Assessment of thin bony structures using cone-beam computed tomography.

Changes in Organs at Risk Dose Estimates Due to Anatomic Changes and Registration Method During Head and Neck Radiotherapy and its Relationship to Percent Weight Loss

AbstractThe objective of this ex vivo cadaver study was to determine the accuracy of cone beam computed tomography(CBCT) and 3D stereolithographic(STL) model in identifying and measuring the anterior loop length(ANLL) of the mental nerve. A total of 12 cadavers (24 mental nerve plexus) were used for this study. Standardized CBCT scans of each mandible were obtained both with and without radiographic contrast tracer injected into the mental nerve plexus. STL models of the two acquired CBCT images were made. ANLL were measured using CBCT, STL and anatomy. The measurements obtained from the CBCT images and STL models were then analyzed and compared with the direct anatomic measurements. Paired sample t-test was used. P values less than .05 was considered statistically significant. The mean difference between CBCT and anatomic measurement was 0.04mm and not statistically significant (p= .332) while the mean difference between STL and anatomic measurement was 0.4mm and statistically significant (p=.042). There was also a statistical significant difference between CBCT and STL (p=.048) with the mean difference of 0.35mm. Therefore, CBCT is an accurate and reliable method in determining and measuring the ANLL while the STL over or underestimated the ANLL by as much as 1.51mm and 1.83mm respectively.

Background:The accuracy of three-dimensional (3D) reconstructions from cone-beam computed tomography (CBCT) has been particularly important in dentistry, which will affect the effectiveness of diagnosis, treatment plan, and outcome in clinical practice. The aims of this study were to assess the linear, volumetric, and geometric accuracy of 3D reconstructions from CBCT and to investigate the influence of voxel size and CBCT system on the reconstructions results.Methods:Fifty teeth from 18 orthodontic patients were assigned to three groups as NewTom VG 0.15 mm group (NewTom VG; voxel size: 0.15 mm; n = 17), NewTom VG 0.30 mm group (NewTom VG; voxel size: 0.30 mm; n = 16), and VATECH DCTPRO 0.30 mm group (VATECH DCTPRO; voxel size: 0.30 mm; n = 17). The 3D reconstruction models of the teeth were segmented from CBCT data manually using Mimics 18.0 (Materialise Dental, Leuven, Belgium), and the extracted teeth were scanned by 3Shape optical scanner (3Shape A/S, Denmark). Linear and volumetric deviations were separately assessed by comparing the length and volume of the 3D reconstruction model with physical measurement by paired t-test. Geometric deviations were assessed by the root mean square value of the imposed 3D reconstruction and optical models by one-sample t-test. To assess the influence of voxel size and CBCT system on 3D reconstruction, analysis of variance (ANOVA) was used (α = 0.05).Results:The linear, volumetric, and geometric deviations were −0.03 ± 0.48 mm, −5.4 ± 2.8%, and 0.117 ± 0.018 mm for NewTom VG 0.15 mm group; −0.45 ± 0.42 mm, −4.5 ± 3.4%, and 0.116 ± 0.014 mm for NewTom VG 0.30 mm group; and −0.93 ± 0.40 mm, −4.8 ± 5.1%, and 0.194 ± 0.117 mm for VATECH DCTPRO 0.30 mm group, respectively. There were statistically significant differences between groups in terms of linear measurement (P < 0.001), but no significant difference in terms of volumetric measurement (P = 0.774). No statistically significant difference were found on geometric measurement between NewTom VG 0.15 mm and NewTom VG 0.30 mm groups (P = 0.999) while a significant difference was found between VATECH DCTPRO 0.30 mm and NewTom VG 0.30 mm groups (P = 0.006).Conclusions:The 3D reconstruction from CBCT data can achieve a high linear, volumetric, and geometric accuracy. Increasing voxel resolution from 0.30 to 0.15 mm does not result in increased accuracy of 3D tooth reconstruction while different systems can affect the accuracy.

