Study On The Orbital Volume Growth By Spiral CT

Objective To study the orbital volume growth and its relation with gender, age, the distance of interzygoma and orbital cavity depth by low-dose CT and establish CT measurement criteria of orbital volume and explore their clinical usefulness.Methods Scans were retrospectively reviewed by two observers unaware of the mAs setting used. Diagnostic image quality was assessed by scoring for three anatomical structures: optic nerve, extraocular muscles, uncinate process. 123 patients (64 males, 59 females) underwent low-dose CT scanning, The measurements were performed in the original or reconstructive CT images, including orbital volume, the length of globe anterioposterior axis, horizontal transverse axis, the distance of interzygoma, orbital cavity depth. The orbital volume difference among groups of age and gender were analyzed, The correlation between orbital volume and the distance of interzygoma, orbital cavity depth were estimated.Results Radiation doses for routine sinus CT can be reduced by 50% for the evaluation of normal structures without seriously jeopardizing image quality. A strong linear correlation was observed between age and orbital volume (r=0.817, p<0.05) under 14 years, orbital volume in man is bigger than in woman after 14 years. A linear correlation was also found between orbital volume and the distance of interzygoma (r=0.624, p<0.01). The ratio of eyeball/orbit descending with age.Conclusion This study provides quantitative data, in normal subjects of different ages on the orbital volume and showes the ratio of eyeball/orbit descending with age. These data may serve as a basis for further studies on the morphological changes of eyeball and orbit in various orbital diseases.