Fast three-dimensional superimposition of cone beam computed tomography for orthopaedics and orthognathic surgery evaluation

Abstract

The aim of this study was to validate a method for fast three-dimensional (3D) superimposition of cone beam computed tomography (CBCT) in growing patients and adults (surgical cases). The sample consisted of CBCT scans of 18 patients. For 10 patients, as the gold standard, the spatial position of the pretreatment CBCT was reoriented, saved as a reoriented volume, and then superimposed on the original image. For eight patients, four non-growing and four growing, the pre- and post-treatment scans were superimposed. Fast voxel-based superimposition was performed, with registration at the anterior cranial base. This superimposition process took 10–15 s. The fit of the cranial base superimposition was verified by qualitative visualization of the semi-transparent axial, sagittal, and coronal cross-sectional slices of all corresponding anatomical structures. Virtual 3D surface models of the skull were generated via threshold segmentation, and superimposition errors in the reoriented models and the results of treatment for the treated cases were evaluated by 3D surface distances on colour-coded maps. The superimposition error of the spatial reorientation and for growing and non-growing patients was <0.5 mm, which is acceptable and clinically insignificant. The voxel-based superimposition method evaluated was reproducible in different clinical conditions, rapid, and applicable for research and clinical practice.

Reliability of three-dimensional anterior cranial base superimposition methods for assessment of overall hard tissue changes: A systematic review

“…Pre-and posttreatment images were registered on the anterior cranial base surface on all studies, 3,7,12,16,21,25 and one was also superimposed on the left zygomatic arch. 12 …”

“…A third study 3 that used a sample of CBCT images of 18 patients also assessed the voxel-based method. A total of 10 patients were used as a reference standard, reorienting the spatial position of the pretreatment CBCT volume and then superimposing on the original image.…”

“…It is known that the further the region of interest is relative to the superimposition structures, the larger the theoretical error of measurement. Weissheimer et al 3 also tested the voxel-based method, and their results revealed that distances in the anterior cranial base between registered surface scans were ,0.5 mm for most regions, indicating reliable superimposition. Nevertheless, the statistical analysis was not reported and therefore their conclusion should be taken warily.…”

“…[1][2][3] Conventional lateral cephalometric radiographs have proven to be an invaluable part of initial and final orthodontic records to quantify and determine craniofacial growth changes and effects of orthodontic treatment. 1,4 However, two-dimensional (2D) cephalometric radiographs suffer from a number of inherent flaws, such as errors generated because of inadequate patient head position, alignment of the imaging device, inherent geometric distortions, and differential magnification created by projection distance and beam divergence.…”

“…[12][13][14] One of the main challenges of 3D superimposition of serial images is to understand that linear/angular measurements in 2D and 3D images are not directly comparable because of differences in size, shape, and relative spatial location of the skeletal, dental, and soft tissue between the two imaging systems. 4,15 The following three general methods of 3D cephalometric superimposition have been published and used for clinical diagnosis and assessment of orthodontic treatment outcomes: (1) voxel based, 3,4,[16][17][18][19] (2) landmark based, 7,20 and (3) surface based. 4,21 A review addressing the 3D CBCT superimposition methods was published in 2015.…”