To establish a noninvasive method for estimating mechanical integrity of artery, we examined arteries of the human aged eighties by tensile and internal pressure tests, as well as sheep and cow as comparative data. It was shown that strength and elongation decreased approximately a half and a quarter respectively than young artery specimens. We found that a relationship between E_<th> and strength has been obtained, which allows the estimation of arteriosclerosis in term of the strength. Then, a system for estimating the stiffness E_<th> has been developed using the ultrasound B-mode image of in vivo artery. The software permits to estimate E_<th> in real time, and a few minutes for the both side of the common carotid artery. Some clinical data were also obtained such as E_<th>-age relation, E_<th>s for both side of the common carotid artery, distribution of E_<th>, and E_<th>-IMT (Intima Media Thickness) relation. The result indicated that the E_<th> and strength are useful symptom indices for arteriosclerosis, especially for finding the beginning sclerosis that would start early twenties.
