Lang P, Steiger P, Genant H K, Chafetz N, Lindquist T, Skinner S, Moore S
Department of Radiology, University of California, San Francisco 94143.
J Comput Assist Tomogr. 1988 May-Jun;12(3):459-64. doi: 10.1097/00004728-198805010-00020.
Three-dimensional (3D) CT and 3D magnetic resonance (MR) imaging were performed in four patients with congenital dysplasia of the hip. Two patients were studied by 3D CT and two by 3D MR. Prior to volume segmentation, two-dimensional (2D) MR image preprocessing was used to correct for nonuniform signal intensity distribution from local variations in field strength and coil response. An unsharp mask of the original MR scan was computed by extreme blurring of the image to suppress the details of the object. The unsharp mask was divided into the image on a pixel-by-pixel basis. For improved object contrast first and second echo images were combined in a 1:2 ratio. To add an additional feature for volume segmentation, 2D MR image homogeneity was computed based on 3 X 3 pixel neighborhoods. Volume segmentation was performed using one feature for CT, i.e., attenuation range, and two features for MR, i.e., signal intensity and image homogeneity range. Three dimensional CT and 3D MR demonstrated the 3D relationships of femoral heads and acetabula. Three-dimensional CT was limited to patients who had ossified femoral heads, whereas 3D MR demonstrated the cartilaginous femoral head. The extent of acetabular coverage on which the mode of therapy is based was shown. Three-dimensional MR permitted imaging without gonadal irradiation. The 2D MR image preprocessing described here should provide even better results in objects with greater contrast, i.e., nonosseus structures, and those of larger size with relation to image degradation from partial volume effect.
对4例先天性髋关节发育不良患者进行了三维（3D）CT和三维磁共振（MR）成像检查。2例患者接受了3D CT检查，2例接受了3D MR检查。在进行容积分割之前，使用二维（2D）MR图像预处理来校正由于场强局部变化和线圈响应导致的信号强度分布不均匀。通过对原始MR扫描图像进行极度模糊处理以抑制物体细节，从而计算出模糊掩膜。将模糊掩膜逐像素地与图像相除。为了提高物体对比度，将第一回波图像和第二回波图像按1:2的比例进行合并。为了给容积分割增加一个额外特征，基于3×3像素邻域计算2D MR图像同质性。使用一个CT特征（即衰减范围）和两个MR特征（即信号强度和图像同质性范围）进行容积分割。三维CT和三维MR显示了股骨头与髋臼的三维关系。三维CT仅限于股骨头已骨化的患者，而三维MR则显示了软骨股骨头。显示了作为治疗模式依据的髋臼覆盖范围。三维MR允许在不进行性腺辐射的情况下成像。这里描述的二维MR图像预处理在具有更大对比度的物体（即非骨性结构）以及相对于部分容积效应导致的图像退化而言尺寸更大的物体中应该能提供更好的结果。
