Ultrasound-based Velocity Vector Imaging in the Carotid Bifurcation: Repeatability and an In Vivo Comparison With 4-D...

Area of Science:

• Medical Imaging
• Cardiovascular Science
• Biomedical Engineering

Background:

• Complex blood flow patterns in the carotid bifurcation are crucial for understanding atherosclerosis.
• Ultrasound-based velocity vector imaging (US-VVI) is a promising, yet unvalidated, technique for in vivo analysis of these flows.
• Adaptive velocity compounding is a specific US-VVI method requiring validation.

Purpose of the Study:

• To validate the in vivo performance of adaptive US-VVI against 4-D flow MRI in the carotid bifurcation.
• To assess the repeatability of US-VVI for blood flow measurements.
• To compare 2-D velocity vector fields and temporal velocity profiles between US-VVI and 4-D flow MRI.

Main Methods:

• Acquired high frame rate US-VVI and 4-D flow MRI data from 20 healthy volunteers' carotid bifurcations.
• Performed semiautomatic registration of 60 US-VVI datasets and 4-D flow MRI data.
• Compared 2-D velocity vector fields using cosine similarity and RMSE; analyzed temporal profiles and determined inter/intraobserver agreement for US-VVI.

Main Results:

• Successful registration in 83% of cases, demonstrating good agreement between US-VVI and 4-D flow MRI.
• High cosine similarities and low RMSE for velocity magnitudes, with temporal profiles showing high resemblance (similarity indices 0.87 and 0.80).
• US-VVI exhibited good repeatability, with a highest bias and standard deviation of 1.7 and 11.7 cm/s, respectively.

Conclusions:

• US-VVI demonstrates good agreement in both vector angles and velocity magnitudes compared to 4-D flow MRI.
• The high spatiotemporal resolution of US-VVI allows detection of small, short-duration recirculating flow regions missed by 4-D flow MRI.
• US-VVI is validated as a reliable in vivo tool for analyzing complex carotid bifurcation blood flow.