Ultrashort Echo Time (UTE) Magnetic Resonance Imaging of Bone

 描述（由申请人提供）：自1895年伦琴拍摄第一张X线照片以来，骨的定量成像在医学中一直具有核心重要性。目前的金标准技术DEXA测量骨矿物质密度（BMD）。然而，大部分骨，包括有机基质和骨水，它们一起占骨体积的约60%，是不可接近的。BMD本身仅能以30- 50%的准确率预测骨质疏松性骨折。从60岁到80岁，整体骨折风险增加了13倍，但单独的BMD只能预测骨折风险增加一倍。此外，最近的研究表明，骨髓肥胖在影响骨的数量和质量方面起着积极的作用。有相当大的兴趣，更全面的评价骨质量，不仅使用有关骨矿物质，但有机基质，骨水和骨髓脂肪的信息。所有这些因素都可能在维持皮质骨和松质骨的生物力学完整性方面发挥作用。 磁共振成像（MRI）通常用于诊断软组织疾病。然而，由于其短T2*，使用所有临床序列，骨是“不可见的”。我们开发了TE为8 µs的2D和3D UTE序列，比传统TE短约1000倍。这使得可以检测皮质骨中的多种水成分以及松质骨中的脂肪含量和组成。孔隙水含量提供了皮质孔隙度的替代测量。胶原结合水提供了有机基质密度的间接测量。骨髓脂肪含量和组成提供了BMD独立的骨折危险因素。这将是一个重大的进展，发展UTE MRI技术，以评估孔隙率和有机基质密度的皮质骨，以及骨髓脂肪含量和组成的松质骨。 本研究旨在开发并联合收割机新型3D UTE MRI技术，以评价皮质骨和松质骨，从而全面了解骨表征及其与功能的相关性。为了实现这一目标，在目标1中，我们将评价3D UTE MRI技术用于评估皮质骨。我们将确定UTE测量胶原结合水和孔隙水的准确性，并将UTE MRI指标（胶原结合水和孔隙水含量、T1、T2* 和MTR）与皮质骨的生物力学特性相关联。在目标2中，我们将评价3D UTE MRI技术用于评价骨小梁。我们将确定骨髓脂肪含量和组成的3D UTE MRI测量的准确性，并将3D UTE MRI指标与MR波谱（MRS）指标以及松质骨的生物力学特性相关联。在目标3中，我们将应用经验证的3D UTE MRI技术研究一组绝经前妇女和两组绝经后妇女的缓慢或快速骨丢失。我们将比较不同组的3D UTE MRI和MRS指标，并将结果与BMD和生化标志物相关联。这项工作将提供准确的3D UTE MRI和MRS生物标志物，这可能是重要的评估骨质量，并可能有重大影响的诊断和治疗监测的OP。

 DESCRIPTION (provided by applicant): Quantitative imaging of bone has been of central importance in medicine since Roentgen produced the first radiograph in 1895. The current gold standard technique DEXA measures bone mineral density (BMD). However, the majority of bone, including the organic matrix and bone water which together occupy ~60% of bone by volume is inaccessible. BMD by itself only predicts osteoporotic fractures with an accuracy of 30-50%. The overall fracture risk increases 13-fold from ages 60 to 80, but BMD alone only predicts a doubling of the fracture risk. In addition, recent studies demonstrate that bone marrow adiposity plays an active role in affecting bone quantity and quality. There is considerable interest in more comprehensive evaluation of bone quality using information not only about bone mineral, but organic matrix, bone water and marrow fat. All of these factors may play a role in maintaining the biomechanical integrity of cortical and trabecular bone. Magnetic resonance imaging (MRI) is routinely used in the diagnosis of soft tissue disease. However, bone is "invisible" using all clinical sequences due to its short T2*. We have developed 2D and 3D UTE sequences with TEs of 8 µs that are ~1000 times shorter than conventional TEs. This makes it possible to detect multiple water components in cortical bone, and fat content and composition in trabecular bone. The pore water content provides a surrogate measure of cortical porosity. Collagen-bound water provides an indirect measure of organic matrix density. Marrow fat content and composition provide BMD independent fracture risk factors. It would be a major advance to develop UTE MRI techniques to evaluate porosity and organic matrix density in cortical bone, as well as marrow fat content and composition in trabecular bone. This study aims to develop and combine novel 3D UTE MRI techniques to evaluate cortical and trabecular bone offering full insight into bone characterization and correlation with function. To achieve thi goal, in Aim 1 we will evaluate 3D UTE MRI techniques for assessment of cortical bone. We will determine the accuracy of UTE measurement of collagen-bound and pore water, and correlate UTE MRI metrics (collagen-bound and pore water content, T1, T2* and MTR) with biomechanical properties of cortical bone. In Aim 2 we will evaluate 3D UTE MRI techniques for evaluation of trabecular bone. We will determine the accuracy of 3D UTE MRI measurement of marrow fat content and composition and correlate 3D UTE MRI metrics with those from MR spectroscopy (MRS) as well as biomechanical properties of trabecular bone. In Aim 3 we will apply the validated 3D UTE MRI techniques to study one group of premenopausal women and two groups of postmenopausal women with slow or fast bone loss. We will compare the 3D UTE MRI and MRS metrics in different groups and correlate the results with BMD and biochemical markers. This work will provide accurate panels of 3D UTE MRI and MRS based biomarkers which may be important for assessing bone quality, and may have a major impact on the diagnosis and therapeutic monitoring of OP.