3D Cone Beam Research Articles

The influence of the segmentation process on 3D measurements from cone beam computed tomography-derived surface models

To compare the accuracy of linear and angular measurements between cephalometric and anatomic landmarks on surface models derived from 3D cone beam computed tomography (CBCT) with two different segmentation protocols was the aim of this study. CBCT scans were made of cadaver heads and 3D surface models were created of the mandible using two different segmentation protocols. A high-resolution laser surface scanner was used to make a 3D model of the macerated mandibles. Twenty linear measurements at 15 anatomic and cephalometric landmarks between the laser surface scan and the 3D models generated from the two segmentation protocols (commercial segmentation (CS) and doctor's segmentation (DS) groups) were measured. The interobserver agreement for all the measurements of the all three techniques was excellent (intraclass correlation coefficient 0.97-1.00). The results are for both groups very accurate, but only for the measurements on the condyle and lingual part of the mandible, the measurements in the CS group is slightly more accurate than the DS group. 3D surface models produced by CBCT are very accurate but slightly inferior to reality when threshold-based methods are used. Differences in the segmentation process resulted in significant clinical differences between the measurements. Care has to be taken when drawing conclusions from measurements and comparisons made from different segmentations, especially at the condylar region and the lingual side of the mandible.

3-Dimensional analysis for class III malocclusion patients with facial asymmetry

ObjectivesThe aim of this study is to investigate the correlation between 2-dimensional (2D) cephalometric measurement and 3-dimensional (3D) cone beam computed tomography (CBCT) measurement, and to evaluate the availability of 3D analysis for asymmetry patients.Materials and MethodsA total of Twenty-seven patients were evaluated for facial asymmetry by photograph and cephalometric radiograph, and CBCT. The 14 measurements values were evaluated and those for 2D and 3D were compared. The patients were classified into two groups. Patients in group 1 were evaluated for symmetry in the middle 1/3 of the face and asymmetry in the lower 1/3 of the face, and those in group 2 for asymmetry of both the middle and lower 1/3 of the face.ResultsIn group 1, significant differences were observed in nine values out of 14 values. Values included three from anteroposterior cephalometric radiograph measurement values (cant and both body height) and six from lateral cephalometric radiographs (both ramus length, both lateral ramal inclination, and both gonial angles). In group 2, comparison between 2D and 3D showed significant difference in 10 factors. Values included four from anteroposterior cephalometric radiograph measurement values (both maxillary height, both body height) and six from lateral cephalometric radiographs (both ramus length, both lateral ramal inclination, and both gonial angles).ConclusionInformation from 2D analysis was inaccurate in several measurements. Therefore, in asymmetry patients, 3D analysis is useful in diagnosis of asymmetry.

Bayesian Estimation Applied to Stochastic Localization with Constraints due to Interfaces and Boundaries

Purpose. We present a systematic Bayesian formulation of the stochastic localization/triangulation problem close to constraining interfaces.Methods. For this purpose, the terminology of Bayesian estimation is summarized suitably for applied researchers including the presentation of Maximum Likelihood (ML), Maximum A Posteriori (MAP), and Minimum Mean Square Error (MMSE) estimation. Explicit estimators for triangulation are presented for the linear 2D parallel beam and the nonlinear 3D cone beam model. The priors in MAP and MMSE optionally incorporate (A) the hard constraints about the interface and (B) knowledge about the probability of the object with respect to the interface. All presented estimators are compared in several simulation studies for live acquisition scenarios with 10,000 samples each.Results. First, the presented application shows that MAP and MMSE perform considerably better, leading to lower Root Mean Square Errors (RMSEs) in the simulation studies compared to the ML approach by typically introducing a bias. Second, utilizing priors including (A) and (B) is very beneficial compared to just including (A). Third, typically MMSE leads to better results than MAP, by the cost of significantly higher computational effort.Conclusion. Depending on the specific application and prior knowledge, MAP and MMSE estimators strongly increase the estimation accuracy for localization close to interfaces.

