Reduction of cone-beam CT artifacts in a robotic CBCT device using saddle trajectories with integrated infrared tracking.

BACKGROUND: Cone beam computed tomography (CBCT) is widely used in many medical fields. However, conventional CBCT circular scans suffer from cone beam (CB) artifacts that limit the quality and reliability of the reconstructed images due to incomplete data. PURPOSE: Saddle trajectories in theory might be able to improve the CBCT image quality by providing a larger region with complete data. Therefore, we investigated the feasibility and performance of saddle trajectory CBCT scans and compared them to circular trajectory scans. METHODS: We performed circular and saddle trajectory scans using a novel robotic CBCT scanner (Mobile ImagingRing (IRm); medPhoton, Salzburg, Austria). For the saddle trajectory, the gantry executed yaw motion up to ± 10 ∘ $\pm 10^{\circ }$ using motorized wheels driving on the floor. An infrared (IR) tracking device with reflective markers was used for online geometric calibration correction (mainly floor unevenness). All images were reconstructed using penalized least-squares minimization with the conjugate gradient algorithm from RTK with 0.5 × 0.5 × 0.5 mm 3 $0.5 \times 0.5\times 0.5 \text{ mm}^3$ voxel size. A disk phantom and an Alderson phantom were scanned to assess the image quality. Results were correlated with the local incompleteness value represented by tan ( ψ ) $\tan (\psi)$ , which was calculated at each voxel as a function of the source trajectory and the voxel's 3D coordinates. We assessed the magnitude of CB artifacts using the full width half maximum (FWHM) of each disk profile in the axial center of the reconstructed images. Spatial resolution was also quantified by the modulation transfer function at 10% (MTF10). RESULTS: When using the saddle trajectory, the region without CB artifacts was increased from 43 to 190 mm in the SI direction compared to the circular trajectory. This region coincided with low values for tan ( ψ ) $\tan (\psi)$ . When tan ( ψ ) $\tan (\psi)$ was larger than 0.02, we found there was a linear relationship between the FWHM and tan ( ψ ) $\tan (\psi)$ . For the saddle, IR tracking allowed the increase of MTF10 from 0.37 to 0.98 lp/mm. CONCLUSIONS: We achieved saddle trajectory CBCT scans with a novel CBCT system combined with IR tracking. The results show that the saddle trajectory provides a larger region with reliable reconstruction compared to the circular trajectory. The proposed method can be used to evaluate other non-circular trajectories.

Spiral volumetric optoacoustic tomography for imaging whole-body biodynamics in small animals.

Fast tracking of biological dynamics across multiple murine organs using the currently commercially available whole-body preclinical imaging systems is hindered by their limited contrast, sensitivity and spatial or temporal resolution. Spiral volumetric optoacoustic tomography (SVOT) provides optical contrast, with an unprecedented level of spatial and temporal resolution, by rapidly scanning a mouse using spherical arrays, thus overcoming the current limitations in whole-body imaging. The method enables the visualization of deep-seated structures in living mammalian tissues in the near-infrared spectral window, while further providing unrivalled image quality and rich spectroscopic optical contrast. Here, we describe the detailed procedures for SVOT imaging of mice and provide specific details on how to implement a SVOT system, including component selection, system arrangement and alignment, as well as the image processing methods. The step-by-step guide for the rapid panoramic (360°) head-to-tail whole-body imaging of a mouse includes the rapid visualization of contrast agent perfusion and biodistribution. The isotropic spatial resolution possible with SVOT can reach 90 µm in 3D, while alternative steps enable whole-body scans in less than 2 s, unattainable with other preclinical imaging modalities. The method further allows the real-time (100 frames per second) imaging of biodynamics at the whole-organ level. The multiscale imaging capacity provided by SVOT can be used for visualizing rapid biodynamics, monitoring responses to treatments and stimuli, tracking perfusion, and quantifying total body accumulation and clearance dynamics of molecular agents and drugs. Depending on the imaging procedure, the protocol requires 1-2 h to complete by users trained in animal handling and biomedical imaging.

