Cone-beam Computed Tomography Settings Research Articles

Effect of different cone beam computed tomography settings on artifact production in titanium and zirconia dental implants: An in vitro study.

The use of dental implants in the treatment of edentulous patients is increasing. Zirconia implants are an alternative to titanium implants, offering advantages in terms of aesthetics and biological compatibility. However, the number of artifacts observed on radiographic images with zirconia implants compared to titanium implants is yet to be determined. The purpose of this study was to evaluate the impact of different cone-beam computed tomography (CBCT) parameters on the production of artifacts in zirconia and titanium implants. A dry human mandible was coated with wax to simulate human soft tissues and examined. Subsequently, titanium and zirconia implants were placed at the same points in the posterior region of the mandible. The production of artifacts on CBCT scans was evaluated using 2 parameters. The first parameter, the standard deviation within the region of interest (SDROI), is based on a comparison of the gray levels at implant and control areas. The second parameter was the contrast-to-noise ratio (CNR), which was evaluated for different protocols created by various combinations of the field of view (FOV) area, milliampere [mA] intensity and metal artifact reduction (MAR) programs. The study found that zirconia implants produced more artifacts than titanium implants. However, the production of artifacts in zirconia implants could be significantly reduced by increasing the mA values, performing CBCT scans with smaller FOV areas, and enabling MAR programs. The production of artifacts is a disadvantage of zirconia implants, but this drawback can be mitigated by selecting appropriate protocols for the CBCT device.

Comparative Evaluation of Artifacts Originated by Four Different Post Materials Using Different CBCT Settings.

Forty premolar teeth were used in this study. Root canals were treated, and teeth were randomly distributed into four subgroups (n = 10) for the preparation of post materials: titanium, gold (Nordin), quartz fiber (Bisco DT Light), and glass fiber (Rely X). The CBCT images were taken with two different kVps, three different metal artifact reduction (MAR) algorithm options, and two different resolutions. For each protocol, the effective dose was calculated according to the dose area production (DAP) value. The standard analysis of variance technique and the Tukey multiple comparison adjustment method were used to assess interactions among material types, kVp, MAR, and voxel settings. More artifacts were found in the middle third than in the cervical third (p < 0.05). The mean value of artifacts was highest for gold (Nordin), 90 kVp, no MAR, and 100 voxel size. Glass or quartz fiber posts at low resolution, with high MAR and 96 kVp, originated fewer artifacts. Moreover, the use of 90 and 96 kVp with 200 voxel size and high MAR provided the least amount of radiation. The best setting for radiographic follow-up of post materials on the Planmeca ProMax is 96 kVp with low resolution and high MAR; this setting produced one of the lowest effective doses. This study estimated the best scanning protocol by lowering the effective dose to a minimum level according to the "as low as reasonably achievable" principle, as well as assessing the tooth region and the post material generating the fewest artifacts, in order to prevent image interpretation challenges such as false-positive and false-negative results stemming from the deterioration of the visibility of the root canal due to perforation, fractures, and voids in the root canal region.

Effects of Exposure Parameters and Voxel Size for Cone-Beam Computed Tomography on the Image Matching Accuracy with an Optical Dental Scan Image: An In Vitro Study

This study is aimed at assessing the effects of exposure parameters and voxel size for cone-beam computed tomography (CBCT) on the image matching accuracy with an optical dental scan image. CBCT and optical scan images of a dry human mandible were obtained. Different CBCT settings were used: tube voltage, 60, 80, and 100 kVp; tube current, 6 and 8 mA; and voxel size, 100, 200, and 300 μm. Image matching between the CBCT and optical scan images was performed using implant planning software by dental professionals (n = 18). The image matching accuracy in each combination of CBCT settings was evaluated by assessing the linear discrepancy between the three-dimensionally reconstructed radiological image and the registered optical scan image using an image analysis software program. The Kruskal-Wallis test and a post hoc Mann–Whitney U test with Bonferroni correction were used to compare the accuracy of image registration between the groups (α = 0.05). Overall, the image matching accuracy was not significantly different between tube voltage and current settings; however, significantly higher image registration errors were found at the combination of 100 kVp tube voltage/8 mA tube current (F = 8.44, P < 0.001). Changes in voxel sizes did not significantly interfere with the image registration results. No interaction was found among voltage, current, and voxel size in terms of image registration accuracy (F = 2.022, P = 0.091). Different exposure parameter settings in tube voltage and tube current did not significantly influence the image matching accuracy between CBCT and optical dental scan images; however, a high radiation dose could be inappropriate. The image matching accuracy was not significantly affected by changing the voxel sizes of CBCT.

