Individual 3-D image prototyping models for orbital reconstruction

Objective To fabricate a rapid prototyping(RP) 3-D image models for individual reconstruction of orbital bony loss. Methods The skull was placed on a helical CT scanner table and the Frankfort plane was perpendicular to the table. The CT data was obtained by a Aquilion (TOSHIBA, Japan) with 1 mm thickness section in spiral mode. By adjusting of CT threshold value and pixels in order to stack the segmental defects, we obtained an approximate 3-dimension visual model of the scanned skull using MedGraphics software. An orbital RP model based on the dataset of the 3-dimension visual model was fabricated by RP machine. Both 3-dimension visual model and RP model were measured against the skull with several anatomic landmarks to examine the accuracy of the models, and the errors were analysed. Results Integrity precision rapid RP models of the orbital region were reconstructed. The anterior orbital rim, middle orbital section and posterior orbital section were all fabricated. Optic foramen, superior orbital fissure, infraorbital foramen ,inferior orbital fissure, lacrimal sac socket and naso-lacrimal duct were shown clearly. But some fine hole and slot, such as the anterior ethmoidal foramen, posterior ethmoidal foramen and zygomaticofrontal suture were not obviously seen. The mean difference between the 3-dimension visual model and the skull was 0.10±1.02mm. For the RP and dry skull, the mean difference was 0.22±1.04mm. There were no statistical differences between them. Conclusions Integrity precision orbital RP models were fabricated which fulfilled the requirements of the individual reconstruction with bony orbital pathologic changes. The keys to fabricate the precision orbital RP models included a closer cooperation between the surgeon and engineer, thin CT slice in 1mm thick and an appropriated threshold value. Better results for the orbital deformities should be achieved for the contour of orbital region or eye function.