Abstract: Objective To show imaging findings of inferior orbital fissure(IOF)and groove(IOG)on axial CT scans and to discover their anatomic variations,so as to avoid misdiagnosing them as orbital fracture.Methods25normal skull were used to investigate the configurations of IOF and IOG.Five skulls were performed axial CT scans.20normal orbital axial scans were studied as well.MPR and RT-3D recon-structions were used in this study.Results skulls scans and normal orbital images on axial CT showed three sorts of findings:(1)single bony dehiscence between lateral and inferior walls;(2)first type of dou-ble bony dehiscence between lateral and inferior walls,among the dehiscence interposing a small bone.The long axis of the small bone was parallel to orbital wall;(3)second type of double bony dehiscence between lateral and inferior walls,but the long axis of the small bone was in anteroposterior direction.Anatomy and variation of three sorts of CT findings were corresponded respectively to:(1)a baseball club-shaped IOF;(2)a"V"-shaped IOF,that is composed of both of lateral and internal ramus,lateral ramus situates between the zygoma and the lateral portion of greater wing of sphenoid,and internal ramus between the maxilla and the internal portion of greater wing of sphenoid,both rami intercross caudally and open upwards in a"V"-shaped configuration;(3)a deep IOG with a protuberant lateral wall.Con - clusion Familiarity of imaging features on the axial CT scans and understanding of their anatomy of IOF and IOG would be helpful for avoiding misdiagnosis of orbital fracture.

Key words: inferior orbital fissure, inferior orbital groove, computed tomography, X-ray