杉本 恒美¹, 上羽 貞行¹, 伊東 紘一²

Tsuneyoshi SUGIMOTO¹, Sadayuki UEHA¹, Kouichi ITOH²

¹東京工業大学精密工学研究所, ²自治医科大学臨床病理

¹Tokyo Instuitute of Technology, Precision and Intelligence Laboratory, ²Jichi Medical School, Department of Clinical Pathology

キーワード : Tissue hardness, Radiation force, Viscoelastic model, Voigt model

Several techniques for measuring tissue hardness have been proposed which might provide an effective means for screening of the disease. However, no practical measurement technique has yet been established. We have proposed a new measurement technique to determine tissue hardness, in which the radiation force is employed to deform the tissue. The deformation is measured by the pulse Doppler method. The advantage of this technique is that it makes it possible to evaluate tissue hardness from only the time dependance of relative displacement. By using the Voigt model, the viscoelastic value is derived from a change in deformation. Two-laminated agar samples are employed, and a fundamental experiment is carried out to obtain the viscoelastic diagrams. These diagrams demonstrate the feasibility of the hardness measurement. On the basis of the study of safety, we show that the value of I_spta(spatial peak temporal average) can be kept under 240 (mW/cm²) by reducing the reputation ratio of burst pulses. This result suggests that a hardness measurement is possible without measuring the absolute value of the deformation. This proposed measurement technique can be used in vivo.