3D CBCT Images Research Articles

Radiation safety guidelines For 3D CBCT Imaging: A dental review

Radiation safety guidelines For 3D CBCT Imaging: A dental review

Radiation safety guidelines For 3D CBCT Imaging: A dental review

Radiation safety guidelines For 3D CBCT Imaging: A dental review

Can artificial intelligence-driven cephalometric analysis replace manual tracing? A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to investigate the accuracy and efficiency of artificial intelligence (AI)-driven automated landmark detection for cephalometric analysis on two-dimensional (2D) lateral cephalograms and three-dimensional (3D) cone-beam computed tomographic (CBCT) images. An electronic search was conducted in the following databases: PubMed, Web of Science, Embase, and grey literature with search timeline extending up to January 2024. Studies that employed AI for 2D or 3D cephalometric landmark detection were included. The selection of studies, data extraction, and quality assessment of the included studies were performed independently by two reviewers. The risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. A meta-analysis was conducted to evaluate the accuracy of the 2D landmarks identification based on both mean radial error and standard error. Following the removal of duplicates, title and abstract screening, and full-text reading, 34 publications were selected. Amongst these, 27 studies evaluated the accuracy of AI-driven automated landmarking on 2D lateral cephalograms, while 7 studies involved 3D-CBCT images. A meta-analysis, based on the success detection rate of landmark placement on 2D images, revealed that the error was below the clinically acceptable threshold of 2mm (1.39mm; 95% confidence interval: 0.85-1.92mm). For 3D images, meta-analysis could not be conducted due to significant heterogeneity amongst the study designs. However, qualitative synthesis indicated that the mean error of landmark detection on 3D images ranged from 1.0 to 5.8mm. Both automated 2D and 3D landmarking proved to be time-efficient, taking less than 1min. Most studies exhibited a high risk of bias in data selection (n = 27) and reference standard (n = 29). The performance of AI-driven cephalometric landmark detection on both 2D cephalograms and 3D-CBCT images showed potential in terms of accuracy and time efficiency. However, the generalizability and robustness of these AI systems could benefit from further improvement. PROSPERO: CRD42022328800.

Does Chin-Throat Length Relate to Oropharyngeal Volume, Minimum Axial Area, and Polysomnographic Indices?

OBJECTIVE To evaluate the correlation between chin-throat length and oropharyngeal volume, minimum axial area, and polysomnographic indices in patients undergoing orthodontic treatment. METHODS The study enrolled 73 patients (35 men and 38 women) who met the inclusion criteria. The face scanner created a 3D facial simulation, and chin-throat length was subsequently measured. 3D CBCT images were used to simulate 2D lateral cephalometric images. Oropharyngeal volume and minimum axial area were determined using Dolphin imaging software, and airway function was assessed through unattended at-home overnight polysomnography. Pearson correlation coefficients were then used to determine the correlations between chin-throat length and oropharyngeal volume, minimum axial area, and polysomnographic indices. Additional correlations were explored between age, BMI, cephalometric variables, and oropharyngeal volume, and minimum axial area. Finally, multiple regression analysis was used to analyse the factors having an influence on the correlations. RESULTS Chin-throat length was positively correlated with oropharyngeal volume and minimum axial area. SNB, ANB, Co-Gn, and Go-Gn were also observed to be positively correlated with oropharyngeal volume and minimum axial area. Multiple regression analysis demonstrated that the factor influencing the correlation of chin-throat length with oropharyngeal volume and with minimum axial area was mandibular length; however, the correlations were only observed among men. No correlation was evident between chin-throat length and polysomnographic indices. CONCLUSIONS Chin-throat length is positively correlated with oropharyngeal volume and minimum axial area but has no association with polysomnographic indices. Mandibular length may influence upper airway dimensions. KEYWORDS chin-throat length, oropharyngeal volume, minimum axial area, polysomnographic indices

Potential S1 Nerve Root Blocks Associated with Sacroiliac Joint Injections.

