Morra A, Calgaro A, Cioffi V, Pravato M, Cova M, Pozzi Mucelli R
Istituto di Radiologia dell'Università, Trieste.
Radiol Med. 1998 Jul-Aug;96(1-2):29-34.
Virtual endoscopy is a new 3D technique which permits to depict the inner surface of anatomic cavities. We report our experience in the study of the nasal cavity and paranasal sinuses.
CT examinations of the maxillofacial region were obtained using 1.5 or 3.0 mm slices, 1.5 or 3.0 mm table feed, 120 kV, 140 mA, 2 s scan time, standard and high resolution algorithms for bony structures and a field of view of 14-16 cm. The images were transferred on a workstation and processed with the Navigator virtual endoscopy software (General Electric). A threshold value ranging -300 to -550 UH was applied.
We report a series of virtual images of the nasal cavity which includes rhinopharynx vault, torius tubarius, choanae, turbinates, tubal orifice and osteomeatal complex. Moreover, images of frontal sinus and tear duct, of polyps and fracture of maxillary sinus are also presented. 3D virtual endoscopy provides a clear visualization of the anatomic structures of the nasal cavity and sinuses. The images are similar to those of conventional endoscopy. Moreover virtual endoscopy visualizes the paranasal sinuses, which are not accessible at conventional endoscopy. The main limitations of this new technique are the arbitrary choice of the threshold value and the homogenization of different tissue densities, which reduces the contrast resolution.
Virtual endoscopy can presently be considered a complementary technique of the standard axial and coronal CT examination. It provides an effective demonstration of the anatomy of these structures and shows areas which are difficult to visualize with conventional endoscopy. This technique could be of help in didactical activity; its clinical application has to be verified.
虚拟内窥镜检查是一种新的三维技术，可用于描绘解剖腔的内表面。我们报告了我们在鼻腔和鼻窦研究中的经验。
使用1.5或3.0毫米层厚、1.5或3.0毫米床进、120千伏、140毫安、2秒扫描时间、用于骨结构的标准和高分辨率算法以及14 - 16厘米的视野获取颌面区域的CT检查。图像传输到工作站并用Navigator虚拟内窥镜软件（通用电气）进行处理。应用范围为-300至-550 UH的阈值。
我们报告了一系列鼻腔的虚拟图像，包括鼻咽穹窿、咽鼓管圆枕、鼻后孔、鼻甲、咽鼓管开口和鼻窦开口复合体。此外，还展示了额窦和泪道、息肉以及上颌窦骨折的图像。三维虚拟内窥镜检查能清晰显示鼻腔和鼻窦的解剖结构。这些图像与传统内窥镜检查的图像相似。此外，虚拟内窥镜检查能显示传统内窥镜检查无法触及的鼻窦。这项新技术的主要局限性在于阈值的任意选择以及不同组织密度的均匀化，这降低了对比分辨率。
目前，虚拟内窥镜检查可被视为标准轴位和冠状位CT检查的补充技术。它能有效展示这些结构的解剖情况，并显示传统内窥镜检查难以观察到的区域。这项技术可能有助于教学活动；其临床应用有待验证。
