Development of measurement technique of living body flexibility by indentation test using concentrated mass model

Abstract

Palpation is an important diagnostic technique in medicine. However, it is subjective, and successful diagnosis depends on the skill and experience of the doctor. Therefore, a quantitative method for measuring the hardness of the living body and detecting abnormal tissue is desirable. In this paper, we propose a concentrated mass model of the body to analyze its motion in an indentation test. The model consists of masses, connecting springs, connecting dampers, base support springs, and base support dampers. The mass is the mass of the elastic body, the connecting spring is derived from the normal stress, and the base support spring is derived from the shear stress. Furthermore, we develop a method to measure the Young's modulus and the position of abnormal tissue with the model when a column contactor is pressed into the body. To confirm the validity of the method, we measured the Young's modulus of silicone. The measurement results by the proposed method agreed with the value obtained with a parallel disk rotary rheometer. Moreover, our method gave accurate values for the Young's modulus of the second layer of two-layered silicone and the distance from the surface to the second layer. These results confirmed that our method is capable of measuring the Young's modulus of the soft materials and the boundary depth in two-layered objects.

Keywords

• biomedical measurement
• biological soft tissue
• identification
• modeling
• simulation
• elasticity
• concentrated mass model
• palpation