Fotobiomodulación con láser de baja intensidad en el tratamiento integral ortodóntico: reporte de un caso / Photobiomodulation with low intensity laser in comprehensive orthodontic treatment: report of a case

El apiñamiento dental es una maloclusión frecuen-te y junto con los requerimientos de estética dental son una causa habitual de la solicitud de tratamien-to ortodóncico. El tiempo que demanda y las moles-tias que pudiera ocasionar el tratamiento produce inquietud en los pacientes y un esfuerzo de los or-todoncistas para optimizar el tiempo y prevenir los efectos adversos. Los tratamientos odontológicos multidisciplinarios permiten una mejor respuesta estética, funcional y de estabilidad post tratamiento. El tiempo de alineación dentaria y finalización, en los pacientes tratados con láser de baja intensidad po-dría mejorar tanto los índices gingivales como la res-puesta al dolor. Adicionalmente, las corticales óseas de los pacientes con ortodoncia tratados con láser, podrían verse menos afectadas en comparación con las de los pacientes no tratados. Se presenta un caso de fotobioestimulación con láser de baja intensidad aplicado en un paciente en fase de alineación, que forma parte de un estudio prospectivo aleatorizado que se desarrolla en la FOUBA y fue aprobado por el comité de Ética de la institución. El paciente aceptó y firmó el consentimiento informado. Finalizada la etapa de alineación, se evaluó la efectividad de la te-rapia con láser de baja intensidad actualmente de-nominada fotobiomodulación en incisivos superiores en la fase de alineación para acelerar el movimiento dentario, la respuesta gingival, el dolor, el estado de la cortical alveolar vestibular y la estética del perfil (AU)

Dental crowding, which is a frequent malocclusion, and dental aesthetic requirements are a common cause for requesting orthodontic treatment. The time that the treatment requires and the inconvenience that it could cause worries the patient and makes orthodontists strive to optimize time and prevent adverse effects. Multidisciplinary treatments would allow a better aesthetic, functional and post-treatment stability response. The dental alignment and completion time in patients treated with low-intensity laser could improve both gingival indices and response to pain. Additionally, the bone cortical of orthodontic patients treated with laser could be less affected compared to those of untreated patients. A case of low-intensity laser photobiostimulation applied to a patient in the alignment phase is presented, which is part of a prospective randomized study carried out at FOUBA and was approved by the institution's Ethics Committee. The patient accepted and signed the informed consent. After the alignment phase, the effectiveness of low-level laser therapy actually called photobiomodulation in upper incisors in the alignment phase is evaluated to accelerate tooth movement; the gingival response; the pain; the vestibular alveolar cortical and the aesthetics of the profile (AU)

Automated cortical thickness measurement of the mandibular condyle head on CBCT images using a deep learning method.

This study proposes a deep learning model for cortical bone segmentation in the mandibular condyle head using cone-beam computed tomography (CBCT) and an automated method for measuring cortical thickness with a color display based on the segmentation results. In total, 12,800 CBCT images from 25 normal subjects, manually labeled by an oral radiologist, served as the gold-standard. The segmentation model combined a modified U-Net and a convolutional neural network for target region classification. Model performance was evaluated using intersection over union (IoU) and the Hausdorff distance in comparison with the gold standard. The second automated model measured the cortical thickness based on a three-dimensional (3D) model rendered from the segmentation results and presented a color visualization of the measurements. The IoU and Hausdorff distance showed high accuracy (0.870 and 0.928 for marrow bone and 0.734 and 1.247 for cortical bone, respectively). A visual comparison of the 3D color maps showed a similar trend to the gold standard. This algorithm for automatic segmentation of the mandibular condyle head and visualization of the measured cortical thickness as a 3D-rendered model with a color map may contribute to the automated quantification of bone thickness changes of the temporomandibular joint complex on CBCT.

Quality of Endodontic Treatment and Prevalence of Apical Radiolucencies in a Bulgarian Subpopulation: a CBCT Analysis.

