Three-Dimensional Cephalometric Landmarking and Frankfort Horizontal Plane Construction: Reproducibility of Conventional and Novel Landmarks

Abstract

In some dentofacial deformity patients, especially patients undergoing surgical orthodontic treatments, Computed Tomography (CT) scans are useful to assess complex asymmetry or to plan orthognathic surgery. This assessment would be made easier for orthodontists and surgeons with a three-dimensional (3D) cephalometric analysis, which would require the localization of landmarks and the construction of reference planes. The objectives of this study were to assess manual landmarking repeatability and reproducibility (R&R) of a set of 3D landmarks and to evaluate R&R of vertical cephalometric measurements using two Frankfort Horizontal (FH) planes as references for horizontal 3D imaging reorientation. Thirty-three landmarks, divided into “conventional”, “foraminal” and “dental”, were manually located twice by three experienced operators on 20 randomly-selected CT scans of orthognathic surgery patients. R&R confidence intervals (CI) of each landmark in the -x, -y and -z directions were computed according to the ISO 5725 standard. These landmarks were then used to construct 2 FH planes: a conventional FH plane (orbitale left, porion right and left) and a newly proposed FH plane (midinternal acoustic foramen, orbitale right and left). R&R of vertical cephalometric measurements were computed using these 2 FH planes as horizontal references for CT reorientation. Landmarks showing a 95% CI of repeatability and/or reproducibility > 2 mm were found exclusively in the “conventional” landmarks group. Vertical measurements showed excellent R&R (95% CI < 1 mm) with either FH plane as horizontal reference. However, the 2 FH planes were not found to be parallel (absolute angular difference of 2.41°, SD 1.27°). Overall, “dental” and “foraminal” landmarks were more reliable than the “conventional” landmarks. Despite the poor reliability of the landmarks orbitale and porion, the construction of the conventional FH plane provided a reliable horizontal reference for 3D craniofacial CT scan reorientation.

Automatic Three-Dimensional Cephalometric Landmarking via Deep Learning

“…Interestingly, landmarks localized on the craniofacial foramens showed excellent accuracy results, with 99.1% ( n = 220) of the landmarks located within 2mm from the reference. These “novel” landmarks, which could not be localized on 2D cephalograms, could be used in future 3D cephalometric analyses (Naji et al 2014; Lim et al 2019; Dot et al 2021).…”

“…The reference data used to train and test our DL model were either the single annotations ( n = 178) or the average of the 6 annotations ( n = 20, test set only). The scans annotated six times were part of a previous repeatability and reproducibility (R&R) study, which could be used to evaluate intra and interobserver variability of the reference test (Dot et al 2021). In the test set, some CT scans showed missing dental landmarks: 16O ( n = 1), 26O ( n = 1), 31A ( n = 2), 31E ( n = 2), 36O ( n = 1), 46O ( n = 2).…”

“…Cephalometric analysis is used to measure the deviation of the skeletal and dentoalveolar parts of the maxilla and the mandible in relation to the skull base, using measurements between specific landmarks placed on each of these structures. The reference method for 3D cephalometric analysis is manual landmarking, which requires around 15 minutes for a highly experienced and trained operator (Hassan et al 2013; Dot et al 2021).…”

Effects of an Online Supervised Exercise Training in Children with Obesity during the COVID-19 Pandemic

“…WC was measured using a flexible inch tape, in the horizontal plane midway between the lowest ribs and the iliac crest [ 34 , 35 ]. The measurement was taken on the child in an upright position, without shoes, with their heels together and toes apart, hands at sides, aligning the head in the Frankfort horizontal plane [ 36 ]. BMI was calculated as body weight (kilograms) divided by height (meters squared), and was transformed into BMI z-scores using WHO reference values [ 37 ].…”

Correlación tomográfica de la distancia transversal mandibular y la inclinación de molares inferiores permanentes

“…Sin embargo, es bastante aceptable utilizarlo como referencia horizontal incluso para medidas verticales porque no presentan variaciones significativas. Otro plano que se considera en algunos estudios es el plano sagital medio definido por Nasion (Na), Basion (Ba) y Espina nasal anterior (ANS) (Cevidanes et al 2009;Dot et al 2021).…”