Expanding the limits of endoscopic intraorbital tumor resection using 3-dimensional reconstruction

Abstract Introduction: Endoscopic orbital surgery is a nascent field and new tools are required to assist with surgical planning and to ascertain the limits of the tumor resectability. Objective: We purpose to utilize three-dimensional radiographic reconstruction to define the theoretical lateral limit of endoscopic resectability of primary orbital tumors and to apply these boundary conditions to surgical cases. Methods: A three-dimensional orbital model was rendered in 4 representative patients presenting with primary orbital tumors using OsiriX open source imaging software. A 2-Dimensional plane was propagated between the contralateral nare and a line tangential to the long axis of the optic nerve reflecting the trajectory of a trans-septal approach. Any tumor volume falling medial to the optic nerve and/or within the space inferior to this plane of resectability was considered theoretically resectable regardless of how far it extended lateral to the optic nerve as nerve retraction would be unnecessary. Actual tumor volumes were then superimposed over this plan and correlated with surgical outcomes. Results: Among the 4 lesions analyzed, two were fully medial to the optic nerve, one extended lateral to the optic nerve but remained inferior to the plane of resectability, and one extended both lateral to the optic nerve and superior to the plane of resectability. As predicted by the three-dimensional modeling, a complete resection was achieved in all lesions except one that transgressed the plane of resectability. No new diplopia or vision loss was observed in any patient. Conclusion: Three-dimensional reconstruction enhances preoperative planning for endoscopic orbital surgery. Tumors that extend lateral to the optic nerve may still be candidates for a purely endoscopic resection as long as they do not extend above the plane of resectability described herein.

【摘要·引言】内镜眼眶手术（Endoscopic orbital surgery）是一门新兴领域，亟需配套工具辅助手术规划，并明确肿瘤可切除性的边界。
【研究目的】本研究旨在利用三维放射学重建（three-dimensional radiographic reconstruction）明确原发性眼眶肿瘤内镜下切除术的理论侧方切除边界，并将该边界条件应用于临床手术病例中。
【研究方法】本研究采用OsiriX开源成像软件，为4例原发性眼眶肿瘤代表性患者构建三维眼眶模型。沿对侧鼻孔与视神经长轴切线（该切线反映经鼻中隔入路（trans-septal approach）的手术轨迹）绘制二维平面。凡位于视神经内侧，或处于该切除平面下方的肿瘤体积，无论其向视神经外侧延伸范围多大，均被视为理论上可切除，因无需进行视神经牵拉。随后将实际肿瘤体积与该术前规划模型进行叠加，并与患者的手术结局进行相关性分析。
【研究结果】纳入分析的4例病灶中，2例完全位于视神经内侧，1例向视神经外侧延伸但仍处于切除平面下方，1例同时向视神经外侧延伸且超出切除平面上方。正如三维建模所预测，除1例突破切除平面的病灶外，其余病灶均实现完整切除。所有患者均未出现新发复视或视力丧失。
【研究结论】三维重建可优化内镜眼眶手术的术前规划。只要未超出本文所述的切除平面，向视神经外侧延伸的肿瘤仍可考虑行单纯内镜下切除术。