Feasibility Simulations of Dual-Layer Flat Panel Detectors for Bone Mineral Density Estimation

Bone mineral density (BMD) measurement plays a crucial role in the diagnosis and management of osteoporosis. The most widely used clinical method is dual-energy x-ray absorptiometry (DXA), where image scanning using fan-beam x-rays requires complex alignment mechanisms and switching of tube voltages and filters for dual-shot x-ray imaging. To simplify the BMD measurement system, a dual-layer flat panel detector (DFD) can be employed to acquire x-ray images with single-shot x-rays without scanning. In this paper, we study the feasibility of a single-shot approach using DFD in measuring BMD based on a second-order polynomial in comparison with conventional DXA scanning. We first synthesize x-ray spectra for different conditions of DFD and next conduct noise sensitivity analysis by adding log-uniform distributed noise to the input log intensities. Condition numbers of the BMD measurement functions and beam-hardening effect according to the soft-tissue thickness are also observed. Through extensive simulations, we observed that the noise sensitivity performance of the single-shot approach based on DFD could be better than the dual-shot approach based on a single flat panel detector if the switching filters are not employed. When the noise variance at the inputs was 10 −9 , the single-shot BMD estimate showed a lower mean square error of 7.99 × 10 −4 than the dual-shot case of 13.8 × 10 −4 . This approach can be effectively utilized as a preliminary screening method prior to DXA scanning in clinical settings.