Electromagnetic bone-assessment apparatus and method

Abstract

Non-invasive quantitative in-vivo electromagnetic evaluation of bone is performed by subjecting bone to an electrical excitation wave-form supplied to a pair of electrodes on opposite sides of a bony member, and involving a repetitive finite duration signal consisting of plural frequencies that are in the range 0 Hz-200 MHz. Signal-processing of a bone-current response signal and a bone-voltage response signal is operative to sequentially average the most recently received given number of successive bone-current and bone-voltage response signals to obtain an averaged per-pulse bone-current signal and an averaged per-pulse bone-voltage signal, and to produce their associated Fourier transforms. These Fourier transforms are further processed to obtain the frequency-dependent bone-admittance function. In a separate operation, the same electrodes respond to the same excitation signal via a medium of known electromagnetic properties and path length to establish a reference-voltage signal and reference-current signal, which are processed to produce their associated Fourier transforms. These two Fourier transforms are further processed to produce a frequency-dependent reference-admittance function, which together with the bone-admittance function are processed to derive the frequency-dependent bone-conductivity real function, .sigma.'.sub.b (f), and frequency-dependent dielectric bone-permittivity real function, .di-elect cons.'.sub.b (f). The function .sigma.'.sub.b (f) is related to the energy loss in the bony member, and the function .di-elect cons.'.sub.b (f) is related to the energy storage in the bony member. 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 .sigma.'.sub.b (f) and .di-elect cons.'.sub.b (f), whereby to generate the indicated estimates of bone status, namely, bone-density, bone-architecture, bone-strength and bone-fracture risk.