Accuracy Of Scanning Research Articles

Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery

Objective. To investigate the impact of scan path optimization on the dose accuracy and beam delivery time (BDT) of proton pencil beam scanning in the dose-driven continuous scanning (DDCS). Approach. A diverse set of six clinical plans, representing various spot patterns and treatment sites, was used to evaluate the effectiveness of scan time optimization and scan length optimization. The DDCS dose discrepancy and BDT with optimized scan paths was compared to the default serpentine scan path. Main results. Both scan time optimization and scan path optimization were able to reduce the DDCS dose discrepancy compared to the default serpentine scan path. All plans, except for the layer repainting lung plan, achieved a 2%/2 mm gamma pass rate of over 99% and less than 1% PTV DVH root mean square error (RMSE) through scan path optimization. In the case of the layer repainting lung plan, when compared to the default serpentine scan path, the 2%/2 mm gamma pass rate showed improvements from 91.3% to 93.1% and 95.8%, while the PTV DVH RMSE decreased from 2.1% to 1.7% and 1.1% for scan time optimization and scan length optimization, respectively. Although scan time optimization resulted in shorter total scan times for all plans compared to the default scan path and scan length optimization tended to have longer total scan times. However, due to the short total scan times and their minimal contribution to the total BDT, the impact of scan path optimization on the total BDT was practically negligible. Significance. Both scan time optimization and scan length optimization proved to be effective in minimizing DDCS dose discrepancy. No definitive winner can be determined between these two optimization approaches. Both scan time and scan length optimization had minimal effect on the total BDT.

Accuracy of intraoral scan with prefabricated aids and stereophotogrammetry compared with open tray impressions for complete-arch implant-supported prosthesis: A clinical study.

The aim of this clinical study was to compare the accuracy of intraoral scan system (IOS) with prefabricated aids and stereophotogrammetry (SPG) compared with open tray implant impression (OI) for complete-arch implant-supported fixed dental prostheses (CIFDP). Patients needing CIFDP were enrolled in this study. OI, reference standard, IOS with prefabricated aids, and SPG were performed for each patient. Distance and angle deviations between all pairs of abutment analogs, root mean square (RMS) errors between the aligned test and reference model, and chairside time were measured. The effect of inter-abutment distance, jaw (maxilla or mandible), number of implants, and arch length on deviations was analyzed. The mixed effect model was applied to analyze deviations and RMS errors. Fifteen consecutive individuals (6 females and 9 males, 47-77 years old) with 22 arches (9 upper and 13 lower jaws) and 115 implants were included. There was no significant difference in distance deviation comparing SPG and IOS with OI (p > .05). IOS showed a significantly greater angle deviation and RMS errors than SPG (median 0.40° vs. 0.31°, 69 μm vs. 45 μm, p < .01). The inter-abutment distance was negatively correlated with the accuracy of SPG and IOS (p < .05). The chairside time for IOS, SPG, and OI was 10.49 ± 3.50, 14.71 ± 2.86, and 20.20 ± 3.01 min, respectively (p < .01). The accuracy of SPG and IOS with prefabricated aids was comparable. IOS was the most efficient workflow.

Accurate atomic scanning transmission electron microscopy analysis enabled by deep learning

Accurate atomic scanning transmission electron microscopy analysis enabled by deep learning

Hysteresis modeling and compensation of a piezoelectric fast steering platform using multiple NARMA-L2 models

The piezoelectric fast steering platform (PFSP) enhances the scanning capabilities of lidar systems for autonomous vehicles. However, hysteresis nonlinearity degrades the scanning accuracy of the PFSP. To meet this challenge, this paper proposes a novel approach for hysteresis modeling and compensation using multiple nonlinear autoregressive moving average (NARMA)-L2 models. First, the hysteresis model is partitioned into a collection of submodels based on the K-means methodology, where the feature vector stems from the classical Bouc–Wen (CBW) model. Each submodel describes the dynamics of a specific hysteresis segment by a single NARMA-L2 model. The composite neural network (CNN), formed by combining two multilayer perceptron (MLP) networks, is trained to estimate the hysteresis output of the single NARMA-L2 model. Compared to the submodels obtained by evenly partitioning according to the input range, the submodels obtained by K-means partitioning offer higher hysteresis modeling accuracy. To compensate for the hysteresis nonlinearity, a novel adaptive Multi-NARMA-L2 (AMNL2) controller is then designed by online adjusting the parameters of the CNN. Furthermore, an adaptive filter is proposed to alleviate the oscillation caused by high-frequency disturbances during switching. Finally, experiments demonstrate that the AMNL2 controller outperforms the traditional MNL2 controller and the proportional–integral–derivative (PID) controller.

