Individualized assessment of osteoporotic fracture risk at the spine using ultra-low dose MDCT imaging techniques and non-dedicated routine MDCT exams

骨质疏松症被定义为一种骨骼疾病，其特征是骨骼强度下降，使个人容易发生骨折的风险增加。特别是，骨质疏松性椎体骨折会降低生活质量，增加发病率和死亡率，导致严重的社会经济负担。临床危险因素和基于双能X射线吸收法(DXA)的骨密度(BMD)测量目前被用于确定骨折风险和启动适当的(药物)治疗。然而，有和没有骨质疏松性骨折的受试者的骨密度值是重叠的。在非专用临床常规多探测器计算机断层扫描(MDCT)检查中，椎体骨密度评估在预测偶发性椎体骨折方面优于基于DXA的BMD。此外，基于MDCT的有限元模型(FEM)已被证明比BMD更能改进椎骨强度预测。我们研究项目的目标是(I)开发用于定量骨骼评估的专用超低剂量MDCT成像和(Ii)转换非专用临床常规MDCT检查，以充分利用它们来预测脊椎特定的骨折风险。对于超低剂量成像，将开发迭代重建算法以提高诊断图像质量。此外，将研究一种受压缩传感启发的策略，即广为人知的稀疏采样CT，以一种根本不同的方式减少辐射暴露。这种方法允许获得较少数量的投影，而每个单独的投影图像的辐射曝光量仍然很高。稀疏采样采集的明显好处是改善了每个投影的质量，同时避开了电子读出噪声的影响。由于骨强度的生物力学模型依赖于不同的采集参数和含碘静脉造影剂的应用，因此必须考虑这些因素才能进行可靠的机会性骨质疏松筛查。将建立一条全自动化管道，以读取非专用常规MDCT数据并将其标准化，对每个椎体进行分段，并使用骨密度、骨骼纹理分析和有限元分析来确定椎体特定的骨折风险。PI可以显示基于已完成的DFG资助的骨质疏松症成像研究项目的相关出版物，以成功执行该提案，这需要放射科医生、物理学家和生物工程师进行跨学科的研究工作。

Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength predisposing an individual to an increased risk of fractures. In particular, osteoporotic vertebral fractures are associated with a reduced quality of life and increased morbidity and mortality leading to a severe socio-economic burden. Clinical risk factors and Dual-energy-X-ray-absorptiometry (DXA)-based Bone Mineral Density (BMD) measurements are currently used to determine fracture risk and to initiate appropriate (drug) therapy. However, BMD values of subjects with versus without osteoporotic fractures overlap. Vertebral BMD assessment in non-dedicated clinical routine Multi-Detector Computed Tomography (MDCT) exams was superior to DXA-based BMD to predict incidental vertebral fractures. Furthermore, MDCT-based Finite Element Models (FEM) have shown to improve vertebral bone strength prediction beyond BMD. The objectives of our research project are (i) to develop dedicated ultra-low dose MDCT imaging for quantitative bone assessment and (ii) to convert non-dedicated clinical routine MDCT exams to use them adequately to predict vertebral-specific fracture risk. For ultra-low dose imaging, iterative reconstruction algorithms for improved diagnostic image quality will be developed. Furthermore, a compressed sensing inspired strategy, widely known as sparse-sampling CT will be investigated to reduce radiation exposure in a fundamentally different way. This approach allows acquiring a reduced number of projections, while the radiation exposure remains high for each individual projection image. The clear benefit of sparse-sampling acquisitions is an improved quality for each projection while circumventing the influence of electronic readout noise. As the biomechanical modeling of bone strength is dependent on different acquisition parameters and the application of iodine-containing intravenous contrast agent, these have to be taken into account to perform a reliable opportunistic osteoporosis screening. A fully-automated pipeline will be established to read and standardize the non-dedicated routine MDCT data, segment each vertebra and determine vertebra-specific fracture risk using BMD, bone texture analysis, and FEM. The PIs can show project-related publications based on already completed DFG-funded research projects in the context of osteoporosis imaging to successfully perform the proposal, which requires interdisciplinary research effort by radiologists, physicists, and bioengineers.