Microstructure Characterization of Cancellous Bone Based on Ultrasonic C-Scan Imaging

Abstract

Ultrasonic backscatter signals can reflect the microstructural information of cancellous bone. The goal of this study is to characterize the microstructure of cancellous bone in the mesoscale and estimate trabecular thickness (Tb.Th), trabecular bone separation (Tb.Sp), bone volume fraction (BV/TV) and structure model index (SMI) based on ultrasonic C-scan imaging. Nine cuboid cancellous bone samples were prepared in this experiment. The bone samples were scanned using an ultrasound C-scan equipment with a 30 MHz focused transducer. The −6 dB lateral resolution of the transducer was 0.157 mm. The scanning interval was 0.05 mm. The scanning region of interest was 10 × 10 mm in the center of the cancellous bone sample. The cancellous bone images were obtained based on time of flight (TOF) and amplitude (AMP). The trabecular microstructure information was analyzed based on the ultrasonic C-scan images and compared with those obtained by μ-CT. The microstructure of trabecular bone can be clearly seen in the TOF and AMP images. The microstructure estimated based on the ultrasonic images was similar to the μ-CT provided results. The estimated parameters including Tb.Th, Tb.Sp, BV/TV and SMI had an average estimation error of 21, 22, 17 and 12% with a moderate correlation to the μ-CT measured results. The results demonstrated that ultrasonic C-scan imaging can be used to evaluate cancellous bone’s microstructure.