Sensitivity analysis on imaging the calcaneus using microwaves

Abstract

The bone quality is associated with changes in its dielectric properties (permittivity and conductivity). The feasibility of detecting changes in these properties was evaluated by using a tomographic array of 16 monopole antennas with z-polarized microwaves at 1.3 GHz. The direct electromagnetic problem was solved computationally with the finite-difference-time-domain (FDTD) method. Local and global sensitivity analyses were implemented for identifying the parameters that most affect the detection. Magnitude and phase of the transmission coefficient of the antennas were evaluated separately. It was observed that the direct problem is highly sensitive to the dielectric properties of the tissues surrounding the calcaneus and to those of the calcaneus itself. Global and local sensitivity methods have shown evidence for feasible detection of variations in dielectric properties of the bone supporting the simplification of considering only two homogeneous media (calcaneus and surrounding tissue).