Which imaging technique may underestimate the degree of stenosis in tortuous vessels?

• A. MRI
• B. Digital subtraction angiography
• C. CT scan
• D. Ultrasound

Answer: (B)

Digital subtraction angiography (DSA) is a technique used to visualize blood vessels by subtracting pre-contrast images from post-contrast images, allowing clear visualization of the vascular structure. However, in cases of tortuous vessels, this method may not accurately represent the degree of stenosis due to the complex geometry of the vessels. The twisting and turns can cause an underestimation of the actual degree of narrowing, as the contrast medium may not flow adequately through these irregular paths, leading to artifacts in the images.

This limitation arises because DSA relies on producing a two-dimensional representation of a three-dimensional structure, which can significantly affect the interpretation in the presence of anatomical variations such as tortuosity. Therefore, while DSA is a powerful diagnostic tool, its efficacy can be compromised in situations where vessels have a non-linear configuration, making it challenging to assess stenosis accurately.