Background: The use of 3D printing in medical education, prosthetics, and preoperative planning requires dimensional accuracy of the models compared to the replicated tissues or organs. Objective. To determine the dimensional accuracy of 3D-printed models replicated from metacarpal bones from cadavers. Methods: Fifty-two models were 3D-printed using fused deposition modeling (FDM), stereolithography (SLA), digital light processing (DLP), and binder jetting method from 13 right first metacarpal bones of cadavers from the College of Medicine, University of the Philippines Manila. Six dimensional parameters of the 3D-printed models and their control bones were measured using 0.01 mm calipers — length, midshaft diameter, base width, base height, head width, and head height. Mean measurements were compared using non-inferiority testing and multidimensional scaling. Results: Mean measurements of the 3D-printed models were slightly larger than their control bones (standard deviation range: 1.219-4.264; standard error range, 0.338-1.183). All models were found to be at least 90% accurate and statistically non-inferior compared to control bones. DLP-printed models were the most accurate (base width, 99.62 %) and most similar to their control bone (–0.05, 90% CI –0.34, 0.24). Through multidimensional scaling, DLP-printed models (coordinate = 0.437) were the most similar to the control bone (coordinate = 0.899). Conclusion The 3D-printed models are dimensionally accurate when compared to bones.
Stereolithography ; Dimensional Measurement Accuracy ; Printing, Three-Dimensional

PURPOSE: This study was conducted to evaluate the accuracy of linear measurements of 3-dimensional (3D) images generated by cone-beam computed tomography (CBCT) and facial scanning systems, and to assess the effect of scanning parameters, such as CBCT exposure settings, on image quality. MATERIALS AND METHODS: CBCT and facial scanning images of an anthropomorphic phantom showing 13 soft-tissue anatomical landmarks were used in the study. The distances between the anatomical landmarks on the phantom were measured to obtain a reference for evaluating the accuracy of the 3D facial soft-tissue images. The distances between the 3D image landmarks were measured using a 3D distance measurement tool. The effect of scanning parameters on CBCT image quality was evaluated by visually comparing images acquired under different exposure conditions, but at a constant threshold. RESULTS: Comparison of the repeated direct phantom and image-based measurements revealed good reproducibility. There were no significant differences between the direct phantom and image-based measurements of the CBCT surface volume-rendered images. Five of the 15 measurements of the 3D facial scans were found to be significantly different from their corresponding direct phantom measurements (P < .05). The quality of the CBCT surface volume-rendered images acquired at a constant threshold varied across different exposure conditions. CONCLUSION: These results proved that existing 3D imaging techniques were satisfactorily accurate for clinical applications, and that optimizing the variables that affected image quality, such as the exposure parameters, was critical for image acquisition.
Anthropometry ; Cone-Beam Computed Tomography ; Dimensional Measurement Accuracy ; Imaging, Three-Dimensional

PURPOSE: This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., 0degrees), +10degrees, +12degrees, -12degrees, and -10degrees with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant. RESULTS: The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of -12degrees, -0.66 to -0.11 at -10degrees, -0.51 to +0.19 at 0degrees, -0.64 to +0.08 at +10degrees, and -0.64 to +0.1 at +12degrees. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9. CONCLUSION: Changing the slice orientation in the range of -12degrees to +12degrees reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.
Comprehension ; Cone-Beam Computed Tomography* ; Dental Implants ; Dental Occlusion ; Dimensional Measurement Accuracy ; Mandible ; Sheep ; Titanium

Diagnosis is a critical step in clinical treatment. Meta-analysis is a useful tool for evaluating the accuracy of diagnostic tests and can be used to obtain precise accuracy estimates when small studies for a given test and subject pool are available. Meta-analysis uses statistical techniques to combine and compare data from different studies, thus increasing the power of the estimates of diagnostic accuracy in primary research. Meta-analysis of diagnostic tests summarizes the accuracy of diagnosis. Therefore, it is necessary for clinicians to understand meta-analytical procedures for diagnostic tests. Herein, we describe the basic steps in a meta-analysis to evaluate test accuracy: 1) describing the results of individual studies, 2) searching for heterogeneity, 3) testing for the threshold effect, 4) deciding on the model for statistical pooling, 5) dealing with heterogeneity, and 6) interpreting meta-analysis results of diagnostic tests. Meta-analysis of diagnostic test accuracy provides useful information for clinical practice and for the formulation of questions to be tested in future studies.
Diagnosis ; Diagnostic Tests, Routine* ; Dimensional Measurement Accuracy ; Meta-Analysis as Topic ; Population Characteristics ; Research Design

