3D Cone-beam Computed Tomography Research Articles

Real Time 4D-Cone Beam CT via Single-Angle Projection with Dual Attention Mechanism

The hypothesis is that dual attention integrated Residual Network (DA-ResNet) together with a Principal Component Analysis (PCA) model accurately maps the measured on-treatment CBCT projections from different phases to each phase's 3D-CBCT real timely. Finally, it achieves real time 4D-CBCT. The DA-ResNet contains a CBAM (Convolutional Block Attention Module) and a SPA (Spatial Pyramid Structure). Hundreds of forward projections from one view of patient 4D-CT were simulated to train DA-ResNet. The extracted motion features were expressed as PCA coefficients. To test DA-ResNet performance, several single measured on-treatment projection is sent into it and the network output several groups of PCA coefficients real timely. Each group of PCA coefficient stands for the corresponding deformation field between the 0% phase and the predicted phase that the PCA label stands for. In labels such as Mean Absolute Error (MAE), R square, Normalized Cross Correlation (NCC), Structural Similarity Index Measure (SSIM) were used to evaluate DA-ResNet performance with other state-of-the-art networks such as CNN/Unet/ResNet. DA-ResNet outperforms other popular networks on all of the quantification labels, with MAE (14.41 ± 8.85), R square (0.95 ± 0.07) in PCA coefficient prediction, and NCC (0.9981 ± 0.0006), SSIM (0.98 ± 0.04) in image reconstruction. Compared with conventional ResNet, DA-ResNet reduced MAE by 79%. Meanwhile R square rises from 0.88 to 0.95, NCC rises from 0.996 to 0.998, SSIM rises from 0.94 to 0.98. DA-ResNet offers a solution for real time on-treatment 4D-CBCT image guidance by using single 2D on-line projections. It offers better motion prediction and image reconstruction accuracy compared with traditional deep learning networks (e.g., CNN/Unet/ResNet). The initial results are promising. The prospect of clinical application needs further clinical verification.

The Suitability of Trabecular Patterns in the Assessment of Dental Implant Osseointegration Process through 2D Digital and 3D CBCT Radiographs.

The research aims to determine the suitability of the trabecular pattern in the assessment of the dental implant osseointegration process through two-dimensional (2D) digital and three-dimensional (3D) cone-beam computed tomography (CBCT) radiographs. This is a correlation description that explains the relationship between variables. The population consisted of 24 data points on 3D CBCT and 2D digital radiographs from the procedure after dental implants were inserted into the tibia of a New Zealand white rabbit (Oryctolagus cuniculus) on days 3, 14, and 28. The radiograph was selected based on the region of interest (ROI), which covers the peri-implant area with a width of 1 mm and length following the height of the implant. The ROI was analyzed for trabecular thickness (Tb.Th), separation (Tb.Sp), number (Tb.N), and fractal dimension. The intraclass correlation coefficient (ICC) was used to statistically test the data to assess the consistency of intraobserver measurements and the r value (Pearson's correlation coefficient). This determines the correlation between trabecular patterns in both radiographic modalities and the Bland-Altman plot to observe the limits of acceptable discrepancies. The ICC test showed high intraobserver consistency in trabecular pattern measurements on 2D digital radiographs and 3D CBCT. The trabecular space pattern and number showed an r value of 0.88 with radiographic modalities of 0.72 mm and 0.018, respectively. Additionally, the trabecular thickness and fractal dimension had an insignificant correlation, with an r value of 0.22, and the mean of the 2D radiograph was lower than that of CBCT. The 2D radiograph and 3D CBCT showed correlations in the trabecular number and space results but had no correlation in the trabecular thickness and fractal dimension results. Based on intraclass correlation analysis, 3D CBCT appeared to be more reliable for measuring trabecular patterns (Tb.Th, Tb.Sp, Tb.N, and fractal dimension) than 2D radiograph.

Investigating the link between frontal sinus morphology and craniofacial characteristics with sex: A 3D CBCT study on the South Indian population.

