Dental Cone-beam Computed Tomography Images Research Articles

Beam alignment and image distortion assessment of dental cone beam computed tomography (CBCT) system

Cone-beam computed tomography (CBCT) technique has been widely used in dental imaging as it offers different image views such as panoramic, cephalometric, tomographic, and three dimensions (3D). This study aimed to assess image distortion due to beam misalignment for CBCT system using phantom study. A ball phantom was scanned with default exposure setting for standard panoramic imaging (68 kV, 8 mA and patient size of M) using Planmeca ProMax CBCT unit. Three different measurements were performed on the phantom images such as distance measurement between the centre of the middle ball and rear middle ball, distance measured from the centre of middle ball to tenth ball (left and right), and measurement of both vertical and horizontal distance of any four balls. From the findings, most of measured distance between middle ball and rear middle ball were below the acceptable level, but two measurements exceeded the reference value by 6% and 75%. Similar with the measured distances of the tenth balls, two measurements exceeded the acceptable level by 3% and 28%. The vertical and horizontal distance of 4 balls were slightly differ from standard value with overall magnification of 1.06 and percentage error of 6%. The beam alignment and patient positioning should be accurately evaluated to avoid image distortion and misdiagnosis in dental CBCT images.

Automatic Segmentation of Individual Tooth in Dental CBCT Images From Tooth Surface Map by a Multi-Task FCN

Accurate and automatic segmentation of individual tooth is critical for computer-aided analysis towards clinical decision support and treatment planning. Three-dimensional reconstruction of individual tooth after the segmentation also plays an important role in simulation in digital orthodontics. However, it is difficult to automatically segment individual tooth in cone beam computed tomography (CBCT) images due to the blurring boundaries of neighboring teeth and the similar intensities between teeth and mandible bone. In this work, we propose the use of a multi-task 3D fully convolutional network (FCN) and marker-controlled watershed transform (MWT) to segment individual tooth. The multi-task FCN learns to simultaneously predict the probability of tooth region and the probability of tooth surface. Through the combination of the tooth probability gradient map and the surface probability map as the input image, MWT is used to automatically separate and segment individual tooth. Twenty-five dental CBCT scans are used in the study. The average Dice similarity coefficient, Jaccard index, and relative volume difference are 0.936 (±0.012), 0.881 (±0.019), and 0.072 (±0.027), respectively, and the average symmetric surface distance is 0.363 (±0.145) mm for our method. The experimental results demonstrate that the multi-task 3D FCN combined with MWT can segment individual tooth of various types in dental CBCT images.

CAROTID ARTERY CALCIFICATIONS DETECTED BY CBCT IN PATIENTS WITH A HISTORY OF HYPERTENSION

<h3>Background</h3> One of the most common sites for the formation of vascular calcifications is in the branches of the common carotid artery. More frequently, these are formed by the calcification of existing plaques along the vascular wall. Numerous studies utilizing other modalities have revealed a positive correlation between vascular calcifications and hypertension; however, there is a need for investigation of the incidence of these pathologies using cone beam computed tomography (CBCT) technology and for exploring the factors that influence their presence or detection. <h3>Objective(s)</h3> The aim of this study was to determine the proportion of patients who have a positive history of hypertension and a positive finding of carotid artery calcification (CAC) and to determine if there are factors that predispose certain groups of patients to carotid artery calcifications, including patient age, gender, and history of antihypertensive medication use. <h3>Study Design</h3> This retrospective study focused on 608 randomly selected patients who received dental CBCT imaging studies at Stony Brook School of Dental Medicine. Relevant patient demographic characteristics and medical history were extrapolated from the patients' electronic health records. The data were analyzed for statistical significance using Pearson's correlation and logistic regression. <h3>Results</h3> A total of 608 patient records (mean age = 62.6 years) with equal gender distribution were screened. Of these, 108 (17.76%) cases showed an incidence of CAC. 240 records indicated a positive history of hypertension (HTN), and 87 patient records (36.25%) showed a positive history of HTN and presence of carotid calcification. A strong male predilection (2:1) was observed for the concurrent positive history of HTN and presence of CAC. The mean age for the presence of a CAC in patients with and without HTN were 71.5 and 71.8, respectively. <h3>Discussion/Conclusions</h3> Our findings suggest a significant correlation between history of hypertension and the presence of CAC, with a strong predilection for men. No significant correlation was observed between antihypertensive medications and CAC.

Bone Volume Assessment Around Dental Implants After Open Maxillary Sinus Elevation Surgery: A Quantitative Approach to CBCT Images.