PURPOSE: This study evaluated the effect of various head orientations during cone-beam computed tomography (CBCT) image acquisition on linear measurements of potential implant sites. MATERIALS AND METHODS: Six dry human skulls with a total of 28 implant sites were evaluated for seven different head orientations. The scans were acquired using a Hitachi CB-MercuRay CBCT machine. The scanned volumes were reconstructed. Horizontal and vertical measurements were made and were compared to measurements made after simulating the head position to corrected head angulations. Data was analyzed using a two-way ANOVA test. RESULTS: Statistical analysis revealed a significant interaction between the mean errors in vertical measurements with a marked difference observed at the extension head position (P<0.05). Statistical analysis failed to yield any significant interaction between the mean errors in horizontal measurements at various head positions. CONCLUSION: Head orientation could significantly affect the vertical measurements in CBCT scans. The main head position influencing the measurements is extension.
Cone-Beam Computed Tomography* ; Dental Implants ; Dimensional Measurement Accuracy ; Head* ; Humans ; Patient Positioning ; Skull

PURPOSE: This study assessed the accuracy of linear and angular measurements on panoramic radiographs taken at different positions in vitro. MATERIALS AND METHODS: Two acrylic models were fabricated from a cast with normal occlusion. Straight and 75degrees mesially and lingually angulated pins were placed, and standardized panoramic radiographs were taken at standard position, at an 8degrees downward tilt of the occlusal plane compared to the standard position, at an 8degrees upward tilt of the anterior occlusal plane, and at a 10degrees downward tilt of the right and left sides of the model. On the radiographs, the length of the pins above (crown) and below (root) the occlusal plane, total pin length, crown-to-root ratio, and angulation of pins relative to the occlusal plane were calculated. The data were subjected to repeated measures ANOVA and LSD multiple comparisons tests. RESULTS: Significant differences were noted between the radiographic measurements and true values in different positions on both models with linear (P<0.001) and those with angulated pins (P<0.005). No statistically significant differences were observed between the angular measurements and baselines of the natural head posture at different positions for the linear and angulated pins. CONCLUSION: Angular measurements on panoramic radiographs were sufficiently accurate and changes in the position of the occlusal plane equal to or less than 10degrees had no significant effect on them. Some variations could exist in the pin positioning (head positioning), and they were tolerable while taking panoramic radiographs. Linear measurements showed the least errors in the standard position and 8degrees upward tilt of the anterior part of the occlusal plane compared to other positions.
Dental Occlusion ; Dimensional Measurement Accuracy ; Head ; Lysergic Acid Diethylamide ; Posture ; Radiography, Panoramic

PURPOSE: This study was performed to investigate the intra- and inter-observer variability in linear measurements with axial images obtained by PreXion (PreXion Inc., San Mateo, USA) and i-CAT (Imaging Sciences International, Xoran Technologies Inc., Hatfield, USA) CBCT scanners, with different voxel sizes. MATERIALS AND METHODS: A cylindrical object made from nylon with radiopaque markers (phantom) was scanned by i-CAT and PreXion 3D devices. For each axial image, measurements were taken twice in the horizontal (distance A-B) and vertical (distance C-D) directions, randomly, with a one-week interval between measurements, by four oral radiologists with five years or more experience in the use of these measuring tools. RESULTS: All of the obtained linear measurements had lower values than those of the phantom. The statistical analysis showed high intra- and inter-observer reliability (p=0.297). Compared to the real measurements, the measurements obtained using the i-CAT device and PreXion tomography, on average, revealed absolute errors ranging from 0.22 to 0.59 mm and from 0.23 to 0.63 mm, respectively. CONCLUSION: It can be concluded that both scanners are accurate, although the linear measurements are underestimations, with no significant differences between the evaluators.
Cone-Beam Computed Tomography* ; Dimensional Measurement Accuracy ; Nylons ; Observer Variation ; Reproducibility of Results

