Three-dimensional analysis of the airway with cone-beam computed tomography

Association among craniofacial morphology, ethnicity, and risk of pediatric sleep-related breathing disorders: A multicenter study

INTRODUCTION

Craniofacial morphology and ethnicity may be risk factors for sleep-related breathing disorder (SRBD) in children but have not yet been assessed in an international multicenter study. The objectives of this study were to assess the association among craniofacial features, self-reported ethnicity, and risk of SRBD in children undergoing orthodontic treatment.

METHODS

Children aged 5-18 years who presented for orthodontic evaluation were enrolled in the United States, South Africa, South Korea, Saudi Arabia, and Japan. The risk of SRBD was defined as answering ≥0.33 positive responses to the Pediatric Sleep Questionnaire. Craniofacial features included measurements in sagittal and vertical dimensions to evaluate the cranial base, maxillomandibular and dental relationships, and nasopharyngeal airway dimensions. Logistic regression was performed to assess the association among craniofacial features, ethnicity, age, body mass index, and risk of SRBD.

RESULTS

Data were obtained from 602 patients from 5 sites. A total of 76 patients (12.6%) had a risk of SRBD. The mean age was 12.5 years. Male gender (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.0-3.4; P = 0.041), Middle Eastern ethnicity (OR, 10.2; 95% CI, 4.1-25.4; P = 0.001), body mass index (OR, 1.1; 95% CI, 1.04-1.10; P = 0.001), gonial angle (OR, 0.91; 95% CI, 0.85-0.98; P = 0.011), and inferiorly positioned hyoid (OR, 1.1; 95% CI, 1.0-1.2; P = 0.002) were significantly associated with the risk of SRBD.

CONCLUSIONS

In an ambidirectional cohort study across 5 sites, male gender, Middle Eastern ethnicity, body mass index, gonial angle, and inferiorly positioned hyoid were associated with the risk of SRBD in children undergoing orthodontic treatment.

Reliability and accuracy of a semi-automatic segmentation protocol of the nasal cavity using cone beam computed tomography in patients with sleep apnea

OBJECTIVES

The objectives of this study included using the cone beam computed tomography (CBCT) technology to assess: (1) intra- and inter-observer reliability of the volume measurement of the nasal cavity; (2) the accuracy of the segmentation protocol for evaluation of the nasal cavity.

MATERIALS AND METHODS

This study used test-retest reliability and accuracy methods within two different population sample groups, from Eastern Asia and North America. Thirty obstructive sleep apnea (OSA) patients were randomly selected from administrative and research oral health data archived at two dental faculties in China and Canada. To assess the reliability of the protocol, two observers performed nasal cavity volume measurement twice with a 10-day interval, using Amira software (v4.1, Visage Imaging Inc., Carlsbad, CA). The accuracy study used a computerized tomography (CT) scan of an OSA patient, who was not included in the study sample, to fabricate an anthropomorphic phantom of the nasal cavity volume with known dimensions (18.9 ml, gold standard). This phantom was scanned using one NewTom 5G (QR systems, Verona, Italy) CBCT scanner. The nasal cavity was segmented based on CBCT images and converted into standard tessellation language (STL) models. The volume of the nasal cavity was measured on the acquired STL models (18.99 ± 0.066 ml).

RESULTS

The intra-observer and inter-observer intraclass correlation coefficients for the volume measurement of the nasal cavity were 0.980-0.997 and 0.948-0.992 consecutively. The nasal cavity volume measurement was overestimated by 1.1%-3.1%, compared to the gold standard.

CONCLUSIONS

The semi-automatic segmentation protocol of the nasal cavity in patients with sleep apnea and by using cone beam computed tomography is reliable and accurate.

CLINICAL RELEVANCE

This study provides a reliable and accurate protocol for segmentation of nasal cavity, which will facilitate the clinician to analyze the images within nasoethmoidal region.

