Cone Beam Computed Tomography Unit Research Articles

An overview of artificial intelligence based applications for assisting digital data acquisition and implant planning procedures.

To provide an overview of the current artificial intelligence (AI) based applications for assisting digital data acquisition and implant planning procedures. A review of the main AI-based applications integrated into digital data acquisitions technologies (facial scanners (FS), intraoral scanners (IOSs), cone beam computed tomography (CBCT) devices, and jaw trackers) and computer-aided static implant planning programs are provided. The main AI-based application integrated in some FS's programs involves the automatic alignment of facial and intraoral scans for virtual patient integration. The AI-based applications integrated into IOSs programs include scan cleaning, assist scanning, and automatic alignment between the implant scan body with its corresponding CAD object while scanning. The more frequently AI-based applications integrated into the programs of CBCT units involve positioning assistant, noise and artifacts reduction, structures identification and segmentation, airway analysis, and alignment of facial, intraoral, and CBCT scans. Some computer-aided static implant planning programs include patient's digital files, identification, labeling, and segmentation of anatomical structures, mandibular nerve tracing, automatic implant placement, and surgical implant guide design.

Cone-Beam CT of the Extremities in Clinical Practice.

Cone-beam CT (CBCT) is a promising tool with increasing applications in musculoskeletal imaging due to its ability to provide thin-section CT images of the appendicular skeleton and introduce weight bearing, which accounts for loading forces that typically interact with and affect this anatomy. CBCT devices include an x-ray source directly opposite a digital silicon detector panel that performs a single rotation around an object of interest, obtaining thin-section images. Currently, the majority of research has been focused on the utility of CBCT with foot and ankle pathologic abnormalities, due to the complex architectural arrangement of the tarsal bones and weight-bearing nature of the lower extremities. Associated software can provide a variety of options for image reconstruction, including metal artifact reduction, three-dimensional biometric measurements, and digitally reconstructed radiographs. Advancements in this technology have allowed imaging of the knee, hip, hand, and elbow. As more data are published, it is becoming evident that CBCT provides many additional benefits, including fast imaging time, low radiation dose, lower cost, and small equipment footprint. These benefits allow placement of CBCT units outside of the traditional radiology department, including the orthopedic clinic setting. These technologic developments have motivated clinicians to define the scope of CBCT for diagnostics, surgical planning, and longitudinal imaging. As efforts are made to create standardized protocol and measurements, the current understanding and surgical approach for various orthopedic pathologic conditions will continue to shift, with the hope of improving outcomes. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Proposed Diagnostic Reference Levels in the Missouri/Southern Illinois Region Associated with Cone-beam Computed Tomography Use in Endodontics

IntroductionDiagnostic reference levels (DRLs) are intended to improve patient safety and ensure that patient ionizing radiation doses are as low as reasonably achievable. The purpose of this dosimetry study was to establish regional DRL levels for cone-beam computed tomography (CBCT) imaging for specialty endodontics. Another aim was to compare phantom-measured ionizing radiation dose index 1 (DI1) index doses to the manufacturer-provided dose area product (DAP) radiation output values for each of the CBCT machines studied, to ascertain their degree of correlation. DAP refers to the dose area product, a measure of radiation dose monitoring which represents the dose within the beam times the area within the beam at that position. MethodsA thimble ionization chamber and polymethyl methacrylate phantom were used to obtain DI1 values using the SEDENTEXTCT method from 21 different CBCT units. DRLs were calculated based on the 75th percentile (third quartile) of the median output values. ResultsThe proposed DRL from the CBCT units surveyed has a DAP value of 838 mGy cm2 and a DI1 value of 3.924 mGy. DAP versus DI1 values of 500.6 mGy cm2 versus 2.006 mGy, and 838 mGy cm2 versus 3.906 mGy represented the third quartile of the median values for the 4-cm × 4-cm and 5-cm × 5-cm field of views (FOVs), respectively. ConclusionsThe DI1 and DAP values strongly correlated when 3 outlier CBCT machines (J Morita Veraview X800) using a novel 360° (full rotation) acquisition mode were excluded. The importance of selectable exposure parameters as directly related to ionizing radiation output is illustrated among the CBCT units surveyed. Although the actual FOV that is selected is ultimately dictated by the specific clinical requirements, a 4-cm × 4-cm FOV is recommended for specialist endodontics practice, whenever clinically practical, based on the decreased ionizing radiation output, as compared to that from a 5-cm × 5-cm FOV.