INTRODUCTION: The advent of Cone Beam Computed Tomography (CBCT) in endodontics has enhanced the diagnosis of periapical radiolucencies and the assessment of endodontically treated teeth. AIM: The purpose of this study was to assess the prevalence of periapical radiolucencies in a Bulgarian subpopulation and the quality of previous endodontic treatment using CBCT scans. MATERIALS AND METHODS: This study included 2795 roots from 160 Large FOV CBCT which were evaluated by two independent examiners using two scoring systems: CBCT-PAI and PESS. RESULTS: The inter-examiner agreement spanned from strong to almost perfect (0.892 and 0.983). The prevalence of periapical lesions according to the two scoring systems was 23.1% and 12.9 %, respectively. The prevalence of endodontically treated teeth was high (34.1%). Sixty-five percent of them presented with signs of periapical radiolucencies, while only 1.4% of all non-treated roots had a periapical lesion. A significant association between periapical disease, poor quality of the root canal filling and inadequate coronal seal was found (p<0.001). CONCLUSIONS: The prevalence of periapical disease in endodontically-treated teeth in the Bulgarian subpopulation was high. Poor qual-ity of the root canal filling and inadequate coronal seal were assessed as prognostic determinants of treatment failure. CBCT techniques can augment conventional diagnostic techniques in the field of endodontics.

Comparison of Smartphone Augmented Reality, Smartglasses Augmented Reality, and 3D CBCT-guided Fluoroscopy Navigation for Percutaneous Needle Insertion: A Phantom Study.

PURPOSE: To compare needle placement performance using an augmented reality (AR) navigation platform implemented on smartphone or smartglasses devices to that of CBCT-guided fluoroscopy in a phantom. MATERIALS AND METHODS: An AR application was developed to display a planned percutaneous needle trajectory on the smartphone (iPhone7) and smartglasses (HoloLens1) devices in real time. Two AR-guided needle placement systems and CBCT-guided fluoroscopy with navigation software (XperGuide, Philips) were compared using an anthropomorphic phantom (CIRS, Norfolk, VA). Six interventional radiologists each performed 18 independent needle placements using smartphone (n = 6), smartglasses (n = 6), and XperGuide (n = 6) guidance. Placement error was defined as the distance from the needle tip to the target center. Placement time was recorded. For XperGuide, dose-area product (DAP, mGy*cm2) and fluoroscopy time (sec) were recorded. Statistical comparisons were made using a two-way repeated measures ANOVA. RESULTS: The placement error using the smartphone, smartglasses, or XperGuide was similar (3.98 ± 1.68 mm, 5.18 ± 3.84 mm, 4.13 ± 2.38 mm, respectively, p = 0.11). Compared to CBCT-guided fluoroscopy, the smartphone and smartglasses reduced placement time by 38% (p = 0.02) and 55% (p = 0.001), respectively. The DAP for insertion using XperGuide was 3086 ± 2920 mGy*cm2, and no intra-procedural radiation was required for augmented reality. CONCLUSIONS: Smartphone- and smartglasses-based augmented reality reduced needle placement time and radiation exposure while maintaining placement accuracy compared to a clinically validated needle navigation platform.

Sacroiliac joint injections with the guidance of three-dimensional cone beam computed tomography (3D-CBCT) and fluoroscopy fusion.

BACKGROUND: We describe our diagnostic sacroiliac joint (SIJ) injection technique under the guidance of three-dimensional cone beam computed tomography (3D-CBCT) fused with real-time fluoroscopy. METHODS: A retrospective review of 17 patients (mean age 55.4 (range 40-74) years) who received a total of 23 diagnostic SIJ injections between March 2016 and November 2017 were performed. Pre- and post-procedure pain scores were reviewed from the medical records and then these findings were correlated with which patients were and were not diagnosed with SIJ pain by clinical management. The final diagnosis of SIJ-related pain was made in cases with at least 50% symptomatic improvement following SIJ-specific pain treatments. RESULTS: Some 87% (n=20/23) of injections achieved more than 50% pain relief after the diagnostic SIJ injection. The final diagnosis of the target SIJ-related pain after follow-up and management was found in 90% (n=18/20) of cases. There were two cases with positive tests diagnosed as non-SIJ pain including one with the diagnosis of femuroacetabular impingement and one with pain related to loosening of knee hardware. The sensitivity, specificity, positive predictive value, and negative predicative value of diagnostic SIJ injections were 100%, 60%, 89%, and 100%, respectively, with a 40% false-positive rate. There were no procedure-related complications. CONCLUSION: 3D-CBCT fused with real-time fluoroscopy for SIJ injection is accurate and safe.

