Pozzi Mucelli R, Morra A, Calgaro A, Cova M, Cioffi V
Istituto di Radiologia, Università, Trieste.
Radiol Med. 1997 Nov;94(5):440-6.
We applied the new technique of virtual endoscopy to the middle ear because this anatomical area is characterized by favorable contrast.
CT examinations of the petrous bone were obtained using 1.5 mm thick 1 coronal axis slices, with 1 mm or 1.5 mm table feed, 120 kV, 140-170 mA and 2 s scan time. The images were reconstructed with the high resolution algorithm for bony structures and a small field of view (9.6 cm), separately for the right and left petrous bone. The images were then transferred on a workstation and processed with the Navigator virtual endoscopic software (General Electric). A threshold value ranging -350 to -600 HU was applied.
A series of images is acquired as the virtual endoscope moves from the external auditory canal to the middle ear cavity. Images of the anterior, medial, and posterior surfaces of the middle ear are presented. Different views of the ossicles are also presented. High quality images were always obtained for the middle ear structures, including the ossicles. CT endoscopy of the middle ear provides a new view of the anatomy of this complex area. It has some advantages and disadvantages; the former can be summarized as follows: -demonstration of areas which are difficult to show with endoscopy because of the presence of membrana tympani; -the virtual endoscope can be placed in several positions and therefore it can be inserted in all sites and tortuous places of anatomical cavity; -nice and effective demonstration of the ossicular chain including the stapes. The disadvantages are related to the fact that the endoscopic reconstruction (such as any other three-dimensional reconstruction) is a representation of surfaces where different densities are necessarily homogenized.
CT virtual endoscopy of the middle ear can currently be considered a complementary technique to conventional CT because it permits better anatomical detailing of this complex region.
我们将虚拟内窥镜新技术应用于中耳，因为该解剖区域具有良好的对比度。
使用1.5毫米厚的冠状轴位切片进行颞骨CT检查，床进为1毫米或1.5毫米，管电压120千伏，管电流140 - 170毫安，扫描时间2秒。分别对左右颞骨，用高分辨率算法重建骨结构图像，视野为小视野（9.6厘米）。然后将图像传输到工作站，并用Navigator虚拟内窥镜软件（通用电气公司）进行处理。应用的阈值范围为-350至-600亨氏单位。
随着虚拟内窥镜从外耳道移动到中耳腔，可获取一系列图像。展示了中耳前、内、后表面的图像，还展示了听小骨的不同视图。对于包括听小骨在内的中耳结构，总能获得高质量的图像。中耳CT内窥镜为这个复杂区域的解剖结构提供了新的视角。它有一些优点和缺点；优点可总结如下： - 能够显示因鼓膜存在而难以用内窥镜显示的区域； - 虚拟内窥镜可放置在多个位置，因此可插入解剖腔的所有部位和曲折处； - 能很好且有效地展示包括镫骨在内的听骨链。缺点与以下事实有关，即内窥镜重建（如任何其他三维重建）是对不同密度必然被均匀化的表面的一种呈现。
目前，中耳CT虚拟内窥镜可被视为传统CT的一种补充技术，因为它能更好地详细显示这个复杂区域的解剖结构。
