Development of a simple softness measurement method using a wearable force sensor and depth camera for remote edema palpation

Abstract

Telemedicine is becoming increasingly vital in improving access to healthcare in rural areas, increasing diagnostic efficiency, and reducing medical costs. Palpation is an essential diagnostic method that is widely used to assess a patient's physical condition, and there are significant benefits to performing it remotely. However, there has been relatively little research on remote palpation, and the few studies that do exist have tended to use robotic manipulators, which come with several challenges such as initial cost, safety, and operability. Therefore, we proposed a form of palpation where nurses or the patient's family perform the palpation on behalf of the doctor and transmit the sensing results. This study presents the development of a palpation system that can acquire the mechanical properties of the target tissue in real time by touching it with the hands without interfering with the user's sense of touch. Our system features a simple yet effective configuration, comprising only a force sensor attached to the user's nail and a depth camera. The results of calibration experiments using urethane gel confirmed that the proposed system can measure Young's modulus with a mean absolute error of 26.15% when pressed in to produce a displacement of 4 mm. In addition, to apply this system to remote edema assessment, a classification model was created to discriminate edema grade into five levels using sensor data in a dry lab. The results of repeated and nested 10-fold cross-validation confirmed that edema could be discriminated with a median accuracy of 60.57%. This system is expected to provide accurate diagnostic information to doctors in remote areas and to improve the local medical system.