Three-dimensional Cone Beam CT Research Articles

Mandibular Posterior Anatomic Limit for Distalization in Patients With Various Patterns of Third Molar Impactions: A Three-Dimensional Cone Beam CT (CBCT) Study.

The aim was to compare and evaluate the variation in the mandible's posterior anatomic limits (MPAL) stratified by different third molar impaction patterns utilizing cone-beam CT (CBCT) in individuals with skeletal Class III malocclusion. The sample consisted of CBCT records of 80 samples of Class III patients categorized based on the pattern of their third molar impaction. The shortest linear distances from the distal root of the second mandibular molar to the inner cortex of the mandibular body were measured at the crown level, at the cementoenamel junction (CEJ), and at the depths of 4, 6, and 8mm from the CEJ, all parallel to the posterior occlusal line. The MPAL of the four groups were compared. The Shapiro-Wilk test for normality was performed. The Kruskal-Wallis test was performed to compare the MPAL distances between the groups. Significant differences were noted between the four groups at every level. MPAL distances decreased towards apex in all the groups and was least at the 8mm root level. The greatest MPAL distances were noted in the no-impaction group followed by the horizontal. At 8mm, the MPAL were 4.2+/-1.3 in Group 3 (Control), 3.3+/-0.9 in Group 1 and 2.7+/-0.05 mm in Group 2. Though the amount of space available for distalization was greatest for the mesioangular group at the crown level, it was least at the 8mm level compared to other groups. MPAL distances were shortest at the root level in Class III patients who had mesioangularly impacted third molars and care should be taken before attempting distalization in them.

Age estimation based on 3D pulp segmentation of first molars from CBCT images using U-Net.

To train a U-Net model to segment the intact pulp cavity of first molars and establish a reliable mathematical model for age estimation. We trained a U-Net model by 20 sets of cone-beam CT images and this model was able to segment the intact pulp cavity of first molars. Utilizing this model, 239 maxillary first molars and 234 mandibular first molars from 142 males and 135 females aged 15-69 years old were segmented and the intact pulp cavity volumes were calculated, followed by logarithmic regression analysis to establish the mathematical model with age as the dependent variable and pulp cavity volume as the independent variable. Another 256 first molars were collected to estimate ages with the established model. Mean absolute error and root mean square error between the actual and the estimated ages were used to assess the precision and accuracy of the model. The dice similarity coefficient of the U-Net model was 95.6%. The established age estimation model was [Formula: see text] (V is the intact pulp cavity volume of the first molars). The coefficient of determination (R2), mean absolute error and root mean square error were 0.662, 6.72 years, and 8.26 years, respectively. The trained U-Net model can accurately segment pulp cavity of the first molars from three-dimensional cone-beam CT images. The segmented pulp cavity volumes could be used to estimate the human ages with reasonable precision and accuracy.

Landmark-free morphometric analysis of knee osteoarthritis using joint statistical models of bone shape and articular space variability.

Purpose: Osteoarthritis (OA) is a common degenerative disease involving a variety of structural changes in the affected joint. In addition to narrowing of the articular space, recent studies involving statistical shape analysis methods have suggested that specific bone shapes might be associated with the disease. We aim to investigate the feasibility of using the recently introduced framework of functional shapes (Fshape) to extract morphological features of OA that combine shape variability of articular surfaces of the tibia (or femur) together with the changes of the joint space. Approach: Our study uses a dataset of three-dimensional cone-beam CT volumes of 17 knees without OA and 17 knees with OA. Each knee is then represented as an object (Fshape) consisting of a triangulated tibial (or femoral) articular surface and a map of joint space widths (JSWs) measured at the points of this surface (joint space map, JSM). We introduce a generative atlas model to estimate a template (mean) Fshape of the sample population together with template-centered variables that model the transformations from the template to each subject. This approach has two potential advantages compared with other statistical shape modeling methods that have been investigated in knee OA: (i)Fshapes simultaneously consider the variability in bone shape and JSW, and (ii)Fshape atlas estimation is based on a diffeomorphic transformation model of surfaces that does not require a priori landmark correspondences between the subjects. The estimated atlas-to-subject Fshape transformations were used as input to principal component analysis dimensionality reduction combined with a linear support vector machine (SVM) classifier to identify the morphological features of OA. Results: Using tibial articular surface as the shape component of the Fshape, we found leave-one-out cross validation scores of for the classification based on the bone surface transformations alone, for the classification based on the residual JSM, and for the classification using both Fshape components. Similar results were obtained using femoral articular surfaces. The discriminant directions identified in the statistical analysis were associated with medial narrowing of the joint space, steeper intercondylar eminence, and relative deepening of the medial tibial plateau. Conclusions: The proposed approach provides an integrated framework for combined statistical analysis of shape and JSPs. It can successfully extract features correlated to OA that appear consistent with previous studies in the field. Although future large-scale study is necessary to confirm the significance of these findings, our results suggest that the functional shape methodology is a promising new tool for morphological analysis of OA and orthopedics data in general.

