3D Cephalometric Analysis Research Articles

3D Cephalometric Normality Range: Auto Contractive Maps (ACM) Analysis in Selected Caucasian Skeletal Class I Age Groups.

The objective of this paper is to define normal values of a novel 3D cephalometric analysis and to define the links through an artificial neural network (ANN). Methods: One hundred and fifteen CBCTs of Class I young patients, distributed among gender-adjusted developmental groups, were selected. Three operators identified 18 cephalometric landmarks from which 36 measurements were obtained. The repeatability was assessed through the ICC. Two-dimensional values were extracted by an automatic function, and the mean value and standard deviation were compared by paired Student’s t-tests. Correlation coefficient gave the relationships between 2D and 3D measurements for each group. The values were computed with the ANN to evaluate the parameters normality link and displayed by Pajek software. Results: The ICC assessed an excellent (≥0.9) repeatability. Normal values were extracted, and compared with 2D measurements, they showed a high correlation on the mid-sagittal plane, reaching 1.00, with the lowest 0.71 on the lateral plane. The ANN showed strong links between the values with the centrality of the go-sagittal plane compared to the rest. Conclusions: The study provides a set of 3D cephalometric values obtained by the upper and lower 95% CI for the mean divided into the developmental stage subgroups. The two-dimensional measurements showed variable concordance, while the ANN showed a centrality between the parameters.

A three-dimensional cephalometric analysis of Japanese adults and its usefulness in orthognathic surgery: A retrospective study

This study aimed to establish a three-dimensional (3D) cephalometric analysis of craniofacial morphology and discuss its theoretical usefulness in orthognathic patients.Cone-beam computed tomography (CBCT) images of Japanese subjects with skeletal Class I malocclusion before treatment were selected from among 1000 patients so that samples matched a historic 2D cephalometric cohort with normal occlusion using propensity score matching. In each CBCT image, 67 3D measurements were calculated based on manually identified landmarks. The mean and standard deviation of the measurements were calculated and used as the normative range for each sex. To confirm the usefulness of the 3D measurements, pre- and post-treatment CT data of nine jaw deformity patients who underwent orthognathic surgery with two-dimensional planning (2DP) in the past were used. Pre- and post-treatment CT values were evaluated with a paired t-test as well as a Z-score, which was calculated using the aforementioned normative range, and then categorized into five groups (“deteriorated”, “no improvement”, “over-treatment”, “no change”, “improvement”) with −1 < Z-score < 1 considered normal.Fifty-six patients were matched to normal skeletal 1 subjects. The normative range of 67 items indicating 3D craniofacial morphology of the Japanese was calculated. Postoperatively, the horizontal position of the pogonion to the mid-sagittal plane significantly decreased (p = 0.043) and “improved”; however, the ramus axis on the right side significantly increased (p = 0.005) and “deteriorated”. Maxillary yaw and the horizontal position of the gonion also tended to “deteriorated”.The normative range for the 3D cephalometric analysis in Japanese has been established. Given findings of deteriorated maxillomandibular yawing after surgery when using conventional 2DP, 3D cephalometric measurements should be used when planning jaw positions after surgery for orthognathic patients.

Міофункціональні апарати в комплексному лікуванні пацієнтів із зубощелепними аномаліями на тлі шкідливих звичок

