Position Identification of Inclusions in Soft Objects by Indentation Testing

The incidence rate of breast cancer for women in Japan is increasing each year. The three main methods of screening for breast cancer are finger palpation, mammography and breast ultrasound. These methods must be improved to decrease the incidence rate. This involves the development of personal, easy-to-use devices that facilitate cancer diagnosis. This study evaluates an indentation device developed to imitate traditional finger palpation and identify the position of the tumor inside the breast. The identification procedure is based on the extended Hertzian contact theory, which was developed to evaluate the elasticity of a thin specimen. In this extended theory, the thickness effect of the specimen is represented by a thickness parameter, and the position can be identified by the analysis of the effect. The procedure is verified by using FEM for ideal inclusion model in soft object, and the accurateness of the identification is discussed for the development. In the verification, some difference in the identified position between the condition and the result of FEM is observed with the difference of the identified elasticity of the object. It was reported that the approximation of accurate elasticity could affect the accuracy of position identification. Subsequently, the identification accuracy of Young’s modulus and thickness of specimen is discussed considering the problem of inclusion. Using the proposed approach, high accuracy can be observed in the range of 5 mm to 15 mm; however, a greater level of accuracy in identification remains to be achieved in other ranges. Thus, it is concluded that identification is possible using the extended Hertzian contact theory; however, for accurate identification of cancer position in a breast, the theory requires further modification.