A comparative study of the diagnostic capabilities of 2D plain radiograph and 3D cone beam CT sialography

The aim of this study was to compare the diagnostic capabilities of two-dimensional sialography with a novel three-dimensional technique using cone beam CT (CBCT). 47 subjects underwent parotid or submandibular gland sialography over a 2 year period using both plain imaging and CBCT. Both image sets were anonymized and independently reviewed by three certified oral and maxillofacial radiologists blinded to the clinical data. McNemar's χ(2) test was used to determine differences between the two modalities for feature visualization and interpretation. CBCT outperformed plain imaging with respect to visualization of the gland parenchyma (p < 0.001) and identification of sialoliths (p = 0.02). Plain imaging outperformed CBCT for the identification of strictures (p = 0.04); however, the negative per cent agreement ("specificity") between the two imaging modalities was 100%. Although both imaging modalities performed equally in identifying normal and abnormal sialographic examinations, CBCT demonstrated a high negative per cent agreement for normal glands and a high positive per cent agreement ("sensitivity") for abnormal glands with inflammatory changes. CBCT sialography allowed better visualization of gland parenchyma and identification of sialoliths. The high negative per cent agreement for strictures suggests that, if strictures are identified on CBCT images, then obstruction can be ruled in. Relative to plain images, the high negative per cent agreement for normal glands suggests that, if an abnormal finding is detected on CBCT images, then disease can be ruled in, and the high positive per cent agreement for glands with inflammatory changes suggests that inflammation can be ruled out if these changes are not seen on CBCT images.

Modified method of analysis for surgical correction of facial asymmetry

Introduction:The aim of this article was to present a new method of analysis using a three dimensional (3D) model of an actual patient with facial asymmetry, for the assessment of her facial changes and the quantification of the deformity. This patient underwent orthodontic and surgical treatment to correct a severe facial asymmetry.Materials and Methods:The surgical procedure was complex and the case was challenging. The treatment procedure required an orthodontic approach followed by Le Fort I osteotomy, bilateral sagittal split osteotomy, septorhinoplasty and chin advancement. The imaging devices used in this paper is the 3dMDface system (Atlanta, GA) and the Kodak 9500 Cone Beam 3D system device (Atlanta, GA). 3D digital stereophotogrammetric cameras were used for image acquisition and a reverse modeling software package, the Rapidform 2006 Software (INUS Technology, Seoul, Korea) was applied for surface registration. The images were also combined and analyzed using the 3dMD vultus (Atlanta, GA) software and InVivoDental 5.2.3 (San Jose, CA). All data gathered from previously mentioned sources were adjusted to the patient's natural head position.Results:The 3D images of the patient were taken and analyzed in three time frames; before orthodontics and surgical treatment (T1), at the end of orthodontic therapy and before surgery (T2) and about 2 months after surgery (T3). The patient showed significant improvement of her skeletal discrepancy between T1 and T3. In addition, there were some dentoalveolar changes between T1 and T2 as expected. The 3D analysis of surgical changes on the 3D models correlated very well to the actual surgical movements.Conclusions:The use of these 3D imaging tools offer a reliable accuracy to accessing and quantifying changes that occur after surgery. This study shows supportive evidence for the use of 3D imaging techniques.

A method for measuring three-dimensional mandibular kinematicsin vivousing single-plane fluoroscopy

Accurate measurement of the three-dimensional (3D) motion of the mandible in vivo is essential for relevant clinical applications. Existing techniques are either of limited accuracy or require the use of transoral devices that interfere with jaw movements. This study aimed to develop further an existing method for measuring 3D, in vivo mandibular kinematics using single-plane fluoroscopy; to determine the accuracy of the method; and to demonstrate its clinical applicability via measurements on a healthy subject during opening/closing and chewing movements. The proposed method was based on the registration of single-plane fluoroscopy images and 3D low-radiation cone beam CT data. It was validated using roentgen single-plane photogrammetric analysis at static positions and during opening/closing and chewing movements. The method was found to have measurement errors of 0.1 ± 0.9 mm for all translations and 0.2° ± 0.6° for all rotations in static conditions, and of 1.0 ± 1.4 mm for all translations and 0.2° ± 0.7° for all rotations in dynamic conditions. The proposed method is considered an accurate method for quantifying the 3D mandibular motion in vivo. Without relying on transoral devices, the method has advantages over existing methods, especially in the assessment of patients with missing or unstable teeth, making it useful for the research and clinical assessment of the temporomandibular joint and chewing function.

Enter the world of 3D cone beam diagnostics

Enter the world of 3D cone beam diagnostics

Cone-Beam Computed Tomography

The aim of this research was to analyze the influence of the position of the skull during cone-beam computed tomography (CBCT) scan and if the three-dimensional cephalometric measurements are influenced by skull orientation during CBCT scan.The study consisted of 5 CBCT scanning (KODAK 9500 Cone Beam 3D System unit) in 5 different positions of a dry skull. The data were imported in SIMPLANT OMS Software version 13.0. Fifteen three-dimensional cephalometric measurements were calculated; moreover, the mean, the SD, the maximum/minimum Δ, and the maximum/minimum Δ percentage were calculated. The statistical analysis was performed by an independent-samples t-test to evaluate differences between the 5 scans.No difference was found in all the three-dimensional analysis. Twelve of 15 measurements have a Δ greater than 1.5, and 7 of 15 measurements have a Δ greater than 2. Nine of 15 have a Δ percentage greater than 5%. The preliminary results suggest that the three-dimensional cephalometric analysis is influenced by patient scanning position.