The aim of the study. Increasing the effectiveness of complex treatment of patients with a pathological bite through orthodontic treatment, impact on masticatory and facial muscles, conscious elimination of oral habits. Research methods. 30 people aged 9–12 years with acquired maxillomandibular anomalies against the background of oral habits and 15 people of the comparison group were examined and treated. Group I patients (15 people) had orthodontic treatment and elimination of oral habits, and group II patients (15 people) received treatment supplemented with myofunctional devices and myogymnastics. We studied the results of computer tomograms, performed stereotopometric analysis (threedimensional cephalometry), and determined the thickness of the masticatory muscles in symmetrical areas of the face. Secret questionnaires were administered to patients in order to identify stress factors that affect the body, and the relationship between the presence of a stress factor and the appearance of changes in cephalometric indicators was determined. The study was conducted before treatment, after 6 months and after 12 months after the start of active orthodontic treatment. Scientific novelty. Clinical studies have shown that all patients have oral habits that lead to changes in the maxillofacial system. The results of the questionnaire showed that 96.6 % of the examined patients associate them with the presence of stressful factors.The results of the examination, cephalometric analysis and photo report confirm the presence of pronounced disproportions from one jaw or symmetrical parts of the face, shortening of the lower third of the face; prove the presence of an acquired rather than congenital deformation of the facial skeleton, which is combined with a change in the thickness of the masticatory muscles on the side of the deformation. The results of the comparative analysis after 6 and 12 months indicate a more pronounced positive trend towards the normalization of clinical indicators and data of cephalometric analysis in patients of the II group. Conclusions. Oral habits are directly proportional to stress factors, which, according to the results of the examination, are present in 96.6 % of all patients. 3D cephalometric analysis should be included in the mandatory methods of diagnosis of acquired deformities of the maxillofacial area before and at the stages of complex treatment. The results of clinical, x-ray research methods and cephalometric analysis indicate the need to use devices that correct the work of the muscular apparatus and myogymnastics in the complex treatment of patients with maxillomandibular anomalies on the background of oral habits. Key words: oral habits, cephalometric analysis, orthodontic treatment, myofunctional devices, myogymnastics.

Loeys-Dietz and Shprintzen-Goldberg syndromes: analysis of TGF-β-opathies with craniofacial manifestations using an innovative multimodality method

BackgroundElevated transforming growth factor-beta (TGF-β) signalling has been implicated in the pathogenesis of Loeys-Dietz syndrome (LDS) and Shprintzen-Goldberg syndrome (SGS). In this study, we provide a qualitative and quantitative analysis...

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

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.

Three-dimensional analysis of condylar remodeling and skeletal relapse following LeFort-I osteotomy: A one-year follow-up bicenter study

The aim of the study was to quantify the postoperative condylar remodeling after Le Fort I surgery.Patients treated with a Le Fort I osteotomy were investigated. CBCT scans were acquired preoperatively, one week and one year postoperatively. A preoperative 3D cephalometric analysis was performed on the preoperative CBCT. Surgical movements were quantified using a voxel-registration based method (OrthoGnaticAnalyser). After rendering of the condyles from the CBCT, a volumetric analysis was performed. The correlation between the surgical movement of the maxilla and the postoperative condylar volume changes was determined with analysis of variance. ResultsA total of 45 subjects were included in this study. 47 of 90 condyles (52%) showed a mean volume reduction of 93 mm3 (4.9 volume-%) postoperatively. The maxilla was impacted in 12 patients (2.44 ± 2.49 mm) and extruded in 33 patients (1.78 ± 1.29 mm). The maxillary impaction group showed a volume reduction of 50 ± 122 mm3 and the extrusion group showed a mean volume gain of 21 ± 139 mm3 (p = 0.028). ConclusionClinicians should be aware of potential condylar remodeling following solitary Le Fort I osteotomies, particularly in female patients with maxillary impaction.

Three-dimensional analysis of craniofacial morphology in patients with pycnodysostosis.

To perform a 3D cephalometric analysis of the craniofacial characteristics of patients with pycnodysostosis and compare this with a matched control group. This cross-sectional descriptive study assessed eight CBCTs obtained in patients with pycnodysostosis (4 males, 4 females, mean age: 31.8 years). Eight Danish patients with pycnodysostosis were seen at the University's Orthodontic Clinic. All CBCTs were analysed using the Mimics 21.0 software (Materialise®, Belgium) and compared with a control group (6 males, 8 females, mean age: 33.6 years). Interclass correlation coefficient showed excellent intra-rater reliability (> 0.93). All measurements in the 3D cephalometric analysis revealed statistical significance (P<.05) when compared with controls. Patients with pycnodysostosis generally had significantly smaller maxilla in the transverse (P<.001), sagittal (P<.002) and vertical (P<.001) dimensions. Their mandibles were also smaller vertically (P<.001) and in length (P<.001). Gonial angle was significantly larger than controls (P<.001), while mandibular volumes were considerably smaller (P<.001). Patients with pycnodysostosis have significantly smaller jaws in the vertical, sagittal and transverse dimensions compared with controls. Furthermore, the gonial angle was significantly larger, while the volume of the mandible was significantly smaller.

Modern 3D cephalometry in pediatric orthodontics-downsizing the FOV and development of a new 3D cephalometric analysis within a minimized large FOV for dose reduction.