Management of Subintimal Position of Kissing Stents using Re-entry Catheter with Cone Beam-Computed Tomography Image Overlaid onto Live Fluoroscopy

Background Several endovascular or surgical treatments have been proposed to treat total chronic occlusions of the iliac bifurcation. Nowadays, endovascular options are considered as a first choice because of the decreased per-operative morbi-mortality. Nevertheless, unexpected intraoperative events may occur, such as dissection or rupture of the iliac artery. We report a case of inadvertent bilateral false lumen kissing stents positioning, rescued with stents extensions guided with image fusion guidance. Case presentation A 60-year-old male patient referred to our Department because of a severe bilateral claudication, 8 months after an iliac kissing stent for common iliac arteries occlusion. A CT angiography (CTA) was performed, showing a bilateral dissection of the aorto-iliac bifurcation at the proximal part of the stents, which were placed into the false lumen whereas the distal part was into the true lumens (TL). Lower limb perfusion was maintained by inferior mesenteric and hypogastric arteries. As a CTA performed before the first endovascular intervention showed no dissection of the aortic bifurcation, the flaps were probably created during the previous interventions. An endovascular revision was planned. After a bilateral femoral access, the proximal part of the flap was pierced with a needle-based re-entry device, deployed under three-dimensional cone-beam CT image overlay with bi-planar fluoroscopy. The lumen patency was then restored with stents extensions up to the renal ostia. The final angiography showed stents patency. No complication occurred during the intervention. The patient was dismissed the day after, with good arterial femoral pulse and no further complications. An US color Doppler performed one month after the intervention showed satisfactory blood flow of both iliac and femoral arteries as well as a good flow in the lower limbs. Conclusions The integration of modern 3D image guidance and novel endovascular devices allows the management of adverse events with a minimally-invasive approach.

Stability of bioabsorbable fixation systems according to different locations of mandibular fracture: A three-dimensional analysis

This study aimed to elucidate whether the stability of an unsintered hydroxyapatite particles/poly-l-lactide (uHA/PLLA) system is comparable with that of titanium, according to different load-bearing areas of the mandible. The study included patients who underwent open reduction and internal fixation of the mandibular body, angle, or subcondylar fracture. The stability of uHA/PLLA systems was compared between the immediate and 6-month postoperative time points using three-dimensional cone-beam CT image analysis. The positional changes of each landmark were measured in three-dimensional (3D) coordinate systems using simulation software. Among 36 patients, there were more displacements of the landmarks between the immediate and 6-month postoperative time points after subcondylar fracture reduction than after body or angle fracture reductions. Strong upward displacements of the landmarks after subcondylar fracture reduction were found in the lateral pole [mean (SD) = 1.75 (3.16), p-value = 0.003] and medial pole [mean (SD) = 1.64 (2.50), p-value = 0.024], but not in the center. Subgroup analyses revealed similar unstable results in males on the condylar landmarks after subcondylar fracture reduction. There were tendencies for lateral displacement of the coronoid process in the body fracture group [mean (SD) = 0.8 (0.83)] and angle fracture group [mean (SD) = 0.75 (0.58)] postoperatively (p-value = 0.01). This study concluded that bioresorbable osteosynthesis can be recommended for body or angle fractures, while the indication for subcondylar fractures is less clear.