Cone beam computed tomography (CBCT) is an important imaging technique in maxillofacial evaluations. However, application-specific image analysis methods aimed at extracting quantitative information from these images need to be further developed. The aim of this study was to provide a robust and objective method that could assess radiologic changes around dental implants after sinus elevation surgery with simultaneous implant placement. The study was performed retrospectively on patients fulfilling the inclusion criteria. The included patients had been CBCT scanned preoperatively, at baseline (early after surgery), and 6 months postoperatively. In order to quantify the radiologic changes, an image analysis workflow was developed based on the postoperative baseline and 6-month scans. The workflow included metal artefact reduction, registration, and a standardized protocol for semiautomatic segmentation. Validation of different steps of the method was conducted by comparing scans from all time points. Comparison of constant volumes (eg, screws and bony parts not subjected to change) was used. Additionally, the Dice similarity coefficient (DSC) was used to measure the overlap of the segmentations. The study included nine maxillary sinuses from six patients. The bone formation was quantified and visualized in 3D. In the validation, no significant differences were found for the constant volumes at the different scanning time points. The DSC showed accurate results with values > 0.92. The method presented in this study provides an objective and robust evaluation of bone formation around dental implants. The same methodologies can be applied in other studies of dental CBCT images, eg, for comparison of grafting materials or surgical strategies.

Estimated radiation risk of cancer from dental cone-beam computed tomography imaging in orthodontics patients

BackgroundRadiation dose evaluation is important to cone-beam computed tomography (CBCT) for routine orthodontic treatment planning, especially for a significant proportion of children in orthodontic patients. This study evaluated the patient radiation dose and estimated the radiation cancer risk on dental CBCT according to the calculations by the Monte Carlo simulation method.MethodsThe dental CBCT scanner evaluated in this project was the i- CAT® (Imaging Sciences International Inc., PA, U.S.A.) device. Organ doses and effective doses were calculated by using personal computer-based Monte Carlo simulation (PCXMC 2.0 Rotation) software. The cancer risk resulting from the exposure to ionizing radiation was estimated by using the BEIR VII (Biologic Effects of Ionizing Radiation VII) report model, and the risk of exposure-induced death (REID) was assessed by PCXMC 2.0 Rotation software.ResultsThe largest contribution to the organ dose and effective dose at Zref 83 cm positioned in the dental CBCT x-ray beam centerline was from the salivary glands (738.29μGy, 7.38 μSv). The different organ doses showed the maximum values at the different Zref locations, and the largest contribution to the organ dose and effective dose of all simulated positions was from the thyroid (928.77μGy, 37.5 μSv). The REID values in the 10-year olds (22.6 × 10− 7, female; 19 × 10− 7, male) were approximately double than those in 30-year olds (10.4 × 10− 7, female; 8.88 × 10− 7, male) for all cancers. The highest change during age range from 10 to 30 was shown in breast cancer of females.ConclusionsAlthough individual cancer risk estimates as a function of gender and age are small, the concern about the risks from dental CBCT is related to the rapid increase in its use for orthodontic practice, especially in children patients.

Metal Artifact Suppression in Dental Cone Beam Computed Tomography Images Using Image Processing Techniques

Dental cone beam computed tomography (CBCT) images suffer from severe metal artifacts. These artifacts degrade the quality of acquired image and in some cases make it unsuitable to use. Streaking artifacts and cavities around teeth are the main reason of degradation. In this article, we have proposed a new artifact reduction algorithm which has three parallel components. The first component extracts teeth based on the modeling of image histogram with a Gaussian mixture model. Striking artifact reduction component reduces artifacts using converting image into the polar domain and applying morphological filtering. The third component fills cavities through a simple but effective morphological filtering operation. Finally, results of these three components are combined into a fusion step to create a visually good image which is more compatible to human visual system. Results show that the proposed algorithm reduces artifacts of dental CBCT images and produces clean images.

Translational motion correction algorithm for truncated cone-beam CT using opposite projections.

Cone-beam computed tomography (CBCT) is widely used in various medical imaging applications, including dental examinations. Dental CBCT images often suffer from motion artifacts caused by involuntary rigid motion of patients. However, earlier motion compensation studies are not applicable for dental CBCT systems using truncated detectors. This study proposes a novel motion correction algorithm that can be applied for truncated dental CBCT images. We propose a two-step method for motion correction. First, we estimate the relative displacement of each pair of opposite projections by finding the motion vector that maximizes the two-dimensional correlation coefficients of the opposite projections. Second, we convert the relative displacement into the absolute coordinate motion that yields the highest image sharpness of the reconstruction image. Using the motion vectors in the absolute coordinate system, motion artifacts are then compensated by modifying the trajectory of the source and detector during the back-projection step of the image reconstruction process. In simulation, the proposed method successfully estimated the true relative displacement. After converting to the absolute coordinate motions, the motion-compensated image was close to the ground-truth image and exhibited a lower mean-square-error than that of the uncompensated image. The results from the real data experiment also confirmed that the proposed method successfully compensated for the motion artifacts. The experimental results confirmed that the proposed method was applicable to most dental CBCT systems using a truncated detector without any use of an additional motion tracking system nor prior knowledge.

