Abstract
Osteoarthritis [OA] is common disease among elderly persons. However, it is difficult to quantify the degree of cartilage degradation clinically. We have studied the quantitative estimation method of cartilage degradation using ultrasonic wave. Our final goal is to propose a non-invasive estimation method of cartilage degradation using ultrasonic echo through the skin. For simulation of ultrasonic propagation from skin to cartilage, numerical analysis was performed. The analysis models consist of cartilage and skin layer. Thickness of skin layer varied from 4mm to 10mm by 2mm. Furthermore, in the skin, adipose tissue that scatters ultrasonic was considered. Degree of cartilage degradation was varied in 4 steps. Ultrasonic propagations from various incident angles to these analysis models were calculated. We investigated that three indices about relations between angle and the signal intensity depended on cartilage degradation. Influence analysis about these indices was performed. In analysis model without the adipose tissue, sensitivities of Kurtosis and B/(A+B) about cartilage degradation were 0.77 and -0.03, respectively. Meanwhile, in analysis model with the adipose tissue, sensitivities of Kurtosis and B/(A+B) about cartilage degradation were 0.02 and -0.04, respectively. From these results, Kurtosis is strongly affected by the adipose tissue, and B/(A+B) is not affected by the adipose tissue. Using these indices, non-invasive estimation of cartilage degradation may be possible.