Design and practice of an emergency blood allocation system based on radiofrequency identification technology.

Currently, blood allocation is solely done by scanning barcode labels for each bag of blood, with low efficiency. However, the rapid allocation of emergency blood is required owing to the rapid increase in blood consumption during unconventional emergencies. This study aimed to design and apply radiofrequency identification (RFID) technology for the rapid allocation of blood in batches with advantages in time, efficiency and accuracy. A blood emergency allocation system based on RFID technology was designed using a multi-label anti-collision algorithm and tested with automatic information check, a comparative study of scanning speed and accuracy, data analysis and other methods. The optimal packing quantities of suspended red blood cells and fresh frozen plasma were 40 and 50 bags per box, respectively. The application of rapid batch allocation of blood using RFID technology was performed, and the data sent and received by RFID scanning and barcode scanning were compared. The designed RFID blood emergency allocation system could effectively achieve the rapid and batch allocation of emergency blood and has the advantages of stability, efficiency and accuracy in blood emergency allocation and management.

Effect of novel prefabricated auxiliary devices attaching to scan bodies on the accuracy of intraoral scanning of complete-arch with multiple implants: An in-vitro study

ObjectivesTo examine the effect of novel prefabricated auxiliary devices with different geometric features called Scan Body Clasp (SBC) at different levels on the accuracy of intraoral scanning of complete-arch with multiple implants. MethodsAn edentulous maxilla 4-implant model and SBCs with different geometric features (flat or curved) were fabricated by a 3D printer (AccuFab-C1s, 3DShining, Hangzhou, China). Test scans were performed using an intraoral scanner (Aoralscan 3, 3DShining, Hangzhou, China) software version 1.0.0.3104 under different scenarios: group A (CO), without any SBCs; group B&C (LC&HC), with curved SBCs adjacent to and away from the mucosa; group D&E (LF&HF), with flat SBCs adjacent to and away from the mucosa. 20 scans were done for each group (CO, LC, HC, LF and HF). Reference Scans were obtained by digitizing the model in group A using a dental laboratory scanner (D2000, 3Shape, Copenhagen, Denmark). The related files were imported into inspection software for trueness and precision assessment. Statistical analysis was performed with One-way ANOVA, Independent-Sample T test for trueness values. Kruskal-Wallis test and Mann-Whitney test were used to assess the precision values. The level of significance was set at α=0.05. ResultsGroups with SBCs demonstrated trueness enhancement, among which LF revealed the best trueness. Significant differences were also found between LF and HC (p < .01), LF and HF (p < .001), LC and HF (p < .01). LF and HF showed precision enhancement. The best precision was LF, which was found to be more precise than LC (p < .001) and HC (p < .001). HF was more precise than LC (p < .001) and HC (p < .001). ConclusionsAttaching the scan bodies with SBCs at different levels significantly influenced the scanning accuracy. The SBCs near the mucosa result in superior trueness, while the flat morphology benefits the precision. Clinical significanceThe results demonstrated the feasibility of the SBCs in enhancing intraoral complete-arch implant scanning accuracy. Among the configurations tested in the present study, low-level and flat surfaces of the artificial landmarks may be the potential pivotal elements to optimizing long-span scanning accuracy.

Magnetization in superconducting corrector magnets and impact on luminosity–calibration scans in the Large Hadron Collider

Superconducting accelerator magnets have a nonlinear dependence of field on current due to the magnetization associated with the iron or with persistent currents in the superconducting filaments. This also gives rise to hysteresis phenomena that create a dependence of the field on the powering history. Magnetization effects are of particular importance for luminosity–calibration scans in the Large Hadron Collider, during which a small number of Nb–Ti superconducting orbit correctors are excited at low field and with frequent flipping of the sign of the current ramp. This paper focuses on the analysis of special measurements carried out to estimate these nonlinear effects under the special cycling conditions used in these luminosity scans. For standard powering cycles, we evaluate the effect of the main magnetization loop; for complex operational schemes, magnetization-branch transitions occur that depend on the details of the current cycle. The modelling of these effects is not included in the magnetic field prediction software currently implemented in the LHC control system; here we present an approach to predict the transitions between the main magnetization branches. The final aim is to estimate the impact of magnetic hysteresis on the accuracy of luminosity-calibration scans.