A retrospective comparison of the location and diameter of the inferior alveolar canal at the mental foramen and length of the anterior loop between American and Taiwanese cohorts using CBCT

The aim was to retrospectively compare the measurements of the location and size of the inferior alveolar canal at the mental foramen and the length of the anterior loop between two cohorts of Americans and Taiwanese using cone-beam computed tomography (CBCT). CBCT was performed with an I-CAT(®) Cone-Beam 3D Dental Imaging System and reconstructed into multiple-plane views to measure two populations. There was no statistically significant difference (P=0.2681) in the distance from the mental foramen to the inferior border of the mandible (mandibular border height) between Americans (9.84±2.01mm) and Taiwanese (10.13±1.66mm). No significant difference was found (p=0.1161) in the inferior alveolar canal diameter between these two cohorts (2.26±0.67 and 2.13±0.47mm, respectively). However, the anterior loop length of Taiwanese (7.61±1.81mm) was significantly longer than that of Americans (6.22±1.68mm) (P<0.0001). Our study indicated that (1) the location of mental foramen of Americans was closer to the inferior border of the mandible than Taiwanese; (2) the diameter of the inferior alveolar canal of Americans was larger than Taiwanese; (3) the anterior loop of Taiwanese was longer than Americans. These differences may be, at least partly, due to the racial influence and this information may possess potential valuable clinical relevance.

SU-E-I-14: Evaluation of Image Quality Parameters of Small and Full Field of View Cone Beam Computed Tomography Dental Imaging Systems.

CBCT systems are being used in dental preoperative planning, which rely on 3D surface model representations of the jaw, using a segmentation algorithm for extracting the bony tissues. However, CBCT systems have differences of imaging parameters, which affect the image quality and segmentation process, influencing the accuracy of the 3D surface models used in preoperative implant planning. The purpose of this study was to evaluate image quality parameters of different types of CBCT systems, showing their potentialities and limitations for preoperative planning. Images were acquired using the systems: i-CAT (Imaging Sciences International Inc., USA); ProMax 3Ds (Planmeca Oy, Finland); Kodak 9500 Cone Beam 3D and Kodak 9000C Cone Beam 3D (Kodak Dental Systems, USA). CBCT systems were divided into categories, related to their field of view size: Small Field of View (SFOV) and Full Field of View (FFOV) systems. Image quality parameters evaluated were: CT number accuracy, uniformity, noise level, and artifacts. Measurements were performed in slices around the center of the phantom. CT numbers are highly affected by the amount of mass outside the reconstructed volume, confirming the relation between density variability and imaging volume. The mean CT number shows little correspondence to that of the traditional CT protocols. The variability is especially high in the case for SFOV systems. Uniformity artifacts occur at the top or bottom of the FOV, and Result in voxel values that are unsuitable for CT number accuracy analysis. SFOV systems showed a higher noise level (11,9%) comparing to FFOV systems (4.4%). The experiments showed that the size and position of the FOV affect the image quality for all CBCT systems. The study was limited to the CBCT systems that were accessible when this study was conducted. Whether new CBCT systems models would perform differently remains to be investigated.

MO-D-213CD-04: 4D X-Ray DSA and 4D Fluoroscopy.

1. To understand the application of under sampling and constrained reconstruction to 4D DSA and Fluoroscopy.

An improved method for the removal of ring artifacts in high resolution CT imaging

Abstract In high resolution computed tomography (CT) using flat panel detectors, imperfect or defected detector elements cause stripe artifacts in sinogram which results in concentric ring artifacts in the image. Such ring artifacts obscure image details in the regions of interest of the image. In this article, novel techniques are proposed for the detection, classification, and correction of ring artifacts in the sinogram domain. The proposed method is suitable for multislice CT with parallel or fan beam geometry. It can also be employed for ring artifact removal in 3D cone beam volume CT by adopting a sinogram by sinogram processing technique. The detection algorithm is based on applying data driven thresholds on the mean curve and difference curve of the sinogram. The ring artifacts are classified into three types and a separate correction algorithm is used for each class. The performance of the proposed techniques is evaluated on a number of real micro-CT images. Experimental results corroborate that the proposed algorithm can remove ring artifacts from micro-CT images more effectively as compared to other recently reported techniques in the literature.