Optimisation of Varian TrueBeam head, thorax and pelvis CBCT based on patient size

AbstractPurpose:The aim of this study was to optimise patient dose and image quality of Varian TrueBeam cone beam computed tomography (CBCT) pelvis, thorax and head and neck (H&amp;N) images based on patient size.Methods:An elliptical phantom of small, medium and large size was designed representative of a local population of pelvis, thorax and H&amp;N patients. The phantom was used to establish the relationship between image noise, CT and CBCT exposure settings. Using this insight, clinical images were optimised in phases and the image quality graded qualitatively by radiographers. At each phase, the time required to match the images was recorded from the record and verify system.Results:Average patient diameter was a suitable metric to categorise patient size. Phantom measurements showed the power relationship between noise and CBCT exposure settings of value −0·15, −0·35 and −0·43 for thorax, pelvis and H&amp;N, respectively. These quantitative phantom measurements provided confidence that phased variation of ~±20% in mAs should result in clinically usable images. Qualitative assessment of almost 2000 images reduced the exposure settings in H&amp;N images by −50%, thorax images by up to −66% and pelvis images by up to −80%. These optimised CBCT settings did not affect the time required to match images.Findings:Varian TrueBeam CBCT mAs settings have been optimised for dose and image quality based on patient size for three treatment sites: pelvis, thorax and H&amp;N. Quantitative phantom measurements provided insight into the magnitude of change to implement clinically. The final optimised exposure settings were determined from radiographer qualitative image assessment.

Assessment of the efficiency of a pre- versus post-acquisition metal artifact reduction algorithm in the presence of 3 different dental implant materials using multiple CBCT settings: An in vitro study.

PurposeThe aim of this study was to assess artifacts generated in cone-beam computed tomography (CBCT) of 3 types of dental implants using 3 metal artifact reduction (MAR) algorithm conditions (pre-acquisition MAR, postacquisition MAR, and no MAR), and 2 peak kilovoltage (kVp) settings.Materials and MethodsTitanium-zirconium, titanium, and zirconium alloy implants were placed in a dry mandible. CBCT images were acquired using 84 and 90 kVp and at normal resolution for all 3 MAR conditions. The images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the intensity of artifacts for each combination of material and settings. A 3-factor analysis of variance model with up to 3-way interactions was used to determine whether there was a statistically significant difference in the mean intensity of artifacts associated with each factor.ResultsThe analysis of all 3 MAR conditions showed that using no MAR resulted in substantially more severe artifacts than either of the 2 MAR algorithms for the 3 implant materials; however, there were no significant differences between pre- and post-acquisition MAR. The 90 kVp setting generated less intense artifacts on average than the 84 kVp setting. The titanium-zirconium alloy generated significantly less intense artifacts than zirconium. Titanium generated artifacts at an intermediate level relative to the other 2 implant materials, but was not statistically significantly different from either.ConclusionThis in vitro study suggests that artifacts can be minimized by using a titanium-zirconium alloy at the 90 kVp setting, with either MAR setting.

Cone beam computed tomography artefacts around dental implants with different materials influencing the detection of peri-implant bone defects.

