Precision and reliability of Dolphin 3-dimensional voxel-based superimposition.

Abstract

Superimposition of 2 cone-beam computed tomography images is possible by using landmarks, surfaces, or density information (voxel-based). Voxel-based superimposition is automated and uses the most image content, providing accurate results. Until recently, this superimposition was extremely laborious, but a user-friendly voxel-based superimposition has recently been introduced. Our aim was to evaluate the precision and reliability of Dolphin 3-dimensional voxel-based superimposition (Dolphin Imaging, Chatsworth, Calif). This was a retrospective study using existing scans of 31 surgical orthodontic patients with a mean age of 21±8years (range, 15-47years). Each patient had a presurgical and a postsurgical scan taken within 12months. Surgical patients were used since the reference area for superimposition was not affected by growth or surgical procedures. The volumes were superimposed using voxel-based methods from Dolphin Imaging and a tested method used previously. This method uses 2 open-source programs and takes about 3hours to complete, whereas the Dolphin method takes under 5minutes. The postsurgical scan was superimposed on the presurgical scan at the cranial base. Postsurgical registrations forboth methods were compared with each other using the absolute closest point color map, with emphasis on 7 regions (nasion, A-point, B-point, bilateral zygomatic arches, and bilateral gonions). Intraclass correlations showed excellent reliability (0.96). The mean differences between the 2 methods were less than 0.21mm (voxel size, 0.38). The smallst difference was in the left zygomatic area at 0.09±0.07mm, and the largest was in the right gonial region at 0.21±0.13mm. Dolphin 3-dimensional voxel-based superimposition, a fast and user-friendly method, is precise and reliable.