An energy-difference indicator for improved quantification of bone mineral density using dual-energy CT

Accurate assessment of bone mineral density (BMD), particularly volumetric BMD (vBMD), is central to evaluating bone quality and monitoring bone regeneration. Although dual-energy computed tomography (DECT) combined with virtual monoenergetic imaging (VMI) enhances quantitative imaging, measurements based on single-energy information remain limited by sensitivity and stability. Here, a rabbit tibial defect model was established, with micro-computed tomography used as the reference standard for vBMD. DECT-derived VMIs at low, medium and high energy levels were analysed to extract five quantitative indicators, including three single-energy values, an energy ratio and an energy-difference metric. Quantitative performance was systematically compared using linear regression, cross-validation, prediction-error analysis and Bland-Altman evaluation. The energy-difference metric showed performance comparable to that of the optimal single-energy indicator (VMI40), with marginally better model fit and agreement limits. These results suggest that integrating low- and high-energy information through an energy-difference approach provides a physically interpretable and practical framework for quantitative assessment of bone tissue. However, as this study was conducted in a rabbit model, future human cohort studies are required to confirm its clinical utility.