Detection of bone disease with ultrasound--comparison with bone densitometry

A system for ultrasonic in-vivo examination of a heel bone (calcaneus) was developed. When operating in transmission mode, the system can measure broadband ultrasonic attenuation-BUA, speed of sound--SOS and thickness of bone. BUA and SOS are measured by comparing the pulses transmitted through the heel with the reference pulse transmitted through water. In our approach, we operate in the backscattered mode in addition to transmission. The backscattered ultrasonic technique for bone characterization is very promising because the magnitude of backscattered waves depends on the scattering cross-section of a trabecular structure that, to some extent, describes the microarchitecture of a calcaneus. Additionally, when the backscattered and transmitted signals are compared, some of the signal distortions caused by tissue and bone interfaces are reduced. A set of data representing signals transmitted through the heel and reflected inside a calcaneus for patients with osteoporosis was collected. Several signal-processing techniques were applied in order to smooth the backscattered signal and to calculate a trabecular structure cros-section (TSC) function. Results obtained by these approaches along with a spectral shift method and a standard BUA measurement are presented and compared to X-ray bone mineral density determination results.