Feasibility of frozen soft tissues to simulate fresh soft tissue conditions in cone beam CT scans.

To evaluate the feasibility of frozen soft tissues in simulating fresh soft tissues of pig mandibles using cone beam CT (CBCT). Two fresh pig mandibles with soft tissues containing 2 tubes filled with a radiopaque homogeneous solution were scanned using 4 CBCT units and 2 field-of-view (FOV) sizes each. The pig mandibles were deep-frozen and scanned again. Three cross-sections were exported from each CBCT volume and grouped into pairs, with one cross-section representing a fresh and one a frozen mandible. Three radiologists compared the pairs and attributed a score to assess the relative image quality using a 5-point scale. Mean grey values and standard deviation were obtained from homogeneous areas in the tubes, compared using the Wilcoxon matched-pair signed-rank test and subjected to Pearson correlation analysis between fresh and frozen physical states (α = .05). Subjective evaluation revealed similarity of the CBCT image quality between fresh and frozen states. The distribution of mean grey values was similar between fresh and frozen states. Mean grey values of the frozen state in the small FOV were significantly greater than those of the fresh state (P = .037), and noise values of the frozen state in the large FOV were significantly greater than those of the fresh state (P = 0.007). Both mean grey values and noise exhibited significant and positive correlations between fresh and frozen states (P < 0.01). The freezing of pig mandibles with soft tissues may serve as a method to prolong their usability and working time when CBCT imaging is planned.

Chest Wall to Heart Distance Reproducibility in Postoperative Deep Inspiration Breath-Hold Radiotherapy for Left-Sided Breast Cancer Using an Anzai Laser Sensor With Visual Feedback.

Background Left-sided breast cancer radiotherapy may increase the risk of cardiovascular death due to possible heart irradiation. Thereproducibility of the chest wall to heart distance in deep inspiration breath-hold (DIBH) was studied using a laser sensor with visual feedback. Methodology A total of 10 consecutive postoperative left-sided breast cancer cases receiving DIBH radiotherapy between December 2022 and September 2023 were retrospectively investigated. The prescribed dose was 50 Gy in 25 fractions. An Anzai respiratory gating system, AZ-733VI (Anzai, Tokyo, Japan), was employed that has a laser displacement sensor and a visual feedback device. An Elekta linac with a cone-beam CT unit, Axesse (Elekta AB, Stockholm, Sweden), was used in this study. The interfractional changes in the chest wall to heart distance among 25 fractions were analyzed for each of the 10 patients in each coordinate axis. In addition, the median with the 95% confidence interval (CI) and interquartile range (IQR) for all 250 fractions were calculated in each axis to assess the reproducibility of our DIBH technique. Results The medians of the interfractional changes in the chest wall to heart distance in each of the 10 patients ranged from -2 mm to 3 mm, -1 mm to 3 mm, and -2 mm to 1 mm in the lateral (X), superior-inferior (Y), and anterior-posterior (Z) directions, respectively. For all 10 cases, the medians were 1 mm (95% CI = 0.72 to 1.28 mm) in X, 1 mm (95% CI = 0.76 to 1.24 mm) in Y, and 0 mm (95% CI = -0.20 to 0.20 mm) in Z directions, whereas the IQRs were 4 mm in X, 2 mm in Y and 2 mm in Z directions. The measured IQRs were two to three times smaller than those shown in a previous report without visual feedback, suggesting a clinical advantage of the visual feedback in DIBH for left-sided breast cancer radiotherapy. The DIBH solution shown in this study required approximately 10 minutes from room-in to room-out, thereby not reducing the daily number of patients. Conclusions Our DIBH approach with visual feedback achieved better distance reproducibility between the chest wall and heart by a factor of two to three in terms of IQR compared to the previously reported data without visual feedback. Patient throughput was also favorable. To our knowledge, this is the first report demonstrating the chest wall to heart distance reproducibility in DIBH with visual feedback.

