Background: This study aimed to select the optimum computerized (CT) Slice thickness by analyzing its effect on the volumes and dosimetric parameters in treatment planning of low grade Glioma. Material and Methods: Fused brain CT and magnetic resonance imaging (MRI) images of 17 patients were used for treatment planning for three-dimensional conformal radiation therapy (3D-CRT) and Intensity-modulated radiation therapy (IMRT) using CT dataset with the thickness of 1. 5 mm, 3, 5, and 10 mm Slice. Volume of target and organs at risk (OARs), dosimetric parameters and contouring times using the reconstructed images were compared with the original dataset. Results: Using larger than 3 mm Slice thicknesses resulted in significant increase up to 76% in target volumes as well as the volumes of OARs (p-value<0. 05). The variation in normalization point coordinates was also significant using larger than 3 mm Slice thicknesses. The contouring time of tumor and OARs using the original data set was up to 35% more compared to the 3 mm dataset. Dosimetric parameters were comparable for 1. 5 and 3 mm datasets, however, significant difference of up to 200% was observed for 5 and 10 mm datasets (P<0. 05). Conclusions: CT Slices larger than 3mm resulted in significant inaccuracies in volumes and dose coverage of target and OARs. Although using the Slice thickness larger than 1. 5 mm reduced contouring time significantly, this Slice thickness is only recommended when the oncologist is not concerned about the dose received by the small critical organs especially those adjacent to the tumor.

Background: Detailed knowledge of the three-dimensional (3D) anatomical structures in precise treatment planning prior to implant placement is necessary. The choice of imaging techniques plays an important role in achieving the required information to measure exact dimensions. Cone beam computed tomography (CBCT) has increasingly been used for diagnosis and treatment in the fields of periodontology, endodontic, and orthodontics. It is also used as the preoperative evaluation of patients who are candidates for dental implant treatment. Dental implant placement is an important application of CBCT in dentistry. One of the features of CBCT is the possibility of changing the Slice thickness while reviewing images. In this study, we examined the linear measurement accuracy of CBCT for determining the height of alveolar crest to the mental foramen in cross-sectional view with different Slice thicknesses and in tangential view. Methods: We used five dry human mandibles in this study. Then the distance from the highest tip of alveolar crest to the upper border of mental foramen was measured by digital caliper (as gold standard) and on CBCT images in cross sectional view with 1, 3, 5, 7 and 9 mm Slice thicknesses and in tangential view. Data were analyzed using IBM SPSS Statistics software version 22, paired t test, and inter class correlation. Results: Data were collected by evaluation of 5 dry mandible and 240 measurements. There were significant differences only in tangential view and 1 mm Slice thickness option in cross-sectional view with the gold standard (P = 0. 003 and P = 0. 018 respectively). The results did not show any differences between the observers (P < 0. 001). Conclusions: Our results indicated that cross-sectional view is more accurate than tangential view, and 3 and 5 mm Slice thicknesses are preferred for measurement.

Objective: Cone beam computed tomography (CBCT) is applied for the imaging of the maxillofacial and dental structures, particularly for surgical treatments and dental implants. The aim of this study was to assess the effect of Slice thickness on the accuracy of CBCT linear measurements.Methods: In this diagnostic accuracy study, forty-two titanium pins with the same dimensions were inserted into seven dry sheep mandibles. The length of the pins before the insertion was carefully measured by a digital caliper, (0.01mm accuracy). Imaging of the mandible performed using CBCT New Tom VGi. After image reconstruction by NNT Viewer, linear measurements were made on cross-sectional Slices (thicknesses of 0.125, 0.5, 1 and 2mm) by three radiologists. The accuracy of measurements assessed using descriptive indices and compared between different Slice thicknesses by repeated measures ANOVA.Results: Repeated measures ANOVA showed a significant difference between different Slice thicknesses (P=0.024). According to the least significant difference (LSD) test, the difference in absolute errors was significant in all thicknesses (P=0.024). Measurements at 0.125 mm thickness were significantly different from others, with a higher error rate (mean absolute error=0.17). Measurements at 0.5mm thickness showed a significant difference with those at 0.125 and 2mm (mean absolute error=0.15). Measurements at 2mm thickness were significantly different from those at 0.125 mm thickness (mean absolute error=0.13).The average error rate was lower in 2mm thickness and the measurements were more accurate.Conclusion: A statistically significant difference was seam between CBCT measurements and actual sizes in different Slice thicknesses. The differences were below 1mm, and clinically acceptable.

