应用计算机辅助三维重建技术重建和测量视神经管和管内结构

Computer aided 3 D reconstruction and measurement of optic canal and intracanalicular structures

目的 重建人视神经管和管内结构，为视神经减压术提供解剖参考数据，为进一步探索视神经间接损伤的病理机制提供形态学依据。方法 应用计算机辅助三维重建技术重建６ 例成人视神经管及管内结构，并用计算机图像分析系统测量视神经管的厚度，视神经管、管内段视神经、硬膜鞘、蛛网膜下腔的横截面积和蛛网膜下腔的容积。在重建的三维模型上，对管内各结构间的空间关系进行系统观察。结果 视神经管内壁中部厚度为（０－４５ ±０－３５）ｍｍ ，是视神经管壁最薄的部位。管中部横截面积为（１８－２１ ±２－５０）ｍｍ２ ，是视神经管最狭窄的部位。蛛网膜下腔在颅口、中部及眶口处的横截面积分别为（４－４５±１－１２）ｍｍ２、（２－６８±１－３２）ｍｍ２ 、（１－２３±０－８３）ｍｍ２ ，依次呈逐渐减小趋势，其容积为（２１－１６±４－３１）ｍｍ３，可能为损伤后视神经水肿、硬膜出血的代偿空间。结论 视神经管内代偿扩张的空间有限，所以视神经轻度水肿和视神经鞘内少量出血就可能使视神经受压。当视神经间接损伤后，视神经管最狭窄的中部对视神经的束缚作用可能最强，而从视神经管的颅口到眶口段，代偿扩张空间逐渐减小。因此。

Objective To reconstruct the human optic canal and its inner structures, and to provide knowledge of this region in detail for optic nerve decompression and further understanding on the pathologic mechanisms of indirect optic nerve injury Methods 6 optic canals and its inner structures were reconstructed by using a computer aided 3 dimensional (3 D) reconstruction system Quantitative measurement for the canal wall thickness, bony canal transverse area, optic nerve transverse area, dual sheath transverse area, subarachnoid space transverse area, and subarachnoid space volume were done by means of the computer morphometric analysis system The detailed spatial relations among intracanalicular structures were also carefully identified on the 3 D models Results The thinnest portion of the canal was the middle part of the medial wall (0 45±0 35)mm, and the narrowest space was in the middle part of the optic canal [the transverse area was (18 21±2 50)mm 2] The volume of subarachnoid space which can be considered the compensatory space for distention incurred by the hemorrhage, optic nerve edema, or hematoma was (21 16±4 31)mm 3 At the cranial opening, the middle part and orbital opening, its transverse area was (4 45±1 12)mm 2, (2 68±1 32)mm 2, (1 23±0 83)mm 2, respectively Conclusions In the middle part, the restraining of the bony canal on injured nerve may be the most powerful Since the compensatory space was limited, even a tiny amount of blood or swelling of the nerve may cause optic compression Because the compensatory space for distention gradually decreases from cranial end to orbital end, the middle part and the anterior part of the optic canal and dural sheath are critical in optic nerve decompression