A systematic review of the techniques for automatic segmentation of the human upper airway using volumetric images

The human upper airway is comprised of many anatomical volumes. The obstructions in the upper airway volumes are needed to be diagnosed which requires volumetric segmentation. Manual segmentation is time-consuming and requires expertise in the field. Automatic segmentation provides reliable results and also saves time and effort for the expert. The objective of this study is to systematically review the literature to study various techniques used for the automatic segmentation of the human upper airway regions in volumetric images. PRISMA guidelines were followed to conduct the systematic review. Four online databases Scopus, Google Scholar, PubMed, and JURN were used for the searching of the relevant papers. The relevant papers were shortlisted using inclusion and exclusion eligibility criteria. Three review questions were made and explored to find their answers. The best technique among all the literature studies based on the Dice coefficient and precision was identified and justified through the analysis. This systematic review provides insight to the researchers so that they shall be able to overcome the prominent issues in the field identified from the literature. The outcome of the review is based on several parameters, e.g., accuracy, techniques, challenges, datasets, and segmentation of different sub-regions. Flowchart of the search process as per PRISMA guidelines along with inclusion and exclusion criteria.

Assessment of the accuracy of imaging software for 3D rendering of the upper airway, usable in orthodontic and craniofacial clinical settings

BACKGROUND

Several semi-automatic software are available for the three-dimensional reconstruction of the airway from DICOM files. The aim of this study was to evaluate the accuracy of the segmentation of the upper airway testing four free source and one commercially available semi-automatic software. A total of 20 cone-beam computed tomography (CBCT) were selected to perform semi-automatic segmentation of the upper airway. The software tested were Invesalius, ITK-Snap, Dolphin 3D, 3D Slicer and Seg3D. The same upper airway models were manually segmented (Mimics software) and set as the gold standard (GS) reference of the investigation. A specific 3D imaging technology was used to perform the superimposition between the upper airway model obtained with semi-automatic software and the GS model, and to perform the surface-to-surface matching analysis. The accuracy of semi-automatic segmentation was evaluated calculating the volumetric mean differences (mean bias and limits of agreement) and the percentage of matching of the upper airway models compared to the manual segmentation (GS). Qualitative assessments were performed using color-coded maps. All data were statistically analyzed for software comparisons.

RESULTS

Statistically significant differences were found in the volumetric dimensions of the upper airway models and in the matching percentage among the tested software (p < 0.001). Invesalius was the most accurate software for 3D rendering of the upper airway (mean bias = 1.54 cm³; matching = 90.05%) followed by ITK-Snap (mean bias =  - 2.52 cm³; matching = 84.44%), Seg 3D (mean bias = 3.21 cm³, matching = 87.36%), 3D Slicer (mean bias =  - 4.77 cm³; matching = 82.08%) and Dolphin 3D (difference mean =  - 6.06 cm³; matching = 78.26%). According to the color-coded map, the dis-matched area was mainly located at the most anterior nasal region of the airway. Volumetric data showed excellent inter-software reliability (GS vs semi-automatic software), with coefficient values ranging from 0.904 to 0.993, confirming proportional equivalence with manual segmentation.

CONCLUSION

Despite the excellent inter-software reliability, different semi-automatic segmentation algorithms could generate different patterns of inaccuracy error (underestimation/overestimation) of the upper airway models. Thus, is unreasonable to expect volumetric agreement among different software packages for the 3D rendering of the upper airway anatomy.

Airway morphology and its influence on OSA severity and surgical intervention: a retrospective study

Introduction: The aim was to assess the relationship between airway morphology and surgical intervention in a cohort of patients presenting with increased body mass index (BMI) and a confirmed diagnosis of obstructive sleep apnoea (OSA). A secondary aim was to revisit the relationship between morphology and OSA severity.

Methods: A retrospective analysis was conducted of pre-operative maxillofacial 3D-CT scans of thirty-two patients with a confirmed diagnosis of OSA who received treatment from an ear nose and throat specialist (ENT). Lateral cephalograms were imported into Quick Ceph Studio (Quick Ceph Systems Inc, San Diego, CA, USA) after which linear and angular measurements of selected hard and soft tissues were obtained. 3D-CT images were loaded into the software program 3dMDVultus (3dMD) which permitted 3D visualisation of the airway. Measurements were repeated 3 times on the images of six patients after an interval of two weeks to establish the intraclass correlation coefficient (ICC) for intra-examiner accuracy and reliability. Logistic regression was applied to determine the relationships between morphology, OSA and surgical treatments.