This study was conducted to evaluate variations in and the prevalence of the lingual concavity. Images were taken between January 1, 2011, and August 31, 2015, from a total of 104 patient charts randomly selected from a private practice. These images were acquired from a single cone beam computerized tomography (CBCT) machine. The CBCTs were reviewed in cross-sectional images in both the left and right anterior incisor and posterior molar regions. These scans were classified into 1 of 3 categories-parallel, concave, or convex-based on the measurements of the level of concavity degree as well as the mandibular morphology observed. Lingual concavity characteristics including depth, angulation, and vertical location were also measured. Most of the posterior mandibular CBCT scans were classified as concave. Although there was no significant difference detected for race or gender, statistical significance was noted with regard to age, with an increase in prevalence observed at age 63 years and older. Of the 3 different morphological classifications used, the vast majority were identified as concave in the posterior mandibular regions and parallel in the anterior mandibular region. There was a significant decrease in concavity VL/height (bone loss) associated with age, which was most commonly seen in edentulous areas.

Accuracy of alveolar bone height and thickness measurements in cone beam computed tomography: a systematic review and meta-analysis

Purpose: The accurate localization of lung tumors when performing stereotactic body radiotherapy (SBRT) is challenging because the breathing motion can cause imaging artifacts. To address this motion, an internal target volume (ITV) is created based on maximum intensity projections (MIP) reconstructed from all phases of the respiratory cycle by finding the maximum electron density at every voxel within the 4DCT. To assess whether a target volume created from the average intensity projections (AIP) of electron densities can also aid localization, the visualized tumor in cone-beam CT (CBCT) is compared to the ITV as delineated on the 4DCT using the MIP and the AIP datasets. Methods: The tumor was delineated on sixty- five kilovoltage CBCT datasets (CBCT ITV). The distances in each dimension were measured and the mean differences between the CBCT and both the AIP and MIP ITV were analyzed. Results: The mean differences between the CBCT ITV and AIP ITV are 0.06 ± 0.20 cm, −0.10 ± 0.27 cm, and 0.14 ± 0.26 cm in the axial, sagittal, and coronal dimensions respectively. The mean differences between CBCT ITV and the MIP ITV are −0.13 ± 0.19 cm, −0.24 ± 0.31 cm, and −0.06 ± 0.25 cm. In corresponding dimensions, the mean difference between CBCT ITV and AIP ITV is statistically greater than the mean difference between CBCT ITV and MIP ITV (p-value < 0.02) Conclusions: Accurately aligning the target in the lung is difficult without a method to visualize the intended area of treatment. The CBCT ITV is larger than the AIP ITV in the axial and coronal dimensions and is smaller than the MIP ITV in all dimensions. This indicates that CBCT ITV can be better evaluated using AIP ITV and MIP ITV as lower and higher limits for localization, respectively.

Real-time Intraoperative Computed Tomography Assessment of Quality of Permanent Interstitial Seed Implantation for Prostate Cancer

Accuracy of magnetic resonance imaging–cone beam computed tomography rigid registration of the head: an in-vitro study

