Session: P2C

implemented by measuring the speed-of-sound (SOS) or broadband ultrasound attenuation (BUA) in the calcaneus using two aligned transducers. These modalities allow measurements of bone tissues only at certain locations due to the arrangement of transducers. The accuracy of these techniques moreover is affected by many factors including geometry of the bone and the thickness of soft tissues. To alleviate these complications, we extensively applied ultrasonic backscattered signals to assess bone tissues using a 1 MHz single element transducer. The acquired backscattered signals were digitalized at a 20 MHz sampling frequency and 12-bits resolution. The m parameter of Nakagami distribution, a more sensitive and feasible parameter to quantify bone properties than that of backscattered strengths validated from results of both computer simulation and previous measurements, was on-line calculated from digital backscattered signals. The clinical assessment of bone tissues was performed on 41 osteoporotic patients of whom examinations were carried out by applying both ultrasound, was implemented in both the tibia and the calcaneus, and dual-energy X-ray absorptiometry (DEXA), was to measure bone mineral density (BMD) in the hip. Those m parameters measured from both the cancellous bone of the tibia and the calcaneus were normalized by that from the central portion of the tibia. Fairly linear relationships were found between the BMD of the hip and those normalized m parameters acquired from the cancellous bone of the tibia (correlation coefficient, r = 0.61) and that from the calcaneus (r = 0.63). It remains not fully clear about whether current ultrasonic backscattering technique or DEXA has a better accuracy to assess the bone tissues. However, ultrasonic backscattering technique using one transducer has a further potential to quantitatively assess the bone tissues for clinically diagnosis due to it is free of radiation and that BMD measured from DEXA naturally has lost an information of bone properties in the thickness direction. This work was supported by National Science Council, Taiwan, R.O.C. of the grants: NSC 90-2213-E-033-022 and NSC 91-2320-B-033-001