Three-Dimensional UTE Magnetic Resonance Imaging of the Osteochondral Junction

摘要 骨关节炎是美国最流行的疾病之一，影响着5000多万美国人 每年的成本超过600亿美元。与办公自动化相关的主要公共卫生问题包括 随着我们社会的老龄化，它可能会变得更加重要。骨性关节炎被认为是一种完整的关节疾病 通常累及所有组成关节组织的病理变化。人们越来越感兴趣的是 骨软骨交界处(OCJ)，它包括骨深部未钙化层之间的组织 软骨和骨小梁的骨髓间隙。它包括深部的放射状未钙化软骨， 潮标、钙化软骨(CC)和软骨下骨(SCB)板。虽然这些组织是无血管的，但 正常关节，在骨性关节炎中，破骨细胞被激活，并通过软骨下骨板形成通道，允许 血管和神经从骨髓延伸到深层软骨。这与一系列 异常，包括局部炎症和金属蛋白酶活性上调，细胞外基质 降解，软骨承载能力降低，退行性改变。OCJ可能会发生变化 这些变化可能与其发病机制有关。磁共振成像 磁共振成像(MRI)被广泛用于直接、非侵入性评价关节软骨，在关节软骨损伤中发挥着重要作用。 骨性关节炎的临床诊断和治疗。然而，OCJ区的磁共振成像由于平均时间短而困难 桡骨深部未钙化关节软骨、钙化软骨、 和软骨下骨，当使用常规脉冲序列时，这会导致很少或没有信号。 在这项研究中，我们的目标是发展3D绝热反转恢复制备的超短回波时间锥(3D Ir-cones)技术用于直接体积形态成像和OCJ定量标测 验证信号源，并最终开发可用于眼球关节活体成像的平移3D红外视锥技术。 在目标1中，我们将进一步开发和验证3D IR锥体技术，用于形态和定量 身体膝关节骨软骨标本的OCJ成像(n=10)。我们将调查 空间分辨率、长T2抑制、射频功率和梯度强度以及T1、T2*和 3T Bruker小口径扫描仪和临床3T扫描仪OCJ成像中的质子密度加权， 分别进行了分析。我们将把形态和定量的锥体表现与微CT和组织学相关联。在AIM 2 我们将开发平移3D IR锥体技术，用于OCJ的形态和定量成像 健康志愿者和人工全膝关节置换术患者各10个膝关节。被切除的人 来自相对正常(n=10)和更多退变区域(n=10)的骨软骨样本将被重新扫描 使用临床和3D IR-CONES序列，然后进行微CT成像和组织学检查。体内和体外3D IR- OCJ的锥体成像将与µCT成像和组织学进行比较和对照。

Abstract Osteoarthritis (OA) is one of the most prevalent diseases in the US, affecting over 50 million Americans with an annual cost of more than $60 billion per year. The major public health issues associated with OA are likely to become even more important as our society ages. OA is considered a whole joint disease with pathologic changes that often involve all of the constituent joint tissues. Of increasing interest is the region of the osteochondral junction (OCJ), which encompasses the tissues between the deep uncalcified layers of cartilage and the marrow spaces of the trabecular bone. It includes the deep radial uncalcified cartilage, tidemark, calcified cartilage (CC), and subchondral bone (SCB) plate. While these tissues are avascular in the normal joint, in OA, osteoclasts are activated and form channels through the subchondral bone plate, allowing blood vessels and nerves to extend from the marrow into deep cartilage. This is associated with a cascade of abnormalities, including local inflammation and upregulation of metalloproteinase activity, extracellular matrix degradation, reduction of cartilage load-bearing capacity, and degenerative change. The OCJ may change dramatically in OA, and these changes may be relevant in its pathogenesis. Magnetic resonance imaging (MRI) is widely used to directly and non-invasively evaluate articular cartilage and plays an important role in the clinical diagnosis and treatment of OA. However, MRI of the OCJ region is difficult due to the short mean transverse relaxation times (i.e., short T2 or T2*) of deep radial uncalcified articular cartilage, calcified cartilage, and subchondral bone, which result in little or no signal when conventional pulse sequences are used. In this study we aim to develop 3D adiabatic inversion recovery prepared ultrashort echo time Cones (3D IR-Cones) techniques for direct volumetric morphological imaging and quantitative mapping of the OCJ, to validate the signal sources, and finally develop translational 3D IR-Cones techniques for OCJ imaging in vivo. In Aim 1 we will further develop and validate 3D IR-Cones techniques for morphological and quantitative imaging of the OCJ in osteochondral samples from cadaveric human knee joints (n=10). We will investigate the effect of spatial resolution, long T2 suppression, RF power, and gradient strengths, as well as T1, T2*, and proton density weightings in OCJ imaging on a 3T Bruker small-bore scanner and a clinical 3T scanner, respectively. We will correlate morphological and quantitative Cones findings with µCT and histology. In Aim 2 we will develop translational 3D IR-Cones techniques for morphological and quantitative imaging of the OCJ in knee joints of healthy volunteers (n=10) and patients subject to total knee replacement (n=10). The excised osteochondral samples from relatively normal (n=10) and more degenerated regions (n=10) will be re-scanned with clinical and 3D IR-Cones sequences, followed by µCT imaging and histology. In vivo and ex vivo 3D IR- Cones imaging of the OCJ will be compared and correlated with µCT imaging and histology.