Intraoral digital implant scans: Parameters to improve accuracy.

To report the means to maximize the predictability and accuracy of intraoral digital implant scans through the evaluation of operator and patient-related factors. A search of published articles related to factors that can decrease the scanning accuracy of intraoral digital implant scans was completed in four data sources:MEDLINE, EMBASE, EBSCO, and Web of Science. All studies related to variables that can influence the accuracy of intraoral digital implant scans obtained by using intraoral scanners (IOSs) were considered. These variables included ambient lighting, scanning pattern, implant scan body (ISB) design, techniques for splinting ISBs, arch location, implant position, and inter-implant distance. Among operator-related factors, ambient lighting conditions, scanning pattern, and ISB design (material, geometry, and retention design) can impact the accuracy of intraoral digital implant scans. The optimal ISB for maximizing IOS accuracy is unclear; however, polymer ISB can wear with multiple reuse and sterilization methods. Among patient-related factors, additional variables should be considered, namely arch (maxillary vs. mandibular arch), implant position in the arch, inter-implant distance, implant depth, and angulation. Ambient lighting conditions should be established based on the IOS selected to optimize the accuracy of intraoral digital implant scans. The optimal scanning pattern may vary based on the IOS, clinical situation, and the number of implants. The optimal ISB design may vary depending on the IOS used. Metallic implant scan bodies are preferred over polymer ISB designs to minimize wear due to multiple use and sterilization distortion. Among patient-related factors, additional variables should be considered namely the arch scanned, implant position in the arch, inter-implant distance, implant depth, and angulation. The impact of these factors may vary depending on the IOS selected.

Additively manufactured devices with varying designs and sizes for acquiring initial intraoral implant scans.

Dental literature has reported greater intraoral scanning accuracy when implant scan bodies (ISBs) are connectedcompared with non-connected methods. Initial intraoral digital implant scans are required for the fabrication of a custom framework to connect implant scan bodies (IOSFix; IOSFix Dental). This calibrated metal framework is used to acquire definitive intraoral implant scans. However, the acquisition of initial intraoral implant scans can be challenging when ISBs are not connected. This article describes a step-by-step technique for connecting ISBs by using additively manufactured devices to acquire initial intraoral implant scans. This technique aims to facilitate the recording of initial intraoral implant scans, provide different device designs and sizes to connect ISBs, and reduce chairside time.

Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners.

To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs). A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05). Trueness ranged from 91 to 139μm and precision ranged from 5 to 23μm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11μm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4μm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision. Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Evaluation of scanning accuracy for two commercially available intraoral scanners in reproducing orthodontic bracket dimensions.

The aim of this study was to compare the scanning accuracy of two different intra-oral scanners- MEDIT i500 and TRIOS 3 shape in reproducing orthodontic bracket dimensions. This in vivo cross-sectional study comprised seven subjects with a full complement of permanent dentition without third molars. Complete arch scanning was carried out with two intraoral scanners, such as MEDIT i500, TRIOS 3 shape, after bonding with brackets. The control group consisted of bracket dimensions measured directly by using Vernier calipers before bonding. Bracket dimensions of three-dimensional (3D) images were measured by using OrthoAnalyzer software. The accuracy of intraoral scanning was investigated by comparing bracket dimensions among the three groups using One-way ANOVA and Post-Hoc Tukey HSD test, and by evaluating outcomes for each quadrant and an individual tooth in complete-arch scans. When comparing bracket dimensions of 3D images with manual measurements using a traditional Vernier caliper, MEDIT i500 showed no significant difference when compared to the control group (p>0.05) in full arch scanning as well as the quadrant and single tooth scans in complete arch scanning. TRIOS 3 shape showed a significant difference when compared to the control and MEDIT i500 group (p<0.05) for all parameters. MEDIT i500 showed higher accuracy and better reproduction of orthodontic bracket dimensions than TRIOS 3 shape.