Metal Artifact Reduction by Using MARS System of a CBCT Unit with Different Components of Fixed Orthodontic Appliances: An In vitro CBCT Analysis

Introduction: During Cone beam computed tomography (CBCT) imaging in the head and neck region of patients who are undergoing fixed orthodontic treatment, the different components of fixed orthodontic appliances can produce various metal artifacts which may degrade the diagnostic image quality in the region of interest. Therefore, the metal artifact reduction software (MARS) system can be used in most CBCT units to reduce the amount of artifacts generated from various fixed orthodontic appliance components including skeletal anchorage devices. Aims and objectives: The main purpose of this study was to quantitatively evaluate the effectiveness of MARS system of a CBCT unit in reducing the amount of artifacts generated by various fixed orthodontic appliance components during CBCT imaging. Materials and methods: Four dental arch shaped phantoms that were fabricated along with different fixed orthodontic appliance components (metal bracket, molar band, transpalatal arch, mini-implant) underwent CBCT scanning without and with the MARS setting option. After using the MARS system of a CBCT unit, the reduction in the amount of artifacts that were generated by various fixed orthodontic appliance component was calculated by using Google Colab software that utilized Python code and OpenCV system to generate a binary mask image. The resulting mask image highlights the areas where artifacts are detected, allowing for further analysis or visual inspection. The contours found within the mask image represent the boundaries of the artifact regions. Results: After calculating the percentage decrease in artifact area for each component of fixed orthodontic appliance, one-way analysis of variance (ANOVA) test was performed to compare the percentage decrease in artifact area for each component of fixed orthodontic appliances. *P-values are calculated using one-way analysis of variance ( p &lt; 0.05). The percentage decrease in artifact area for different components of fixed orthodontic appliance ranged from 39.67% to 48.58%. The stainless steel bracket showed the significant artifact area reduction with a mean percentage decrease of 48.58% as compared to other components. Conclusion: The effect of MARS system in reducing the amount of metal artifacts generated varied according to the component type of fixed orthodontic appliance and, MARS system was more efficient for stainless steel brackets as compared to other components. CBCT imaging of head and neck region can be carried out without taking off the orthodontic appliances by applying MARS system which can significantly decrease the artifact area.

A simplified low-cost phantom for image quality assessment of dental cone beam computed tomography unit.

A standardised testing protocol for evaluation of a wide range of dental cone beam computed tomography (CBCT) performance and image quality (IQ) parameters is still limited and commercially available testing tool is unaffordable by some centres. This study aims to assess the performance of a low-cost fabricated phantom for image quality assessment (IQA) of digital CBCT unit. A customised polymethyl methacrylate (PMMA) cylindrical phantom was developed for performance evaluation of Planmeca ProMax 3D Mid digital dental CBCT unit. The fabricated phantom consists of four different layers for testing specific IQ parameters such as CT number accuracy and uniformity, noise and CT number linearity. The phantom was scanned using common scanning protocols in clinical routine (90.0 kV, 8.0 mA and 13.6 s). In region-of-interest (ROI) analysis, the mean CT numbers (in Hounsfield unit, HU) and noise for water and air were determined and compared with the reference values (0 HU for water and -1000 HU for air). For linearity test, the correlation between the measured HU of different inserts with their density was studied. The average CT number were -994.1 HU and -2.4 HU, for air and water, respectively and the differences were within the recommended acceptable limit. The linearity test showed a strong positive correlation (R2 = 0.9693) between the measured HU and their densities. The fabricated IQ phantom serves as a simple and affordable testing tool for digital dental CBCT imaging.