Background: Measurement of craniofacial parameters plays an important role in sex determination in forensic science. The present study was done using cone beam computed tomography (CBCT) scans to evaluate the morphologic structure of the frontal sinuses and compare it with the width of nasal, cranial, maxillary and mandibular width which might help us in sex determination. Methods: A cross-sectional retrospective study was conducted using 142 full field of view (FOV) scans of patients archived from the department. The width of the nose, cranium, maxilla, and mandibular width was measured and compared with the frontal sinus between the two sexes. Results: A paired t-test was done to compare the linear measurements for both sexes' right and left frontal sinuses. The measurements were higher in males when compared to females. There was a statistically significant asymmetry (larger dimension on the left side) of the anterioposterior (p-value of 0.012) and superior-inferior dimensions in males (p-value of 0.135). Spearman's correlation showed that frontal sinus correlated with other craniofacial parameters like nasal, cranial, maxillary and mandibular width among both sexes. The frontal sinus, nasal, cranial, maxillary and mandibular widths were higher in males when compared to females (independent t-test). Discriminant function scores showed 66-68% accuracy to discriminate sex, using the anteroposterior dimension and mandibular width. Conclusions: The measurement of craniofacial parameters using CBCT can aid in determining the sex of unidentified and decomposed bodies.

Incidental finding of impacted supernumerary teeth in cone-beam computed tomography 3D

Objectives: To evaluate the value of cone-beam CT (CBCT) in the diagnosis and orientation of impacted supernumerary teeth in the dental arches.
 Case Report: A 50 year old man came to the Udayana University Hospital with the chief complaint of missing bilateral posterior teeth of the mandible and wanted to make denture. Before the treatment begin, a panoramic radiographic examination was performed. The panoramic image shows an impacted supernumerary teeth on the inferior from lower right premolar. Due to the inability to determine the precise position of those teeth within the mandible and the possible vital structures surrounding, a CBCT imaging was taken. Examination of the images from the CBCT shows an impacted supernumerary teeth in the area of teeth 44 and 46.
 Conclusion: The position of the supernumerary teeth is varied in the mandible, and often causes permanent dentition complications. In this case CBCT imaging two supernumerary teeth were found in the tooth area 44-45 and 45-46. apical of the two germ teeth appear to be fully formed. Supernumerary crowns between teeth 44-45 inclined buccally & between teeth 45-46 lingually. CBCT is crucial for exact localization, for treatment planning, and for the surgical approach in cases of multiple supernumerary teeth.

4D-CT deformable image registration using unsupervised recursive cascaded full-resolution residual networks.

A novel recursive cascaded full-resolution residual network (RCFRR-Net) for abdominal four-dimensional computed tomography (4D-CT) image registration was proposed. The entire network was end-to-end and trained in the unsupervised approach, which meant that the deformation vector field, which presented the ground truth, was not needed during training. The network was designed by cascading three full-resolution residual subnetworks with different architectures. The training loss consisted of the image similarity loss and the deformation vector field regularization loss, which were calculated based on the final warped image and the fixed image, allowing all cascades to be trained jointly and perform the progressive registration cooperatively. Extensive network testing was conducted using diverse datasets, including an internal 4D-CT dataset, a public DIRLAB 4D-CT dataset, and a 4D cone-beam CT (4D-CBCT) dataset. Compared with the iteration-based demon method and two deep learning-based methods (VoxelMorph and recursive cascaded network), the RCFRR-Net achieved consistent and significant gains, which demonstrated that the proposed method had superior performance and generalization capability in medical image registration. The proposed RCFRR-Net was a promising tool for various clinical applications.

Comparative evaluation of mutagenic effects of two cone-beam computed tomography in oral mucosa cells.

This pilot study aimed to evaluate the mutagenic effects in cells of the oral mucosa after exposure to two different cone beam computed tomography (CBCT). Eighteen adults were submitted to the different CBCT (Carestream CS8100 3D and I-CAT). The cells were collected immediately before the CBCT exposure and 10 days later, when the material was placed on a slide and stained using the Feulgen/Fast Green technique. Microscopic analysis counted micronuclei and other nuclear alterations, which are indicative of cytotoxicity such as pyknosis, karyolysis, karyorrhexis, and binucletion. 2000 cells were analyzed. The statistical analysis was performed with the Wilcoxon Signed-Rank test to compare the frequency of cellular alterations, and the Mann-Whitney U test to compare different CBCTs, both with a significance level of 5%. There was no statistically significant difference in the micronucleated cell count before and after the exposition to the ionizing radiation from I-CAT (p = .298) and CS8100 3D (p = .203) A significate increase of pyknosis (p < .001), karyolysis (p < .001), karyorrhexis (p < .001), and binucletion (p < .001) were noted on I-CAT CBCT. There was no statistically significant difference in cellular alterations in CS8100 3D CBCT. Despite the increase in micronuclei after exposure, this study indicates that there is no evidence of genotoxicity. On the other hand, the I-CAT CBCT produced cytotoxic effects.