Dose reduction achieved by downsizing the field of view (FOV) in CBCT scans has brought no benefit for pediatric orthodontics, until now. Standard 2D or 3D full-size cephalometric analyses require large FOVs and high effective doses. The aim of this study was to compare a new 3D reduced-FOV analysis using the Frankfurt horizontal (FH) plane as reference plane with a conventional full-size analysis using the Sella-Nasion (S-N) plane as reference plane. Thirty-eight CBCT data sets were evaluated using full- and reduced-FOV analysis. The measurements of a total of 20 skeletal and dental standard 3D full-size variables were compared with the measurements of 22 corresponding 3D reduced-FOV variables. Statistical analysis was performed to prove mathematic relation between standard and alternative variables. Regression analyses were carried out. Coefficients of determination (R2) between 0.15 and 0.95 (p < 0.001-0.055) were described. All variables showed obvious relations of different strength except for SNA and its alternative Po_R-Or_R-A (°) (R2 = 0.15, p = 0.055), but a second variable Ba_A (mm) showed stronger relation (R2 = 0.28, p = 0.003). All standard variables related to the reference plane S-N could be described with alternative variables related to the FH. Further research should define more reliable landmarks for coordinate systems and reference points. Minimized large FOVs meet the demand of 3D cephalometric analyses and enable the application of CBCT scans in pediatric orthodontic patients in many specific indications. Dose reduction is accompanied by increasing access to all the advantages of 3D imaging over 2D imaging.

Surgery-first Approach Using Virtual Setup for the Treatment of Dentoskeletal Deformities

Purpose: to evaluate the accuracy of Computer-Assisted Surgical Simulation (CASS) in the surgery-first treatment of Dentoskeletal Deformities. Materials and methods: Ten patients with different dentoskeletal deformities, were involved in this study. Preoperative clinical evaluation, photographs, study models, and 2D lateral cephalometry were adopted for orthodontic evaluation if the case is eligible for the surgery- first approach. MSCT (in DICOM format), and optical scanning of the study model (in STL format) were adopted and imported to MIMICS software for construction of virtual 3D composite model. The virtual surgical simulation was performed on the light of the preclinical evaluation and preoperative records, then the occlusal splints and surgical guides were designed to transfer the planned surgery to the reality. For evaluation of the virtual surgical simulation 3D cephalometric analysis for the planned and postoperative readings. Result: No significant difference between the planned and postoperative 3D cephalometric analysis. Conclusion: Surgery First cases needed thorough orthodontic and surgical planning. Virtual surgical planning with subsequent designed occlusal splints and cutting guides allow for accurate transfer of the virtual planning into reality.

Construction and validity of a midsagittal plane based on the symmetry of a 3-dimensional model of the relevant cranial base

The midsagittal plane (MSP) is the foundation for 3-dimensional (3D) cephalometric analyses. This article aimed to provide a protocol to construct a reliable and accurate MSP for 3D cephalometric craniofacial analysis. Cone-beam computed tomography data of 16 adult patients without obvious bilateral asymmetry were collected. The model of the anterior cranial base and sphenoid bone was constructed, and the candidate MSP was determined on the basis of the symmetry of this model. Intraclass correlation coefficients were used to assess intra- and interexaminer reliability of the candidate MSP. To investigate the accuracy of this candidate MSP, we constructed a true plane of symmetry of craniomaxillofacial structure and a control plane on the basis of 3 cranial midline points. We then compared these with the candidate MSP. This candidate MSP resembled the true plane of symmetry with all the mean absolute errors<1mm, and all the absolute errors for the candidate MSP were significantly smaller than the control plane (P≤0.002). The relative intra- and interexaminer reliability for this candidate MSP was almost perfect (intraclass correlation coefficients>0.9). The candidate MSP constructed using this method was thought to be reliable and accurate for 3D cephalometric analysis in patients without obvious cranial asymmetry.

Three-Dimensional Computer-Assisted Orthognathic Surgery: Traditional Hybrid Versus Full Digital Planning Models.