A Survey on Cone-beam Computed Tomography Usage Among Endodontists in the United States

IntroductionThe aim of the study was to investigate the accessibility and frequency of cone-beam computed tomography (CBCT) usage and to assess the economic and logistical factors involved with its usage among active American Association of Endodontists (AAE) members, utilizing a web-based survey. MethodsA survey of 19 questions was sent to 3,071 AAE members addressing participant access to, along with financial and logistical aspects of CBCT imaging. Descriptive analysis was performed and Fisher exact test utilized to test associations between groups (P < .05). ResultsThe overall response rate was 14.7% (n = 544). Ninety-five percent of respondents (n = 486) had an in-office CBCT unit, with those graduating after the year 2000 statistically more likely to have one (P < .05). Utilization of CBCT imaging for every case was reported by 40% of providers. Eighty-nine percent reported taking the scan at the consultation visit and 20% included this charge with the consultation fee. For those who charged for the scan separately, 85% charged more than $100. Providers who paid off their unit did so within 1–2 years (41%), 3–4 years (36%), 4–5 years (12%), and 5+ years (11%). Limited field of view was utilized by 95% of respondents. Fifty-eight percent reported interpreting the scans themselves, 38% send only if pathology is expected, and 3% always send their scans to a radiologist. ConclusionsIn conclusion, accessibility and utilization of CBCT imaging among United States endodontists has increased and acquisition of this equipment has not made a long lasting financial burden on providers.

Evaluation of 2- and 3-dimensional anatomic parameters of C-shaped root canals with cone beam computed tomography, microcomputed tomography, and nanocomputed tomography

The objective of this study was to evaluate 2-dimensional (2D) and 3D morphometric parameters of C-shaped root canals on cone beam computed tomography (CBCT) and microcomputed tomography (microCT) images using nanocomputed tomography (nanoCT) as the reference standard. Sixty mandibular molars with C-shaped canals were individually scanned using nanoCT and microCT. Cone beam computed tomography acquisitions were then performed with 4 CBCT systems, using high and standard resolutions. The 2D parameters of roundness and major and minor diameters were obtained in the cross sections of the root canals at 1, 2, and 3 mm from the root apex. The 3D parameters of surface area, volume, and structure model index were measured considering the entire extension of the root canals. Absolute error (AE) in measurement was calculated against the nanoCT values. Data were statistically analyzed with the Shapiro-Wilk test and analysis of variance (α=0.05). No significant differences in AE were discovered for the 2D parameters among microCT and the CBCT scans. The AE values for the 3D parameters of volume and surface area were significantly smaller in microCT compared to all CBCT units (P < .05). Significantly lower AE values for surface area were observed in high resolution compared to standard resolution for all CBCT units (P < .05). Structure model index did not differ significantly among microCT and all CBCT protocols. Cone beam computed tomography images showed accuracy for evaluating 2D parameters and over- and underestimation for 3D parameters.

Effect of Field of View and Voxel Size on CBCT-Based Accuracy of Dynamic Navigation in Endodontic Microsurgery: An In Vitro Study

IntroductionThis study aimed to evaluate the influence of field of view (FOV) and voxel size on the accuracy of dynamic navigation (DN)–assisted endodontic microsurgery (EMS). MethodsNine sets of maxillary and mandibular 3-dimensional–printed jaw models composed of 180 teeth were divided into 9 groups with different FOVs (80 × 80 mm, 60 × 60 mm, and 40 × 40 mm) and voxel sizes (0.3 mm, 0.16 mm, and 0.08 mm). The endodontic DN system was used to plan and execute the EMS. The accuracy of the DN-EMS was represented by the platform deviation, end deviation, angular deviation, resection angle, and resection length deviation. Statistical analyses were performed using SPSS 24.0, and the significance level was set at P < .05. ResultsThe average platform deviation, end deviation, angular deviation, resection angle, and resection length deviation were 0.69 ± 0.31 mm, 0.93 ± 0.44 mm, 3.47 ± 1.80°, 2.35 ± 1.76°, and 0.41 ± 0.29 mm, respectively. No statistically significant differences in accuracy were observed between the nine FOV and voxel size groups. ConclusionsFOV and voxel size did not appear to play an important role in the accuracy of DN-EMS. Considering the image quality and radiation dose, it is reasonable to select a limited FOV (such as 40 × 40 mm and 60 × 60 mm) to cover only the registration device, involved teeth, and periapical lesion. The voxel size should be selected according to the required resolution and cone-beam computed tomography units.