Sacroiliac (SI) joint dysfunction is a common cause of lower back pain. The diagnosis of SI joint pain remains challenging. Sacroiliac joint injection remains the gold standard of diagnosis of SI joint pain as well as providing therapeutic effect. One complication related to SI joint injection is temporary numbness and weakness of the leg. To evaluate the anatomy of the SI joint and the flow of the contrast in the sacroiliac joint and to understand how local anesthetic can affect the nerve roots and cause temporary weakness and numbness of the leg. Study Design. Retrospective case series. Setting. Academic medical center. Patients who underwent SI joint injection with three-dimensional cone beam computed tomography with fluoroscopy (3D-CBCT) imaging were identified through retrospective review of two providers' case log from the electronic medical record. The cone beam CT images were reviewed to study the contrast spread and flow in the SI joint. 27/32 patients with the mean age of 56 years (range 39-87 years), 20 females, and 7 males were included in this study. After reviewing cone beam CT images, 4/27 (14.8%) patients showed contrast spread in the SI joint and spread into the S1 posterior neuroforamen. The remainder 23/27 (85.2%) patients had contrast localized in the SI joint. Limitations. Small population size, retrospective review of medical records. Our results indicate that the injection of lower concentration of local anesthetic with less volume may be necessary to decrease the risk of S1 nerve root block and epidural block. Furthermore, to improve the specificity of a diagnostic SI injection, an appropriate evaluation should be considered to rule out any S1 nerve pathology as a significant pain generator.

Investigating focal spot position drift in a mobile imaging system equipped with a monobloc-based x-ray generator.

Misalignment or double-contouring artifacts can appear in high-resolution 3D cone beam computed tomography (CBCT) images, potentially indicating geometric accuracy issues in the projection data. Such artifacts may go unnoticed in low-resolution images and could be associated with changes in the focal spot (FS)position. High-resolution 3D-CBCT imaging by a mobile imaging device with a large gantry clearance offers more versatility for clinical workflows in image-guided brachytherapy (IGBT), intraoperative radiation therapy (IORT), and spinal, as well as maxillofacial surgery. However, misalignment or double-contouring artifacts hinder workflow advancements in these domains. This paper introduces intrinsic calibration and geometrical correction methods as extensions to a well-established technique for addressing geometrical deviations resulting from factors such as gravity or mechanical inconsistencies. These extensions cover shifts and drifts of the FS depending on FS size selection, temperature, tube current, and tube potential. The proposed methods effectively mitigate artifacts in high-resolution CBCT images stemming from geometrical inaccuracies in projection data, without requiring additional equipment like a pinholedevice. Geometrical offsets and drifts of the x-ray tube FS were characterized on a mobile multi-purpose imaging system, the ImagingRing-m. A pinhole-like experiment was simulated by adjusting the movable collimation unit to a small rectangular aperture within the FS size range. The influence of filament selection, that is, FS size, temperature, the relatively low tube currents, as well as tube potential settings have been studied on two different monobloc types sharing the same x-ray tube insert. The Catphan 504 and an Alderson head phantom were used to assess resulting imageartifacts. Switching the FS size to one different from what was used for geometrical (gravitation, mechanical variations) calibration induced the most notable position changes of the x-ray FS, resulting in double-contouring artifacts and blurring of high-resolution 3D-CBCT images. Incorporating these shifts into a geometrical correction method effectively minimized these artifacts. Thermal drifts exhibited the second largest geometrical changes, comparable to FS size shifts across the thermal operating conditions of the x-ray system. The proposed thermal drift compensation markedly reduced thermal drift effects. Tube current and potential had little impact within the range of available tube currents, eliminating the need for compensation in currentapplications. Augmenting the geometrical calibration pipeline with proposed FS drift compensations yielded significant enhancements in image quality for high-resolution reconstructions. While compensation for thermal effects posed challenges, it proved achievable. The roles of tube current and potential were found to benegligible.

DeAPIR: Efficient and Enhanced Dental Arch-Guided Panoramic Image Reconstruction from CBCT Data

Dental CBCT and panoramic imaging play a pivotal role in dental diagnosis and treatment planning, alongside the indispensable use of computed tomography (CT) and X-ray imaging in dentistry, particularly for surgical planning. Given the widespread adoption of dental cone beam CT in clinics today, we explore a novel approach in this study—utilizing CT’s three-dimensional (3D) data to reconstruct a two-dimensional (2D) panoramic dental image. This method eliminates the requirement for an extra panoramic scan. In this work, we propose a novel framework to generate an enhanced and extended 2D panoramic view by using the dental arch extracted from 3D CBCT. Our method involves segmenting the patient’s dental arch from their 3D CBCT image by identifying horizontal slices with above-average intensity, followed by morphological operations, including dilation, Gaussian filtering, and skeletonization, to delineate the dental arch line. Additionally, we extend the dental arch beyond the wisdom teeth using quadratic curve fitting. Finally, we employ Maximum Intensity Projection on rotated cubic segments aligned with the dental arch curve to produce captivating panoramic images. The panoramic view produced using our proposed method, when compared to the results obtained from BlueSky and OpenInventor, exhibited superior enhancements and greater accuracy in panoramic visualization.