Sub-centimetre integration of scanning measurements: UAV and terrestrial-based, for determining the shape of a shell structure

The conducted research was related to the integration of scanning measurements taken from a drone and terrestrial stations for the observatory dome. Each method has certain limitations in the scanning head positioning concerning the building object. As a result, there are gaps and measurement errors in each point cloud. The integrated cloud allows for full coverage of the object with points. It also allows for replacing data points with measurement errors with observations from the second method. The accuracy of UAV scanning can be improved with results from other measurement methods. The research aimed to integrate the UAV and terrestrial cloud in a way, that would raise the accuracy of UAV measurements to a level comparable to terrestrial scanning. The research was able to integrate clouds with an average error of 6 mm. Further analysis showed that the differences between UAV and terrestrial measurements are generally within 5 mm.

Evaluating the Accuracy of UAV and TLS for 3D Indoor Modelling in Large-Scale Building Environments

The accuracy of 3D indoor reconstructed models is critical in various applications such as indoor navigation, virtual reality (VR), and building information modelling (BIM). This research study aims to evaluate the accuracy of Unmanned Aerial Vehicles (UAV) and Terrestrial Laser Scanning (TLS) for 3D indoor modelling in large-scale building environments. To achieve this, several evaluations were made towards the number of point clouds, estimated costs and accuracy of the 3D indoor reconstructed model generated from dense point clouds acquired by Unmanned Aerial Vehicle (UAV) and Terrestrial Laser Scanner (TLS). A small indoor classroom was selected for this study approximately 100m2. In UAV data acquisition, three (3) flight missions were set up at the front, left and right views. Meanwhile, five (5) scanning stations were placed on-site for the TLS method. Due to various different flight mission views in the UAV dataset, the number of point clouds was quite higher compared to the TLS method. However, a better-quality visualization of the TLS model has been obtained as opposed to the UAV 3D model. For the required time to generate a 3D model, it showed that UAV processing time was more consuming lots of time than the TLS method, especially when georeferencing the overlapping photographs. In terms of accuracy, the RMSE value from TLS was better than UAV at 0.003m compared to UAV at 0.021m. Overall, this study provides insights into the accuracy and suitability of UAV and TLS for 3D indoor modelling in large-scale building environments. The results can inform decision-making processes in various industries such as architecture, engineering, and construction, where accurate and reliable 3D models are crucial for design, planning, and management purposes.

3D Scan of Hardness Imprints for the Non-destructive In-Situ Structural Assessment of Operated Metal Components

The structural integrity of operated components can be assessed by non-destructive mechanical tests performed in-situ with portable instruments. Particularly promising in this context are small scale hardness tests supplemented by the mapping of the residual imprints left on metal surfaces. The data thus collected represent the input of inverse analysis procedures, which determine the material characteristics and their evolution over time. The reliability of these estimates depends on the accuracy of the geometry scans and on the robustness of the data filtering and interpretation methodologies. The objective of the present work is to evaluate the accuracy of the 3D reconstruction of the residual deformation produced on metals by hardness tests performed at a few hundred N load. The geometry data are acquired by portable optical microscopes with variable focal distance. The imperfections introduced by the imaging system, which may not be optimized for all ambient conditions when used in automatic mode, are analysed. Representative examples of the output produced by the scanning tool are examined, focusing attention on the experimental disturbances typical of onsite applications. Proper orthogonal decomposition and data reduction techniques are applied to the information returned by the instrumentation. The essential features of the collected datasets are extracted and the main noise is removed. The results of this investigation show that the accuracy achievable with the considered equipment and regularization procedures can support the development of reliable diagnostic analyses of metal components in existing structures and infrastructures.

