Orbital Volume Measurement In Alive Body Using Three-dimensional CT And Its Clinical Significance

Objective: To confirm accurancy of three-dimensional CT for measurement of orbital volume. To explore the correlation between the enlargment of orbital volume and enophthalmos In blow-out fracture; the correlation between the volume of orbital tumor and exophthalmos by three-dimensional CT.Method: First, a comparetive study between the direct measurement and the three-dimensional CT measurement was carried out on fifteen orbits of six adult skull samples. Second, we collected 10 patients with orbital blow-out fracture and 11 patients with orbital tumor, using their normal orbital as controls. We measured their orbital and tumor volume by three-dimensional CT, measured the enophthalmos or exophthalmos by the Hertel exophthalmeter. Statistical analysis was carried out In these data.Result:1. No significant difference was detected between the results of the direct measurement and the three-dimensional CT measurement. The measuring guidelines of the orbital three-dimensional CT measurement are utility and reliable, may allow to reflect really the shape and size of the orbit.2. The orbital volume In patients with blow-out fracture was significantly Increased compared with that of normal controls, there were highly correlation between enophthalmos and enlargment of orbital volume (r=0. 982, P<0. 01). the linear regression equation about enophthalmos (y) and the enlargment orbital volume(x) Is y=0. 171+0. 776x. (P<0. 01)3. There were highly correlation between exophthalmos and tumor volume In patients with orbital tumor (r=0. 888, P<0. 01) ; similarly, there were highly correlation between the enlargment of orbital volume and tumor volume(r=0.843, P<0.01).the linear regression equation about exophthalmos (y), tumor volume (xj and the enlargment of orbital volume Is y=0. 212+0. 794x,-0. 255x2 (P<0. 02) .Conclusion: The results of the orbital three-dimensional CT measurement Is more accurate and precise, the method can satisfied the clinical needs of orbital measurement. For a 1ml Increment In orbital tumor, there Is a corresponding exophthalmos Increment of 0. 8mm on the Hertel exophthalmeter; for a 1ml increment in bony volume, there is a corresponding enophthalmos decrement of 0.8mm on the Hertel exophthalmeter. Thus indicating the need for surgical correction.