Characterization and potential applications of a dual-layer flat-panel detector.

Dual-energy (DE) x-ray imaging has many clinical applications in radiography, fluoroscopy, and CT. This work characterizes a prototype dual-layer (DL) flat-panel detector (FPD) and investigates its DE imaging capabilities for applications in two-dimensional (2D) radiography/fluoroscopy and quantitative three-dimensional (3D) cone-beam CT. Unlike other DE methods like kV switching, a DL FPD obtains DE images from a single exposure, making it robust against patient and system motion. The DL FPD consists of a top layer with a 200µm-thick CsI scintillator coupled to an amorphous silicon (aSi) FPD of 150µm pixel size and a bottom layer with a 550µm thick CsI scintillator coupled to an identical aSi FPD. The two layers are separated by a 1-mm Cu filter to increase spectral separation. Images (43×43cm2 active area) can be readout in 2×2 binning mode (300µm pixels) at up to 15 frames per second. Detector performance was first characterized by measuring the MTF, NPS, and DQE for the top and bottom layers. For 2D applications, a qualitative study was conducted using an anthropomorphic thorax phantom containing a porcine heart with barium-filled coronary arteries (similar to iodine). Additionally, fluoroscopic lung tumor tracking was investigated by superimposing a moving tumor phantom on the thorax phantom. Tracking accuracies of single-energy (SE) and DE fluoroscopy were compared against the ground truth motion of the tumor. For 3D quantitative imaging, a phantom containing water, iodine, and calcium inserts was used to evaluate overall DE material decomposition capabilities. Virtual monoenergetic (VM) images ranging from 40 to 100keV were generated, and the optimal VM image energy which achieved the highest image uniformity and maximum contrast-to-noise ratio (CNR) was determined. The spatial resolution of the top layer was substantially higher than that of the bottom layer (top layer 50% MTF=2.2mm-1 , bottom layer=1.2mm-1 ). A substantial increase in NNPS and reduction in DQE were observed for the bottom layer mainly due to photon loss within the top layer and Cu filter. For 2D radiographic and fluoroscopic applications, the DL FPD was capable of generating high-quality material-specific images separating soft tissue from bone and barium. For lung tumor tracking, DE fluoroscopy yielded more accurate results than SE fluoroscopy, with an average reduction in the root mean square error (RMSE) of over 10×. For the DE-CBCT studies, accurate basis material decompositions were obtained. The estimated material densities were 294.68 17.41 and 92.14 15.61mg/ml for the 300 and 100mg/ml calcium inserts, respectively, and 8.93 1.45, 4.72 1.44, and 2.11 1.32mg/ml for the 10, 5, and 2mg/ml iodine inserts, respectively, with an average error of less than 5%. The optimal VM image energy was found to be 60keV. We characterized a prototype DL FPD and demonstrated its ability to perform accurate single-exposure DE radiography/fluoroscopy and DE-CBCT. The merits of the DL detector approach include superior spatial and temporal registration between its constituent images, and less complicated acquisition sequences.

Shape prior metal artefact reduction algorithm for industrial 3D cone beam CT

ABSTRACT Metal artefact reduction has become a challenging issue for practical X-ray CT applications since metal artefacts severely cause contrast degradation and the misinterpretation of information about the property and structure of a scanned object. In this paper, we propose a methodology to reduce metal artefacts in a three-dimensional industrial cone beam CT system. We develop a registration technique managing the three dimensional data in order to find accurate segmentation regions needed for the proposed algorithm. Through various simulations and experiments, we verify that the proposed algorithm reduces metal artefacts successfully.

Evaluation of mallear ligaments in different voxel resolutions using cone beam computed tomography.