Results: A positive correlation was found between age and the apnoea-hypopnea index (AHI). Morphological measurements of the airway did not exhibit a positive relationship with OSA severity. Posterior airway space at the level of the uvula and tongue, the length of the soft palate and position of the hyoid bone were significantly associated with BMI. No variables were found to be correlated with uvulopalatopharyngoplasty (UPPP) surgery. Notwithstanding, airway length and posterior airway space at the level of the uvula tip were significantly associated with tongue channelling.

Conclusions: Radiographic airway assessment is an invaluable and opportunistic tool for screening OSA but requires judicial use in its prescription and interpretation. There is little correlation between OSA severity and airway morphology and between surgical intervention and morphology. Additional factors need to be considered before a treatment modality is considered and is best managed in a multidisciplinary setting.

Fully automatic segmentation of sinonasal cavity and pharyngeal airway based on convolutional neural networks

INTRODUCTION

This study aimed to test the accuracy of a new automatic deep learning-based approach on the basis of convolutional neural networks (CNN) for fully automatic segmentation of the sinonasal cavity and the pharyngeal airway from cone-beam computed tomography (CBCT) scans.

METHODS

Forty CBCT scans from healthy patients (20 women and 20 men; mean age, 23.37 ± 3.34 years) were collected, and manual segmentation of the sinonasal cavity and pharyngeal subregions were carried out by using Mimics software (version 20.0; Materialise, Leuven, Belgium). Twenty CBCT scans from the total sample were randomly selected and used for training the artificial intelligence model file. The remaining 20 CBCT segmentation masks were used to test the accuracy of the CNN fully automatic method by comparing the segmentation volumes of the 3-dimensional models obtained with automatic and manual segmentations. The accuracy of the CNN-based method was also assessed by using the Dice score coefficient and by the surface-to-surface matching technique. The intraclass correlation coefficient and Dahlberg's formula were used to test the intraobserver reliability and method error, respectively. Independent Student t test was used for between-groups volumetric comparison.

RESULTS

Measurements were highly correlated with an intraclass correlation coefficient value of 0.921, whereas the method error was 0.31 mm³. A mean difference of 1.93 ± 0.73 cm³ was found between the methodologies, but it was not statistically significant (P >0.05). The mean matching percentage detected was 85.35 ± 2.59 (tolerance 0.5 mm) and 93.44 ± 2.54 (tolerance 1.0 mm). The differences, measured as the Dice score coefficient in percentage, between the assessments done with both methods were 3.3% and 5.8%, respectively.

CONCLUSIONS

The new deep learning-based method for automated segmentation of the sinonasal cavity and the pharyngeal airway in CBCT scans is accurate and performs equally well as an experienced image reader.

Deep Learning Based Airway Segmentation Using Key Point Prediction

The purpose of this study was to investigate the accuracy of the airway volume measurement by a Regression Neural Network-based deep-learning model. A set of manually outlined airway data was set to build the algorithm for fully automatic segmentation of a deep learning process. Manual landmarks of the airway were determined by one examiner using a mid-sagittal plane of cone-beam computed tomography (CBCT) images of 315 patients. Clinical dataset-based training with data augmentation was conducted. Based on the annotated landmarks, the airway passage was measured and segmented. The accuracy of our model was confirmed by measuring the following between the examiner and the program: (1) a difference in volume of nasopharynx, oropharynx, and hypopharynx, and (2) the Euclidean distance. For the agreement analysis, 61 samples were extracted and compared. The correlation test showed a range of good to excellent reliability. A difference between volumes were analyzed using regression analysis. The slope of the two measurements was close to 1 and showed a linear regression correlation (r2 = 0.975, slope = 1.02, p < 0.001). These results indicate that fully automatic segmentation of the airway is possible by training via deep learning of artificial intelligence. Additionally, a high correlation between manual data and deep learning data was estimated.

A consideration of factors affecting palliative oral appliance effectiveness for obstructive sleep apnea: a scoping review

STUDY OBJECTIVES

This scoping review allows physicians, researchers, and others interested in obstructive sleep apnea to consider effectiveness of oral appliances (OAs). The intent is to improve understanding of OA effectiveness by considering morphologic interaction in patients with obstructive sleep apnea.

