Variogram methods for the analysis of bony trabecular shadows in plain radiographs

Conventionally, trabecular morphology is described from thin sections on the basis of visual inspection and basic biometric parameters such as mean trabecular plate thickness, bone density, etc. In the clinical situation non-invasive studies of mineralised tissues may be undertaken using densitometric measurements. A little-explored non-invasive alternative is to study the organisation of shadows of trabeculae in plain radiographs. In radiographic images cancellous bone appears as a texture made up of the superimposed shadows of trabeculae from many planes. In this paper some early attempts to adapt modern image processing techniques to the analysis of trabecular architecture are reviewed. A new statistical technique based on variograms is applied to the investigation of anisotropy in trabecular radiographs and to changes in anisotropy with age. The results of regression analyses of variograms indicate that they can clearly demonstrate age-related changes in trabecular architecture and discriminate between the pattern of ageing in males and females. This approach shows promise as a useful research and investigative tool in a variety of contexts.