A NEW METHOD TO DETERMINE VOLUMETRIC BONE MINERAL DENSITY FROM BI-PLANAR DUAL ENERGY RADIOGRAPHS USING A FINITE ELEMENT MODEL: AN EX-VIVO STUDY

摘要

Finite element models (FEMs) derived from QCT-scans were developed to evaluate vertebral strength but QCT scanners limitations are restrictive for routine osteoporotic diagnosis. A new approach-considers using bi-planar dual energy (BP2E) X-rays absorptiometry to build vertebral FEM. The purpose was to propose a FEM based on BP2E absorptiometry and to compare the vertebral strength predicted from this model to a QCT-based FEM. About 46 vertebrae were QCT scanned and imaged with BP2E X-rays. Subject-specific vertebral geometry and bone material properties were obtained from both medical imaging techniques to build FEM for each vertebra. Vertebral body volumetric bone mineral density (vBMD) distribution and vertebral strength prediction from the BP2E-based FEM and the QCT-based FEM were compared. A statistical error of 7 mg/cm3 with a RMSE of 9.6 and a R~2 of 0.83 were found in the vBMD distribution differences between the BP2E-based and qCT-based FEM. The average vertebral strength was 3321 N± 1657 and 3768 N± 1660 for the qCT-based and BP2E-based FEM, respectively, with a RMSE of 641N and R2 of 0.92. This method was developed to estimate vBMD distribution in lumbar vertebrae from a pair of 2D-BMD images and demonstrated to be accurate to personalize the mechanical properties in vitro.