Quantitative CT in the measurement of bone quantity and bone quality for assessing osteoporosis

The biomechanical strength of the skeleton, and hence the risk of future fractures, depends on both the bone quantity (assessed in terms of bone mineral density) and bone quality (assessed in terms of the integrity of its internal architecture). Precise methods of measuring the calcium-equivalent density of both the trabecular and cortical components of vertebral bone using quantitative computed tomography are presented. For a group of post-menopausal Kuwaiti females, we have shown that the trabecular and cortical components are highly correlated with each other at both the L3 and L4 lumbar vertebral levels, with correlation coefficients of 0.78 and 0.74 (P < 0.0001) respectively. We have explored the anisotropic distribution of trabecular bone and considered the use of the standard deviation and the coefficient of variation of trabecular CT numbers as texture indicators and surrogate measures of bone quality. The coefficient of variation was the better texture indicator: used with bone mineral density values it successfully discriminated between two classes of patients (those with fractures and those without) with high sensitivity (> or = 89%) and specificity (> or = 82%).