Threshold-Based Segmentation for Landmark Detection Using CBCT Images

The aim of this study is to examine the influence of threshold-based segmentation on the mean error of automatic landmark detection in 3D CBCT images. A GUI was developed for radiologists, allowing manual landmark identification and visualization of CBCT images. After a threshold-based segmentation, a semi-automatic algorithm for landmark detection was designed using the anatomic definition of each landmark. A step of 50 Hounsfield units was used for threshold variation to assess the detection error. 5 CBCT images were used to validate the proposed approach. The measurement of error detection for one patient was influenced by the threshold variation. For this patient, the error changed from 1.49 mm to 10.32 mm at a low threshold value, while for another patient, the error changed from 1.96 mm to 12.28 mm at high a threshold value. In a CBCT scanner, the choice of threshold value for segmentation can be an important factor in causing error in measurements.

Evaluation of root canal morphology of mandibular central and lateral incisor in Mosul city by using CBCT

Background: Lower incisor endodontic treatment failures are primarily due to missing canals, notably the lingual canal. Aim: The incisors' root architecture and the number of canals of the mandibular would be evaluated using computed tomography using a cone beam (CBCT). Methods: 220 patients with age (18-75) years who visited Al Noor Dental Center in Mosul over the course of two years had their 780 central and lateral incisors of the jaw evaluated using 3D CBCT images. The classification of the Vertucci system was applied to determine how the root canal was shaped. Results: A comparison between the incisors of lateral and central canal shape using the Vertucci method, the number of central incisors with only one root was higher than the lateral incisors with the roots of the same number. Where it was found that the central incisors of the first type are 377 teeth, while the number of incisors Lateral 358, the number of incisors in the second type was 5 teeth, and the lateral 3 teeth. Conclusions: The root morphology of the sexes differs significantly. Various morphological alterations should be anticipated by the dental professional when undertaking endodontic treatment. To ascertain the morphological traits of the conductor's anterior tooth roots, additional research is required.

Assessing the Impact of Transcutaneous Maxillary Distraction Osteogenesis on Pharyngeal Airway Volume in Children with Cleft Lip and Palate: A 3D Evaluation Study.

Cleft lip and cleft palate (CLCP) patients often have a retrusive maxilla and a severe skeletal Class III malocclusion, which can result in velopharyngeal insufficiency (VPI). The aim of this study was to evaluate the changes in the volume of the 3D airway in CLCP children after maxilla distraction using the transcutaneous maxillary distraction osteogenesis (TMDO) method. 15 children with bilateral or unilateral CLCP were included in the study. 3D CBCT images were taken before and after distraction and were segmented and reconstructed to create a 3D airway model. The airway was divided into three regions: the upper, oropharyngeal, and hypopharyngeal airway. Pearson correlation tests were used to assess correlations between volume changes and corresponding skeletal and dental landmark movements (Point N, ANS, A, B, Pog, U1, and L1). The results showed that the ANS point advanced 9.85 ± 3.60 mm, and the A point advanced 14.22 ± 4.57 mm. The total airway volume change increased by 2535.06 ± 2791.80 mm3. However, there was no significant correlation between the A/ANS/U1 and the three different airway regions. Only B/Pog/L1 showed a positive correlation with these airway regions, with a high correlation between B/Pog/L1 and the hypopharyngeal airway region. TMDO can result in greater anterior advancement of the maxilla and an increase in airway volume, but the changes in bony landmarks did not show a strong positive correlation with the increase in airway volume as expected. Further investigation is needed to analyze the influence of surrounding soft tissue on the changes in airway volume.