Investigating the link between frontal sinus morphology and craniofacial characteristics with sex: A 3D CBCT study on the South Indian population

Background: Measurement of craniofacial parameters plays an important role in sex determination in forensic science. The present study was done using cone beam computed tomography (CBCT) scans to evaluate the morphologic structure of the frontal sinuses and compare it with the width of nasal, cranial, maxillary and mandibular width which might help us in sex determination. Methods: A cross-sectional retrospective study was conducted using 142 full field of view (FOV) scans of patients archived from the department. The width of the nose, cranium, maxilla, and mandibular width was measured and compared with the frontal sinus between the two sexes. Results: A paired t-test was done to compare the linear measurements for both sexes' right and left frontal sinuses. The measurements were higher in males when compared to females. There was a statistically significant asymmetry (larger dimension on the left side) of the anterioposterior (p-value of 0.012) and superior-inferior dimensions in males (p-value of 0.135). Spearman's correlation showed that frontal sinus correlated with other craniofacial parameters like nasal, cranial, maxillary and mandibular width among both sexes. The frontal sinus, nasal, cranial, maxillary and mandibular widths were higher in males when compared to females (independent t-test). Discriminant function scores showed 66-68% accuracy to discriminate sex, using the anteroposterior dimension and mandibular width. Conclusions: The measurement of craniofacial parameters using CBCT can aid in determining the sex of unidentified and decomposed bodies.

Faster and lower dose imaging: evaluating adaptive, constant gantry velocity and angular separation in fast low-dose 4D cone beam CT imaging.

The adoption of four-dimensional cone beam computed tomography (4DCBCT) for image-guided lung cancer radiotherapy is increasing, especially for hypofractionated treatments. However, the drawbacks of 4DCBCT include long scan times (∼240s), inconsistent image quality, higher imaging dose than necessary, and streaking artifacts. With the emergence of linear accelerators that can acquire 4DCBCT scans in a short period of time (9.2s) there is a need to examine the impact that these very fast gantry rotations have on 4DCBCT image quality. This study investigates the impact of gantry velocity and angular separation between x-ray projections on image quality and its implication for fast low-dose 4DCBCT with emerging systems, such as the Varian Halcyon that provide fast gantry rotation and imaging. Large and uneven angular separation between x-ray projections is known to reduce 4DCBCT image quality through increased streaking artifacts. However, it is not known when angular separation starts degrading image quality. The study assesses the impact of constant and adaptive gantry velocity and determines the level when angular gaps impair image quality using state-of-the-art reconstruction methods. This study considers fast low-dose 4DCBCT acquisitions (60-80s, 200-projection scans). To assess the impact of adaptive gantry rotations, the angular position of x-ray projections from adaptive 4DCBCT acquisitions from a 30-patient clinical trial were analyzed (referred to as patient angular gaps). To assess the impact of angular gaps, variable and static angular gaps (20°, 30°, 40°) were introduced into evenly separated 200 projections (ideal angular separation). To simulate fast gantry rotations, which are on emerging linacs, constant gantry velocity acquisitions (9.2s, 60s, 120s, 240s) were simulated by sampling x-ray projections at constant intervals using the patient breathing traces from the ADAPT clinical trial (ACTRN12618001440213). The 4D Extended Cardiac-Torso (XCAT) digital phantom was used to simulate projections to remove patient-specific image quality variables. Image reconstruction was performed using Feldkamp-Davis-Kress (FDK), McKinnon-Bates (MKB), and Motion-Compensated-MKB (MCMKB) algorithms. Image quality was assessed using Structural Similarity-Index-Measure (SSIM), Contrast-to-Noise-Ratio (CNR), Signal-to-Noise-Ratio (SNR), Tissue-Interface-Width-Diaphragm (TIW-D), and Tissue-Interface-Width-Tumor (TIW-T). Patient angular gaps and variable angular gap reconstructions produced similar results to ideal angular separation reconstructions, while static angular gap reconstructions produced lower image quality metrics. For MCMKB-reconstructions, average patient angular gaps produced SSIM-0.98, CNR-13.6, SNR-34.8, TIW-D-1.5mm, and TIW-T-2.0mm, static angular gap 40° produced SSIM-0.92, CNR-6.8, SNR-6.7, TIW-D-5.7mm, and TIW-T-5.9mm and ideal produced SSIM-1.00, CNR-13.6, SNR-34.8, TIW-D-1.5mm, and TIW-T-2.0mm. All constant gantry velocity reconstructions produced lower image quality metrics than ideal angular separation reconstructions regardless of the acquisition time. Motion compensated reconstruction (MCMKB) produced the highest contrast images with low streaking artifacts. Very fast 4DCBCT scans can be acquired provided that the entire scan range is adaptively sampled, and motion-compensated reconstruction is performed. Importantly, the angular separation between x-ray projections within each individual respiratory bin had minimal effect on the image quality of fast low-dose 4DCBCT imaging. The results will assist the development of future 4DCBCT acquisition protocols that can now be achieved in very short time frames with emerging linear accelerators.

