Bone mineral density estimation from a plain X-ray image by learning decomposition into projections of bone-segmented computed tomography

TL;DR

This study introduces a novel, efficient method for estimating bone mineral density from plain X-ray images by learning to decompose projections of bone-segmented QCT, enabling early osteoporosis screening with limited data.

Contribution

The paper presents a new approach that accurately estimates BMD from X-ray images using decomposition into QCT projections, reducing data requirements compared to existing multi-stage methods.

Findings

High correlation with DXA and QCT BMD measurements (0.880 and 0.920)

Low measurement variability with CV of 3.27-3.79%

Validated across multiple poses and clinical scenarios

Abstract

Osteoporosis is a prevalent bone disease that causes fractures in fragile bones, leading to a decline in daily living activities. Dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) are highly accurate for diagnosing osteoporosis; however, these modalities require special equipment and scan protocols. To frequently monitor bone health, low-cost, low-dose, and ubiquitously available diagnostic methods are highly anticipated. In this study, we aim to perform bone mineral density (BMD) estimation from a plain X-ray image for opportunistic screening, which is potentially useful for early diagnosis. Existing methods have used multi-stage approaches consisting of extraction of the region of interest and simple regression to estimate BMD, which require a large amount of training data. Therefore, we propose an efficient method that learns decomposition into projections of bone-segmented QCT for BMD estimation under limited datasets. The proposed method achieved high accuracy in BMD estimation, where Pearson correlation coefficients of 0.880 and 0.920 were observed for DXA-measured BMD and QCT-measured BMD estimation tasks, respectively, and the root mean square of the coefficient of variation values were 3.27 to 3.79% for four measurements with different poses. Furthermore, we conducted extensive validation experiments, including multi-pose, uncalibrated-CT, and compression experiments toward actual application in routine clinical practice.