Three-dimensional (3D) computer-aided planning has truly revolutionized orthognathic surgery (OGS) treatment, but no study has compared the traditional hybrid and full 3D digital planning models. This study compared these virtual planning models in the treatment of asymmetric maxillomandibular disharmony. Young adult patients with an asymmetric skeletal class III deformity who underwent 3D computer-aided 2-jaw OGS using hybrid (alginate dental impression, 2D cephalometric tracings, manual-guided stone model surgery, occlusion setup, and splint fabrication; n = 30) or full digital (laser-scanned dentition, 3D cephalometric tracings, virtual-based occlusion setup and surgery, and computer-generated surgical splint; n = 30) planning models were consecutively recruited. Preoperative and postoperative 3D cephalometric analyses (dental relation, skeletal assessments based on sagittal and frontal views, and soft tissue evaluations) were adopted for intragroup and intergroup comparisons. Postoperative patient-perceived satisfaction with facial appearance was also recorded. Both hybrid and full digital planning groups had significant (all P < 0.05) improvements after surgery with respect to facial convexity, incisor overjet, and frontal symmetry parameters. The full 3D digital planning-based OGS treatment had similar (all P > 0.05) 3D cephalometric-derived outcomes (preoperative, postoperative, and treatment-induced change data) and patient-perceived outcomes compared with the traditional hybrid 3D planning method. For the decision-making process in selecting the planning model, multidisciplinary teams could consider additional parameters such as patient comfort, storage needs, convenience for data reuse, overall planning time, availability, and costs.

Development of the Algorithm for 3D Cephalometric Analysis of Planning Surgical Interventions for Congenital and Acquired Defects and Deformities of the Facial Skeleton

Development of the Algorithm for 3D Cephalometric Analysis of Planning Surgical Interventions for Congenital and Acquired Defects and Deformities of the Facial Skeleton

Landmark-Based Versus Voxel-Based 3-Dimensional Quantitative Analysis of Bimaxillary Osteotomies: A Comparative Study

We compared the accuracy of landmark-based and voxel-based 3-dimensional (3D) analysis to quantify the osseous movements of the maxilla and mandible after bimaxillary osteotomy. Cone beam computed tomography (CBCT) scans of 15 patients who had undergone bimaxillary osteotomy were randomly selected from the database. Before surgery, CBCT scanning was performed and an individualized 3D virtual surgical plan made for all patients. During surgery, the mandibular and maxillary segments were positioned as planned using 3D-milled interocclusal splints. At 1week after surgery, a postoperative CBCT scan was acquired. All pre- and postoperative CBCT data were rendered in 3 dimensions. The 3D virtual head models were superimposed on the cranial base. The 3D surgical movements of the maxilla and mandible were quantified using conventional landmark-based 3D cephalometric analyses and voxel-based 3D analyses (OrthoGnathicAnalyser). This process was performed by the same observer 3 times. The intraclass correlations and Bland-Altman plots were computed to quantify the measurement errors and reproducibility of both methods. High intraclass correlation coefficients were found for both methods. The voxel-based analyses yielded a higher correlation concerning the maxilla and distal mandible (r=0.98) compared with the landmark-based cephalometric analyses (r=0.90). The use of voxel-based 3D analyses in the quantification of osseous movements was more reliable and reproducible than the use of conventional landmark-based 3D analyses.

Automatic three-dimensional cephalometric annotation system using three-dimensional convolutional neural networks: a developmental trial

ABSTRACTAutomatic annotation for three-dimensional (3D) cephalometric analysis has been limited by computational complexity and computing performance. The purpose of this study was to evaluate the accuracy of our newly-developed automatic 3D cephalometric annotation system using a deep learning algorithm. Our model system mainly consisted of a 3D convolutional neural network and image data resampling. Discrepancies between the referenced and predicted coordinate values in three axes and in 3D distance were calculated to yield prediction errors of 3.26, 3.18, and 4.81 mm (for three axes) and 7.61 mm (for 3D). Moreover, there was no difference (p > 0.05) among the landmarks of three groups (midsagittal plane, horizontal plane and mandible). Although our 3D convolutional neural network-based annotation system could not achieve the level of accuracy demanded by immediate clinical applications, it can nevertheless serve as an initial approximate guide to landmarks, thus reducing the time needed for annotation.

The Drilling Guiding Templates and Pre-Bent Titanium Plates Improves the Operation Accuracy of Orthognathic Surgery With Computer-Aided Design and Computer-Aided Manufacturing Occlusal Splints for Patients With Facial Asymmetry.

