Non-invasive functional assessment and evaluation of treatment response in the articular cartilage using high-magnetic resonance imaging

为探索侵袭性较小的关节疾病(如骨关节炎)患者的可靠成像技术，我们进行了以下基础实验和临床研究：(1)研制了一种适用于3-T磁共振成像的新型射频线圈。研究了信号采集能力、信号一致性和安全性。(2)开发了专门用于评价髋关节和膝关节软骨在MR图像上的计算机程序。利用该程序计算了不同部位软骨基质的厚度和MR参数(T2值)，重复性较好。(3)采用手术切除的股骨头骨折患者软骨-骨标本，对软骨MR参数与软骨基质蛋白多糖、胶原、水含量的相关性进行了评价。在这些基质中，胶原含量与MR T2值高度相关。(4)磁共振成像…评估T2的可行性评估髋关节发育不良患者早期髋臼和股骨软骨的变化。对9名正常人(9个髋关节)和14名髋关节发育不良患者(15个髋关节)的髋关节进行3T磁共振成像，获得髋关节矢状位T2像。比较正常组、关节炎前期组和早期关节炎组在髋臼和股骨软骨上端的T2值和T2映射的视觉表现，包括梯度T2、低T2和高T2模式。T2标测分型可以早期发现髋关节发育不良患者的骨关节退行性变和软骨基质发育障碍。(5)以T2软骨作为软骨基质变化的替代指标，前瞻性评价了机械负荷系统MR成像评价膝关节承载功能的临床可行性。对22名健康志愿者(男9名，女13名，平均年龄25岁)进行了3.0T磁共振成像，获得了股骨-胫骨内侧关节和外侧关节的矢状位T2图。在加载条件下，在磁共振成像过程中施加相当于体重50%的轴向压缩力。比较负重区股骨和胫骨软骨在加载和卸载条件下的T2值。磁共振成像结合机械加载的临床可行性被证明可以检测加载过程中T2软骨的特定部位的变化。从负荷的响应性来看，T2评估可以通过揭示与软骨局部应力集中有关的病理情况，灵敏地检测软骨和半月板的早期退行性变化。较少

To investigate reliable imaging technology with less invasiveness for patients with joint disorder, such as osteoarthritis, we conducted following basic experiments and clinical investigations.(1) New radio-frequency (RF) coils, which are applicable to 3-T MR imaging, were developed for hip and knee joint. Ability of signal acquisition, signal uniformity, and safety were investigated.(2) Computer programs specific to assessment of hip and knee cartilage on MR images were developed. Using the programs, thickness and MR parameters (T2 values) of cartilage matrix were calculated at various sites, with high reproducibility.(3) Using resected human cartilage-bone specimen from patients with fracture of the femoral head, correlation of MR parameters of cartilage and cartilage matrix quantity such as proteoglycan, collagen and water, were evaluated. Among those matrixes, collagen content was highly associated with MR T2 values.(4) The feasibility of T2 assessment using magnetic resonance imag … More ing at 3T was assessed for evaluating early changes in the acetabular and femoral cartilages for patients with hip dysplasia. Sagittal T2 maps of the hip were obtained using 3T MR imaging in 9 normal volunteers (9 hips) and in 14 patients (15 hips) with hip dysplasia at pre-or early-arthritic stages. T2 values and the visual appearance of T2 mapping, including gradient T2,low T2,and high T2 patterns, were compared at the superior zones of the acetabular and femoral cartilages among the normal, pre-arthritic, and early-arthritic groups. T2 mapping classification enabled the early detection of osteoarthritic degeneration and the detection of developmental disorders of cartilage matrix in patients with hip dysplasia.(5) Clinical feasibility of MR imaging with a mechanical loading system for evaluation of load-bearing function in knee joints was prospectively assessed, using cartilage T2 as a surrogate of cartilage matrix changes. Sagittal T2 maps of the medial and lateral femoro-tibial joints of 22 healthy volunteers (nine men, 13 women; mean age, 25 years) were obtained using 3.0 T MR imaging. Under loading conditions, an axial compression force of 50% of body weight was applied during MR imaging. T2 values of the femoral and tibial cartilage at the weight-bearing area were compared between loading and unloading conditions. The clinical feasibility of MR imaging with mechanical loading was demonstrated to detect site-specific changes in cartilage T2 during loading. From responsiveness of loading, T2 evaluation may allow sensitive detection of early degenerative changes in the cartilage and meniscus, by revealing pathological conditions related to localized stress concentration in the cartilage. Less