Automated measurement for image distortion analysis in 2D panoramic imaging of dental CBCT system: A phantom study

IntroductionThe daily image quality assessment involves large datasets that consume a lot of time and effort. This study aims to evaluate a proposed automated calculator for image distortion analysis in 2-dimensional (2D) panoramic imaging mode for a dental cone beam computed tomography (CBCT) system in comparison with present manual calculations. MethodsA ball phantom was scanned using panoramic mode of the Planmeca ProMax 3D Mid CBCT unit (Planmeca, Helsinki, Finland) with standard exposure settings used in clinical practice (60 kV, 2 mA, and maximum FOV). An automated calculator algorithm was developed in MATLAB platform. Two parameters associated with panoramic image distortion such as balls diameter and distance between middle and tenth balls were measured. These automated measurements were compared with manual measurement using the Planmeca Romexis and ImageJ software. ResultsThe findings showed smaller deviation in distance difference measurements by proposed automated calculator (ranged 3.83 mm) as compared to manual measurements (ranged 5.00 for Romexis and 5.12 mm for ImageJ software). There was a significant difference (p < 0.05) on the mean measured ball diameter between automated and manual measurement. For ball diameter measurement, there is a moderate positive correlation between automated measurement with the manual measurements (r = 0.6024 and r = 0.6358 for Romexis and ImageJ, respectively). However, there is a negative correlation between automated measurement for the distance difference with manual methods (r = −0.3484 and r = −0.3494 for Romexis and ImageJ, respectively). There was a good approximation between automated and ImageJ measurement of ball diameter in comparison to reference value. ConclusionIn conclusion, the proposed automated calculator provides faster method with an accurate and acceptable results for daily-basis image quality test in dental panoramic mode of a Dental CBCT imaging system in comparison to current manual method. Implications for practiceAn automated calculator is recommended for image distortion analysis on phantom images in routine image quality assessment for dental panoramic mode of Dental CBCT imaging system that may involve analysis of large image datasets. It offers improvement in routine image quality practice in term of time and accuracy.

Effect of a Motion Artifact Correction System on Cone-Beam Computed Tomography Image Characteristics.

Determine the effect of the motion correction system on cone-beam computed tomography (CBCT) image quality parameters, artifacts, and contrast-to-noise ratio (CNR) using different motion settings. A customized phantom insert array was prepared using SEDENTEX CT IQ Phantom (Leeds Test Objects, Yorkshire, England) stabilized over a rotating electric turntable. Thirty baseline CBCT scans were acquired with standardized technique factors on the ProMax 3D (Planmeca, Helsinki, Finland) machine using combinations of different motion settings, including no motion, three- and six-degree motion, and with and without the use of a motion correction system. The standardized images were exported to ImageJ software. Image quality parameters, artifacts, and CNRvalues were evaluated and compared among the different acquisition settings. The use of the motion correction system algorithm compared with the different motion settings showed a statistically significant difference for all the parameters (p<0.05) except for artifact values for six-degree motion (p<0.07). The effect of different motion settings on the parameters was not statistically significant. The use of a motion correction system, a proprietary algorithm-based system incorporated in the ProMax 3D CBCT unit, deteriorates the image quality characteristics evaluated in this in vitro study, namely artifact value and CNR. Its use in clinical settings might be limited to situations where patient motion is expected and appropriate head stabilization is not possible due to age or disease.

A comparative study of paranasal sinus and nasal cavity anatomic variations between the Polish and Turkish Cypriot Population with CBCT

