ESTIMATION OF WAVE DISPERSION AND ATTENUATION FOR THE ASSESSMENT OF HEALING BONES
V.Potsika, V.Protopappas, M.Vavva, K.Raum, D.Rohrbach, D.Polyzos, D.I.Fotiadis(UDC: 616-001.5-073:537.874.4)
Abstract:
Quantitative ultrasound has recently gained significant interest as a diagnostic tool of the bone healing process. Several multiple scattering theories have been proposed for the investigation of wave scattering in nonhomogeneous media, which however cannot provide realistic dispersion and attenuation estimations for different particle types and volume concentrations. In this study, we use an iterative effective medium approximation (IEMA) (Aggelis et al. 2004) to carry out wave dispersion and attenuation predictions in the callus region at different healing stages. The geometry and the material properties are derived from scanning acoustic microscopy images (SAM) of sheep healing tibia obtained at the third, sixth and ninth postoperative week (Anderson et al. 2008). The callus is assumed to be a composite medium consisted of blood and osseous tissue. The average particle diameters and the volume concentration were 350μm and 44.75% in week 3, 200μm and 38.67% in week 6, 120μm and 22.67% in week 9, respectively. Wave dispersion and attenuation are estimated for frequencies from 24 – 1200 kHz. Group velocity was found to decrease with increasing frequency, while the attenuation coefficient was found to increase in the examined frequency range. The results indicate that the scattering effects are more pronounced in the early healing stages. In conclusion, IEMA can provide reasonable predictions and could be thus exploited for bone healing assessment.