Three-Dimensional Evaluation of the Mandibular Lingula on ConeBeam Computed Tomographic Images in The Turkish Population

Objective: The purpose of this study was to provide morphometric and anatomical data for mandibular lingula (Li) in The Turkish population using three dimensional-cone beam computed tomography (3D-CBCT) images. Methods: CBCT images of the patients taken between July 2020 and March 2021, were retrieved from the archival records. A total of 100 Li’s of 50 patients who met the criteria of this study were evaluated. The distances between the tip of the Li and ramal landmarks/occlusal plane were measured and the shape of the Li was evaluated on 3D-CBCT images. Results: CBCT images of the 50 patients (19 males and 31 females) with an age range of 18 to 56 years were included in this study. Significant differences were found for the measurements of right LP (p < 0.001), left LP (p = 0.003), right LOP (p = 0.016) and left LOP (p = 0.007) between genders. A significant difference was observed for LI (p = 0.024) between the left and right sides. Regarding the shape of the Li significant difference was found between the right and left sides (p = 0.003), while no significant differences were observed among genders on either both sides. Conclusion: This study contributes additional data to the literature about the location and morphology of the Li in Turkish subpopulation. These results provide a reference for the clinicians regarding the procedures involving mandibular ramus to perform maneuvers in safe margins.

Evaluation of Morphology and Prevalence of Palatogingival Grooves on Affected Maxillary Anterior Teeth using Cone-Beam Computed Tomography

Background: Palatogingival groove (PG), a developmental anomaly, originates in cingulum and extends to varying distances apically. It is an ideal pathway for oral bacteria to invade periodontal tissues causing periodontal damage, pulp necrosis, apical periodontitis and endo-periodontal deformity which is not easily perceived until sinus tract infection appears in mouth. It presents a challenge to most clinicians as it requires an interdisciplinary approach to diagnosis and treatment planning.
 Aim and Objective: To evaluate the prevalence and characteristics of palatogingival grooves (PGs) in maxillary anterior teeth on CBCT.
 Materials and Methods: CBCT examinations of 707 teeth in 120 patients (Female-41, Male-79) were evaluated retrospectively. Maxillary central incisors, lateral incisors and canine were investigated for the presence or absence of PGs and PG type using the Gu classification (type I, II, or III). 3D CBCT images were used for evaluation of PGs. Radiographic features of PGs were noted and differences were evaluated and results were obtained. Differences was considered significant for p ≤ 0.05.
 Results: The PGs were observed in 61 teeth. Type 1 PG is found more prevalent in males (30.37%) than in females (12.19%) followed by type 2(male-12.65%, females-4.87%) and type 3 (male-3.75%). Higher prevalence for Type 1 PG was seen in the lateral incisor followed by central incisor and canine and had a male predominance. Type 2 PG showed equal prevalence for lateral & central incisor and male predominance. Type 3 PG showed higher prevalence for lateral incisors and male predominance.
 Conclusion: Prevalence of PGs was found to be 8.62%. PG facilitate bacterial colonization leading to periodontitis, pulp necrosis and endo-periodontal lesion in an apparently normal tooth which pose challenges in its diagnosis and management for survival of tooth.

Characterization of a Commercial Bioluminescence Tomography System for Pre-Clinical Radiation Research

<h3>Purpose/Objective(s)</h3> To advance image-guided irradiation for soft tissue targeting and treatment assessment, we collaborated with our industrial partner and developed a bioluminescence tomography system (BLT, MuriGlo) for pre-clinical radiation research. We characterize the system performance and demonstrate its capability in target localization for radiation guidance. <h3>Materials/Methods</h3> MuriGlo consists of four-mirror system, filters, lens and CCD camera, enabling a compact imaging platform and multi-projection and multi-spectral BLT. The imaging mouse bed includes a base, and a detachable and transportable bed, allowing animal imaged in MuriGlo and transferred to small animal radiation research platform (SARRP) for CBCT imaging and BLT-guided irradiation. A transparent polycarbonate plate covering the middle of the mouse bed is used to support and image animal at 180⁰ projection under the bed. We investigated its effects on optical signal acquisition, 3D BLT reconstruction accuracy and dosimetric impact. Imaging phantoms are designed to evaluate 2D imaging resolution, focal plane, depth of field, signal acquisition linearity, imaging uniformity and distortion. An optimization routine with pinhole camera model was developed to map 2D bioluminescence images (BLIs) to the surface of the numerical mesh of imaged object generated from the CBCT image. The mapped BLIs are used as input data for BLT reconstruction. Spectral derivative method with compressed sensing conjugate gradient algorithm was implemented for BLT volumetric reconstruction. To minimize the ambient temperature in affecting in vivo bioluminescence signal intensity and spectrum, a temperature control module was also developed to maintain consistent temperature in the MuriGlo imaging chamber. Phantom and glioblastoma (GBM) mouse model will be used to validate the localization accuracy of the BLT system for guidance. <h3>Results</h3> The depth of field of MuriGlo was measured at 24mm, and the focal plane is set at 16mm above the mouse bed to have clear surface BLIs of mouse at all projections. The linearity between signal and exposure time from 0.1 to 180s is within 0.6% deviation. Our initial test shows within a given region of interest, the image uniformity is within 5% variation and image shift due to distortion is within 0.25mm. The data mapping from the 2D BLIs to 3D CBCT image is within 0.6mm. With temperature control turned on, the imaging chamber could be warmed up to 37°C from room temperature in 13 mins. Our phantom test shows MuriGlo can localize 3D bioluminescent target at 1mm accuracy and only 0.2mm deviation was observed for the case with and without transparent plate. <h3>Conclusion</h3> This work is the first systematic study in characterizing the commercial BLT-guided system for pre-clinical radiation research. We expect the information and methods developed in this study will support MuriGlo users, cross different institutes, in performing accurate image-guided radiation research and facilitating study reproducibility.

