Vessel wall detection and blood noise reduction in intravascularultrasound imaging

摘要

Scattering from blood limits the contrast between the vessel wallnand the lumen in intravascular ultrasound imaging. This makes itndifficult to localize the vessel wall, especially on still images. Thisnpaper presents a method for automatic detection of vessel walls andnreduction of blood noise based on correlation of the RF-signal betweennadjacent frames. The ultrasound RF-signal is quadrature demodulated,ndigitized, stored in memory, and transferred to a computer fornprocessing and analysis. The absolute value of the cross-correlationncoefficient between two adjacent frames is used to differentiate betweennstationary and fluctuating signals. Models and numerical calculationsnpresented in this work indicate that the cross-correlation coefficientnobtained from a radially dilating vessel wall will be larger than 0.8nunder standard 20 MHz imaging conditions. The corresponding value fromnblood is less than 0.2 for blood velocities exceeding 0.5 cm s-1n. The blood-noise filter is based on detecting this difference inncorrelation and displays vessel wall regions with no modifications,nwhile regions detected as blood are rejected. A simplified vessel-wallndetector that is suitable for real-time implementation is proposed. Thenperformance of this detector and the blood noise filter are demonstratednby in vitro experiments