PURPOSE: This study aimed to assess the reliability of measurements performed on three-dimensional (3D) virtual models of maxillary defects obtained using cone-beam computed tomography (CBCT) and 3D optical scanning. MATERIALS AND METHODS: Mechanical cavities simulating maxillary defects were prepared on the hard palate of nine cadavers. Images were obtained using a CBCT unit at three different fields-of-views (FOVs) and voxel sizes: 1) 60x60 mm FOV, 0.125 mm3 (FOV60); 2) 80x80 mm FOV, 0.160 mm3 (FOV80); and 3) 100x100 mm FOV, 0.250 mm3 (FOV100). Superimposition of the images was performed using software called VRMesh Design. Automated volume measurements were conducted, and differences between surfaces were demonstrated. Silicon impressions obtained from the defects were also scanned with a 3D optical scanner. Virtual models obtained using VRMesh Design were compared with impressions obtained by scanning silicon models. Gold standard volumes of the impression models were then compared with CBCT and 3D scanner measurements. Further, the general linear model was used, and the significance was set to p=0.05. RESULTS: A comparison of the results obtained by the observers and methods revealed the p values to be smaller than 0.05, suggesting that the measurement variations were caused by both methods and observers along with the different cadaver specimens used. Further, the 3D scanner measurements were closer to the gold standard measurements when compared to the CBCT measurements. CONCLUSION: In the assessment of artificially created maxillary defects, the 3D scanner measurements were more accurate than the CBCT measurements.
Cadaver ; Cone-Beam Computed Tomography ; Dimensional Measurement Accuracy ; Linear Models ; Maxillofacial Prosthesis ; Palate, Hard ; Silicones

PURPOSE: The goal of this study was to investigate the level of agreement between tumor sizes measured on ultrasonography (US) and in pathological specimens of papillary thyroid carcinomas (PTCs) and to identify the US characteristics contributing to discrepancies in these measurements. METHODS: We retrospectively reviewed the US findings and pathological reports of 490 tumors in 431 patients who underwent surgery for PTC. Agreement was defined as a difference of <20% between the US and pathological tumor size measurements. Tumors were divided by size into groups of 0.5-1 cm, 1-2 cm, 2-3 cm, and ≥3 cm. We compared tumors in which the US and pathological tumor size measurements agreed and those in which they disagreed with regard to the following parameters: taller-than-wide shape, infiltrative margin, echogenicity, microcalcifications, cystic changes in tumors, and the US diagnosis. RESULTS: The rate of agreement between US and the pathological tumor size measurements was 64.1% (314/490). Statistical analysis indicated that the US and pathological measurements significantly differed in tumors <1.0 cm in size (P=0.033), with US significantly overestimating the tumor size by 0.2 cm in such tumors (P<0.001). Cystic changes were significantly more frequent in the tumors where US and pathological tumor size measurements disagreed (P<0.001). CONCLUSION: Thyroid US may overestimate the size of PTCs, particularly for tumors <1.0 cm in size. This information may be helpful in guiding decision making regarding surgical extent.
Decision Making ; Diagnosis ; Dimensional Measurement Accuracy ; Humans ; Pathology, Surgical ; Retrospective Studies ; Thyroid Gland* ; Thyroid Neoplasms* ; Ultrasonography

PURPOSE: Cone-beam computed tomography (CBCT) is widely used for 3-dimensional assessments of cranio-maxillofacial relationships, especially in patients undergoing orthognathic surgery. We have introduced, for reference in CBCT cephalometry, an anatomical mid-sagittal plane (MSP) identified by the nasion, the midpoint between the posterior clinoid processes of the sella turcica, and the basion. The MSP is an updated version of the median plane previously used at our institution for 2D posterior-anterior cephalometry. This study was conducted to test the accuracy of the CBCT measures compared to those obtained using standard posterior-anterior cephalometry. MATERIALS AND METHODS: Two operators measured the inter-zygomatic distance on 15 CBCT scans using the MSP as a reference plane, and the CBCT measurements were compared with measurements made on patients' posterior-anterior cephalograms. The statistical analysis evaluated the absolute and percentage differences between the 3D and 2D measurements. RESULTS: As demonstrated by the absolute mean difference (roughly 1 mm) and the percentage difference (less than 3%), the MSP showed good accuracy on CBCT compared to the 2D plane, especially for measurements of the left side. However, the CBCT measurements showed a high standard deviation, indicating major variability and low precision. CONCLUSION: The anatomical MSP can be used as a reliable reference plane for transverse measurements in 3D cephalometry in cases of symmetrical or asymmetrical malocclusion. In patients who suffer from distortions of the skull base, the identification of landmarks might be difficult and the MSP could be unreliable. Becoming familiar with the relevant software could reduce errors and improve reliability.
Cephalometry ; Cone-Beam Computed Tomography ; Dimensional Measurement Accuracy ; Humans ; Malocclusion ; Orthognathic Surgery ; Sella Turcica ; Skull Base