A Novel Method for Estimation of Femoral Neck Bone Mineral Density Using Forearm Images from Peripheral Cone Beam Computed Tomography

The main goal of osteoporosis treatment is prevention of osteoporosis-induced bone fracture. Dual-energy X-ray absorptiometry (DXA) and quantitative computed tomographic imaging (QCT) are widely used for assessment of bone mineral density (BMD). However, they have limitations in patients with special conditions. This study evaluated a method for diagnosis of osteoporosis using peripheral cone beam computed tomography (CBCT) to estimate BMD. We investigated the correlation between the ratio of cortical and total bone areas of the forearm and femoral neck BMD. Based on the correlation, we established a linear transformation between the ratio and femoral neck BMD. We obtained forearm images using CBCT and femoral neck BMDs using dual-energy X-ray absorptiometry (DXA) for 23 subjects. We first calculated the ratio of the cortical to the total bone area in the forearm from the CBCT images, and investigated the relationship with the femoral neck BMDs obtained from DXA. Based on this relationship, we further investigated the optimal forearm region to provide the highest correlation coefficient. We used the optimized forearm region to establish a linear transformation of the form to estimate femoral neck BMD from the calculated ratio. We observed the correlation factor of r = 0.857 (root mean square error = 0.056435 g/cm2; mean absolute percentage error = 4.5105%) between femoral neck BMD and the ratio of the cortical and total bone areas. The strongest correlation was observed for the average ratios of the mid-shaft regions of the ulna and radius. Our results suggest that femoral neck BMD can be estimated from forearm CBCT images and may be useful for screening osteoporosis, with patients in a convenient sitting position. We believe that peripheral CBCT image-based BMD estimation may have significant preventative value for early osteoporosis treatment and management.