Amplitude modulation excitation for cancellous bone evaluation using a portable ultrasonic backscatter instrumentation

Abstract

Background: The ultrasonic backscatter (UB) has the advantage of non-invasively obtaining bone density and structure, and it is expected to be an assessment tool for osteoporosis early diagnosis. The previous UB measurements were all based on exciting a short single-pulse and analyzed the ultrasonic signals backscattered in bone. Purpose: This study aims to investigate an amplitude modulation (AM) ultrasonic excitation with UB measurements for estimating bone characteristics. Methods: The AM multiple lengths excitation and backscatter measurement (AM-UB) functions were integrated into a portable ultrasonic instrument for bone characterization. The apparent integrated backscatter coefficient in the AM excitation (AIBAM) was calculated on the AM-UB instrumentation. The correlation coefficients of the AIBAM estimating volume fraction (BV/TV), structure model index (SMI), and bone mineral density (BMD) were analyzed. Results: Significant correlations (|R| = 0.82 – 0.93, p < 0.05) were found between the AIBAM, BV/TV, SMI, and BMD. When increasing the AM excitation length, the AIBAM values show more stabilized both in 1.0 MHz and 3.5 MHz measurements. The recommendations in AM-UB measurement were that the avoided length (T1) should be less than AM excitation length, and the analysis length (T2) should be appropriately long but not more than AM excitation length. Conclusions: This study conducts an AM-UB measurement for cancellous bone characterization. Increasing AM excitation length can significantly improve AIBAM values stability with varied analyzed signals. The study suggests the portable AM-UB instrument with the integration of real-time analytics software that might provide a potential tool for osteoporosis early screening.