METHODS

Morphologic and biomechanical criteria for positional alterations of the mandible assessed success rates of OA appliances. Searches of databases (Medline, PubMed, The Cochrane Library, EBSCO) using terms: OA treatment effectiveness and positive and/or negative outcome predictors. Craniofacial predictors of OAs and obstructive sleep apnea biomechanical factors of anatomical traits associated with OA effectiveness were included. Databases searched radiographic cephalometric imaging for morphology/phenotypes and apnea-hypopnea index responses. Articles were excluded if title or abstract was not relevant or a case report. If the analysis did not report mean or standard deviation for apnea-hypoxia index, it was excluded. No language, age, or sex restrictions were applied.

RESULTS

Analysis of 135 articles included in searched literature indicated alterations in musculature and pharyngeal airway structure through OA use. These alterations were individually unpredictable with wide variability 61.81% ± 12.29 (apnea-hypoxia index mean ± standard deviation). Morphologic variations as predictors were typically weak and idiosyncratic. Biomechanical factors and wide variations in the metrics of appliance application were unclear, identifying gaps in knowledge and practice of OAs.

CONCLUSIONS

An integrated basis to identify morphologic and biomechanical elements of phenotypic expressions of sleep-disordered breathing in the design and application of OAs is needed. Current knowledge is heterogeneous and shows high variability. Identification of subgroups of patients with obstructive sleep apnea responding to OAs is needed.

Association between degenerative temporomandibular joint disorders, vertical facial growth, and airway dimension

BACKGROUND

The goal of this study was to determine whether preexisting degenerative temporomandibular joint (TMJ) disorders are associated with hyperdivergent facial phenotype and decreased airway dimensions.

METHODS

Cone-beam computed tomography scans of adult female and male individuals, 16 years of age and older, distributed in a case group defined as those with degenerative temporomandibular joint disorder (dTMJD; n = 31) or controls with normal TMJ findings (n = 242) were included. Odds ratios were calculated based on facial type and gender. Analysis of variance was used to compare the airway volume and cross section and mandibular measurements between the groups.

RESULTS

Condylar, ramus, and mandibular heights were significantly smaller in the case group compared with the control group. The odds of having a long face subject was significantly higher (P < 0.00001) in the dTMJD group than in the control group with 81% of the dTMJD subjects versus 11% of the control group having long vertical facial dimensions. The smallest cross-sectional area of the airway of the dTMJD group was significantly narrower (P < 0.0361) compared with the controls. Within the control group, ramus height and mandibular alveolar housing for central incisors were significantly smaller (P < 0.0001; P < 0.007) in the long face subjects.

CONCLUSIONS

The study shows that a long facial type is associated with findings of degenerative TMJ disorders and related condylar growth disturbances. These degenerative and growth changes may contribute to specific skeletal and dentofacial adaptations resulting in smaller condylar process, mandibular ramus, and body height; thinner alveolar housing at the lower incisor region; and smaller cross-sectional area of the airway.

Radiographic Evaluation of the Hyoid Bone Position and Pharyngeal Airway Depth in Anteroposterior Dysplasia

Introduction

The pharyngeal airway, tongue, and hyoid bone are correlated. The hyoid bone is connected to the pharynx, mandible, and cranium through muscles and ligaments and its position with respect to them determines the tongue posture and function. It also plays an important role in maintaining the airway and upright natural head position. Different skeletal patterns have different morphologies and shapes of the mandible, which might be affected by the position of the hyoid bone and the pharyngeal airway depth. This cephalometric study was conducted to relate the pharyngeal airway depth and the hyoid bone position of different skeletal patterns in sagittal dimension, and it determines and compares the linear parameters of the pharyngeal airway depth in Class I, II, and III malocclusion groups and anteroposterior, vertical, and angular positions of the hyoid bone positions in Class I, II, and III malocclusion groups.

Materials and methods

Lateral cephalometric radiographs selected for study were divided into three groups of 30 samples each based on ANB angle and β angle into skeletal Class I, Class II, and Class III, respectively. Five linear measurements for the pharyngeal airway depth, four linear measurements for anteroposterior position, two linear measurements for vertical position, and one angular measurement for angular hyoid bone position were made.

