Purpose: In a previous paper we reported the detection of floating plaque (FP) as an area of high brightness by the B-flow method. The purpose of the present study was to analyze this phenomenon in detail, and here we report the mechanism underlying it. Subjects and methods: Between August 2003 and September 2004, we examined 255 cervical carotid arteries using the B-mode method of ultrasonography (LOGIC 7 system, GE) with a 3-10-MHz broadband linear array transducer. We analyzed the size and oscillation speed of FP, and the frame rate (FR) of the B-flow method. Results: Eight FPs were recognized by B-flow imaging in 7 carotid arteries in 6 patients aged between 62 and 86 years. Five of them were men with an average age of 73 years. All the plaques were displayed as areas of high brightness by B-flow imaging. We altered the FR while observing the rate at which flaps were displayed at high brightness, and found high rates of detection at 23 Hz and 16 Hz, indicating that a high FR tends to detect FP at a high rate. The high brightness is thought to be due to weak signal inhibition of FP by tissue equalization. Conclusion: B-flow is a useful new approach for detecting micro FP.
