High-resolution Imaging Analysis of Bone and Cartilage Lesions with MR Microscopy.

在代谢性骨疾病和骨软骨发育不良中观察到的骨结构变化太小，以至于不能在放射学图像中检测到。这些仅在0.15 mm厚的骨小梁表面和直径为0.15 mm的骨单位中观察到。然而，最近，发展的高抛出率梯度系统和表面线圈使它有可能检测到这样的微观变化的MR images.Materials和方法：我们使用了一个小的表面线圈专门设计的手指成像（GE，图1）的1.5 T临床MR扫描仪（Signa Horizon，GE）。线圈为鸟笼型，具有正交系统，阻抗为50欧姆，符合LEC 601-1的安全标准。本文对5例正常人和3例甲状旁腺功能亢进患者的第二节中指骨进行了MR显微镜检查，视野（FOV）为2 ~ 4cm，矩阵为512 × 512，层厚1 mm，扫描开始采用梯度回波（GRASS）序列，为获得更好的S/N比，改用3DGRASS序列。将线圈放置在一个圆顶型的塑料台上，置于受检者的腹部，使受检者在成像过程中不会感到不适（图2）。结果：我们可以获得质量良好的MR图像，并在MR显微镜上检测到哈弗系统（图3）。甲状旁腺功能亢进者哈弗斯管轻度扩张，可探测数目增多。窄窗宽的图像显示有助于区分哈弗氏管和噪声。结论：MR显微镜可作为诊断代谢性骨疾病和轻微软骨损伤的辅助手段。

The structural changes of bone observed in metabolic bone diseases and osteochondral dysplasias are too small to detect in radiologic images. Those are only microscopically observed on the surface of trabeculae of 0.15 mm thickness and in osteons of 0.15 mm in diameter. Recently, however, development of high threw rate gradient system and surface coils make it possible to detect such microscopic change on MR images.Materials and Methods : We used a small surface coil specially designed for finger imaging (GE, Fig. 1) on a 1.5-T clinical MR scanner (Signa Horizon, GE). The coil is bird-cage type with a quadrature system, impedance of 50 ohm, and in accordance with the safety standard of LEC 601-1. We performed MR microscopy of the second middle phalanges of five normal volunteers and three patients with hyperparathyroidism.Field of view (FOV) was from 2 to 4 cm, matrices were 512x512, and slice thickness was 1 mm. We used gradient echo (GRASS) sequence at the beginning, and then changed to 3D GRASS sequence for better S/N ratio. The coil was placed on a plastic table of dome type set on the examine's abdomen, so that the examine did not feel discomfort during the imaging (Fig. 2).Results : We could obtain good quality MR images, and detect the Haversian system on the MR microscopy (Fig. 3). Slightly dilatation and increase of detected number of the Haversian canal was observed in the patients with hyperparathyroidism. Image display of a narrow window width was useful to distinguish the Haversian canal from noise. In addition, detailed structure of the interphalangeal joint could be observed.Conclusion : MR microscopy may be an useful adjunct in diagnosis of metabolic bone diseases and minimal cartilage trauma.