Results

The pharyngeal airway depth was found to show no statistically significant difference between Class I and Class III malocclusions. The pharyngeal airway depth in Class II malocclusion was found to be statistically smaller at D1 as compared to that in Class I and Class III malocclusions, whereas it remained the same at the rest of the locations measured, i.e., D2, D3, D4, and D5. The Class III malocclusion group showed a significant statistical difference in the anteroposterior hyoid bone position at all levels (i.e., H1, H2, H3, and H4) as compared to the Class II malocclusion group, whereas it showed a statistically significant difference as compared to the Class I malocclusion group at H1 and H3. The angular inclination of the hyoid bone in the Class II malocclusion group showed a statistically significant difference with the Class I and Class III malocclusion group but the Class III malocclusion group showed no significant difference statistically when compared to the Class I malocclusion group.

Conclusion

The pharyngeal airway depth in the Class II malocclusion group was also found to be narrower at the superiormost level measured at the posterior nasal spine from the posterior pharyngeal wall. The hyoid bone position was variable in angular and anteroposterior dimensions among different malocclusion groups.

How to cite this article

Chauhan R, Bagga DK, et al. Radiographic Evaluation of the Hyoid Bone Position and Pharyngeal Airway Depth in Anteroposterior Dysplasia. Int J Clin Pediatr Dent 2019;12(2):101–106.

Evaluation of upper airway volume and craniofacial volumetric structures in obstructive sleep apnoea adults: A descriptive CBCT study

OBJECTIVE

The aim of this investigation was to assess, with a descriptive three-dimensional evaluation, the volume of upper airway (UAWV) and the volume of craniofacial structures in adult patients suffering from obstructive sleep apnoea (OSA) and compare them to the corresponding findings in adults with no sleep disorders.

MATERIALS AND METHODS

The sample consisted of 54 adult males, 27 suffering from OSA diagnosed by means of the Apnoea Hypopnea Index and 27 with no history of sleep disorders. All subjects had a cone beam computerized tomography scan performed with the same head position. UAWV was assessed with the Amira® software, and craniofacial volumes by means of a specially developed data-processing program, which allowed the construction of tetrahedrons using anatomical landmarks. Assessed volumes were naso-maxillary, cranium upper anterior, oral cavity, post-oral cavity, hyoid to mandible, and post-hyoid. SPSS (version 19.0) was used for the statistical analysis. The Levene's test for Equality of Variance, the t-test for Equality of Means and the Mann-Whitney test were used to evaluate the variables. The level of significance was set at P ≤ 0.05.

RESULTS

The mean value of UAWV was smaller in the OSA group. The post-hyoid volume, the calculated posterior volume, and the ratio of posterior to total volume showed differences between the groups.

CONCLUSIONS

Craniofacial structures did not show significant differences between the groups, but in the OSA group the posterior space released for upper airway was significantly bigger and UAWV was significantly smaller.

Comparison of Imaging Softwares for Upper Airway Evaluation: Preliminary Study

The interest about upper airway evaluation has increased lately. Therefore, many softwares have been developed aiming to improve and facilitate the analysis of airway volume. The objective of this study was to compare two different softwares packages, Mimics and Dolphin, in their accuracy and precision in upper airway space measurements. Preoperative cone beam computed tomography scans of nine nonsyndromic patients submitted to surgically assisted rapid maxillary expansion were included in this study. The imaging exams were converted to DICOM (digital imaging and communications in medicine) files and imported to the softwares. The mean volume for the Dolphin group (G1) was 10.791 cm ³ (SD = 4.269 cm ³ ) and for the Mimics group (G2) was 10.553 cm ³ (SD = 4.564 cm ³ ). There was no statistically significant difference between the two groups ( p  = 0.105).

Hyoid bone position in different facial skeletal patterns

Background

Hyoid bone plays a significant role in physiological functions of craniofacial region and it’s position adapts to changes of the head. The purpose of this study was to determine the position of the hyoid bone among subjects with class I, class II and class III skeletal patterns and evaluate the gender differences.

Material and Methods

One hundred and ten lateral cephalograms (59 females and 51 males) from different skeletal patterns (class I, II and III) were selected. The skeletal patterns were determined according to ANB angle. Using MicroDicom software, different linear and angular measurements (6 variables) was carried out to determine the position of hyoid bone. Intraclass correlation coefficient was used to verify reliability. Descriptive statistics of the variables were calculated and analyzed using two-way ANOVA and Bonferroni statistical methods.

