A preliminary study on quantification of spontaneous echo contrast in superficial vein.

Many occlusive diseases of blood vessels in the body are known, including the eye. Spontaneous echo contrast observed by ultrasound in physiological blood stream is known as a phenomenon reflecting the aggregation and dissociation process of red blood cells, mainly studied by mock-flow experiments. High-frequency ultrasound equipment is a useful tool to detect delicate changes of echo contrast caused by ambient forces or even temperature. However, there are few literature reports describing quantitatively these echo contrast changes in clinical setting. We propose a method to describe these phenomena quantitatively by applying it in the stop-flow experiment performed in vivo. A set of successive cross sectional ultrasound images over seconds are stored in the newly developed diagnostic system, with scanning a region of 1 cm x 1 cm x 3 cm using a 30-MHz transducer and subjected to histogram analysis to follow changes of echo contrast in a section of vein cavity along the time course. The cross sectional image has a resolution of 512x512x8 bits. A vessel wall is refined by using adaptive smoothing and enhancing preprocessing methods, so that it allows for calculating speckles inside the vessel cavity distinctly separated from the wall. Thus, changes in the frequencies of brightness of the speckles in one specific section are visualized along the time course. By stopping the blood flow, the number of bright speckles increases to maximum. By releasing the blood flow, the number of bright speckles decreases to the basic level. Those changing set of brightness along the time course in a specific section may reflect the variation of causal mechanisms related to rouleau formation of red blood cells, different from spectral analysis.