The aim of this study was to assess the visibility of discomallear ligament and anterior mallear ligament together with anatomical morphometric measurements of petrotympanic fissure, and to determine whether the mallear ligaments correlate with the bone compartment changes of temporomandibular joint. Cone beam CT images of 275 patients were evaluated retrospectively. The visibility of discomallear and anterior mallear ligaments were evaluated by two observers. The petrotympanic fissure was classified into four groups. Morphologic features of petrotympanic fissure and mandibular fossa were also measured in sagittal, axial and three-dimensional cone beam CT reconstructed images. Pearson's χ2 test and Student's t-test were performed for statistical analysis of differences voxel sizes, age, gender, localization, temporomandibular joint and measurements (p < 0.05). Intra- and interobserver reliability was also performed. Type 3 petrotympanic fissure was more frequent in male, whereas females showed Type 1 and Type 2 petrotympanic fissure structures (p < 0.05). Anterior mallear ligament visibility on cone beam CT images was statistically higher in bone compartment changes of temporomandibular joint. In cone beam CT images, petrotympanic fissure tunnel types 1, 2, 3 and 4 were seen in 11.5, 35.63, 51.34 and 1.53% of patients, respectively. Knowledge of the anatomy may help in identifying temporomandibular joint pain and auditory symptoms due to temporomandibular disorder. Further cross-sectional studies with larger populations are needed to investigate the physiopathological relation of both disorders.

Three-dimensional CBCT images registration method for TMJ based on reconstructed condyle and skull base.

A method was introduced for three-dimensional (3D) cone-beamCT (CBCT) images registration of temporomandibular joint (TMJ). This study aimed to provide quantitative and qualitative analysis of TMJ bone changes in two-dimensional (2D) and 3D and to provide the technique for computer-aided diagnosis of temporomandibular joint disorders inthe future. 10 TMJ samples of six patients were obtained from Peking University Hospital of Stomatology. Four of the six patients imaged bilateral TMJs and the other two patients only imaged unilateral TMJ. Each sample consisted of two images from the same TMJ taken at different times. First, condyle and skull base were segmented semi-automatically for 3D model reconstruction. Then the segmented condyle and skull base were registered separately. Registration process can be divided into two processes of rough registration and fine registration. Rough registration step was achieved by selecting corresponding points manually and initialized fine registration. Condyle and skull base were fine registered by minimizing mean square error of condyle (MSEcondyle) and skull base (MSEskull) respectively. Qualitative assessment of osseous component changes utilized 2D color-fused model and 3D surface-fused model and quantitative analyses the convergence of this method used the mean square error of the model (MSEmodel). Independent repeated experiments were carried out to test the stability of our 3D registration method. Sufficiently alignment was achieved. Osseous abnormality and morphology changes were displayed using fusion model. MSEmodelof condylar registration and skull base registration declined 51.80% and 64.58% compared with that before registration. Quantitative analysis verified the stability of the method. The proposed method completed 3D TMJ registration for different physiological structure. The result of this method was accurate, reproducible and not relied on the experience of operators.

IP007. Simplified Translumbar Treatment of a Type II Endoleak Using CT Fusion in Hybrid Room

A 74-year-old man underwent endovascular aneurysm repair (EVAR) of a 5.0-cm infrarenal abdominal aortic aneurysm (AAA) with a stent graft. Endoleaks were not detected at the time of the completion angiogram. Follow-up aortic duplex study obtained 1 month later showed the presence of a small type II endoleak arising from the inferior mesenteric artery (IMA). The endoleak persisted and increased in size, with a subsequent sac diameter increase 3 years after EVAR. A follow-up computed tomography angiogram (CTA) showed the presence of type II endoleak, with retrograde filling by the IMA and connection to a complex network of lumbar vessels. The AAA sac increased in size to 5.8 cm. Decision was made to proceed with treatment to obliterate this endoleak. We describe a novel approach in treating a persistent type II endoleak related to the IMA and the lumbar outflow vessels using a simplified translumbar approach. Using TrackVision software, we were able to delineate the track to the level of the endoleak. The software program allowed us to access the endoleak through a translumbar approach. A three-dimensional cone-beam CT scan without contrast injection was used to identify the location of the endograft to match the exact position of the endoleak noted on the previous CTA in the superimposed prone position. After the entry and target trajectories were identified using both of the fused data sets, the model and planned trajectories were then exported into the TrackVision software, creating a virtual needle track. A 20-cm long, 18-gauge Chiba needle was used to access the endoleak cavity. Using progress and bull’s eye views, we were able to track the needle into the endoleak. The endoleak was then visualized using contrast showing feeding of the endoleak through the IMA. This entire region was then coil embolized with a total of four 4-mm × 3-mm Tornado Embolization Coils followed by one 5-mm × 10-cm and two 10-mm × 15-cm Nester Embolization Coils. After coil embolization the IMA was not visualized. The patient was seen in follow-up 1 month following the procedure with complete obliteration of the endoleak and decrease in sac size to 5.3 cm. This simplified approach at treating complex endoleaks has allowed the procedure to be performed with minimal fluoroscopy and digital subtraction angiography imaging. In addition, the length of the procedure has become significantly shortened with the use of the virtual needle track.Fig 2View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Three-dimensional cone-beam CT sialography in non tumour salivary pathologies: procedure and results.