To investigate the diagnostic accuracy of cone beam computed tomography (CBCT) for the diagnosis of peri-implant bone defects of titanium (Ti), zirconium dioxide (ZrO2 ) or titanium-zirconium (Ti-Zr) alloy implants. Ti, Ti-Zr or ZrO2 implants with two diameters (3.3mm, 4.1mm) and one length (10mm) were inserted in the angle of the mandible of six fresh defrosted pig jaws. Out of the 12 implants inserted, 6 served in the test group with standardized buccal peri-implant bone defects, whereas 6 served as control without bone defects. CBCTs were performed with three acquisition protocols (standard, high and low dose) using two devices. Four observers analysed CBCTs as follows: (a) presence of a peri-implant defect; (b) presence of peri-implant artefacts and impact on defect diagnosis; and (c) linear measurements of buccal peri-implant defect including height and width (in mm). CBCT device, CBCT settings, implant material, implant diameter and observer background did not significantly influence diagnostic accuracy. The sensitivity and specificity values were high for defect detection. ZrO2 led to a lower than average diagnostic accuracy (0.781). The linear measurements of peri-implant defect were underestimated by <1mm on average. The subjective impact of artefacts on defect diagnosis was significantly affected by implant material and observer background. CBCT showed high diagnostic accuracy for peri-implant bone defect detection regardless of the device, imaging setting or implant material used. If CBCT is indicated to assess peri-implant bone disease, low dose protocols could be a promising imaging modality.

KVp, mA, and voxel size effect on 3D voxel-based superimposition.

To evaluate the effect of changing kVp, mA, and voxel size on the accuracy of voxel-based superimposition on the anterior cranial base. Cone beam computed tomography (CBCT) scans were taken on a phantom skull using different kVp, mA, and voxel size combinations. CBCT scans were superimposed using commercially available software. Two separate open-source software programs were used to generate a three-dimensional (3D) color map objective assessment of the differences in seven different regions: Nasion, Point A, Zygomatic (right and left), Point B, and Gonial (right and left). Each region had around 200 points that were used to calculate the mean differences between the superimpositions. Intraclass correlation showed excellent reliability (0.95). Lowering the kVp made the biggest difference, showing an average discrepancy of 0.7 ± 0.3 mm, and a high mean of 1.4 ± 0.3 in the Right Gonial region. Lowering the mA showed less of a discrepancy, with an average of 0.373 ± 0.2 mm, and the highest discrepancy, also on the Right Gonial Area, of 0.7 ± 0.1 mm. The voxel size had the least impact on the accuracy of registered volumes, with mean discrepancy values of less than 0.2 mm. Using different CBCT settings can affect the accuracy of the voxel-based superimposition method. This is particularly the case when using low kVp values, while changes in mA or voxel sizes did not significantly interfere with the superimposition outcome.

Influence of Cone Beam Computed Tomography Settings on Implant Artifact Production: Zirconia and Titanium.

This in vitro study assessed the artifact production related to titanium and zirconia implants in cone beam computed tomography (CBCT) and compared the effect of different protocol settings on image quality for both materials. A titanium implant and a zirconia implant were placed in a dry mandible. CBCT scans were obtained separately for each implant using the ProMax 3D (Planmeca) unit; 20 protocols were tested with varying kilovoltage (70 to 90 kVp) and resolution (high and low), and with and without a metal artifact reduction tool. Standard deviation and contrast-noise ratio were calculated in regions of interest adjacent and distant to the implant. The zirconia produced more artifacts and its images were more affected by the different protocols than titanium. High kVps and an activated metal artifact reduction tool decreased the standard deviation values related to both implants. Activation of the metal artifact reduction tool also increased contrast-noise ratio values for both implants, whereas increasing kVp improved them only on titanium images. The standard deviation and contrast-noise ratio were not affected by resolution. The zirconia implant generated more image artifacts than the titanium implant. Increasing kVp and the metal artifact reduction tool are efficient in decreasing the CBCT artifacts for both implants, whereas resolution does not affect their production.

Higher Resolution in Cone Beam Computed Tomography Is Accompanied by Improved Bone Detection in Peri-implant Bone Despite Metal Artifact Presence.