Comparison of infrazygomatic crest bone screw position using a postero-anterior cephalogram versus cone-beam computed tomography: a cross sectional study

Abstract Background The position of infrazygomatic crest bone screws is an important consideration in determining the success of orthodontic treatment. The aim of this study was to compare the position of infrazygomatic crest (IZC) bone screws in relation to skeletal and dental parameters using postero-anterior (PA) cephalograms and cone beam computed tomography (CBCT). Methods A CBCT scan and a PA cephalogram were taken of 19 patients (8 males; 11 females) after IZC bone screw placement. Each CBCT image was reconstructed and oriented using the CS 3D CBCT software (Carestream Dental LLC, Atlanta, USA) and was subsequently analysed. The landmarks were traced on the PA cephalogram. The angulation of the IZC bone screw was measured with respect to three skeletal and two dental landmarks and compared between the two imaging modalities. A paired t-test was applied to compare the means of different variables between the PA cephalogram and CBCT scan. Results The results showed no statistically significant difference between the two imaging modalities with respect to four landmarks, i.e., the inter-jugale plane, the mid sagittal plane, the zygomatic arch and the perpendicular long axis to the 1st molar but a small statistically significant difference was seen with respect to measurements from the facial surface of the 1st molar (P ≤ 0.05). Conclusion The angulation and position of an IZC bone screw are consistent between the two imaging modalities. A PA cephalogram may be used as a substitute for a CBCT scan to reduce the radiation exposure to patients.

CBCT Evaluation of Lingual Foramen and its Anatomic Variations in Northeast Indian Population.

The identification of nearby neurovascular structures is a vital part of dental implant treatment planning. Commonly two implants are placed in the mandibular inter foraminal region to support the overdenture. Placing dental implants in this region is considered relatively safe. The purpose of this study was to employ cone beam computed tomography (CBCT) on a representative sample of Northeast Indians to find out the location and distribution of lingual foramen in the anterior mandible. A total of 104 CBCT scans were performed using the Cranex 3D CBCT system. Three Oral and Maxillofacial Radiologists agreed on a visibility grade for assessing the lingual foramen using a 3-point scale. The number and presence of foramina were noted. On cross-sectional pictures, the distance in millimeters between the crest of the alveolar ridge and the superior cortical margin of the foramen was determined. Furthermore, the analysis of the distribution of lingual foramina in terms of frequency and percentages was performed. Scan results showed that the lingual foramen was clearly visible in 65.4% of cases, somewhat visible in 12.5% of scans, and not visible at all in 22.1% of cases. Half of the people in the study had two foramina, whereas 27.9 percent had one and 22.1 percent had none. The mean distance from the crest of the alveolar ridge was 10.84 mm in males whereas 9.91 mm in females. The Northeast Indian population exhibits an unusually high prevalence of lingual foramen in the anterior portion of the mandible. This research will aid in the precise pre-operative identification of the position and number of lingual foramina prior to surgical treatments involving the midline of the mandible.

CBCT for Diagnostics, Treatment Planning and Monitoring of Sinus Floor Elevation Procedures.

