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

在代谢性骨病和骨软骨发育不良中观察到的骨结构变化太小，无法在放射图像中检测到。这些仅在0.15 mm厚的骨小梁表面和0.15 mm直径的骨中显微镜下可见。然而，近年来，高抛速梯度系统和表面线圈的发展使得在MR图像上检测这种微观变化成为可能。材料和方法：我们在1.5 t临床MR扫描仪（Signa Horizon， GE）上使用专门为手指成像设计的小表面线圈（GE，图1）。该线圈为鸟笼式正交系统，阻抗为50欧姆，符合LEC 601-1安全标准。我们对5名正常志愿者和3名甲状旁腺功能亢进患者的第二中指骨进行了磁共振显微镜检查。视场（FOV）范围为2 ~ 4 cm，矩阵为512x512，切片厚度为1 mm。我们开始使用梯度回波（GRASS）序列，然后改为3D GRASS序列，以获得更好的信噪比。将线圈置于置于被检查者腹部的圆顶式塑料台上，使被检查者在成像过程中无不适（图2）。结果：我们可以获得高质量的MR图像，并在MR显微镜上检测到Haversian系统（图3）。甲状旁腺功能亢进患者哈弗森管轻度扩张，检出数目增加。窄窗宽的图像显示有助于从噪声中区分哈弗森运河。此外，还可以观察到指间关节的详细结构。结论：磁共振显微镜可作为代谢性骨病和轻度软骨损伤诊断的辅助手段。

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.