Facial asymmetry is a common maxillofacial deformity which requires surgery to recover the 3-dimensional relationship of bones. The computer-aided design and computer-aided manufacturing (CAD/CAM) has been developed and applied to improve orthognathic analysis and surgery design. How to accurately realize the preoperative design of orthognathic surgery with CAD/CAM occlusal splints during operation remains a big problem. In this study, 24 consecutive patients with facial asymmetry were recruited and assigned to 2 groups. For Group A, CAD/CAM was applied to designing and producing not only the occlusal splints, but also the drilling guiding templates and pre-bent titanium plates, and for Group B CAD/CAM was applied for occlusal splints only. Postoperative clinical examinations, symmetry evaluation through 3D cephalometric analysis, accuracy comparison using color distance maps and quantitative accuracy analysis were performed. Symmetry evaluation showed that patients of both groups achieved improved facial symmetry after surgery. The color distance maps and quantitative accuracy analysis together demonstrated significantly less difference found between virtual simulated surgery and postoperative CT scan data in Group A than in Group B. In conclusion, by navigation with the drilling guiding templates and pre-bent titanium plates, the facial symmetry for patients with facial asymmetry was successfully restored after orthognathic surgery, same as applying CAD/CAM occlusal splints only. However, the drilling guiding templates and pre-bent titanium plates would provide a more accurate performance according to preoperative simulation, especially for proximal mandibular segments.

A computer-assisted optimization approach for orthognathic surgery planning

Abstract Orthognathic surgery is used to treat misaligned jaws in adults by repositioning them. Intervention planning has to take into account different clinical, anatomical, functional, and aesthetic parameters to determine the optimal position. Current planning systems usually present 3D surface models obtained from a CT or Cone-Beam scan of the patient. The surgeon then interactively positions the upper and lower jaw. Thus, the surgeon can manually optimize anatomical aspects but has to consider functional and aesthetic effects simultaneously, which may be error-prone. We are developing a computer-assisted planning system which generates an optimized position for both jaws based on different analyses (cephalometric, plaster model, photostat) of the head, using a gradient descent algorithm. For this purpose, landmarks are interactively identified on a 3D surface representation. The system is developed as a plugin for MITK utilizing a knowledge base realized in the sematic web standard RDFS, which is queried with SPARQL requests. In a preliminary evaluation with five different cases we compare the automatically generated planning proposal with the planning results of a maxillofacial expert (ground truth). Good general agreement is observed, although more research for the identification and development of 3D cephalometric analyses is needed.

In vivo reliability of 3D cephalometric landmark determination on magnetic resonance imaging: a feasibility study.

3D cephalometric analysis performed on cone-beam or multi-slice computed tomography (CBCT, MSCT) has superior diagnostic value compared to 2D cephalometry based on radiographs. However, this comes at the expense of increased radiation risks for the predominantly young patients. Magnetic resonance imaging (MRI) has the potential to overcome this diagnostic dilemma but has not been established for 3D cephalometry so far. Since landmark reliability forms the basis for 3D cephalometry, we evaluated the in vivo reliability of established 3D landmarks using MRI. Sixteen orthodontic patients underwent MRI at 3Tesla using a 0.5 mm 3D sequence. On each MRI scan, 44 cephalometric landmarks were determined. Image analysis was performed twice by two independent observers. Intra- and inter-rater agreement was assessed by mean measurement errors and intraclass correlation coefficients (ICCs). Measurement errors were calculated as Euclidean distances and distances for x-, y-, and z-coordinates. Overall, MRI-based 3D cephalometric landmarks revealed a high reliability comparable to prior in vivo studies using CBCT/MSCT. Intra- and inter-rater ICCs were consistently higher than 0.9. Intra-rater comparisons showed mean measurement differences (ranges) of 0.87mm (0.41-1.63) for rater I and 0.94mm (0.49-1.28) for rater II. Average inter-rater difference was 1.10mm (0.52-2.29). Distinct differences in reliability between the various landmarks were observed, corresponding well with the landmarks' specific shapes. The present study demonstrates that MRI enables reliable determination of 3D cephalometric landmarks in vivo. This study emphasizes the potential of MRI to perform treatment planning and monitoring in orthodontics as well as oral and maxillofacial surgery without radiation exposure.

