Photon-counting detector CT virtual monoenergetic imaging for bone mineral density quantification: Validation with Micro-CT

Volumetric bone mineral density (vBMD) is crucial for evaluating bone quality. We established rabbit tibial defect models to assess virtual monoenergetic imaging (VMI) based on photon-counting detector CT (PCD-CT) for vBMD quantification, using micro-CT as the reference standard. VMI-derived CT values strongly correlated with micro-CT-measured vBMD across all energies (<i>r</i> > 0.925). The 50 keV VMI achieved the highest correlation with micro-CT (<i>r</i> = 0.951) and the best model fit (<i>R</i> ² = 0.9138), with low prediction errors (MAE = 0.0114 g/cm³; RMSE = 0.0135 g/cm³). In terms of image quality, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were superior at 70 keV. Overall, the energy range of 60-80 keV provided the optimal balance between predictive accuracy and image quality. PCD-CT is poised to play a transformative role in orthopedic research and clinical bone health management by enabling accurate, standardized, and longitudinal quantitative assessment.