The aim of this study was to determine the possibility and extent of artifact reduction by an optimized use of cone beam computed tomography (CBCT) parameter configuration (geometric resolution, implant geometric parameters, and image analyses). It furthermore sought to determine the distance from correctly reproduced bone tissue to an implant, where the grayscale values are equal to the pre-implantation values. Titanium implants were inserted into pig tibia under standardized conditions. CBCT investigations in the form of bone density mapping were performed under various CBCT settings and implantation situations. The circumference of the implants was measured in order to determine the extent of metal artifacts. This was done by determining grayscale and comparing it to the bone area prior to implantation. Using CBCT to determine bone density postimplantation showed a correlation in dependence of CBCT parameter configuration. Higher resolution led to a better detection of correct bone density values in the peri-implant region. Normal bone density values can be recognized at a distance of 370 μm from the implant surface, when the spatial resolution is 125 μm. Therefore, higher resolution in CBCT is accompanied by an improved bone detection in peri-implant bone, despite the presence of metal artifacts. Peri-implant bone defects that extend 400 μm around implants were reliably detected by using a spatial resolution of 125 μm. In specimens, where multiple implants are present in one line, pronounced artifact formations were present. The artifacts were visible as a combination of streak-like hardening and extinction effects. Bone geometric data and density values may be determined correctly in close proximity to the implant surface, and can detect peri-implant bone defects. When multiple implants are placed, the implant radiation direction geometry must be considered.

CBCT assessment of radicular volume loss after rapid maxillary expansion: A systematic review.

BackgroundThe present systematic review analyzed the current literature to investigate whether rapid maxillary expansion (RME) causes radicular resorption, assessed by cone-beam computed tomography (CBCT).Material and MethodsEighteen electronic databases and reference lists of studies were searched up to November 2017. Grey literature was also screened. To be included, articles must be human studies on growing subjects with transversal maxillary deficiency treated with maxillary expansion protocol and with 3-D radiographic assessment of radicular volume by CBCT images. Two authors independently performed study selection, data extraction, and risk of bias assessment. Study characteristics (study design, sample size, age, sex, skeletal maturity, type of appliance, daily activation, teeth evaluated, CBCT settings), and study outcomes (radicular volume loss) were reported according to the PRISMA statement.ResultsOnly 3 articles were considered eligible and an individual analysis of the selected articles was undertaken. The risk of bias assessment revealed low methodological quality for all the studies included. In all the considered studies, significant radicular volume loss was observed in posterior teeth, following RME. When reported in percentage, the radicular volumetric loss was similar between anchored (first molars and first premolars) and unanchored teeth (second premolars).ConclusionsA preliminary evaluation of the patient-related risk factors for RR is warmly advisable when administering RME. Key words:RME, maxillary expansion, root resorption, external root resorption.

Alveolar bone changes after rapid maxillary expansion with tooth-born appliances: a systematic review.

During rapid maxillary expansion (RME), heavy forces are transmitted to the maxilla by the anchored teeth causing buccal inclination and buccal bone loss of posterior teeth. To systematically review the literature in order to investigate whether RME causes periodontal sequelae, assessed by cone-beam computed tomography (CBCT). Fifteen electronic databases and reference lists of studies were searched up to March 2017. To be included in the systematic review, articles must be human studies on growing subjects, with transversal maxillary deficiency treated with RME and with assessment of buccal bone loss by CBCT images. Only randomized and non-randomized trials were included. Two authors independently performed study selection, data extraction, and risk of bias assessment. Study characteristics (study design, sample size, age, sex, skeletal maturity, type of appliance, daily activation, evaluated linear measurements, observation period, CBCT settings), and study outcomes (loss of buccal bone thickness and marginal bone) were reported according to the PRISMA statement. On the basis of the applied inclusion criteria, only six articles, three randomized clinical trials and three controlled clinical trials were included. An individual analysis of the selected articles was undertaken. The risks of bias of the six trials were scored as medium to low. The results of the present systematic review are based on a limited number of studies and only one study included a control group. In all considered studies, significant loss of buccal bone thickness and marginal bone level were observed in anchored teeth, following RME. Further prospective studies correlating the radiological data of bone loss to the periodontal soft tissues reaction after RME are required. A preliminary evaluation of the patient-related risk factors for RR may be advisable when considering to administering RME. This systematic review was registered in the National Institute of Health Research database with an appropriate protocol number (http://www.crd.york.ac.uk/PROSPERO Protocol: CRD42017062645). The present study has not received any contributions from private or public funding agencies.