BackgroundGenetic and environmental factors especially climatic conditions are thought to influence the shape and size of the paranasal sinuses and anatomic variations may create both a diagnostic and therapeutic challenge. However, no study has been published about the climatic adaptation of the paranasal sinus region in different populations. This study aimed to compare the prevalence of anatomical variants in the paranasal sinus and nasal cavity using Cone-Beam Computed Tomography (CBCT) between Polish and Turkish Cypriot populations.MethodsThe material consisted of volumes acquired utilizing Galileos (Sirona, Germany) as well as Newtom 3G (QR Verona, Newtom, Italy) CBCT units. There were examined 356 Polish and 359 Turkish Cypriot patients in whom paranasal sinuses were included in the field of view. Paranasal sinus anatomic variations were assessed in both populations.ResultsIn the Polish population, the most common anatomic variation was septum deviation followed by the Agger nasi cell and concha bullosa with a prevalence of 87.7%, 83.2%, and 54.8% respectively. For the Turkish Cypriot population, the most common anatomic variation was Agger nasi cell followed by concha bullosa and supraorbital ethmoid cells with a prevalence of 81.6%, 68%, and 57.8% respectively. Many anatomic variations were found to show substantial differences among both populations. Incidence rates of hyperpneumatization of the frontal sinus, septum pneumatization, supraorbital ethmoid cells, concha bullosa, uncinate bulla, and internal carotid artery protrusion into the sphenoid sinus were significantly higher in the Turkish Cypriot group, while the incidence of Haller cell, frontal sinus hypoplasia, maxillary sinus hypoplasia, ethmomaxillary sinus, sphenomaxillary plate, and septum deviation were significantly higher in Polish population.ConclusionAccording to the Köppen-Geiger world climatic map, the climate is warmer and drier in Turkish Cypriote populations than in the Polish population. These climatic differences influence the paranasal sinus variations between the Turkish Cypriot and Polish populations that must be taken into account by rhinologic surgeons especially when performing frontal and sphenoid sinus surgery.

Do cone-beam computed tomography low-dose protocols affect the evaluation of the temporomandibular joint?

There is no established acquisition protocol based on scientific evidence for the acquisition of cone-beam computed tomography (CBCT) exams to evaluate the temporomandibular joint (TMJ). To evaluate the influence of acquisition protocols and jaw positioning on the diagnostic accuracy of TMJ condylar morphological alterations (CMA), dimension, position and excursion. Thirty-six TMJs on 18 dry skulls were imaged using a CBCT unit (OP300 Maxio, Instrumentarium, Tuusula, Finland) at two exposure settings (4.5 and 6.3mA), three voxel resolutions (0.085, 0.125 and 0.280 mm), three jaw positions (concentric, anteriorised and posteriorised) and three jaw excursions (normoexcursion, hyperexcursion and hypoexcursion). The macroscopic anatomy examination and high-resolution CBCT images were used as ground truth for CMA. Twenty-five TMJs had at least one CMA with 11 healthy TMJs serving as controls. Three experienced oral and maxillofacial radiologists evaluated the parasagittal images for the presence of CMA, position and excursion and measured dimensions. The area under the ROC curve, sensitivity and specificity were calculated. Weighted Kappa (α=0.05) was used to determine intra- and interexaminer reliability and comparisons between dependent variables analysed by Analysis of Variance at an a prior level of significance of 0.05. The agreement of the evaluation of the position and excursion with the reference standard was high, independent of the protocol (range, 0.75-0.91). Various combinations of acquisition protocols and jaw position did not influence the CMA evaluation. Erosion was overdiagnosed in protocols with larger voxel sizes and the detection of osteophytes greater in images with smaller voxel sizes. The anteroposterior dimension was greater in the open jaw position (p < .05). CBCT protocols using reduced radiation exposure from the CBCT machine evaluated in this study can be used to assess condylar morphology, dimension, position and excursion, without compromising diagnostic performances for these parameters.

Comparison of subjective image analysis and effective dose between low-dose cone-beam computed tomography machines.

To compare the cone-beam computed tomography (CBCT) image quality and effective dose between low-dose scanning and standard manufacturer-recommended protocols among different CBCT units. Three human-equivalent phantoms were scanned using the ultra-low-dose (ULD), low dose (LD), and standard dose (STD) modes of ProMax 3D Mid (Planmeca Oy, Helsinki, Finland) and Orthophos SL (Sirona, Bensheim, German) for the CBCT images. The quality of the dental anatomical images was assessed by four experienced oral and maxillofacial radiologists using a 5-point Likert scale. OnDemand3D (Cybermed Co., Seoul, Korea) was used as the third-party software for viewing. The percentage of absolute agreement was calculated to determine intra- and interrater agreements among the observers. The effective doses for all CBCT scanning protocols were also calculated. The STD protocol yielded a higher image quality than did the ULD and LD protocols in both ProMax 3D Mid and Orthophos SL. The ULD and LD protocols demonstrated an "acceptable-to-good" sense of visual perception of the CBCT images. The visibility scores significantly differed between the ULD and LD and the STD protocols in ProMax 3D Mid and Orthophos SL, except for the 120-kVp setting in ProMax 3D Mid. The average intra- and interrater agreement scores ranged from 0.63 to 0.89 and from 0.44 to 0.76, respectively. The ULD and LD protocols reduced the radiation dose sixfold compared with the STD protocol. High-tube-voltage protocols could remarkably reduce the imaging dose without degrading the image quality. Specifically, ULD and LD CBCT protocols may be adopted as routine practice for diagnosis and treatment planning.

