3D-DXA cortical and trabecular parameters: agreement between hologic densitometers in clinical practice

Three-dimensional dual-energy X-ray absorptiometry (DXA) reconstructs three-dimensional maps of the proximal femur's density distribution from standard hip DXA scans, enabling the estimation of trabecular and cortical bone parameters. The aim of this study was to assess the agreement of these three-dimensional cortical and trabecular femur parameters across different series and models of Hologic densitometers.

The study cohort was composed of 103 women and men recruited from four clinical centers in Spain and France. Subjects had duplicated hip DXA scans using different Hologic scanners from the Horizon, Discovery, and QDR 4500 series. Analyses were performed using 3D-Shaper software. Inter-scanner agreement was evaluated using Deming regression and Bland-Altman analysis. A multiple linear regression was used to investigate the impact of patients' age and BMI on the magnitude of inter-scanner differences. Furthermore, the clinical impact of inter-scanner variability was assessed by evaluating the agreement in the classification of DXA and 3D-Shaper bone parameters as normal, low, or very low density.

The parameters demonstrated strong inter-device agreement across all clinical centers and scanner models, with coefficients of determination greater than 0.91. Absolute biases were less than 2.5 mg/cm³ for integral volumetric (v) bone mineral density (BMD), less than 2.9 mg/cm³ for trabecular vBMD, and less than 1.7 mg/cm² for cortical surface (s) BMD. No statistically significant bias was found between parameters obtained from different scanners. Furthermore, a high classification agreement was found for all parameters, with cortical sBMD reaching the agreement level of standard DXA areal (a) BMD.

Standard and three-dimensional hip bone parameters showed excellent agreement across the evaluated Hologic scanners, with inter-scanner differences rarely affecting density classification. Further studies are needed to confirm generalizability to other Hologic devices.