Effects of various cone-beam computed tomography settings on the detection of recurrent caries under restorations in extracted primary teeth

PurposeThe aim of this study was to assess the ex vivo diagnostic ability of 9 different cone-beam computed tomography (CBCT) settings in the detection of recurrent caries under amalgam restorations in primary teeth.Materials and MethodsFifty-two primary teeth were used. Twenty-six teeth had dentine caries and 26 teeth did not have dentine caries. Black class II cavities were prepared and restored with amalgam. In the 26 carious teeth, recurrent caries were left under restorations. The other 26 intact teeth that did not have caries served as controls. Teeth were imaged using a 100×90-mm field of view and a 0.2-mm voxel size with 9 different CBCT settings. Four observers assessed the images using a 5-point scale. Kappa values were calculated to assess observer agreement. CBCT settings were compared with the gold standard using a receiver operating characteristic analysis. The area under the curve (AUC) values for each setting were compared using the chi-square test, with a significance level of α=.05.ResultsIntraobserver kappa values ranged from 0.366 to 0.664 for observer 1, from 0.311 to 0.447 for observer 2, from 0.597 to 1.000 for observer 3, and from 0.869 to 1 for observer 4. Furthermore, interobserver kappa values among the observers ranged from 0.133 to 0.814 for the first reading and from 0.197 to 0.805 for the second reading. The highest AUC values were found for setting 5 (0.5916) and setting 3 (0.5886), and were not found to be statistically significant (P>.05).ConclusionVariations in tube voltage and tube current did not affect the detection of recurrent caries under amalgam restorations in primary teeth.

Reproducibility and accuracy of linear measurements on dental models derived from cone-beam computed tomography compared with digital dental casts

The aim of this study was to determine the reproducibility and accuracy of linear measurements on 2 types of dental models derived from cone-beam computed tomography (CBCT) scans: CBCT images, and Anatomodels (InVivoDental, San Jose, Calif); these were compared with digital models generated from dental impressions (Digimodels; Orthoproof, Nieuwegein, The Netherlands). The Digimodels were used as the reference standard. The 3 types of digital models were made from 10 subjects. Four examiners repeated 37 linear tooth and arch measurements 10 times. Paired t tests and the intraclass correlation coefficient were performed to determine the reproducibility and accuracy of the measurements. The CBCT images showed significantly smaller intraclass correlation coefficient values and larger duplicate measurement errors compared with the corresponding values for Digimodels and Anatomodels. The average difference between measurements on CBCT images and Digimodels ranged from -0.4 to 1.65mm, with limits of agreement values up to 1.3mm for crown-width measurements. The average difference between Anatomodels and Digimodels ranged from -0.42 to 0.84mm with limits of agreement values up to 1.65mm. Statistically significant differences between measurements on Digimodels and Anatomodels, and between Digimodels and CBCT images, were found. Although the mean differences might be clinically acceptable, the random errors were relatively large compared with corresponding measurements reported in the literature for both Anatomodels and CBCT images, and might be clinically important. Therefore, with the CBCT settings used in this study, measurements made directly on CBCT images and Anatomodels are not as accurate as measurements on Digimodels.