Accuracy comparison of scan segmental sequential ranges with two intraoral scanners for maxilla and mandible

Background/purposeThe accuracy of a full-arch scan by using an intraoral scanner should be validated under clinical conditions. This study aimed to compare the accuracy of full-arch digital impressions in the maxilla and mandible using two intra oral scanners with three different scan segmental sequential ranges. Materials and methodsA dental model with 28 teeth in their normal positions served as the reference. Sixty full-arch scans were performed using Trios 3 and Trios 4, employing scanning strategy O (manufacturer's original method), OH (segmental sequential ranges one half), and TQ (segmental sequential ranges third quarter). Trueness was evaluated by comparing digital impressions with a reference dataset using specialized software. One-way ANOVA and Tukey tests assessed differences between the groups. ResultsFor Trios 3 on the maxilla, no significant difference was found among the groups of trueness; in the mandible, strategy O exhibited a significant difference (P = 0.008) with the highest deviation. For Trios 4 on the maxilla, strategy TQ demonstrated the lowest deviation with a significant difference (P = 0.006); in the mandible, no significant difference was found among the groups of trueness. ConclusionStrategy TQ exhibited the best trueness for Trios 3 and Trios 4, suggesting it may be preferred for higher accuracy. Clinicians should consider these findings when selecting scanning strategies and intraoral scanners for specific cases.

An in vitro Comparison of Accuracy Between Three Different Face Scanning Modalities.

A mannequin head was digitized using a reference scanner (Scan in a Box) to acquire the reference mesh. Subsequently it was scanned with a structured light scanner (Einscan Pro HD), a stereophotogrammetry scanner (RayFace100) and a laser scanner (Proface 3D Mid) to acquire test meshes.Resulting meshes were delineated in four horizontal areas and discrepancies calculated for the complete face and different facial partitions. One-way Anova and pairwise comparisons tests were used to compare trueness and precision between scanners across different areas. Significant differences were detected among scanners for complete face (F (3, 27) =776, P ⟨ 0.01)) and for delineated face areas (F (11, 99) =200.1, P ⟨ 0.01)). Einscan had significantly higher accuracy for the complete face (P⟨0.01) and significantly higher trueness for each facial partition compared to other scanners. RayFace had significantly higher trueness when scanning the middle part of face compared to other facial parts. Proface had significantly lower upper facial third trueness compared to other facial parts. All scanners had accuracy levels below the 2.00mm threshold. Facial scanning accuracy was influenced per scanner used. Scanning trueness per device was influenced by location of surface area. All scanners had accuracy levels within the acceptable accuracy threshold.

Influence of Implant Adjacent Teeth on the Accuracy of Digital Impression.

The aim of this study was to evaluate the effect of adjacent teeth patterns on the accuracy of digital scans of parallel and divergent implants for three-unit prostheses. A maxillary typodont model with implants in the locations of the first premolars and first molars was used to develop three clinical scenarios for three-unit prostheses: (S1) Partially edentulous arch with missing first premolars and first molars only; (S2) partially edentulous arch with missing first premolars, second premolars and first molars; and (S3) partially edentulous arch with missing canines, first premolars, second premolars, first molars, and second molars. On one side, the implants were parallel, and for the other side, the implants had a 15-degree buccolingual angle. With the aid of scan bodies, 10 digital impressions were taken for each scenario and for each side. To evaluate the accuracy, a reverse engineering software was used to measure trueness, precision, and interimplant distance. The best trueness for parallel implants was observed for S2 (30.0 µm), followed by S3 (67.3 µm) and S1 (74.8 µm) (p < 0.001). Likewise, S2 had the best precision for parallel implants (31.3 µm) followed by S3 (38.0 µm) and S1 (70.3 µm) (p < 0.001). For the divergent implants, S2 exhibited the best trueness (23.1 µm), followed by S3 (48.2 µm) and S1 (59.4 µm) (p = 0.007). Similarly, the S2 had the best precision (12.3 µm) followed by S3 (62.1 µm) and S1 (66.9 µm) (p < 0.001). The S2 had the least interimplant distance deviation followed by S1 and S3. The difference was significant for parallel implants (p = 0.03), but insignificant for divergent implants (p = 0.15). Regardless of the presenting scenario, digital implant impressions for three-unit prostheses appear to be clinically accurate. A clear interimplant area between scan bodies enhanced the accuracy of digital impressions. This observation can be attributed to more accessible axial surface scanning of the scan body.

