ULTRASONIC BONE-ASSESSMENT APPARATUS AND METHOD

Non-invasive, quantitative in-vivo ultrasonic evaluation of bone is performed by subjecting bone to an acoustic excitation pulse supplied to one of two transducers on opposite sides of the bone, and involving a composite sine-wave signal consisting of repetitions of plural discrete ultrasonic frequencies that are spaced at approximately 2 MHz. Signal-processing of received signal output of the other transducer is operative to sequentially average the most recently received given number of successive signals to obtain an averaged per-pulse signal and to produce a Fourier transform of this signal. In a separate operation, the same transducer responds to the transmission and reception of the same excitation signal via a medium of known acoustic properties and path length to establish a reference signal, which is processed to produce its Fourier transform. The two Fourier transforms are comparatively evaluated to produce a bone-transfer function, which is then processed to derive the frequency-dependent specific-attenuation and group-velocity functions .mu.(f) and Vg(f) associated with the bone-transfer function. The function Vg(f) is related to the derivative of the phase of the bone-transfer function, as a function of frequency. A neural network, configured to generate an estimate of one or more of the desired bone-related quantities, is connected for response to the functions .mu.(f) and Vg(f), whereby to generate the indicated estimates of bone status, namely, bone-density, bone-strength and fracture risk.