Feasibility of a novel blood noise reduction algorithm to enhance reproducibility of ultra-high-frequency intravascular ultrasound images

Background-Ultra-high-frequency (40- to 50-MHz) intravascular ultrasound (I VUS) improves image quality compared with conventional 20- to 30-MHz IVUS. However, as the frequency of IVUS increases, high-intensity backscatter fro m blood components may cause visual difficulties in discrimination between the lumen and arterial wall structure. The purpose of this study was to eva luate the effect of a novel blood noise reduction algorithm (BNR) on quanti tative coronary ultrasound measurements. Methods and Results-IVUS studies using a 40-MHz transducer were performed i n 35 patients with coronary artery disease. A total of 620 gray-scale image s (310 pairs) were processed with and without the BNR, and lumen cross-sect ional area (CSA) was determined by 2 independent observers. With the BNR, t he intraobserver and interobserver correlation coefficients for lumen CSA w ere significantly improved (0.85 to 0.99 and 0.80 to 0.98, respectively). I n the 270 images (135 pairs) in which vessel wall measurements were possibl e, the BNR significantly improved the intraobserver and interobserver corre lation coefficients for plaque plus media CSA (0.83 to 0.99 and 0.76 to 0.9 7, respectively), whereas no influence was observed for external elastic me mbrane CSA (1.00 to 1.00 and 0.99 to 0.99, respectively). Conclusions-This study demonstrates the feasibility of this novel algorithm to reduce blood noise, thereby enabling accurate lumen border delineation and providing reproducible measurements of both the lumen and plaque plus m edia CSAs, Incorporating a digital BNR may serve as an important adjunct to ultra-high-frequency IVUS imaging for improving accurate quantitative eval uation of vessel dimensions.