Accuracy of biomarkers obtained from cone beam computed tomography in assessing the internal trabecular structure of the mandibular condyle

The aim of this study was to validate the ability of cone beam computed tomography (CBCT) to measure condylar internal trabecular bone structure and bone texture parameters accurately. Sixteen resected condyles of individuals undergoing temporomandibular joint replacement were collected and used as samples. These condyles were then radiographically imaged by using clinically oriented dental CBCT and research oriented micro-computed tomography (micro-CT). The CBCT scans were then compared with the gold standard micro-CT scans in terms of 21 bone imaging parameters. Descriptive histologic investigation of the specimens was also performed. Significant correlations were found for several imaging parameters between the CBCT and micro-CT images, including trabecular thickness (r = 0.92), trabecular separation (r = 0.78), bone volume (r = 0.90), bone surface area (r = 0.79), and degree of anisotropy measurements (r = 0.77). Measurements of trabecular thickness, trabecular separation, bone volume, bone surface area, and degree of anisotropy obtained from high-resolution dental CBCT images may be suitable bone imaging biomarkers that can be utilized clinically and in future research.

Quantification of dental prostheses on cone-beam CT images by the Taguchi method.

The gray values accuracy of dental cone‐beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone‐beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis‐free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis‐free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1–9 were below 12% and gray value differences for ROIs 13–18 away from prostheses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant‐supported titanium prosthesis, and between 46% and 59% for regions between double implant‐supported, nickel‐chromium alloys (Ni‐Cr) prostheses. Quantification of the effect of prostheses and scanning parameters on dental CBCT gray values was assessed.PACS numbers: 87.59.bd, 87.57Q

Value of intra- and post-operative cone beam computed tomography (CBCT) for positioning control of a sphenopalatine ganglion neurostimulator in patients with chronic cluster headache

IntroductionThe objective of this study was to determine whether postoperative control of the neurostimulator placement within the pterygopalatine fossa (PPF) by means of 3-dimensional (3D) cone beam computed tomography (CBCT) was of therapeutic relevance compared to intraoperative CBCT imaging alone. Material and methodsImmediately after implantation of the sphenopalatine ganglion (SPG) neurostimulator, intraoperative CBCT datasets were generated in order to visualize the position of the probe within the PPF. Postoperatively, all patients received a CBCT for comparison with intraoperatively acquired radiographs. ResultsTwenty-four patients with cluster headache (CH) received an SPG neurostimulator. In 4 patients, postoperative CBCT images detected misplacement not found in intraoperative CBCT. In 3 cases, electrode tips were misplaced into the maxillary sinus and in 1 case into the apex of the PPF superior to the suspected location of the SPG. Immediate revision with successful repositioning within 3 days was done in 2 patients and a deferred reimplantation in 1 patient within 6 months. One patient declined revision. ConclusionWe were able to demonstrate the clinical value of postoperative dental CBCT imaging with a wide region of interest (ROI) due to a superior image quality compared with that achieved with intraoperative medical CBCT. Although intraoperative 3D CBCT imaging of electrode placement is helpful in the acute surgical setting, resolution is, at present, too low to safely exclude misplacement, especially in the maxillary sinus. High-resolution postoperative dental CBCT allows rapid detection and revision of electrode misplacement, thereby avoiding readmission and recurrent tissue trauma.

Automated bone segmentation from dental CBCT images using patch-based sparse representation and convex optimization.

Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatment planning of the patients with CMF deformities. However, due to the poor image quality, including very low signal-to-noise ratio and the widespread image artifacts such as noise, beam hardening, and inhomogeneity, it is challenging to segment the CBCT images. In this paper, the authors present a new automatic segmentation method to address these problems. To segment CBCT images, the authors propose a new method for fully automated CBCT segmentation by using patch-based sparse representation to (1) segment bony structures from the soft tissues and (2) further separate the mandible from the maxilla. Specifically, a region-specific registration strategy is first proposed to warp all the atlases to the current testing subject and then a sparse-based label propagation strategy is employed to estimate a patient-specific atlas from all aligned atlases. Finally, the patient-specific atlas is integrated into a maximum a posteriori probability-based convex segmentation framework for accurate segmentation. The proposed method has been evaluated on a dataset with 15 CBCT images. The effectiveness of the proposed region-specific registration strategy and patient-specific atlas has been validated by comparing with the traditional registration strategy and population-based atlas. The experimental results show that the proposed method achieves the best segmentation accuracy by comparison with other state-of-the-art segmentation methods. The authors have proposed a new CBCT segmentation method by using patch-based sparse representation and convex optimization, which can achieve considerably accurate segmentation results in CBCT segmentation based on 15 patients.

The use of cone-beam computed tomography in dentistry: An advisory statement from the American Dental Association Council on Scientific Affairs

The American Dental Association Council on Scientific Affairs (CSA) promotes safe use of cone-beam computed tomography (CBCT) and appropriate professional justification of CBCT imaging procedures. The CSA reviewed the current research literature to develop collaborative guidance regarding the use of CBCT in dentistry with input from a broad group of stakeholder organizations. The Council's principles for CBCT safety may be applied to any number of potential dental CBCT imaging applications. As with other radiographic modalities, CBCT imaging should be used only after a review of the patient's health and imaging history and the completion of a thorough clinical examination. Dental practitioners should prescribe CBCT imaging only when they expect that the diagnostic yield will benefit patient care, enhance patient safety or improve clinical outcomes significantly.