Non-tumour salivary diseases are common. Imaging studies are essential for their diagnosis and before undergoing an endoscopic or surgical treatment. In this study, we aimed at presenting our procedure and results obtained with three-dimensional CBCT (3D-CBCT) sialography for non-tumour salivary gland diseases. Patients with parotid or submandibular salivary symptoms were examined by 3D-CBCT sialography. They received an intraductal injection of 0.5 mL of water-soluble contrast medium maintained in the gland, followed by examination in a NewTom wide-field CBCT device. Images were processed with multiplanar and 3D reconstructions. A ductal exploration could be performed until the fourth divisions. The main lesions found were stones, stenosis, dilatations and "dead tree" appearance of the ductal system. No side effects of the catheterization or the iodine contrast were reported, nor tissue damages related to the contrast keeping technique. 3D-CBCT sialography seems to represent a reliable non-invasive diagnostic tool for ductal salivary diseases. More studies are needed to assess the value of 3D-CBCT sialography compared with conventional imaging.

Set-up errors in head and neck cancer patients treated with intensity modulated radiation therapy: Quantitative comparison between three-dimensional cone-beam CT and two-dimensional kilovoltage images

ObjectivesTo compare the patient set-up error detection capabilities of three-dimensional cone beam computed tomography (3D-CBCT) and two-dimensional orthogonal kilovoltage (2D-kV) techniques. Methods3D-CBCT and 2D-kV projections were acquired on 29 head-and-neck (H&N) patients undergoing Intensity Modulated Radiotherapy (IMRT) on the first day of treatment (time 0) and after the delivery of 40 Gy and 50 Gy. Set-up correction vectors were analyzed after fully automatic image registration as well as after revision by radiation oncologists. The dosimetric effects of the different sensitivities of the two image guidance techniques were assessed. ResultsA statistically significant correlation among detected set-up deviations by the two techniques was found along anatomical axes (0.60 < ρ < 0.72, p < 0.0001); no correlation was found for table rotation (p = 0.41). No evidence of statistically significant differences between the indications provided along the course of the treatment was found; this was also the case when full automatic versus manually refined correction vectors were compared. The dosimetric effects analysis revealed slight statistically significant differences in the median values of the maximum relative dose to mandible, spinal cord and its 5 mm Planning Organ at Risk Volume (0.95%, 0.6% and 2.45%, respectively), with higher values (p < 0.01) observed when 2D-kV corrections were applied. ConclusionA similar sensitivity to linear set-up errors was observed for 2D-kV and 3D-CBCT image guidance techniques in our H&N patient cohort. Higher rotational deviations around the table vertical axis were detected by the 3D-CBCT with respect to the 2D-kV method, leading to a consistent better sparing of organs at risk.

Use of Cone Beam Computerized Tomography (CBCT) in orthodontic diagnosis and treatment planning in the presence of a palatally-impacted canine

Unerupted permanent canines can present orthodontists with special challenges. Conventional two-dimensional panoramic radiographs identify the presence or absence of unerupted canines and can only help approximate their locations, when used with various classification schemes in attempts to describe their locations and estimate treatment difficulties. This article suggests using three-dimensional cone beam CT imaging as a direct objective method of evaluation and treatment planning, thereby eliminating the need for using a subjective system of classifying palatally-impacted permanent canines.