Real-world accuracy of computed tomography in patients admitted with small bowel obstruction: a multicentre prospective cohort study

PurposeSmall bowel obstruction (SBO) is a common surgical emergency. Previous studies have shown the value computed tomography (CT) scanning in both confirming this diagnosis and identifying indications for urgent surgical intervention, such as strangulated bowel or closed loop obstructions. However, most of the literature is based on retrospective expert review of previous imaging and little data regarding the real-time accuracy of CT reporting is available. Here, we investigated the real-world accuracy of CT reporting in patients admitted with SBO.MethodsThis was a multicentre prospective study including consecutive patients admitted with SBO. The primary outcomes were the sensitivity and specificity of CT scanning for bowel obstruction with ischaemia and closed loop obstruction. Data were retrieved from the original CT reports written by on-call radiologists and compared with operative findings.ResultsOne hundred seventy-six patients were included, all of whom underwent CT scanning with intravenous contrast followed by operative management of SBO. Bowel obstruction with ischaemia was noted in 20 patients, with a sensitivity and specificity of CT scanning of 40.0% and 85.5%, respectively. Closed loop obstructions were noted in 26 patients, with a sensitivity and specificity of CT scanning of 23.1% and 98.0%, respectively.ConclusionsThe real-world accuracy of CT scanning appears to be lower than previously reported in the literature. Strategies to address this could include the development of standardised reporting schemas and to increase the surgeon’s own familiarity with relevant CT features in patients admitted with SBO.

Accuracy of Initial Chest Computed Tomography Scan for Diagnosis of COVID-19: A Systematic Review

Abstract Background Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus (SARS- COVID-19) with recent outbreak occurred on 11 March 2020. A computerized tomography (CT) scan for chest was proved to be a helpful tool for diagnosis of COVID-19 pneumonia. But little is known about its diagnostic accuracy. Aim of the Work This systematic review aims at determining current evidence regarding accuracy of initial chest CT scan for detection of COVID-19 infection. Patients and Methods We conducted an electronic search through different databases; PubMed, SCOPUS, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL). We included clinical trials whether randomized or nonrandomized prospective or retrospective cohorts, case control, cross sectional studies and case series larger than 10 cases). All studies that reported data about the diagnostic accuracy of initial chest CT for diagnosis of COVID-19 infection were enrolled. We evaluated the methodological quality for included studies using QUADAS-2 Risk of Bias tool. Results From a total 4617 screened citations, 40 studies met our inclusion criteria. We divided the identified studies into two groups: studies that reported both sensitivity and specificity (6 studies, n = 1431) and studies that included only positive COVID-19 cases from which we could estimate only sensitivity (34 studies, n = 3515). Among six studies that evaluated accuracy of CT chest, there was high sensitivity ranged from to 93% to 100% but CT chest specificity was low ranged from to 10% to 56%. Rest of 34 studies had a wide range of sensitivity between 61% and 100% with few studies reported sensitivity below 80%. Conclusion Our results suggest that CT chest is a great screening tool for COVID-19 with high sensitivity but it had low specificity. However, interpretation of CT chest along with other laboratory could enhance its diagnostic accuracy.

The in-vitro accuracy of fiducial marker-based versus markerless registration of an intraoral scan with a cone-beam computed tomography scan in the presence of restoration artifact.

To determine the effect of restoration artifact ('metal artifact') on registration accuracy of an intraoral scan and cone-beam computed tomography (CBCT) scan, comparing fiducial marker-based registration with markerless registration. A maxillary model was fitted with multiple configurations of zirconia crowns to simulate various states of oral rehabilitation. Intraoral scans and CBCT scans (half and full rotation) were acquired. Registration was performed using markerless (point-based registration with surface-based refinement) and fiducial marker-based registration. Each experimental condition was repeated 10 times (n = 320). The absolute deviation was measured at the canines and first molars, and the average and maximum values were analysed using multiple linear regression. R2 was 0.874 for average error and 0.858 for maximum error. For markerless registration, there were 0.041 mm (p < .001) and 0.045 mm (p < .001) increases in average and maximum error per crown, respectively. For fiducial marker-based registration, the effect of additional crowns was not statistically significant for average (p = .067) or maximum (p = .438) error. For a full arch of crowns, the regression model predicted average and maximum errors of 0.581 and 0.697 mm for the markerless technique, and 0.185 and 0.210 mm for the fiducial marker-based technique. Overall, the fiducial marker-based technique was more accurate for four or more crowns. The half rotation scan increased average error by 0.021 mm (p = .001) and maximum error by 0.029 mm (p < .001). Under the present study's experimental conditions, the fiducial marker-based technique should be considered if four or more full-coverage highly radiopaque restorations are present.