Sinus floor elevation (SFE) is a standard surgical technique used to compensate for alveolar bone resorption in the posterior maxilla. Such a surgical procedure requires radiographic imaging pre- and postoperatively for diagnosis, treatment planning, and outcome assessment. Cone beam computed tomography (CBCT) has become a well-established imaging modality in the dentomaxillofacial region. The following narrative review is aimed to provide clinicians with an overview of the role of three-dimensional (3D) CBCT imaging for diagnostics, treatment planning, and postoperative monitoring of SFE procedures. CBCT imaging prior to SFE provides surgeons with a more detailed view of the surgical site, allows for the detection of potential pathologies three-dimensionally, and helps to virtually plan the procedure more precisely while reducing patient morbidity. In addition, it serves as a useful follow-up tool for assessing sinus and bone graft changes. Meanwhile, using CBCT imaging has to be standardized and justified based on the recognized diagnostic imaging guidelines, taking into account both the technical and clinical considerations. Future studies are recommended to incorporate artificial intelligence-based solutions for automating and standardizing the diagnostic and decision-making process in the context of SFE procedures to further improve the standards of patient care.

Four-Dimensional Cone Beam CT Imaging Using a Single Routine Scan via Deep Learning.

A novel method is proposed to obtain four-dimensional (4D) cone-beam computed tomography (CBCT) images from a routine scan in patients with upper abdominal cancer. The projections are sorted according to the location of the lung diaphragm before being reconstructed to phase-sorted data. A multiscale-discriminator generative adversarial network (MSD-GAN) is proposed to alleviate the severe streaking artifacts in the original images. The MSD-GAN is trained using simulated CBCT datasets from patient planning CT images. The enhanced images are further used to estimate the deformable vector field (DVF) among breathing phases using a deformable image registration method. The estimated DVF is then applied in the motion-compensated ordered-subset simultaneous algebraic reconstruction approach to generate 4D CBCT images. The proposed MSD-GAN is compared with U-Net on the performance of image enhancement. Results show that the proposed method significantly outperforms the total variation regularization-based iterative reconstruction approach and the method using only MSD-GAN to enhance original phase-sorted images in simulation and patient studies on 4D reconstruction quality. The MSD-GAN also shows higher accuracy than the U-Net. The proposed method enables a practical way for 4D-CBCT imaging from a single routine scan in upper abdominal cancer treatment including liver and pancreatic tumors.

OC-0938 ScatterNet for 4D cone-beam CT intensity correction of lung cancer patients

OC-0938 ScatterNet for 4D cone-beam CT intensity correction of lung cancer patients

Mitigation of motion-induced artifacts in cone beam computed tomography using deep convolutional neural networks.

Cone beam computed tomography (CBCT) is often employed on radiation therapy treatment devices (linear accelerators) used in image-guided radiation therapy (IGRT). For each treatment session, it is necessary to obtain the image of the day in order to accurately position the patient and to enable adaptive treatment capabilities including auto-segmentation and dose calculation. Reconstructed CBCT images often suffer from artifacts, in particular those induced by patient motion. Deep-learning based approaches promise ways to mitigate such artifacts. We propose a novel deep-learning based approach with the goal to reduce motion induced artifacts in CBCT images and improve image quality. It is based on supervised learning and includes neural network architectures employed as pre- and/or post-processing steps during CBCT reconstruction. Our approach is based on deep convolutional neural networks which complement the standard CBCT reconstruction, which is performed either with the analytical Feldkamp-Davis-Kress (FDK) method, or with an iterative algebraic reconstruction technique (SART-TV). The neural networks, which are based on refined U-net architectures, are trained end-to-end in a supervised learning setup. Labeled training data are obtained by means of a motion simulation, which uses the two extreme phases of 4D CT scans, their deformation vector fields, as well as time-dependent amplitude signals as input. The trained networks are validated against ground truth using quantitative metrics, as well as by using real patient CBCT scans for a qualitative evaluation by clinicalexperts. The presented novel approach is able to generalize to unseen data and yields significant reductions in motion induced artifacts as well as improvements in image quality compared with existing state-of-the-art CBCT reconstruction algorithms (up to +6.3 dB and +0.19 improvements in peak signal-to-noise ratio, PSNR, and structural similarity index measure, SSIM, respectively), as evidenced by validation with an unseen test dataset, and confirmed by a clinical evaluation on real patient scans (up to 74% preference for motion artifact reduction over standard reconstruction). For the first time, it is demonstrated, also by means of clinical evaluation, that inserting deep neural networks as pre- and post-processing plugins in the existing 3D CBCT reconstruction and trained end-to-end yield significant improvements in image quality and reduction of motionartifacts.