Atypical facial pain related to apical fenestration and overfilling

To report a case of apical fenestration and overfilling in which unusual pain characteristics made differential diagnosis challenging. A 32-year-old woman with diffuse, spontaneous, moderate pain in the maxillary left posterior sector, exacerbated by masticatory and facial muscle movement, with intense sporadic electric-shooting pain, underwent clinical examination and 3D cone beam computed tomography (CBCT). Apical fenestration with protrusion of the mesial root of tooth 26 beyond the buccal cortical plate, extrusion of canal filling material into the soft tissues and a periosteal reaction were detected. Surgery was performed under the operating microscope. The filling material and surrounding fibrous tissue were located, dissected from healthy soft tissues and removed. The mesiobuccal root apex was resected with a bur to within the bony crypt. A root end was prepared and filled with Tech Biosealer RootEnd™ (Isasan, Como, Italy). At the 2-week recall, the patient had complete resolution of the symptoms and good soft-tissue healing. The 1-year recall examination and intra-oral radiography confirmed complete resolution of the symptoms and health of periradicular tissues. Apical fenestration may occur in 9% of cases and may be considered an anatomic predisposing factor for persistent pain after root canal treatment. This complication provides a considerable differential diagnostic challenge and is often misdiagnosed and mistreated. When correctly diagnosed through an accurate, multidisciplinary approach, it may be managed with a simple surgical procedure in which the endodontist should play a key role. Misdiagnosis and over treatment of apical fenestration, through the surgical management of chronic facial pain conditions, could lead to severe exacerbation of chronic pain, which may potentially become persistent or, indeed, intractable.

A method for mandibular dental arch superimposition using 3D cone beam CT and orthodontic 3D digital model

ObjectiveThe purpose of this study was to develop superimposition method on the lower arch using 3-dimensional (3D) cone beam computed tomography (CBCT) images and orthodontic 3D digital modeling.MethodsIntegrated 3D CBCT images were acquired by substituting the dental portion of 3D CBCT images with precise dental images of an orthodontic 3D digital model. Images were acquired before and after treatment. For the superimposition, 2 superimposition methods were designed. Surface superimposition was based on the basal bone structure of the mandible by surface-to-surface matching (best-fit method). Plane superimposition was based on anatomical structures (mental and lingual foramen). For the evaluation, 10 landmarks including teeth and anatomic structures were assigned, and 30 times of superimpositions and measurements were performed to determine the more reproducible and reliable method.ResultsAll landmarks demonstrated that the surface superimposition method produced relatively more consistent coordinate values. The mean distances of measured landmarks values from the means were statistically significantly lower with the surface superimpositions method.ConclusionsBetween the 2 superimposition methods designed for the evaluation of 3D changes in the lower arch, surface superimposition was the simpler, more reproducible, reliable method.

Evaluation of bone changes in the temporomandibular joint using cone beam CT

The aim of this study was to assess bone changes and mobility in temporomandibular joints (TMJs) using cone beam CT (CBCT) in a population sample in Recife, PE, Brazil. The TMJ images of patients treated by a radiologist at a private dental radiology service over a period of 1 year were retrieved from the computer database and assessed using a computer with a 21-inch monitor and the iCAT Cone Beam 3D Dental Imaging System Workstation program (Imaging Sciences International, Hatfield, PA). The Pearson χ(2) test was used to analyse the differences in percentage of bone changes among the categories of mobility (p ≤ 0.05). The McNemar test was used to compare the presence of bone changes in TMJs on the right and left sides (p ≤ 0.05). An adjusted logistic regression model was used to assess the effect of age and gender on the occurrence of bone changes (p ≤ 0.05). Bone changes were present in 227 (71%) patients. Age group and gender showed a statistically significant association with presence of bone changes (p ≤ 0.05). There was no significant difference between the right and left sides (p = 0.556) and in condylar mobility (p = 0.925) with regard to the presence of degenerative bone changes. There is a high prevalence of degenerative bone alteration in TMJs, which is more frequent in women and mostly located in the condyle. The prevalence of degenerative bone changes increases with age. There is no correlation between condylar mobility and the presence of degenerative bony changes in TMJs.

