An image processing method to assess changes in tibial geometry from peripheral quantitative computerised tomography scans

Peripheral quantitative computed tomography (pQCT) can be used to assess the structural and geometrical changes in bone whilst exposing participants to minimal radiation. Structural parameters are analysed automatically, but geometrical measures are not. pQCT images were converted into binary before the region of interest (tibia) was abstracted. A series of functions were applied to the tibia section to obtain the outer geometry. The validity of the method was determined using a uniform object of known diameter. Further investigation assessed natural variation in an able-bodied population over 12 months. Absolute differences in diameter of 1mm were identified from the validation scans. Coefficient of variation was below 4% for total bone area, and density. The proposed method allows increased specificity of the pQCT derived measures and quantifies outer geometry. The natural variation displayed in an able-bodied population must be considered when analysing a clinical population.