Accuracy and Reproducibility of Facial Measurements of Digital Photographs and Wrapped Cone Beam Computed Tomography (CBCT) Photographs.

The study sought to assess whether the soft tissue facial profile measurements of direct Cone Beam Computed Tomography (CBCT) and wrapped CBCT images of non-standardized facial photographs are accurate compared to the standardized digital photographs. In this cross-sectional study, 60 patients with an age range of 18–30 years, who were indicated for CBCT, were enrolled. Two facial photographs were taken per patient: standardized and random (non-standardized). The non-standardized ones were wrapped with the CBCT images. The most used soft tissue facial profile landmarks/parameters (linear and angular) were measured on direct soft tissue three-dimensional (3D) images and on the photographs wrapped over the 3D-CBCT images, and then compared to the standardized photographs. The reliability analysis was performed using concordance correlation coefficients (CCC) and depicted graphically using Bland–Altman plots. Most of the linear and angular measurements showed high reliability (0.91 to 0.998). Nevertheless, four soft tissue measurements were unreliable; namely, posterior gonial angle (0.085 and 0.11 for wrapped and direct CBCT soft tissue, respectively), mandibular plane angle (0.006 and 0.0016 for wrapped and direct CBCT soft tissue, respectively), posterior facial height (0.63 and 0.62 for wrapped and direct CBCT soft tissue, respectively) and total soft tissue facial convexity (0.52 for both wrapped and direct CBCT soft tissue, respectively). The soft tissue facial profile measurements from either the direct 3D-CBCT images or the wrapped CBCT images of non-standardized frontal photographs were accurate, and can be used to analyze most of the soft tissue facial profile measurements.

Accuracy of Miniscrew Insertion Using a Customized Printed Three-Dimensional Surgical Guide (A Comparative Split Mouth Study)

Aim of the study This study was conducted to evaluate the accuracy of a new constructed 3D CBCT image–based surgical guide for miniscrew implantation . Materials and Methods Twenty five adult patients of were included in the current study (13 males and 12 females). Mandibular arch of every patient was randomly divided into : one experimental side ( miniscrews were placed using surgical guide ) and one comparison side ( miniscrews were placed conventionally without surgical guide. For both sides (experimental and comparison side); Linear measurements were recorded on the software of coronal deviations, apical deviations and vertical deviations . Also , angular measurements were recorded in both mesiodistal and buccolingual dimensions for the actual plan and the real mini screws . At the end all deviations were calculated and statistical analysis was performed. Results A significantly higher level of accuracy (lower differences from the actual value) was achieved with the surgical guide technique (p < 0.001) than hand drilling technique for all measurements . Conclusions Three Dimensional surgical guides provide a precise method for miniscrew placement into the dentoalveolar bone.

3D Analysis of Tooth Movement Using 3D Technology.