Evaluation of the cone beam CT for internal target volume localization in lung stereotactic radiotherapy in comparison with 4D MIP images

To investigate whether the three-dimensional cone-beam CT (CBCT) is clinically equivalent to the four-dimensional computed tomography (4DCT) maximum intensity projection (MIP) reconstructed images for internal target volume (ITV) localization in image-guided lung stereotactic radiotherapy. A ball-shaped polystyrene phantom with built-in cube, sphere, and cone of known volumes was attached to a motor-driven platform, which simulates a sinusoidal movement with changeable motion amplitude and frequency. Target motion was simulated in the patient in a superior-inferior (S-I) direction with three motion periods and 2 cm peak-to-peak amplitudes. The Varian onboard Exact-Arms kV CBCT system and the GE LightSpeed four-slice CT integrated with the respiratory-position-management 4DCT scanner were used to scan the moving phantom. MIP images were generated from the 4DCT images. The clinical equivalence of the two sets of images was evaluated by comparing the extreme locations of the moving objects along the motion direction, the centroid position of the ITV, and the ITV volumes that were contoured automatically by Velocity or calculated with an imaging gradient method. The authors compared the ITV volumes determined by the above methods with those theoretically predicted by taking into account the physical object dimensions and the motion amplitudes. The extreme locations were determined by the gradient method along the S-I axis through the center of the object. The centroid positions were determined by autocenter functions. The effect of motion period on the volume sizes was also studied. It was found that the extreme locations of the objects determined from the two image modalities agreed with each other satisfactorily. They were not affected by the motion period. The average difference between the two modalities in the extreme locations was 0.68% for the cube, 1.35% for the sphere, and 0.5% for the cone, respectively. The maximum difference in the centroid position of the cylinder, sphere, and cone was less than 1.4 mm between the two modalities for all motion periods studied. For the ITV volume evaluation, the authors found that both MIP-based and CBCT-based ITVs increased with increases of motion period. Furthermore, the MIP-based ITV volumes were generally larger than those determined from the CBCT images, with the difference in autocontoured volumes being 2.57%, 1.66%, and 1.82% for the sphere, cylinder, and cone, respectively, while these differences increased to 9.57%, 3.52%, 8.71% for the above objects when the gradient method was used. The authors found that the autocontour method was accurate enough to predict the actual ITV values with the absolute differences less than 2.4% comparing to the theoretically predicted values. The extreme location and the centroid position of the objects agree with each other between the two image modalities when the breathing motion is sinusoidal. Although the ITV volumes delineated from both image modalities changed with the motion period, the differences in ITV between the two modalities were minimal when an optimized window level was used. The authors' results suggest that CBCT and MIP images are equivalent in determining an ITV's position in the conditions studied. The CBCT is adequate in providing imaging-guidance for lung cancer treatment.

Cone beam CT guidance provides superior accuracy for complex needle paths compared with CT guidance

To determine the accuracy of cone beam CT (CBCT) guidance and CT guidance in reaching small targets in relation to needle path complexity in a phantom. CBCT guidance combines three-dimensional CBCT imaging with fluoroscopy overlay and needle planning software to provide real-time needle guidance. The accuracy of needle positioning, quantified as deviation from a target, was assessed for inplane, angulated and double angulated needle paths. Four interventional radiologists reached four targets along the three paths using CBCT and CT guidance. Accuracies were compared between CBCT and CT for each needle path and between the three approaches within both modalities. The effect of user experience in CBCT guidance was also assessed. Accuracies for CBCT were significantly better than CT for the double angulated needle path (2.2 vs 6.7 mm, p<0.001) for all radiologists. CBCT guidance showed no significant differences between the three approaches. For CT, deviations increased with increasing needle path complexity from 3.3 mm for the inplane placements to 4.4 mm (p=0.007) and 6.7 mm (p<0.001) for the angulated and double angulated CT-guided needle placements, respectively. For double angulated needle paths, experienced CBCT users showed consistently higher accuracies than trained users [1.8 mm (range 1.2-2.2) vs 3.3 mm (range 2.1-7.2) deviation from target, respectively; p=0.003]. In terms of accuracy, CBCT is the preferred modality, irrespective of the level of user experience, for more difficult guidance procedures requiring double angulated needle paths as in oncological interventions. Accuracy of CBCT guidance has not been discussed before. CBCT guidance allows accurate needle placement irrespective of needle path complexity. For angulated and double-angulated needle paths, CBCT is more accurate than CT guidance.