Impact of bruxism on craniomandibular morphology: A cone-beam computed tomographic study

ABSTRACT Objective The main goal of this work was to address craniomorphological characteristics of patients with bruxism when compared to those without bruxism using cone beam computed tomography (CBCT) imaging. Methods Seventy CBCT images of an equal number (n = 35) of orthodontic patients with and without bruxism (age range, 18–44 years) were retrospectively analyzed. Sagittal evaluation, mandibular shape, and skeletal asymmetry were systematically assessed in both groups. Results Significant differences (p < 0.05) were observed between groups for Right Articular Fossa (AF) – Axial Plane (AP) and Left AF – AP (B > NB), Right Gonial Angle (GA), Left GA, Sella-Nasion and Occlusal Plane (B < NB). Age (13%), Condyle-Gonion (18%), AF to AP (67%), and Mental-AP (16%) had the greatest impact on bruxers. Conclusion In this study, the CBCT 3D image showed significant differences in craniofacial morphology, particularly in the mandibular structure of bruxers compared with non-bruxers.

Accuracy of three-dimensional periodontal ligament models generated using cone-beam computed tomography at different resolutions for the assessment of periodontal bone loss

To develop a method for generating three-dimensional (3D) digital models of the periodontal ligament (PDL) using 3D cone-beam computed tomography (CBCT) reconstruction and to evaluate the accuracy and agreement of the 3D PDL models in the measurement of periodontal bone loss. CBCT data collected from four patients with skeletal Class III malocclusion prior to periodontal surgery were reconstructed at three voxel sizes (0.2 mm, 0.25 mm, and 0.3 mm), and 3D tooth and alveolar bone models were generated to obtain digital PDL models for the maxillary and mandibular anterior teeth. Linear measurements of the alveolar bone crest obtained during periodontal surgery were compared with the digital measurements for assessment of the accuracy of the digital models. The agreement and reliability of the digital PDL models were analyzed using intra- and interexaminer correlation coefficients and Bland-Altman plots. Digital models of the maxillary and mandibular anterior teeth, PDL, and alveolar bone of the four patients were successfully established. Relative to the intraoperative measurements, linear measurements obtained from the 3D digital models were accurate, and there were no significant differences among different voxel sizes at different sites. High diagnostic coincidence rates were found for the maxillary anterior teeth. The digital models showed high intra- and interexaminer agreement. Digital PDL models generated by 3D CBCT reconstruction can provide accurate and useful information regarding the alveolar crest morphology and facilitate reproducible measurements. This could assist clinicians in the evaluation of periodontal prognosis and establishment of an appropriate orthodontic treatment plan.

Radiation safety standards during 3D CBCT imaging: A review in dentistry

The development of cone-beam computed tomography (CBCT) technology altered the practise of oral and maxillofacial radiology. When compared to medical computed tomography, CBCT was quickly adopted in dentistry settings due to its small size, relatively reduced cost, and decreased ionising radiation exposure. CBCT referrals are still being made incorrectly due to a lack of sufficient education among dentists and specialists. Furthermore, in order to get high-quality pictures, operators may raise the radiation dose, exposing the patient to unnecessary hazards. The objective of this review is to give an insight into 3D imaging with CBCT technology and a prudent radiation monitoring during CBCT for the benefit of both patients and dentists.

Characterizations of three-dimensional root morphology and topological location of mandibular third molars by cone-beam computed tomography.

This study aimed to delineate three-dimensional (3D) root morphology and topological locations of mandibular third molars (MTMs) by cone-beam computed tomography (CBCT) in a Chinese adult dental population. Adult patients with MTMs were retrospectively screened based on CBCT images at our institution between January 2018 and December 2019. Root morphology and spatial locations of these teeth were defined based on CBCT 3D images. Potential associations with epidemiological and clinical/radiological parameters were analyzed using Chi-square or Fisher exact test. Two-tailed P values less than 0.05 were considered statistically significant. A total number of 2680 eligible patients (male/female:0.74; 35 ± 10years old) with 4180 MTMs were enrolled. The majority of MTMs had 2 roots 3064 (73.30%), followed by 800 (19.14%) 1 root, 302 (7.22%) 3 roots, and 14 (0.33%) 4 roots. More than half of one-rooted MTMs were convergent, followed by club-shaped and C-shaped. Among MTMs with 2 roots, 2860 (93.34%) were M-D (mesio-distal) types. Most MTMs with 3 roots were M-2D (one root in mesial, two roots in distal) types, followed by 2M-D (two roots in mesial, one root in distal) types, and B-2L (one root in buccal, two roots in lingual) types. The presence of root configurations was significantly associated with the angulation, depth, and width classification in two-rooted MTMs (P < 0.05). Although the morphology and spatial locations of MTMs vary greatly, our results from a large dental population reconfirm that most MTMs have two roots with mesial-distal type of spatial distribution.