Quantitative and qualitative comparisons of pulp cavity volumes produced by cone beam computed tomography and micro-computed tomography through semiautomatic segmentation: An ex vivo investigation

The aim of this study was to measure the volume and visually assess 3-dimensional (3D) virtual models of pulp cavities obtained through semiautomatic segmentation on images from 6 cone beam computed tomography (CBCT) units compared with the reference standard of micro-CT. Fifteen mandibular premolar teeth were scanned with 6 CBCT units: Prexion 3D Elite, i-CAT Next Generation, NewTom 5G, Cranex 3D, 3Shape X1, and Orthophos SL 3D, using the smallest available field of view and highest resolution settings. Pulp cavity volumes were quantitatively assessed by 2 calibrated examiners. The volumes from each CBCT unit were compared with micro-CT. Qualitative assessment of the 3D reconstructions was also performed. Repeated-measures analysis of variance and the Friedman test compared the CBCT reconstructions to micro-CT. Intra- and interexaminer agreements were calculated with the intraclass correlation coefficient and kappa statistic. The CBCT-based volumes were all significantly larger than micro-CT (P ≤ .0061). Prexion, X1, and Orthophos provided the segmentations that most closely resembled the reference standard. Intra- and interexaminer agreements ranged from good to excellent for quantitative measurements. Interexaminer agreement for qualitative evaluation was substantial. Semiautomatic segmentation of CBCT images is a feasible method to produce virtual 3D models of the pulp cavity. Prexion, X1, and Orthophos were the CBCT units that resulted in 3D reconstructions most similar to the reference standard.

The Effect of Different Field of View Sizes on Contrast-to-Noise Ratio of Cone-Beam Computed Tomography Units: An In-Vitro Study.

Objectives: 'Field of view (FOV) size' affects the quality of radiographic images and the radiation dose received by patients. In cone-beam computed tomography (CBCT) FOV should be selected according to therapeutic purposes. While aiming for the highest diagnostic image quality, the radiation dose should be kept to a minimum to reduce the risk for patients. The purpose of this study was to assess the effect of different sizes of FOV on contrast-to-noise ratio (CNR) in five different CBCT units. Materials and Methods: In this experimental study, CBCT scans were taken from a dried human mandible containing a resin block fixed to the lingual cortex and a resin ring was used to simulate soft tissue during scans. Five CBCT units including, NewTom VGi, NewTom GiANO, Soredex SCANORA 3D, Planmeca ProMax, and Asahi Alphard 3030 were evaluated. Each unit had 3 to 5 different FOVs. Images were obtained and analyzed with ImageJ software and CNR was calculated in each image. ANOVA and T-test were used for statistical analysis (P<0.05). Results: Comparison among different FOVs of each unit showed significant CNR reductions in small FOVs (P<0.05). Similar FOV sizes of different CBCT devices were also compared and demonstrated significant differences (P<0.05). Conclusion: A direct relationship between FOV size and CNR was observed in all five CBCT units, but differences in exposure parameters of these units led to variable CNR in FOVs with similar sizes.

Effect of cone-beam CT detector size and projection geometry on scatter-induced image noise