Pre-surgical treatment planning of maxillary canine impactions using panoramicvscone beam CT imaging

The aim of this prospective study was to compare the impact of using two-dimensional (2D) panoramic radiographs and three-dimensional (3D) cone beam CT for the surgical treatment planning of impacted maxillary canines. This study consisted of 32 subjects (19 females, 13 males) with a mean age of 25 years, referred for surgical intervention of 39 maxillary impacted canines. Initial 2D panoramic radiography was available, and 3D cone beam CT imaging was obtained upon clinical indication. Both 2D and 3D pre-operative radiographic diagnostic sets were subsequently analysed by six observers. Perioperative evaluations were conducted by the treating surgeon. McNemar tests, hierarchical logistic regression and linear mixed models were used to explore the differences in evaluations between imaging modalities. Significantly higher confidence levels were observed for 3D image-based treatment plans than for 2D image-based plans (p < 0.001). The evaluations of canine crown position, contact relationship and lateral incisor root resorption were significantly different between the 2D and 3D images. By contrast, pre- and perioperative evaluations were not significantly different between the two image modalities. Surgical treatment planning of impacted maxillary canines was not significantly different between panoramic and cone beam CT images.

Dose indices in dental cone beam CT and correlation with dose–area product

In the 2011 project "Safety and efficacy of a new and emerging dental X-ray modality (SEDENTEXCT)", it was suggested that dose index (DI) and dose-area product (DAP) could be easily measured and used as diagnostic reference levels (DRLs), which would help in the management of radiation doses to patients in optimum exposure settings. Such indices could be directly related to effective dose. The purposes of this study, therefore, were to measure and calculate the DI and DAP in cone beam CT (CBCT) machines and to evaluate the correlation between the two. Dose measurements were performed on three-dimensional cone beam CT (3D-CBCT) machines [3D Accuitomo (J. Morita Mfg. Corp., Kyoto, Japan), Veraviewepocs (J. Morita Mfg. Corp.) and CS9300 (Carestream, New York, NY)] by exposing a cylindrical poly-methyl methacrylate (PMMA) phantom using a CT ionization chamber. These dose measurements were used for the calculation of Dose Indices 1 and 2, according to the methodology suggested by SEDENTEXCT. The DAP was measured using a DAP meter that was attached to the detector to cover the entire irradiated area. The DI1 ranged from 53.6 mR to 216.6 mR, the DI2 ranged from 77.1 mR to 325.0 mR and the DAP ranged from 101.1 mGy cm(2) to 457.9 mGy cm(2), depending on the machines and exposure settings. Index 2 had a better correlation with the DAP than Index 1. The DIs and DAP proposed by SEDENTEXCT may be useful for establishing DRLs for dental CBCT machines; however, further studies are necessary to determine which of these indices provide accurate dose estimates proportionally relating to the effective dose.

Comparison of precision and accuracy of linear measurements performed by two different imaging software programs and obtained from 3D-CBCT images for Le Fort I osteotomy

The purpose of this study was to compare the precision and accuracy of linear measurements for Le Fort I osteotomy performed by two different imaging software programs and obtained from three-dimensional cone beam CT (3D-CBCT) images. The study population consisted of 11 dried skulls submitted to CBCT, which generated 3D images. Linear measurements were based on craniometric anatomical landmarks pre-defined by the authors as specifically used for Le Fort I osteotomy and were identified by two radiologists twice each, independently, using Vitrea 3.8.1 (Vital Images Inc., Plymouth, MN) and open-source digital imaging communication in medicine viewer OsiriX 1.2 64-bit (Pixmeo, Geneva, Switzerland). Subsequently, a third examiner made physical measurements using a digital caliper (167 series; Mitutoyo Sul Americana Ltd, Suzano, SP, Brazil). The results demonstrated a statistically significant difference between OsiriX and the gold standard, especially in the pterygoid process (TPtg L = 0.019, LLpPtg R = 0.016 and LLpPtg L = 0.012). Vitrea showed no statistical difference in comparison with the gold standard, and showed a high level of accuracy in all the measurements performed. The major difference found was 0.42 mm (LLpPtg R). Interexaminer analysis ranged from 0.90 to 0.97 using Vitrea and from 0.8 to 0.97 using OsiriX. Intraexaminer correlation coefficient ranged from 0.90 to 0.98 and from 0.84 to 0.98 for Examiners 1 and 2, respectively, using Vitrea and from 0.93 to 0.99 for Examiner 1 and from 0.64 to 0.96 for Examiner 2 using OsiriX. Vitrea may be considered as precise and accurate, insofar as it was able to perform all the 3D linear measurements. On the other hand, linear measurements performed using OsiriX were not successful in producing accurate linear measurements for Le Fort I osteotomy.