A 3D cephalometric protocol for the accurate quantification of the craniofacial symmetry and facial growth

BackgroundCephalometric analysis is used to evaluate facial growth, to study the anatomical relationships within the face. Cephalometric assessment is based on 2D radiographic images, either the sagittal or coronal planes and is an inherently inaccurate methodology. The wide availability of 3D imaging techniques, such as computed tomography and magnetic resonance imaging make routine 3D analysis of facial morphology feasible. 3D cephalometry may not only provide a more accurate quantification of the craniofacial morphology and longitudinal growth, but also the differentiation of subtle changes in occlusion. However, a reliable protocol for the computation of craniofacial symmetry and quantification of craniofacial morphology is still a topic of extensive research. Here, a protocol for 3D cephalometric analysis for both the identification of the natural head position (NHP) and the accurate quantification of facial growth and facial asymmetry is proposed and evaluated. A phantom study was conducted to assess the performance of the protocol and to quantify the ability to repeatedly and reliably align skulls with the NHP and quantify the degree of accuracy with which facial growth and facial asymmetry can be measured.ResultsThe results obtained show that the protocol allows consistent alignment with the NHP, with an overall average error (and standard deviation) of just 0.17 (9.10e-6) mm, with variations of 0.21 (2.77e-17) mm in the frontonasal suture and 0.30 (5.55e-17) mm in the most prominent point in the chin. The average errors associated with simulated facial growth ranged from 1.83 to 3.75% for 2 years’ growth and from − 9.57 to 14.69% for 4 years, while the error in the quantification of facial asymmetry ranged from − 11.38 to 9.31%.ConclusionsThe protocol for 3D skull alignment produces accurate and landmark free estimation of the true symmetry of the head. It allows a reliable alignment of the skull in the NHP independently of user-defined landmarks, as well as an accurate quantification of facial growth and asymmetry.

Novel method of constructing a stable reference frame for 3-dimensional cephalometric analysis.

Three-dimensional (3D) cephalometric analysis has provided the ability to overcome the limitations of 2-dimensional cephalometrics. However, there is no international standard method for 3D cephalometric analysis yet. Determining the position of the midsagittal plane (MSP) practically is the most important step when constructing a 3D cephalometric reference frame. Recent studies have used several approaches to construct the MSP. In this study, we aimed to determine the true MSP of the skull to establish a stable reference frame for 3D cephalometric analysis. Cone-beam computed tomography data of 12 adult patients were divided into 2 groups: symmetry (n=6) and asymmetry (n=6). The anterior cranial base region model and its mirror model were registered and used to determine the MSP to prevent any influence of the degree of symmetry on the registration of other parts of the skull, particularly for subjects with severe facial or cranial asymmetry. Intraclass correlation coefficients were used to assess intraexaminer and interexaminer reliabilities of the x, y, and z coordinates of all landmarks measured by 2 investigators. The intraclass correlation coefficient values were greater than 0.9, indicating almost perfect agreement. The candidate reference planes constructed using this novel method were thought to be reliable for 3D cephalometric analysis and may expand its clinical applicability in patients with cranial asymmetry.

3D cephalometric analysis using Magnetic Resonance Imaging: validation of accuracy and reproducibility

The aim of this study was to validate geometric accuracy and in vivo reproducibility of landmark-based cephalometric measurements using high-resolution 3D Magnetic Resonance Imaging (MRI) at 3 Tesla. For accuracy validation, 96 angular and 96 linear measurements were taken on a phantom in 3 different positions. In vivo MRI scans were performed on 3 volunteers in five head positions. For each in vivo scan, 27 landmarks were determined from which 19 angles and 26 distances were calculated. Statistical analysis was performed using Bland-Altman analysis, the two one-sided tests procedure and repeated measures one-way analysis of variance. In comparison to ground truth, all MRI-based phantom measurements showed statistical equivalence (p < 0.001) and an excellent agreement in Bland-Altman analysis (bias ranges: −0.090–0.044°, −0.220–0.241 mm). In vivo cephalometric analysis was highly reproducible among the five different head positions in all study participants, without statistical differences for all angles and distances (p > 0.05). Ranges between maximum and minimum in vivo values were consistently smaller than 2° and 2 mm, respectively (average ranges: 0.88°/0.87 mm). In conclusion, this study demonstrates that accurate and reproducible 3D cephalometric analysis can be performed without exposure to ionizing radiation using MRI.