Demonstration of Corkscrew Collaterals in Buerger’s Disease by Superb Microvascular Imaging

Buerger’s disease (Thromboangiitis obliterans) is an inflammatory vaso-occlusive disease that has a predilection for small- and medium-sized arteries. Unlike atherosclerotic changes, the vessel wall usually retains its normal structure. The affected segment often demonstrates thrombotic occlusion and local collateral formation that has a serpiginous or corkscrew appearance. The combination of colour Doppler ultrasound with characteristic appearance of corkscrew-shaped vessels and clinical assessment are important for diagnosis. Demonstration of corkscrew collaterals and depiction of vascular course by colour Doppler sonography may not always be possible due to relatively low resolution. The advanced dynamic flow (ADF) technique has been shown to be superior in demonstrating corkscrew collaterals in Buerger’s disease. Superb microvascular imaging (SMI) is a new flow imaging technique that can demonstrate subtle low-flow components with high detail and resolution. In Doppler ultrasound, there are 2 sources for the signal: blood flow and tissue movement (clutter). However, the clutter signal may superpose with low-flow components. During image processing in conventional Doppler ultrasound, the wall filter cannot distinguish between tissue movement and low-flow components, and it eliminates all clutter signals and low-flow signal is also lost. SMI uses a unique algorithm for isolating and eliminating clutter while preserving the low-flow signals. SMI has higher frame rates and lower pulse repetition frequencies than colour Doppler imaging. We have adapted the SMI technique to map the arterial vasculature with a higher resolution for routine lower extremity Doppler imaging. Herein, we demonstrate the far superior demonstration of corkscrew collaterals in a patient with Buerger’s disease by SMI compared with colour Doppler and ADF.