Alveolar bone loss around incisors in Class I bidentoalveolar protrusion patients: a retrospective three-dimensional cone beam CT study

The aim of this study was to test the null hypothesis that there is no difference in the alveolar bone thickness, bone loss or incidence of fenestrations between upper and lower incisors in skeletal Class I bidentoalveolar protrusive patients before orthodontic treatment. Three-dimensional (3D) cone beam CT (CBCT) images were taken of 24 patients from the Republic of Korea (17 females and 7 males). Reformatted CBCT images were used to measure labial and lingual alveolar bone thickness (ABT) of the 4 upper incisors and 4 lower incisors of the 24 patients (total n = 192 incisors) at every 1/10 of root length (Level 0, cementoenamel junction (CEJ) area; Level 10, root apex area) as well as alveolar bone area (ABA) and alveolar bone loss (%BL) rate to dental root length. The numbers of fenestration teeth were also tallied. All anterior teeth were supported by <1 mm of ABT on the labial surfaces up to root length Level 8. ABA was statistically greater on the lingual aspect than the labial aspect in lower incisors. The %BL was 26.98% in the lower labial region, 19.27% in upper labial aspect and most severe on the lower lingual plate 31.25% compared with the labial plate. There were no significant differences in %BL between subgroups when categorized by sex or age. Fenestrations were 1.37 times more frequent on lower incisors (37) than upper incisors (27). The null hypothesis was rejected, confirming that incisor periodontal support is poor and alveolar bone loss is severe even prior to the start of orthodontic treatment. Careful diagnosis using 3D CBCT images is needed to avoid iatrogenic degeneration of periodontal support around anterior teeth, particularly in the lower lingual bone plate region.

Comparison of linear and angular measurements using two-dimensional conventional methods and three-dimensional cone beam CT images reconstructed from a volumetric rendering programin vivo

The aim of this study was to compare the linear and angular measurements made on two-dimensional (2D) conventional cephalometric images and three-dimensional (3D) cone beam CT (CBCT) generated cephalograms derived from a 3D volumetric rendering program. Pre-treatment cephalometric digital radiographs of 11 patients and their corresponding CBCT images were randomly selected. The digital cephalometric radiographs were traced using Vista Dent OC (GAC International, Inc Bohemia, NY) and by hand. CBCT and Maxilim® (Medicim, Sint-Niklass, Belgium) software were used to generate cephalograms from the CBCT data set that were then linked to the 3D hard-tissue surface representations. In total, 16 cephalometric landmarks were identified and 18 widely used measurements (11 linear and 7 angular) were performed by 2 independent observers. Intraobserver reliability was assessed by calculating intraclass correlation coefficients (ICC), interobserver reliability was assessed with Student t-test and analysis of variance (ANOVA). Mann-Whitney U-tests and Kruskal-Wallis H tests were also used to compare the three methods (P < 0.05). The results demonstrated no statistically significant difference between interobserver analyses for CBCT-generated cephalograms (P < 0.05), except for Gonion-Menton (Go-Me) and Condylion-Gnathion (Co-Gn). Intraobserver examinations showed low ICCs, which was an indication of poor reproducibility for Go-Me and Sella-Nasion (S-N) in CBCT-generated cephalograms and poor reproducibility for Articulare-Gonion (Ar-Go) in the 2D hand tracing method (P < 0.05). No statistical significance was found for Vista Dent OC measurements (P > 0.05). Measurements from in vivo CBCT-generated cephalograms from Maxilim® software were found to be similar to conventional images. Thus, owing to higher radiation exposure, CBCT examinations should only be used when the inherent 3D information could improve the outcome of treatment.

Comparison of alveolar bone loss around incisors in normal occlusion samples and surgical skeletal Class III patients

To test the hypothesis that there is no difference in vertical alveolar bone loss and alveolar bone thickness around maxillary and mandibular central incisors in normal occlusion samples and skeletal Class III malocclusion patients. The study sample comprised 20 Korean normal occlusion subjects (mean age, 22.1 years; group 1) and patients with skeletal Class III malocclusion with anterior open bite (mean age, 22.4 years; group 2). Three-dimensional (3D) cone beam computed tomography (CBCT) images were taken before orthodontic treatment, and sagittal slices chosen at the labio-lingually widest point of the maxillary and mandibular right central incisor were evaluated, respectively. The amount of vertical alveolar bone loss and/or alveolar bone thickness of the labial and lingual plate at the root apex were measured. Group 2 had statistically significant more vertical bone loss than group 1 (P < .05). Alveolar bone at the apex was significantly thinner in group 2 (P < .05), except for the maxillary incisors. Mandibular incisors showed greater alveolar bone loss than was seen in maxillary incisors in both groups, especially at the lingual side in group 2 (P < .05). Overall, alveolar bone thickness at the apex was wider than cementoenamel junction (CEJ) width, except for the mandibular incisors in group 2, for which the percentage was 81.33%. The hypothesis is rejected. Special care should be taken to avoid aggravating preexisting alveolar bone loss in the anterior teeth, especially in the mandible, in skeletal Class III patients, who may be more vulnerable to alveolar bone loss during orthodontic treatment.

Entry level 3D cone beam

Entry level 3D cone beam

High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.