Purpose: Our objective was to evaluate the dynamic time window method (DTWM) for the measurement of speed of sound (SOS) at the 1/3 distal radius in 10 human subjects in vivo. DTWM, which is based on our proprietary probe, is a new method for obtaining the accurate time of flight (TOF) of the first arriving signal (FAS).
Method: This study compared DTWM with three conventional methods, i.e., threshold value method, first of maxima, and zero-crossing method, for the measurement of TOF of FAS.
Results: The highest correlation between SOS and bone mineral density (BMD) was found in the 10 human subjects using DTWM (R DTWM = 0.81, p < 0.005) rather than the three conventional methods (R = 0.37-0.41, p > 0.05). The individual short-term coefficient of variation (CV, from 0.07 to 0.27) and Root-Mean-Square (RMS) of the average CV (CVRMS, 0.18) were used to evaluate the reproducibility of our method (DTWM).
Conclusion: Despite the small population, the results suggest that DTWM improves the accuracy of recognition of SOS in vivo, and might be applied to optimize the clinical assessment of long cortical bone osteoporosis and fracture risk profile.
Keywords: Dynamic time window method (DTWM); Quantitative ultrasound (QUS); Radius; Speed of sound (SOS); Time of flight (TOF).