3D cone beam imaging (CBCT) has allowed clinicians to better understand the anatomical variations of cranial anatomy. One crucial aspect of this technology plays is the understanding of alveolar bone morphology and remodeling. Variations in cortical bone thickness between individuals have been reported. No published study has analyzed the relationship between cortical bone thickness and rate of tooth movement. The aim of this study is to begin answering the question: is there an association between rate of tooth movement and cortical bone thickness? Twenty-three patients underwent extraction of a single premolar in each of the four quadrants prior to orthodontic therapy. Routine clinical records including 3D CBCT images were acquired of all patients prior to first premolar extractions. Rate of tooth movement in each quadrant for each patient was determined via mesiodistal millimetric measurements obtained by a single calibrated operator. With CBCT images, cortical bone thickness was measured at various levels from the alveolar crest along the long axis of the to-be-extracted first premolars. The association between cortical bone thickness and rate of tooth movement was analyzed. Statistically significant associations were found between rate of tooth movement and cortical bone thickness at levels 2mm, 5mm, and 8mm, apical to the alveolar crest in both the right and left maxillary quadrants (p < 0.05). Statistically significant associations were found between rate of tooth movement and cortical bone thickness at levels 5mm and 8mm apical to the alveolar crest in both mandibular quadrants (p < 0.05). Increased cortical bone thickness was associated with decreased rate of tooth movement. There was no statistically significant association between rate of tooth movement and cortical bone thickness 2mm apical to the alveolar crest of the to-be-extracted first premolars in the mandibular left nor right quadrants (p > 0.05). Results suggest an inverse relationship may exist between cortical bone thickness and rate of tooth movement in both the maxilla and mandible. Cortical bone thickness may have the potential to serve as a predictive tool for rate of orthodontic tooth movement.

Influence of type of radiograph and levels of experience and training on reproducibility of the cervical vertebral maturation method

The objective of this study was to assess the reproducibility of cervical vertebral maturation (CVM) method based on the type of radiographic image and the level of experience and level of training of the evaluator. Ten evaluators (5 orthodontic residents and 5 faculty members) were randomly divided into 2 groups: trained and untrained. All participants evaluated 80 radiographic images previously acquired in 4 different formats: (1) 2-dimensional (2D) digital (2D-digital), (2) 2D digitized hard copy from the Iowa Facial Growth Study (American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection), (3) 2D digital reconstructed from a 3-dimensional (3D) radiograph (2D-from 3D), and (4) 3D cone-beam computerized tomographic (3D-CBCT) images. Agreement among evaluators on the morphology of the cervical vertebrae (CV) and the CVM stage of each radiographic image was assessed using Randolph's kappa statistic and Kendall's W coefficient of concordance. Interobserver agreement on the determination of a curvature on the inferior border of the CV was substantial to perfect, whereas agreement on shape was fair to moderate. Overall, the level training in all image types, except 3D-CBCTs, but not the level of experience affected the agreement for shape and curvature of the CVs. Interobserver agreement on CVM staging for all combined images was substantial at 0.72. Faculty had a higher level of agreement than residents except for 2D-digital and 3D-CBCT images, whereas trained evaluators had an overall higher level of agreement than untrained evaluators except for 3D-CBCT images. Interobserver agreement in determining CVM stage was substantial for all images evaluated; experience and training resulted in higher level of agreement for some image types. The 3D-CBCT images did not provide increased interobserver agreement over current 2D-digital lateral cephalograms in determining CVM staging or shape of the CV. The highest agreement in CVM staging was obtained on 2D-digital lateral cephalograms with training.

Az igazságügyi fogorvosszakértés múltja, jelene és jövője

Forensic dentistry dates back more than 200 years. Yet Oscar Amoedo, a Cuban-born dentist, is considered the father of forensic dentistry. He emphasized the dentists’ role in humans’ identification and laid down the general principles of dental identification in his dissertation in 1989. Dental experts must have interdisciplinary knowledge to do his or her job. From the teeth development through the type of materials of various restorations and the appearance of specific diseases, he/she has to consider the entire oral cavity. As it happens today, for the last 60-70 years too, the victim’s dentist testified the positive match by the dental identification. Nowadays, there are available plaster models, paper or digital based patient records, x-rays to support forensic dentistry. In the future, digital technology will make identification even faster and more accurate, and based on the patients’ 3D digital models, CBCT images, or palate samples, artificial intelligence (AI) guided computers will be making identifications even without any human assistance.

Evaluation of sagittal condylar guidance angles using computerized pantographic tracings, protrusive interocclusal records, and 3D-CBCT imaging techniques for oral rehabilitation.

