own radial force after the delivery system sheath is removed). Covered stents (covered stents) are used to isolate aneurysms or sources of bleeding.
3. Embolization: therapeutic vascular occlusion (in AVMs, bleeding, tumors) via a catheter. Metallic coils, plugs, glue, and particles are used.
4. Temporary agents (gelatin sponge) are used in trauma when future vessel recanalization is desired.
5. Permanent particles (polyvinyl alcohol, PVA) are radiolucent, so they are mixed with a contrast agent before administration. They block the lumen by «silting up» the blood flow.

Class and exam questions

What else to study on this topic

• CT and MR angiography in patients with critical limb ischemia and intermittent claudication
• Endovascular treatment of abdominal aortic aneurysms (EVAR) and diagnosis of endoleaks
• Pulmonary embolism (PE): association with lower extremity DVT and CT diagnosis
• Subclavian steal syndrome
• Principles of dual-energy CT (dual source CT) in angiography

Other topics in the "Interventional radiology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.