IntroductionThis article reports experience relating to the measurement of orbital volume by means of cone beam computed tomography (CBCT) and Cranioviewer program software in patients who have undergone enucleation and orbital implantation.Patients and MethodsCBCT scans were made in 30 cases, 10 of which were later excluded because of various technical problems. The study group therefore consisted of 20 patients (8 men and 12 women). The longest follow-up time was 7 years, and the shortest was 1 year. In all 20 cases, the orbital volume was measured with Cranioviewer orbital program software. Slices were made in the ventrodorsal direction at 4.8 mm intervals in the frontal plane, in both bony orbits (both that containing the orbital implant and the healthy one). Similar measurements were made in 20 patients with various dental problems. CBCT scans were recorded for the facial region of the skull, containing the orbital region. The Cranioviewer program can colour the area of the slices red, and it automatically measures the area in mm.ResultsIn 5 of the 20 cases, the first 4 or all 5 slices revealed that the volume of the operated orbit was significantly smaller than that of the healthy orbit, in 12 cases only from 1 to 3 of the slices indicated such a significant difference, and in 3 cases no differences were observed between the orbits. In the control group of patients with various dental problems, there was no significant difference between the two healthy orbits. The accuracy of the volume measurements was assessed statistically by means of the paired samples t-test.SummaryTo date, no appropriate method is avaliable for exact measurement of the bony orbital volume, which would be of particular importance in orbital injury reconstruction. However, the use of CBCT scans and Cranioviewer orbital program software appears to offer a reliable method for the measurement of changes in orbital volume.
The adaptation of quadrilateral analysis can provide accurate 3D characterization of the morphology of the lower face and the floating norm based on millimeter values, which is practical for surgeons. As the 3D extension of quadrilateral analysis could provide references of the lower face, which might be an accurate 3D approach for presurgical planning, the further investigation in bigger sample would be relevant in the practice.
Although some articles have already assessed the reliability of three dimensional (3D) cephalometric landmarks, but the results were questionable because most of them analized the landmarks using linear or angular measurements instead of the coordinates. Therefore, the aim of this study was to eliminate the mistakes of the 3D landmark selection by the means of statistics based landmark selection model and a practically useable decision tree. In our study three medical doctors -the "examiners" -identified 55 particular landmarks on 30 non-orthodontic Cone Beam Computed Tomography (CBCT) scans using the Cranioviewer software. The identification process has been done three times in order to increase the accuracy. Intraclass correlation coefficient and analysis of variance were applied to decrease the intra-and inter-examiner variability, while standard deviation (SD) and mean absolute difference (MAD) were used for characterization of landmark locations. Inaccurate coordinates were grouped according to both the intra-and the inter-examiner deviation of ≥ 1mm and the difference between the two statistical methods (SD vs. MAD). The intra-examiner identification errors were ≤ 1mm. The inter-examiner SD and MAD were ≥ 1mm except in cases of four landmarks with MAD and in cases of two with SD. Inter-examiner deviations were always higher than intra-examiner deviations. Standard deviation distorted more than mean absolute difference. Based on these result we have created a decision tree for landmark selection. Most of the coordinates belong to the landmarks can be reliably adapted to 3D cephalometric, but the statistics based decision model could be useful to eliminate mistakes in landmark selection as well. Since, the statistical rules are summarized like a decision tree it can be easily used in practice.
Cranioviewer 3D craniofacial cephalometric program is suitable for volumetric analysis of the bony orbit on cone-beam computed tomography files. The development of the orbit can be influenced by extraocular muscle movements.
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