Assessing the Efficacy of Planmeca ProMax® 3D Cone-Beam CT Machine in the Detection of Root Fractures With Varied Metal Artifact Reduction Settings and Three Kilovoltage Peak Levels

This study aims to examine the accuracy of cone-beam computed tomography (CBCT) machines in detecting root fracture when using different metal artifact reduction (MAR) settings at different kilovoltage peak (kVp) levels. Sixty-six tooth roots were treated endodontically using a standardized technique. Of these, 33 roots were randomly selected to be fractured; the other 33 roots were intact and used as controls. The roots were placed randomly in prepared beef ribs to mimic the alveolar bone. Imaging was performed by Planmeca ProMax® 3D (Planmeca, Helsinki, Finland) using different MAR settings (no, low, mid, and high) at three different levels of kVp: 70, 80, and 90. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated. There was a significant difference in accuracy when using different MAR settings within the group of 70 kVp. Likewise, within the group of 90 kVp. There was no significant difference between different MAR settings at 80 kVp. Using low MAR/90 kVp had significantly higher accuracy relative to other MAR settings at 90 kVp; it also had the highest values of sensitivity, specificity, and AUC in the study. Using mid and high MAR at 70 kVp or 90 kVp decreased accuracy significantly. Mid MAR/90 kVp was the least effective setting in this study. Using low MAR at 90 kVp significantly increased the accuracy within the group of 90 kVp. In contrast, mid MAR and high MAR in70 and 90 kVp, respectively, decreased accuracy significantly.

Abstract No. 52 Mobile C-Arm–Guided Histotripsy: Assessment of Image Quality in an In Vivo Porcine Model

Histotripsy is an emerging focal tumor therapy that mechanically destroys tissue through focused ultrasound (US). To date, histotripsy has been guided by diagnostic US, which may limit visualization of tumors if obstructed by bone or gas. An alternative guiding approach has been successfully demonstrated using a fixed C-arm which provides sufficient image quality to accurately target tumors and assess histotripsy treatment zones. This study evaluates the feasibility of visualizing histotripsy treatment zones using an iso-centric, flat-panel based mobile C-arm, a more accessible and affordable imaging device. Histotripsy treatments (∼2 cm diameter) were performed in the liver and kidney of two ∼50kg swine with a 700 kHz multi-element therapy transducer and system (HistoSonics) guided by a mobile C-arm (CIOS, Siemens Healthineers). Post-treatment 3D cone-beam CT (CBCT) images were acquired with intravenous contrast with the mobile and a fixed C-arm system (Artis zee, Siemens) with and without a 12-14 L coupling water bath (WB). Image pairs from the fixed and mobile C-arms were registered using manually selected landmarks. Contrast and contrast-to-noise ratios (CNR) were measured using similar regions of interest in the treatment zone and background tissue. To compare treatment zone size and shapes, these were segmented and—to avoid registration errors—aligned about their centroids. The overlap between mobile/fixed C-arm pairs was quantified using the Dice Coefficient (DC, perfect overlap = 1). All treatments were visible in both mobile and fixed C-arm acquisitions. The corresponding CNRs with WB ranged from 2.0 to 7.2 for the mobile and from 1.7 to 3.8 for the fixed C-arm (Table 1). On average, CNRs observed for the kidney (4.1 ± 2.2) were higher than for the liver (2.3 ± 0.62). The lowest grayscale contrast was observed in the liver with WB, which was 44.5 and 79.2 AU for the mobile and fixed C-arm respectively. Comparing treatment overlap resulted in a DC of 0.91 ± 0.05 (range, 0.82 to 0.95). A mobile C-arm demonstrated sufficient image quality to distinguish histotripsy treatment zones from surrounding tissue, even with the attenuating WB present. Treatments in mobile and fixed C-arm images were similar in size/shape. This study supports further investigation of the clinical feasibility of histotripsy guidance with a mobile C-arm.