SU‐E‐J‐178: Image Guidance on the TrueBeam STx: Evaluation of CBCT Imaging Dose and Quality

Purpose: To evaluate the cone beam computed tomography (CBCT) dose and imaging quality of the TrueBeam STx linear accelerator equipped with the X‐Ray Imaging System. Methods: In accordance to the recommendations of TG‐111, a 0.6 cm3 Farmer thimble ionization chamber was used for in‐phantom measurements at the center and periphery (4 cm from edge, 12 oˈclock) of 30 cm diameter × 30 cm length cylindrical phantom. A total of six new CBCTscan protocols were evaluated: 1) head (full trajectory, 100 kVp, 264 mAs, 2) head (half trajectory, 100 kVp, 146.40 mAs), 3) low dose thorax (full trajectory, 125 kVp, 264.00 mAs), 4) pelvis (full trajectory, 125 kVp, 686.40 mAs), 5) pelvis spotlight (half trajectory, 125 kVp, 731.27 mAs), and 6) pelvis spot light (full trajectory 125 kVp, 1318.68 mAs). Doses from MV, portal imaging and kV fluoroscopy were evaluated as well. Image quality was evaluated using the Catphan 504 placed at isocenter and scanned under the exact same parameters as the dosimetric study. Results: The measured dose for CBCT settings 1–6 (center, periphery) are: 1) 0.37cGy, 0.37cGy; 2) 0.2cGy, 0.34cGy; 3) 0.64cGy, 0.64.cGy; 4) 1.64cGy, 1.66cGy; 5) 3.5cGy, 7.27cGy and 6) 6.05cGy, 8.14cGy.With regards to image quality, we observed two general trends: First, comparing the half trajectory reconstructions to the full trajectory reconstructions, shading artifacts are visible in the half trajectory reconstructions. Second, by nature of the half reconstructions under the Thorax and Pelvis protocols, the resolution is degraded by 56%; which is due the fact that the pixel size is larger for the half fan methodology.Conclusion: In this study we evaluated the imaging dose and quality of the TrueBeam STx linear accelerator. The measured doses and image quality are consistent with previous measurements reported in the literature for older generation Varian On‐board Imaging systems (OBIs).

Considerations in the use of cone-beam computed tomography for buccal bone measurements

Cone-beam computed tomography (CBCT) has become a popular modality in research, but it can be misused and misunderstood. Several image quality, bone biology, and statistical factors must be considered before designing CBCT studies or interpreting their results. Studies making small measurements, such as changes in buccal bone thickness, are especially susceptible to these factors. The spatial resolution as determined by a line pair phantom, the CBCT settings used, and a statistical power analysis should be reported in studies that investigate small bony changes. Protocols should therefore be established and followed to minimize the misinterpretation of results and improve the quality of research in this field.

Image quality produced by different cone-beam computed tomography settings

The aim of this study was to evaluate image quality at different cone-beam computed tomography settings and 3 fields of view. A Hitachi CB MercuRay (Hitachi Medical Systems, Tokyo, Japan) was modified to allow different setting combinations. The variables consisted of 4 milliampere settings (2, 5, 10, and 15 mA), 2 kilovolt (peak) settings (100 and 120 kV[p]), presence or absence of a copper filter, and 3 fields of view (6, 9, and 12 in). Thirty-two scans were taken on a cadaver head and 16 scans on a dry skull. The groups were divided by field of view, and the images were ranked by at least 30 judges. Diagnostic quality was addressed in a questionnaire. Descriptive statistics and rankings were calculated with Excel 2003 (Microsoft, Redmond, Wash) and the Friedman and Wilcoxon signed rank tests with SPSS software (version 14.0.1; SPSS, Chicago, Ill). The presence or absence of a filter showed significant differences (P <.006) in 2 pairs of the 9-in field of view. Variation in kilovolt (peak) settings showed significant differences (P <.006) in the 6-in 5-mA images with a filter. Altering the milliampere settings showed significant differences (P <.008) in the 6- and 12-in groups. The 9-in group showed significant differences between 2 mA and 10 and 15 mA. Overall, the 6-, 9-, and 12-in images had diagnostic quality 56%, 99%, and 99% of the time, respectively. Presence or absence of a filter and the kilovolt (peak) setting did not affect overall image quality. Images taken at lower milliampere settings showed good diagnostic quality.