<h3>Objective</h3> The aim of this study was to evaluate the effect of detector size with different projection geometries on scatter-induced image noise in cone beam computed tomography (CBCT). <h3>Study Design</h3> A polymethyl methacrylate phantom containing air and aluminum underwent CBCT scanning positioned in the center of the FOV. Images were acquired with the PaX-i3D Green Premium (Vatech, Korea), which has a narrow vertical detector with off-axis projection geometry and multiple consecutive rotations for small and medium FOVs; the OP300 3D Maxio (Instrumentarium Dental, Tuusula, Finland), with aligned projection geometry for small FOV, and off-axis geometry for medium FOV; and the Promax 3D Max (Planmeca, Helsinki, Finland), which has aligned geometry for small and medium FOVs. Scans were performed using small and medium FOVs, combining tube voltages and tube currents to maintain a fixed normalized dose-area product. Signal difference-to-noise ratio (SDNR) was calculated on two-dimensional projection images and compared using one-way ANOVA with post hoc Tukey tests (α =0.05) between CBCT units. <h3>Results</h3> For small FOVs, Promax showed the highest SDNR compared to OP300 and PaX-i3D, with the difference being statistically significant (p < 0.0001). OP300 exhibited significantly higher SDNR values than PaX-i3D (p < 0.0001). For medium FOVs, Promax had significantly higher SDNR than OP300 and PaX-i3D (p < 0.0001), and no difference was discovered between OP300 and PaX-i3D. Therefore, Promax had the lowest scatter-induced image noise since it has aligned projection geometry in small and medium FOV sizes. For OP300, which has an off-axis geometry, the scatter-induced image noise with the medium FOV was comparable to PaX-i3D. <h3>Conclusion</h3> Reducing the active area of the detector does not result in fewer scattered photons reaching the detector, as it needs more rotations to capture all the projections. Moreover, in off-axis projections there is a lateral off-set of the detector, which results in the center of the FOV being positioned in the edges of the projection images. <b>Statement of Ethical Review</b> Ethical review was sought and study was exempted from ethical review

Establishment of Narrow Root Fracture Models Using Modified Temperature Cycling Method and Diagnosis Using Different Cone-Beam CT Units.

Aim Using a modified thermal cycling method to establish narrow root fracture models and evaluate the diagnosis efficiency of them using four different cone-beam CT (CBCT) units. Methodology. Fifty-six intact teeth were selected, and the crowns of the teeth were embedded using general purpose acrylic resin. 50 root fracture models were established by soaking these teeth in liquid nitrogen and hot water cyclically; 6 teeth were used as the negative control. All the 56 teeth were scanned with the smallest voxel size of four different CBCT units (NewTom VGi, Planmeca Promax 3D Max, Kavo 3D eXam, and Soredex Scanora3D). 10 teeth were randomly selected, and the roots were sliced using slow-speed saw to obtain horizontal root sections. Scanning electron microscope (SEM) was used to measure the width of the fracture lines (FLs). The CBCT images were evaluated for the presence or absence of fracture lines. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the diagnosis of FLs using the four CBCT units. Results Fifty narrow root fracture models were successfully established, and 25 root sections with 45 FLs were acquired. The width of FLs was from 3.43 μm to 143 μm; 32.2% of the points had width under 25 μm, while only 9.6% of them had width over 75 μm. The accuracy was 0.41, 0.54, 0.41, and 0.30 for NewTom VGi, Planmeca Promax 3D Max, Kavo 3D eXam, and Soredex Scanora3D, respectively. Conclusions The modified temperature cycling method is a simple and effective method to establish narrow root fracture models, and the diagnosis efficiency for these narrow fracture lines was quite poor using all the four different CBCT units.

Cone-beam computed tomography-Predictors and characteristics of usage in Australia and New Zealand, a multifactorial analysis.

Cone-beam computed tomography (CBCT) is an increasingly used imaging modality. This study aimed to identify the factors that predict its usage amongst endodontists in Australia and New Zealand and describe usage characteristics. Data were collected via an online questionnaire, with analysis including descriptive statistics, cross-tabulation and multifactorial modelling. Ninety-four endodontists completed the questionnaire who were using CBCT for 7 years (median), over half had a CBCT unit in practice, with most prescribing up to 10scans/month and 55 using a small field of view. Sixty-eight participated in >5 h of CBCT education/year and a third received a specialist-prepared report. The number of prescriptions/month was significantly associated with on-site CBCT units (Exp B: 8.53; 95% CI: 1.46-49.86, p < 0.05) and the number of years of CBCT usage by participants (Exp B: 1.46; 95% CI: 1.17-1.84, p=0.001). CBCT imaging in endodontics is a useful diagnostic aid to decision making and treatment planning, with widespread acceptance and usage.