Construction of reference data for classification of elasticity images of arterial wall

We have developed a phased tracking method (Kanai, H. et al., IEEE Trans. Ultrason. Ferroelect. Freq. Contr. vol.44, no.2, p.791-810, 1996) for measuring the minute change in thickness during one heartbeat and the elasticity of the arterial wall. By comparing pathological findings with the elasticity distribution measured with ultrasound, statistical parameters for respective tissues in the arterial wall were determined. We have already measured the statistical parameters for lipids and a mixture of smooth muscle and collagen fiber (Kanai et al., Circulation, vol.107, p.3019-21, 2003). The paper reports the measurement of elasticity distributions for blood clot and calcified tissue. We discuss whether the measured elasticity distributions can be used as reference data for classifying cross-sectional elasticity images. We also investigated the measurement of elasticity distribution and the correlation between collagen content and elasticity for fibrous tissue. Collagen is supposed to contribute mainly to the stability of the fibrous cap of atherosclerotic plaque. Therefore, such a correlation between elasticity and a tissue element of the wall may provide useful information for the diagnosis of plaque vulnerability.