BACKGROUND: Axiography (condylography) is used to assess the temporomandibular joints (TMJ) function and obtain individual articulator settings. Creating a virtual patient with TMJ dysfunction and determining its individual articulation parameters considerably simplify the procedure and accelerate the diagnosis for further rehabilitation. AIM: To assess the potential of a virtual articulation system using the Avantis 3D software for determining angular parameters of mandibular movement, considering the individual hinge axis position. MATERIALS AND METHODS: The clinical phase of the study included 25 volunteers aged 18–30 years, without complaints of TMJ dysfunction, previous orthodontic treatment, and malocclusion. All volunteers underwent electronic condylography (axiography) using the CADIAX Diagnostic device; the movement of mandible heads during protrusion and mediotrusion was analyzed. The individual values of sagittal condylar inclination (SCI) and Bennett angle on the left and right were obtained. The individual hinge axis was determined, and special radiopaque markers were placed on the skin in the projection of its rotation. Additional markers were placed on the lower edge of the left orbital cavity. Using these markers, cone beam computed tomography (CBCT) was performed in all volunteers, with a 17.5×20.0 matrix size, to create a 3D project, compare CBCT findings with virtual dental models, and generate a reference plane. Virtual occlusion measurements were obtained in terminal positions (protrusion and laterotrusion) using the Trios 3 Basic Pod intraoral scanner. The Avantis 3D software was then used to create 3D scenes based on the obtained measurements and CBCT of the skull. The mean length of each path registered for virtual articulator settings in the Avantis 3D software was approximately 3 mm. The interarticular distance used for the analysis was recalculated using the Avantis 3D software to be equal to the standard intercondylar distance of the articulator, which is 110 mm. Individual SCI and Bennett angle values were obtained for all study subjects. The experimental phase involved phantom models installed in a fully adjustable articulator Reference SL. CBCT was performed with an installed articulator and a maxillary cast, in a zero position, with closed center locks, which was matched to the maxilla present in the CT scan, and a 3D scene was created to measure SCI and Bennett angle values. After detecting the articulator’s hinge axis, electronic measurements of movement were taken, with a predefined SCI of 20–60° (increment 5°) and Bennett angle increments of 6, 12, and 20°. The results were assessed for a path of 3 mm. RESULTS: The mean difference between the compared determination methods of angular parameters obtained during the experimental phase of the study was 3.20±7.22° for the left SCI; 2.09±9.75° for the right SCI; 5.50±11.26° for the left Bennett angle, and 6.40±6.29° for the right Bennett angle. The mean difference between the compared determination methods of angular parameters obtained during the clinical phase of the study was 11.80±6.86° for the left SCI; 12.10±6.08° for the right SCI; 13.0±9.89° for the left Bennett angle, and 10.70±11.48° for the right Bennett angle. CONCLUSION: Both approaches for determining angular parameters can be recommended for use in real-world dental practice. When sophisticated, expensive equipment is not available, a virtual articulation system in the Avantis 3D software can be used as a more simple and affordable technique of measuring angular parameters.

Cone-beam Computed Tomographic–based Assessment of Filled C-shaped Canals: Artifact Expression of Cone-beam Computed Tomography as Opposed to Micro–computed Tomography and Nano–computed Tomography

Purpose: To evaluate the immobilization accuracy of a novel vacuum bite block re-locatable head frame (RHF) system in patients receiving intracranial stereotactic radiation therapy (SRT) by means of an infrared optical tracking system (OTS). Methods and Materials: The RHF was designed for multi-session treatments on the Leksell GammaKnife Perfexion™. In the present REB approved study, the RHF was used for patients undergoing linac-based SRT. A passive optical marker was placed on the bite block as a surrogate for patient motion. The OTS monitored patients continuously throughout each fraction. For each fraction, cone-beam computed tomography (CBCT) was used to verify the patient position at three time points: after the initial setup, pre-delivery following the automatic couch adjustments and post-delivery. To investigate the reliability of the optical measurements, the OTS measurements were compared against the implemented couch shifts for patient setup. Intra-fractional anatomical motion, as measured from the second and third CBCT scans, was compared with the difference in OTS marker positions. Real-time OTS data throughout each fraction was assessed to determine if patients moved by more than 1 mm during treatments. Results: Currently, data from three patients have been analyzed. The couch motion measured from the OTS strongly correlated with the actual reported couch shift (Pearson correlation coefficient of 0.99). Mean differences between OTS and true couch motion were 0.01, 0.0, and 0.04 mm in the lateral, anterior-posterior, and superior-inferior directions, respectively. Mean differences between OTS and CBCT reported motion were 0.37, 0.07, and 0.01 mm respectively with a mean vector magnitude of 0.41 mm. The real-time positional data indicated that there were few instances (3) of patient motion greater than 1mm. Conclusion: The OTS is a reliable tool for evaluation of intra-fraction patient motion. The results of this study indicate that the RHF provides sufficient immobilization accuracy for SRT.