The goal of registering the condylar guidance is to recreate the patient's occlusion as exactly as possible on the articulator, and is therefore essential for successful prosthodontic rehabilitation. Clinical, radiographic, and pantographic methods are used to determine sagittal condylar guidance angles (SCGAs). These methods generate different angles in the same patients. The present study is the first disquisition to evaluate and correlate SCGAs determined by the use of pantographic tracing (PT), protrusive records (PR), and radiographic (CBCT) techniques. The condylar guidance was measured using PT, PR, and CBCT imaging techniques in 23 nonpatient participants aged between 18 and 30 years irrespective of sex. PT was recorded using Cadiax® Compact system, a computerized recorder of SCGAs. PR was obtained using polyvinyl siloxane bite registration material, transferred to a semiadjustable articulator (Denar Mark II, Whip Mix Corp., USA) using facebow transfer (Denar Mark II, Whip Mix Corp., USA) and CR records, to determine SCGAs. Images of the mid-facial region were obtained using CBCT scan for 3D reconstruction. The angle formed between Frankfort horizontal plane (FHP) and a line extending from the most supero-anterior point on the glenoid fossa to the most convex point on the apex of articular eminence (AE) was measured to obtain SCGAs. The mean left and right SCGAs were as follows: PT (34.42° and 33.93°, respectively), PR (32.14° and 31.82°), and CBCT (38.96° and 38.12°). The Pearson coefficients for the correlations with PT and PR on the left and right sides were 0.899 and 0.907, respectively, while it was 0.911 and 0.934, and 0.842 and 0.874 from PT and CBCT, and PR and CBCT, respectively. Strong correlations were found between SCGAs obtained using PT, PR, and CBCT techniques.

2 Clinical use of 4D CBCT: ITV volume and amplitude study

Introduction After the validation of the respiratory correlated CBCT using a dynamic thorax phantom, investigations on the accuracy of the 4D CBCT were made on clinical data (i.e. patients 4D CBCT). A first study consisted in the evaluation of the difference in terms of positioning corrections between 3D CBCT and 4D CBCT images. Then, a second study compared the ITV volume between different imaging modalities (4D CT, 3D CBCT and 4D CBCT) and estimated the interfraction changes in breathing amplitude. Materials and Methods Five patients with a lung tumor treated in ITV strategy were included in the first study. They had both 3D CBCT and 4D CBCT pre-treatment images. A total of 44 CBCT images were retrospectively analyzed. A 4D CBCT image was first acquired and a 3D region-of-interest (ROI) mask registration was computed and applied in order to pre-position the patient. A 3D-CBCT image was then acquired and 3D ROI mask registration was computed but not applied. Only the patients treated with SBRT were included in the second study. A physician delineated ITV on different average images (4D CT, 3D CBCT and 4D CBCT) using a MonacoSim (Elekta) workstation. These contours were compared using a dice coefficient. Tumor motion amplitude from daily 4D CBCT was directly obtained with the on-line reconstruction software Symmetry (Elekta) and the amplitude variation was then computed. Results The average residual positioning corrections between 4D and 3D CBCT images were 0.06, 0.08 and 0.07 cm for LR, SI and AP direction respectively; and were respectively 0.41, 0.62, 0.21° for pitch, roll and yaw. From our preliminary results, the dice coefficients found were 0.77 ± 0.13, 0.70 ± 0.14 and 0.84 ± 0.11 between 4D CT and 4D CBCT, 4D CT and 3D CBCT and 3D CBCT and 4D CBCT images respectively. Interfraction changes in breathing amplitude were negligible in the LR and AP directions. The average breathing amplitude variation was 0.31 cm in SI direction (maximum of 0.44 cm). Conclusion Similar positioning corrections were found using a 3D ROI registration on either a 3D CBCT image or a 4D CBCT image. Since 4D CBCT allows a better visual inspection, it is now systematically used for lung SBRT patient positioning. ITV contours study suggests an overestimation of the ITV from 4D CT images compared to 4D CBCT images. The dice coefficient showed a better correspondence between ITV from 4D CT compared to 4D CBCT than between ITV from 4D CT and 3D CBCT. However, a satisfying correlation between 3D CBCT and 4D CBCT ITV contours was found. Interfractional changes in breathing amplitudes need to be further investigated and compared to treatment margins.