Cervical vertebral column morphology in patients with obstructive sleep apnoea assessed using lateral cephalograms and cone beam CT. A comparative study

Few studies have described morphological deviations in obstructive sleep apnoea (OSA) patients on two-dimensional (2D) lateral cephalograms, and the reliability of 2D radiographs has been discussed. The objective is to describe the morphology of the cervical vertebral column on cone beam CT (CBCT) in adult patients with OSA and to compare 2D lateral cephalograms with three-dimensional (3D) CBCT images. For all 57 OSA patients, the cervical vertebral column morphology was evaluated on lateral cephalograms and CBCT images and compared according to fusion anomalies and posterior arch deficiency. The CBCT assessment showed that 21.1% had fusion anomalies of the cervical column, i.e. fusion between two cervical vertebrae (10.5%), block fusions (8.8%) or occipitalization (1.8%). Posterior arch deficiency occurred in 14% as partial cleft of C1 and in 3.5% in combination with block fusions. The agreement between the occurrence of morphological deviations in the cervical vertebral column between lateral cephalograms and CBCT images showed good agreement (κ = 0.64). Prevalence and pattern in the cervical column morphology have now been confirmed on CBCT. The occurrence of morphological deviations in the cervical vertebral column showed good agreement between lateral cephalograms and CBCT images. This indicates that 2D lateral cephalograms (already available after indication in connection with, e.g. treatment planning) are sufficient for identifying morphological deviations in the cervical vertebral column. For a more accurate diagnosis and location of the deviations, CBCT is required. New 3D methods will suggest a need for new detailed characterization and division of deviations in cervical vertebral column morphology.

Interesting detector shapes for third generation CT scanners

To discuss options in designing detector shapes in third generation CT and to quantify potential cost savings for compact third generation CT systems, and to extend the work from two-dimensional fan-beam CT to three-dimensional cone-beam CT for circular, sequential, and spiral scan trajectories. Third generation CT scanners typically comprise detectors which are flat or whose shape is the segment of a cylinder or a sphere that is focused onto the focal spot of the x-ray source. There appear to be two design criteria that favor this choice of detector shape. One is the possibility of performing fan-beam and cone-beam filtered backprojection in the native geometry (without rebinning) and the other criterion could be to enable the early use of focused antiscatter grids. It is less known, however, that other detector shapes may also have these properties. While these designs have been evaluated for 2D CT from a theoretical standpoint more than one decade ago the authors revisit and generalize these considerations, extend them to 3D circular, sequential, and spiral cone-beam CT and propose an optimal design in terms of detector costs while keeping image quality constant. Their considerations and conclusions are based on considering the sampling density of the x-rays, including the effects of finite focal spot and finite detector element size. Proposing image reconstruction algorithms or numerically evaluating the results by reconstructing simulated projection data is not within the scope of this work. If the detector arc is curved to be nearly concentric with the circle describing the edge of the field of measurement significantly less detector area and detector pixels are required compared to today's third generation CT systems where the detector arc is centered about the focal spot. Combined with a detector that just covers the spiral Tam window cost savings of 60% or more are possible in compact CT systems. In terms of practicability the new designs appear to be nearly as easy to realize as today's third generation systems. Compact CT systems, which require the focal spot to be mounted close to the edge of the field of measurement, may significantly benefit from using detector shapes other than the typical equiangular detector that is focused onto the focal spot.