CT angiography of extremity arteries

Why CT angiography of extremity arteries is performed

Peripheral vascular disease (PVD) is most commonly caused by atherosclerosis, which affects arteries in a multifocal pattern (at multiple sites).

The spectrum of clinical manifestations varies:

• Intermittent claudication (intermittent claudication). Muscle pain during walking, typically associated with proximal arterial lesions.
• Ischaemic rest pain (ischaemic rest pain). Indicates tissue ischemia, most commonly affecting the foot (distal lesion type).

Due to multiple lesions, the modern imaging approach requires performing CT angiography over a vast extent: from the abdominal aorta to the pedal arteries (pedal arteries). The primary goal of pre-intervention imaging is to assess the extent of the process, vascular patency, and create a sort of "roadmap" (roadmap) for endovascular or open surgical access.

Features and technical challenges of CT angiography

The CTA technique requires continuous movement of the scanner table to successfully scan the entire anatomy from the abdomen to the feet during the passage of the contrast bolus.

There are two main technical challenges:

1. Scanner speed. Modern CT scanners operate so rapidly that during scanning they can literally "outrun" the contrast bolus in the arterial phase, resulting in poor visualization of distal vessels.
2. Calcification issue. Atherosclerotically altered peripheral vessels often contain massive calcium deposits. The density of calcifications on CT is comparable to the density of the contrasted vascular lumen. This makes it difficult to differentiate intravascular contrast from wall calcifications.

Due to calcification, the physician may inaccurately assess the degree of stenosis (underestimating or overestimating) and obtain false-positive or false-negative patency results.

How the calcification issue is addressed

To distinguish the contrasted arterial lumen from calcified plaque on CT, special processing and scanning methods are used:

• Post-processing methods: multiplanar reconstructions (MPR) and volume rendering (VRT). They allow the vessel to be viewed from various angles and enable a more accurate assessment of the lumen.
• Dual-energy CT (DECT). Helps programmatically "subtract" calcium from the image.
• Mask subtraction. Theoretically effective, but rarely used in clinical practice due to technical complexities and increased radiation dose.

Note: Radiation exposure in modern CTA protocols is significantly reduced; therefore, for elderly patients with peripheral vascular disease, this factor plays less of a role than diagnostic accuracy.

Class and exam questions

What else to study on this topic

• MR angiography of peripheral arteries (features, Dixon fat suppression)
• Visualization of extremity arteriovenous malformations (AVMs)
• CT semiotics of aortic dissection
• Differential diagnosis of false lumen and aneurysm with thrombus

Other topics in the "Interventional radiology" section

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