Shimizu T, Uesugi Y, Yamamoto K, Aratake K, Nishigaki H, Matsui R, Kawai T, Sueyoshi K, Narabayashi I
Department of Radiology, Osaka Medical College.
Nihon Igaku Hoshasen Gakkai Zasshi. 1996 Oct;56(12):834-8.
To evaluate the usefulness of three-dimensional (3D) CT angiography of the portal vein obtained by using a multiple threshold display, 3D reconstructions were performed in 15 patients. The CT scanner employed was the Toshiba Xvigor. A volume of 150 ml of lopamidol 300 mg1/ml was administered at 3.3 ml/sec intravenously. Portal venous phase helical scanning was initiated 80 seconds after the start of the injection. Helical CT data were acquired using up to 25 continuous 1.0-sec rotations during a single breath-hold with an X-ray beam width of 7 mm and a couchtop movement speed of 7 mm/sec. Axial images were reconstructed at a section interval of 3 mm. Both the shaded surface display (SSD) and multiple threshold display (MTD) were generated by using Xtension with Sparc20. MTD was performed as follows. First, voxels, with higher CT values than that of liver parenchyma, were selected. Then, selected voxels were divided into eight parts, which were each assigned gradations of white to grey. The highest part of selected voxels, with higher CT values than that of the second branch of the portal vein, were set to white and a transparency of 0%. The other seven parts were each assigned transparencies of more than 0%. MTD images were compared with SSD in 15 cases by two radiologists. MTD images were superior to SSD images in quality, because MTD diminished surrounding artifacts due to liver parenchyma and enabled small vessels to be depicted clearly. Based on the above results, it was considered that MTD was a useful method for 3D CT angiography using enhanced helical CT.
为评估采用多阈值显示获得的门静脉三维（3D）CT血管造影的实用性，对15例患者进行了3D重建。使用的CT扫描仪是东芝Xvigor。以3.3 ml/秒的速度静脉注射150 ml含碘帕醇300 mg/ml。注射开始80秒后开始门静脉期螺旋扫描。在单次屏气期间，使用X射线束宽度为7 mm、检查床移动速度为7 mm/秒，进行多达25次连续1.0秒旋转，采集螺旋CT数据。以3 mm的层间距重建轴向图像。使用Sparc20的Xtension生成表面阴影显示（SSD）和多阈值显示（MTD）。MTD的操作如下。首先，选择CT值高于肝实质的体素。然后，将选定的体素分为八个部分，每个部分分别赋予从白色到灰色的灰度。选定体素中CT值高于门静脉第二分支的最高部分设置为白色，透明度为0%。其他七个部分的透明度均设置为大于0%。两名放射科医生对15例患者的MTD图像和SSD图像进行了比较。MTD图像在质量上优于SSD图像，因为MTD减少了肝实质造成的周围伪影，并能清晰显示小血管。基于上述结果，认为MTD是一种使用增强螺旋CT进行3D CT血管造影的有用方法。