Results

The mean distance from the hyoid bone (H) to mandibular plane (MP), to palatal plane (PP), as well as to a third cervical vertebra (C3) was more in males than females (p=0.023, p<0.001, p<0.001 respectively). The mean H to PP distance was significantly more in skeletal class I compared to class III (P=0.01). The mean H to C3 distance was significantly more in skeletal class I compared to class II (P=0.008). The mean angle between H-MP and H-PP did not show any statistical difference among three skeletal classes (p=0.102, P=0.213) and among male and female groups (P=0.172, P=0.904).

Conclusions

The hyoid bone is positioned more superior and posterior in females than males and its location differs among different skeletal classes. It is placed more posterior in skeletal class II patterns and more inferior and anterior in skeletal class I patterns.

Key words:Hyoid bone, Lateral cephalometry, Class III, Class II, skeletal pattern, Orthodontics.

Pharyngeal airspace of asthmatic individuals and those suffering from obstructive sleep apnea syndrome: Study by CBCT

PURPOSE

The objective of the present study was to comparatively evaluate the oropharyngeal space of patients with obstructive sleep apnea syndrome (OSA) and asthma by means of Cone Beam Computed Tomography (CBCT) images.

MATERIAL AND METHODS

The study included individuals with OSA and asthma (n=10), with OSA and without asthma (n=6), asthmatics without OSA (n=6) and healthy individuals (n=25). All patients were evaluated by a pneumologist and submitted to a nocturnal polysomnogram. Participants underwent CBCT examinations using an I-CAT^® device (Imaging Sciences International, Hatfield, PA, U.S.A.) and all images were exported to Dolphin Image 3D^® software. Cephalometric measurements were taken, as well as measurements of length (C), volume (VOL), sagittal area (SA) and minimum cross-sectional area (MCA); an evaluation was made of the format and contour of the upper airway in three dimensions, with p<0.05 considered significant.

RESULTS

In the results of the present study, a statistically significant difference was found between VOL, SA and MCA (p=0.011; p=0.009; p=0.010) with reduced elevated values among the OSA+Asthma, OSA, Asthma and Control groups. Significant differences were seen between the linear (AP), cross-sectional (TR) and mean transverse area (TA) measurements in the group of patients with OSA and asthma as compared to the control group. In the control group, the greatest narrowing of the airway was observed either in the retroglossal or retropalatal area, while more patients in the experimental groups showed narrowing in the retropalatal area.

CONCLUSION

The condition of OSA+asthma was associated with a substantial reduction in upper airway measurements in comparison to controls.

Wearing complete dentures is associated with changes in the three-dimensional shape of the oropharynx in edentulous older people that affect swallowing

OBJECTIVE

To investigate the effects of wearing complete dentures on pharyngeal shape for swallowing in edentulous older people.

BACKGROUND

In the absence of complete dentures, edentulous older people often lose the occlusal support necessary to position the mandible, which leads to an anterosuperior shift of the mandible during swallowing. This may result in pharyngeal shape changes effecting swallowing function in older people. However, the details of this phenomenon are currently unclear.

MATERIALS AND METHODS

Participants were 17 older edentulous volunteers. Cone-beam computed tomography imaging was performed with the participant in the seated position and wearing (i) both maxillary and mandibular dentures, (ii) maxillary dentures only and (iii) no dentures. During imaging, participants were instructed to keep their mouth closed to the mandibular position determined in advance during swallowing for each denture-wearing condition. The volume, height and average cross-sectional area of the velopharynx and oropharynx were measured, and the positions of the epiglottis and mandible were recorded.

RESULTS

While the vertical height of the oral cavity and pharynx significantly decreased, the volume and average cross-sectional area of the oropharynx significantly increased when dentures were not worn (p < 0.01). The absence of dentures caused an anterosuperior shift of the mandible when swallowing and drew the epiglottis forward, resulting in expansion of the oropharynx where the tongue base forms the anterior wall.

CONCLUSION

The absence of dentures results in anatomical changes in oropharyngeal shape that may exacerbate the pharyngeal expansion caused by ageing and reduce the swallowing reserve.

