Characterization of bony tissues from ultrasonic backscattering using statistical models

US backscattered signals of bones, including both the tibia and the calcaneus in the ankle, were acquired from 45 osteoporosis patients (age of 70.4 ± 7.3) and 25 healthy volunteers (age of 22.5 ± 2.5). Measurements were carried out on ten marked locations covering the whole tibia and ten different locations of the calcaneous using a 1 MHz central frequency ultrasound. The sample volume excluding signals from the cortical bone was defined according to the correlation coefficient computed from each acquired RF backscattered signal, digitized at a 100 MHz sampling frequency, and the incident pulse. Backscattered signals were analyzed using statistical models in which statistical parameters including SNR and m parameter of the Nakagami distribution were calculated from envelopes of backscattered signals in the sample volume. Results showed that both SNR and m parameters, measured from the cancellous bone of the tibia and the calcaneus of the ankle, for osteoporotic patients (1.78 ± 0.28 and 0.94 ± 0.24, respectively) are consistently higher than those for healthy subjects (1.42 ± 0.16 and 0.53 ± 0.12, respectively). These results furthermore suggest that backscattering signals in the cancellous bone may be applied to quantitatively assess the bony tissues for the diagnosis of osteoporosis