Utility of 3D Surface Laser Scanning in Brachytherapy of Lip Cancer

The purpose of this study was to investigate and compare microcalcification detectability using Digital Tomosynthesis (DTS), Dual Energy Mammography (DEM) and Cone Beam Computed Tomography (CBCT) with a flat-panel detector. A simulated 3D uncompressed breast approximating the medium sized breast, with 50% adipose and 50% glandular tissue was used. Microcalcifications were modeled as calcium carbonate spheres/ellipsoids with size in full range of 0.1 to 1mm. An amorphous-silicon CsI flatdetector, 2048 × 2048 mm2 at 0.1mm resolution was modeled. Images from the above phantom were simulated using three acquisition protocols for DTS, DEM and CBCT. For DTS, projections data were acquired for an acquisition arc from −200 to 200 with 20 sampling step, and the 3D reconstructed volume was obtained using a Multiple Projection Algorithm (MPA), with a 0.1 mm width between successive tomograms. In the DEM case, two synthetic projection images at 21 and 52 KeV respectively were simulated. A weighted subtraction of low and high — energy digital X-ray images was performed, allowing the removal of background morphology and enhancement of the obscured details. For the last method (CBCT), 181 projections acquired every 20 over a full circular scanning path were used for 3D breast volume reconstruction using the well-known FDK algorithm. The image quality of the reconstructed tomograms was visually assessed and quantified in terms of contrast to noise ratio (CNR), relative detail contrast (RC), as well as Artifacts Spread Function (ASF). The results show that microcalcifications with diameter equal or greater than 0.1mm can be detected, with the CBCT and DTS techniques. Superior quality is demonstrated by CBCT technique in comparison with DTS and DE by means of better microcalcification detection.Keywordsdual energy mammographytomosynthesiscone beam breast CT

Background: Understanding the anatomy of the incisive canal is crucial for effective diagnosis and treatment planning in clinical orthodontics. This is because, during orthodontic tooth movement, there is a risk of contact between the roots of the upper central incisors and the incisive canal. Objective: The aim of this study was to assess the anatomical variability of the incisive canal using cone beam computed tomography (CBCT), as well as to evaluate its correlation with age, sex, and the position of the maxillary central incisors. There are only a few studies on this topic. Materials and methods: We analysed CBCT data from 67 patients aged from 13 to 49 years. This study was conducted at the Wroclaw Medical University. Measurements were performed twice by two independent researchers, and intra-observer error and correlation were calculated. The mean difference between the first and second observations and between observers was also assessed. We examined the dimensions of the incisive canal and its relationship to the roots of the upper central incisors in relation to age and gender. Results: Our study results revealed a significant correlation between the width and length of the incisive canal. Males exhibited a significantly greater canal length at the lowest point of the incisive canal on the palatal wall. Additionally, males had wider canals compared to females. The analysis of canal width and distance between the most mesial point of the root and the line passing through the most anterior point of the incisive canal showed a negative correlation in all age groups of men. The analysis of incisal inclination and incisal canal inclination showed a very strong relationship, especially in the age group of 13 to 20 years. Several potential risk groups of contact between the roots of central incisors and the incisive canal have been identified based on their structure and the planned incisors’ orthodontic movement. Conclusions and implications: Knowledge of the anatomy of the incisive canal and the use of 3D imaging in high-risk patients can prevent resorption of the incisor root by considering the individual anatomical conditions of the patient when planning orthodontic tooth movement. We recommend performing a CBCT scan before starting orthodontic treatment in the case of moderate and significant retraction of the incisors, or a significant change in their inclination due to the wide anatomical diversity of the incisive canal, especially in adult patients.

Monitoring intra- and inter-fraction motion using transperineal ultrasound (TPUS), for patients receiving stereotactic ablative radiotherapy (SABR) to the prostate.