Rajiv Balachandran

Precision of manual landmark identification between as-received and oriented volume-rendered cone-beam computed tomography images

Introduction The objective of this study was to evaluate the effect of the orientation of cone‐beam computed tomography (CBCT) images on the precision and reliability of 3‐dimensional cephalometric landmark identification. Methods Ten CBCT scans were used for manual landmark identification. Volume‐rendered images were oriented by aligning the Frankfort horizontal and transorbital planes horizontally, and the midsagittal plane vertically. A total of 20 CBCT images (10 as‐received and 10 oriented) were anonymized, and 3 random sets were generated for manual landmark plotting by 3 expert orthodontists. Twenty‐five landmarks were identified for plotting on each anonymized image independently. Hence, a total of 60 images were marked by the orthodontists. After landmark plotting, the randomized samples were decoded and regrouped into as‐received and oriented data sets for analysis and comparison. Means and standard deviations of the x‐, y‐, and z‐axis coordinates were calculated for each landmark to measure the central tendency. Intraclass correlation coefficients were calculated to analyze the interobserver reliability of landmark plotting in the 3 axes in both situations. Paired t tests were applied on the mean Euclidean distance computed separately for each landmark to evaluate the effect of 3‐dimensional image orientation. Results Interobserver reliability (intraclass correlation coefficient, >0.9) was excellent for all 25 landmarks for the x‐, y‐, and z‐axes on both before and after orientation of the images. Paired t test results showed insignificant differences for the orientation of volume‐rendered images for all landmarks except 3: R1 left (P = 0.0138), sella (P = 0.0490), and frontozygomatic left (P = 0.0493). Also midline structures such as Bolton and nasion were plotted more consistently or precisely than bilateral structures. Conclusions Orientation of the CBCT image does not enhance the precision of landmark plotting if each landmark is defined properly on multiplanar reconstruction slices and rendered images, and the clinician has sufficient training. The consistency of landmark identification is influenced by their anatomic locations on the midline, bilateral, and curved structures. HighlightsThis study provides insight into influence of orientation of CBCT image on 3D landmark plotting.Landmark plotting was performed by 3 observers blindly and randomly to prevent bias.Excellent interobserver reliability was obtained for as‐received and oriented CBCT data sets on landmark plotting.The locations of landmarks influence the consistency of their identification in both situations.

A pilot study for segmentation of pharyngeal and sino-nasal airway subregions by automatic contour initialization

PurposeThe objective of the present study is to put forward a novel automatic segmentation algorithm to segment pharyngeal and sino-nasal airway subregions on 3D CBCT imaging datasets.MethodsA fully automatic segmentation of sino-nasal and pharyngeal airway subregions was implemented in MATLAB programing environment. The novelty of the algorithm is automatic initialization of contours in upper airway subregions. The algorithm is based on boundary definitions of the human anatomy along with shape constraints with an automatic initialization of contours to develop a complete algorithm which has a potential to enhance utility at clinical level. Post-initialization; five segmentation techniques: Chan-Vese level set (CVL), localized Chan-Vese level set (LCVL), Bhattacharya distance level set (BDL), Grow Cut (GC), and Sparse Field method (SFM) were used to test the robustness of automatic initialization.ResultsPrecision and F-score were found to be greater than 80% for all the regions with all five segmentation methods. High precision and low recall were observed with BDL and GC techniques indicating an under segmentation. Low precision and high recall values were observed with CVL and SFM methods indicating an over segmentation. A Larger F-score value was observed with SFM method for all the subregions. Minimum F-score value was observed for naso-ethmoidal and sphenoidal air sinus region, whereas a maximum F-score was observed in maxillary air sinuses region. The contour initialization was more accurate for maxillary air sinuses region in comparison with sphenoidal and naso-ethmoid regions.ConclusionThe overall F-score was found to be greater than 80% for all the airway subregions using five segmentation techniques, indicating accurate contour initialization. Robustness of the algorithm needs to be further tested on severely deformed cases and on cases with different races and ethnicity for it to have global acceptance in Katradental radKatraiology workflow.

The reliability of different methods of manual volumetric segmentation of pharyngeal and sinonasal subregions

OBJECTIVES The purpose of the study was to test the intra and interobserver reliability of manual volumetric segmentation of pharyngeal and sinonasal airway subregions. STUDY DESIGN Cone beam computed tomography data of 15 patients were collected from an orthodontic clinical database. Two experienced orthodontists independently performed manual segmentation of the airway subregions. Four performance measures were considered to test intra and interobserver reliability of manual segmentation: (1) volume correlation, (2) mean slice correlation, (3) percentage of volume difference, and (4) percentage of nonoverlapping voxels. RESULTS Intra and interobserver reliability was observed to be greater than 0.96 for the entire pharyngeal and sinonasal airway sinus subregions by both observers using the volume correlation method. Mean slice correlation was found to be greater than 0.84, showing the existence of nonoverlapping voxels. Therefore, the percentage of nonoverlapping voxels was used as a reliability measure and was found to be less than 20% for both intra and interobserver markings. CONCLUSIONS The mean slice correlation and percentage of nonoverlapping voxels were the most reliable performance measures of segmentation correctness. Volume correlation and the percentage of volume difference were observed to be the most reliable performance measures for volume correctness.

Orthodontic management of displaced premaxilla in Van der Woude syndrome

Cleft lip and palate is the most common congenital disorder affecting facial region. Van der Woude syndrome is a rare autosomal dominant disorder characterized by varying degree of cleft lip and/or palate, distinctive pits on the lower lip and hypodontia. A case of Van der Woude syndrome treated successfully with fixed orthodontic treatment is presented. The main feature of treatment planning and execution included moving the premaxilla to midline with gentle orthodontic force.