Change of the airway space in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction

BACKGROUND

The purpose of this retrospective study was to develop a two- and three-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether the airway space would be changed in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction.

METHODS

Patients requiring orthognathic surgery from 2012 to 2014 were recruited for this study. CBCT scans were obtained at three points: preoperatively (T0), immediate postoperatively (T1), and after 6 months postoperatively (T2). The nasopharynx, oropharynx, and hypopharynx were measured on the CBCT scan for each patient in a repeatable manner. With the midsagittal plane, linear measurements in the middle of each were obtained. For the CBCT, volumetric measurements of each and total airway were obtained.

RESULTS

A total of 22 consecutive patients (11 men and 11 women) were included in the present study. The total volume was significantly reduced (p < .001). However, the change of the diameter and volume of the nasopharynx was not statistically significant (p = .160, p = .137, respectively). In the oropharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p < .001, p = .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p = .010, respectively). In the hypopharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p = .001, p < .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p < .001, respectively).

CONCLUSIONS

The bimaxillary surgery involving maxillary posterior impaction can reduce the volume of airway in the patients of mandibular prognathism. Although total airway volume was reduced significantly, the changes in the volume and diameter of the nasopharynx were not statistically significant. The maxillary posterior impaction affects on the nasopharyngeal airway minimally.

Comparison of pharyngeal airway dimension, tongue and hyoid bone position based on ANB angle

OBJECTIVE

This study was undertaken to cephalometrically evaluate the pharyngeal airway dimension, tongue and hyoid position in subjects with normal nasorespiratory functions having different dentofacial patterns (A-point-nasion-B-point [ANB] >40 and ANB <40) and to find if a correlation existed.

MATERIALS AND METHODS

Class I and Class II Division I patients were selected randomly. Lateral head cephalograms were taken in normal head position within a lead foil attached to the tongue tip and a barium coating on the dorsal surface of tongue. The lateral cephalograms obtained were traced using lead acetate paper and measurements were taken. Different analyses were done for the pharyngeal airways, hyoid bone, and tongue.

RESULTS

The ANB angle is a significant predictor for Class I and Class II Division I malocclusion, and the mean ANB angle of Class II Division I was different and higher. The overall mean pharynx and hyoid parameters were different and lower in Class II Division I patients than in Class I patients. The mean tongue parameter almost remained the same except for the tongue position (TT-LOP), which was higher in Class II Division I.

CONCLUSION

In general, there was no difference either in the pharyngeal airway anterioposterior dimension or in the position and relationship of the hyoid bone and tongue, between Class I and Class II Division I patients. These findings are consistent with the findings in studies. Anterioposterior dimension of the upper airway is usually maintained by adaptation of both the tongue and the hyoid bone. The result should be viewed in the light of the fact that only anterioposterior dimensions were taken into consideration; the vertical and transverse dimensions of these complex anatomical structures need to have newer three-dimensional (3-D) imaging technique to find if a correlation existed between them, making future studies more comprehensive.

A Method for Accurate Reconstructions of the Upper Airway Using Magnetic Resonance Images

Objective

The purpose of this study is to provide an optimized method to reconstruct the structure of the upper airway (UA) based on magnetic resonance imaging (MRI) that can faithfully show the anatomical structure with a smooth surface without artificial modifications.

Methods

MRI was performed on the head and neck of a healthy young male participant in the axial, coronal and sagittal planes to acquire images of the UA. The level set method was used to segment the boundary of the UA. The boundaries in the three scanning planes were registered according to the positions of crossing points and anatomical characteristics using a Matlab program. Finally, the three-dimensional (3D) NURBS (Non-Uniform Rational B-Splines) surface of the UA was constructed using the registered boundaries in all three different planes.

Results

A smooth 3D structure of the UA was constructed, which captured the anatomical features from the three anatomical planes, particularly the location of the anterior wall of the nasopharynx. The volume and area of every cross section of the UA can be calculated from the constructed 3D model of UA.

Conclusions

A complete scheme of reconstruction of the UA was proposed, which can be used to measure and evaluate the 3D upper airway accurately.