Objectives: The aim of this study was to evaluate the diagnostic accuracy of different filtrations and Slice thicknesses of cone-beam computed tomography (CBCT) in the detection of occlusal caries. Materials and Methods: One-hundred teeth were selected for this ex-vivo experimental study. The CBCT images of the teeth were evaluated and scored by two observers in panoramic and cross-sectional views using different Slice thicknesses and filtrations. Paired t-test, repeated-measures analysis of variance (ANOVA), and the least significant difference (LSD) test were used to compare the data with the histological gold standard. Receiver operating characteristic (ROC) analysis was used to determine the diagnostic accuracy of each Slice thickness and filtration (P<0. 05). Results: The mean score of true caries detection in cross-sectional views was lower than that in panoramic views (P<0. 05). Repeated-measures ANOVA showed a significant difference in the mean of true detections in different thicknesses of cross-sectional views, but this difference was significant only between 5 mm thickness and other thicknesses in panoramic views. On all the views, increasing the thickness decreased the accuracy of caries detection. Repeated-measures ANOVA showed a significant difference between different filtrations; on all the views, increasing the filtration increased the accuracy of caries detection. Conclusions: An increase of filtration of CBCT images increases the accuracy of occlusal caries detection; however, an increase in Slice thickness results in a lower diagnostic accuracy.

Objective(s): Computed tomography (CT) images are used for precise anatomical location of lesions and for accurate attenuation correction in single-photon emission computed tomography (SPECT) image reconstruction in SPECT/CT examination. The aim of this study was to verify the effects of varying CT collimation width and Slice thickness on CT images and on CT attenuation corrected SPECT images. Methods: We acquired SPECT/CT images of a micro-coin phantom and the National Electrical Manufacturers Association body phantom filled with 99mTcpertechnetate while varying the abovementioned CT parameters. The full width at half maximum of the Slice sensitivity profile, the standard deviation of CT image background noise, and the radiation dose from CT scans were evaluated. Subsequently, the percentage contrast, background variability, and absolute recovery coefficient of the SPECT image were measured. Furthermore, we retrospectively reviewed the clinical bone SPECT images of 23 patients, and statistical testing of differences was performed. Results: As the collimation width and reconstruction Slice thickness of the CT image increased, z-axis resolution deteriorated, and background noise decreased. In addition, CT radiation dose decreased with increasing collimation width. Meanwhile, SPECT image quality and quantitative accuracy were unchanged with varying CT collimation width and Slice thickness. There were no notable variations in clinical SPECT images and no statistically significant differences. Conclusion: When high-resolution CT Slices on the z-axis are not required for clinical diagnosis, increasing collimation width or Slice thickness can reduce the radiation dose and image noise with no influence on the quality of SPECT images.

Background: This study aimed to investigate the association between epicardial adipose tissue (EAT) and coronary artery disease (CAD) as well as cardiovascular risk factors. Methods: Complete medical records of subjects were reviewed and cardiovascular risk factors were recorded. Epicardial fat volume (EFV) and epicardial fat thickness (EFT) were measured using digital volumetry of acquired images using a 256-Slice CT-scanner. Calcium score was measured using Agatston method in non-contrast images. After contrast administration, bolus-tract images were obtained. Coronary arteries were assessed using reconstructed images in arterial phase of contrast-enhanced images. EFV and EFT measurements were compared to computed tomography angiography (CTA) findings of coronary arteries. Results: A total of 269 patients (Mean age: 55. 5 ± 12. 1, 44% female) were included. Higher means of EFT and EFV were associated with coronary artery stenosis. However, the correlation coefficients of the arterial stenosis with EFT and EFV were weak. EFV and EFT had a significant association with age (P < 0. 001, P < 0. 001 respectively), body mass index (BMI) (P < 0. 001, P < 0. 001 respectively) and hypertension (P < 0. 016, P < 0. 003 respectively). Diabetes mellitus (DM) and hyperlipidemia were not significantly associated with EFV (P = 0. 069 and 0. 639 respectively) and EFT (P = 0. 103 and 0. 366 respectively). EFV and EFT showed a weak correlation coefficient with calcium scoring (Spearman correlation coefficients: 0. 26 and 0. 22 respectively, both P < 0. 001). In multivariate logistic regression models considering coronary stenosis as dependent variable and EFV, EFT and other CAD risk factors as independent variables, EFV and EFT did not show significant P values and were omitted from the model by other CAD risk factors. Conclusion: Increased EFV and EFT are associated with CAD, age, BMI and hypertension. However, no remarkable association was found between them and calcium score, hyperlipidemia or DM. These variables could weakly predict CAD in univariate models but they are not independent predictive factors for CAD in multivariate models consisting of other CAD risk factors. Hence, EFT and EFV are not independent predictors for CADs when they are considered simultaneously with other CAD risk factors.