Effect of slice inclination and object position within the field of view on the measurement accuracy of potential implant sites on cone-beam computed tomography

PURPOSE: The purpose of this study was to evaluate the accuracy of linear measurements in the horizontal and vertical dimensions based on object position and slice inclination in cone-beam computed tomography (CBCT) images.MATERIALS AND METHODS: Ten dry sheep hemi-mandibles, each with 4 sites (incisor, canine, premolar, and molar), were evaluated when either centrally or peripherally positioned within the field of view (FOV) with the image slices subjected to either oblique or orthogonal inclinations. Four types of images were created of each region: central/cross-sectional, central/coronal, peripheral/cross-sectional, and peripheral/coronal. The horizontal and vertical dimensions were measured for each region of each image type. Direct measurements of each region were obtained using a digital caliper in both horizontal and vertical dimensions. CBCT and direct measurements were compared using the Bland-Altman plot method. P values <0.05 were considered to indicate statistical significance.RESULTS: The buccolingual dimension of the incisor and premolar areas and the height of the incisor, canine, and molar areas showed statistically significant differences on the peripheral/coronal images compared to the direct measurements (P<0.05). Molar area height in the central/coronal slices also differed significantly from the direct measurements (P<0.05). Cross-sectional images of either the central or peripheral position had no marked difference from the gold-standard values, indicating sufficient accuracy.CONCLUSION: Peripheral object positioning within the FOV in combination with applying an orthogonal inclination to the slices resulted in significant inaccuracies in the horizontal and vertical measurements. The most undesirable effect was observed in the molar area and the vertical dimension.

Detection of peri-implant bone defects using cone-beam computed tomography and digital periapical radiography with parallel and oblique projection

PURPOSE: To compare the diagnostic accuracy of cone-beam computed tomography (CBCT) with that of parallel (PPA) and oblique projected periapical (OPA) radiography for the detection of different types of peri-implant bone defects.MATERIALS AND METHODS: Forty implants inserted into bovine rib blocks were used. Thirty had standardized bone defects (10 each of angular, fenestration, and dehiscence defects), and 10 were defect-free controls. CBCT, PPA, and OPA images of the samples were acquired. The images were evaluated twice by each of 2 blinded observers regarding the presence or absence and the type of the defects. The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were determined for each radiographic technique. The 3 modalities were compared using the Fisher exact and chi-square tests, with P<0.05 considered as statistical significance.RESULTS: High inter-examiner reliability was observed for the 3 techniques. Angular defects were detected with high sensitivity and specificity by all 3 modalities. CBCT and OPA showed similar AUC and sensitivity in the detection of fenestration defects. In the identification of dehiscence defects, CBCT showed the highest sensitivity, followed by OPA and PPA, respectively. CBCT and OPA had a significantly greater ability than PPA to detect fenestration and dehiscence defects (P<0.05).CONCLUSION: The application of OPA radiography in addition to routine PPA imaging as a radiographic follow-up method for dental implantation greatly enhances the visualization of fenestration and dehiscence defects. CBCT properly depicted all defect types studied, but it involves a relatively high dose of radiation and cost.

Effect of object position in the field of view and application of a metal artifact reduction algorithm on the detection of vertical root fractures on cone-beam computed tomography scans: An in vitro study

PURPOSE: To assess the effects of object position in the field of view (FOV) and application of a metal artifact reduction (MAR) algorithm on the diagnostic accuracy of cone-beam computed tomography (CBCT) for the detection of vertical root fractures (VRFs). MATERIALS AND METHODS: Sixty human single-canal premolars received root canal treatment. VRFs were induced in 30 endodontically treated teeth. The teeth were then divided into 4 groups, with 2 groups receiving metal posts and the remaining 2 only having an empty post space. The roots from different groups were mounted in a phantom made of cow rib bone, and CBCT scans were obtained for the 4 different groups. Three observers evaluated the images independently. RESULTS: The highest frequency of correct diagnoses of VRFs was obtained with the object positioned centrally in the FOV, using the MAR algorithm. Peripheral positioning of the object without the MAR algorithm yielded the highest sensitivity for the first observer (66.7%). For the second and third observers, a central position improved sensitivity, with or without the MAR algorithm. In the presence of metal posts, central positioning of the object in the FOV significantly increased the diagnostic sensitivity and accuracy compared to peripheral positioning. CONCLUSION: Diagnostic accuracy was higher with central positioning than with peripheral positioning, irrespective of whether the MAR algorithm was applied. However, the effect of the MAR algorithm was more significant with central positioning than with peripheral positioning of the object in the FOV. The clinical experience and expertise of the observers may serve as a confounder in this respect.

Comparison between computed tomography and ultrasonography in detecting foreign bodies regarding their composition and depth: An in vitro study

Statement of the Problem: Impaction of foreign bodies in the soft tissues is a sequela of traumatic and penetrating injuries. Such foreign bodies should be removed due to the complications they cause. Patient's history, clinical evaluation and imaging examinations aid in the proper detection and localization of the foreign bodies

Purpose: The aim of the present study was to compare the sensitivity of computed tomography [CT] and ultrasonography for detecting foreign bodies in in-vitro models simulating facial soft tissues

Materials and Method: Fifty foreign particles with five different compositions including wood, glass, metal, plastic, and stone were embedded in five calf tongues at 1, 2, 3, 4 and 5 cm depths. CT and ultrasonography were compared regarding their capability of detecting and localizing the foreign bodies

Results: Wood and plastic foreign bodies were demonstrated more clearly on ultrasonography images. High density materials such as metal, stone, and glass were detected with almost the same accuracy on CT and ultrasonography examinations. Visibility of the foreign bodies deteriorated on ultrasonography images as their depth increased; however, CT appearances of the foreign particles were not influenced by their depths

Conclusion: Ultrasonography is an appropriate technique for detection of foreign bodies especially the ones with low density. Therefore, it seems logical to perform ultrasonography in combination with CT in cases with the suspicion of foreign body impaction