Automatic segmentation of the nasal cavity and paranasal sinuses from cone-beam CT images

PURPOSE

A patient-specific upper airway model is important for clinical, education, and research applications. Cone-beam computed tomography (CBCT) is used for imaging the upper airway but automatic segmentation is limited by noise and the complex anatomy. A multi-step level set segmentation scheme was developed for CBCT volumetric head scans to create a 3D model of the nasal cavity and paranasal sinuses.

METHODS

Gaussian mixture model thresholding and morphological operators are first employed to automatically locate the region of interest and to initialize the active contour. Second, the active contour driven by the Kullback-Leibler (K-L) divergence energy in a level set framework to segment the upper airway. The K-L divergence asymmetry is used to directly minimize the K-L divergence energy on the probability density function of the image intensity. Finally, to refine the segmentation result, an anisotropic localized active contour is employed which defines the local area based on shape prior information. The method was tested on ten CBCT data sets. The results were evaluated by the Dice coefficient, the volumetric overlap error (VOE), precision, recall, and F-score and compared with expert manual segmentation and existing methods.

RESULTS

The nasal cavity and paranasal sinuses were segmented in CBCT images with a median accuracy of 95.72 % [93.82-96.72 interquartile range] by Dice, 8.73 % [6.79-12.20] by VOE, 94.69 % [93.80-94.97] by precision, 97.73 % [92.70-98.79] by recall, and 95.72 % [93.82-96.69] by F-score.

CONCLUSION

Automated CBCT segmentation of the airway and paranasal sinuses was highly accurate in a test sample of clinical scans. The method may be useful in a variety of clinical, education, and research applications.

Three-dimensional evaluation of upper airway in patients with different anteroposterior skeletal patterns

OBJECTIVES

To investigate variability in the upper airway of subjects with different anteroposterior skeletal patterns by evaluating the volume and the most constricted cross-sectional area of the pharyngeal airway and defining correlations between the different variables.

MATERIAL AND METHODS

The study sample consisted of 60 patients (29 boys, 31 girls) divided into three groups: Class I (1 ≤ ANB ≤ 3), Class II (ANB>3), and Class III (ANB<1), to evaluate how the jaw relationship affects the airway volume and the most constricted cross-sectional area (Min-CSA). Differences between groups were determined using the Tukey-Kramer test. Correlations between variables were tested using Pearson's correlation coefficient.

RESULTS

The volume and the Min-CSA of the pharyngeal airway (PA) were significantly related to anteroposterior skeletal patterns (p < 0.05). The nasopharyngeal airway (NA) volume of Class I and Class III subjects was significantly larger than that of Class II subjects (p < 0.05). The Min-CSA and the length of PA were significantly related to the volume of PA (p < 0.05). The site and the size of the Min-CSA varied among the three groups.

CONCLUSIONS

The volume and the most constricted cross-sectional area of the airway varied with different anteroposterior skeletal patterns. The NA volume of Class I and Class III subjects was significantly larger than that of patients with a Class II skeletal pattern.

Three-dimensional airway evaluation in 387 subjects from one university orthodontic clinic using cone beam computed tomography

OBJECTIVE

To determine the linear, volumetric, and cross-sectional area measurements in a large sample of subjects seeking treatment in a university clinic of orthodontics.

MATERIALS AND METHODS

Cone-beam computed tomography (CBCT) scans from 387 patients were analyzed retrospectively. All scans were loaded into the 3dMDvultus program (Atlanta, Ga) for airway analysis using automated segmentation. Gender, age, height, weight, airway length, volume, and area of maximum constriction were collected.

RESULTS

The rostrocaudal length of the airway increased with age until the age of 15 years in female subjects but continued to increase in male subjects and ranged from 44 to 88 mm over the period of 8 to 18 years of age with the gender data combined. The volume of the airway increased through the entire 11-year age range from 2000 mm(3) to 27,000 mm(3). The rate of airway volume increased at a slower rate in female than in male subjects. The smallest cross-sectional area increased with age ranging from 20 to 250 mm(2) but at a slower rate with female subjects, while male subjects demonstrated a more exponential increase after the age of 13 years.

CONCLUSIONS

The human airway increases in length and volume during a rapid period of craniofacial growth in patients between the ages of 8 and 18 years, and the site of maximum cross-sectional area constriction can vary.