Comparison Between CBCT and Fusion PET/CT-CBCT Guidance for Lung Biopsies.

PURPOSE: To establish the feasibility of performing percutaneous biopsy of lung lesions guided by fusion PET/CT-CBCT and to evaluate whether the metabolic information provided by a prior PET/CT scan add incremental benefits for diagnosis. METHODS: We retrospectively reviewed data from 180 patients who underwent CBCT-guided lung biopsy (group 1-90 cases) or PET/CT-CBCT fusion-guided lung biopsy (group 2-90 cases). Technical and clinical success was calculated. We also evaluated the agreement between biopsy and definitive histology and the possibility to carrying out immunehistochemical and molecular biology analyses. RESULTS: Technical success was achieved in 84/90 (93.3%) cases for group 1 and 89/90 (98.9%) for group 2 cases (p 0.054). Clinical success was achieved in 80/94 (95.2%) cases for group 1 and 88/89 (98.9%) cases for group 2. Sensitivity, specificity, positive and negative predictive values and accuracy rate were, respectively, 94.5%, 100.0%, 100.0%, 73.3% and 95.2% for group 1 and 98.6%, 100.0%, 100.0%, 94.4% and 98.9% for group 2 (p 0.167). Agreement between biopsy and definitive histology was reached in 85.7% for group 1 and in 96.2% for group 2 (p 0.211). Immunohistochemical and molecular biology investigations were possible in 66.7% for group 1 and in 77.0% for group 2 (p 0.297). No major complication occurred. CONCLUSIONS: PET/CT-CBCT-guided lung biopsy is a feasible technique. In our retrospective case series, we found a higher clinical success rate, but no statistical difference was found.

Correlation of objective image quality and working length measurements in different CBCT machines: An ex vivo study.

To investigate potential correlations between objective CBCT image parameters and accuracy in endodontic working length determination ex vivo. Contrast-to-noise ratio (CNR) and spatial resolution (SR) as fundamental objective image parameters were examined using specific phantoms in seven different CBCT machines. Seven experienced observers were instructed and calibrated. The order of the CBCTs was randomized for each observer and observation. To assess intra-operator reproducibility, the procedure was repeated within six weeks with a randomized order of CBCT images. Multivariate analysis (MANOVA) did not reveal any influence of the combined image quality factors CNR and SR on measurement accuracy. Inter-operator reproducibility as assessed between the two observations was poor, with a mean intra-class correlation (ICC) of 0.48 (95%-CI  0.38, 0.59) for observation No. 1. and 0.40 (95%-CI 0.30, 0.51) for observation No. 2. Intra-operator reproducibility pooled over all observers between both observations was only moderate, with a mean ICC of 0.58 (95%-CI 0.52 to 0.64). Within the limitations of the study, objective image quality measures and exposure parameters seem not to have a significant influence on accuracy in determining endodontic root canal lengths in CBCT scans. The main factor of variance is the observer.

Correlation between fusion of spheno-occipital synchondrosis and cervical vertebral maturation: A CBCT and cephalometric assessment.

OBJECTIVE: The aim of this study was to determine among young orthodontic patients the relation between the spheno-occipital synchondrosis (SOS) fusion and the cervical vertebral maturation (CVM) and to look for an eventual impact of gender, skeletal class and vertical pattern on their association. MATERIAL AND METHODS: CBCT scans and lateral cephalometric radiographs of 117 patients, aged between 8 and 18 years, were selected. SOS fusion was assessed on a mid-sagittal cut of the CBCT scans. CVM was evaluated on the lateral cephalograms as well as ANB and GoGn-SN angles. Spearman correlation test was used to assess the relationship between SOS and CVM. Fisher's exact test was performed at every CVM stage to analyse the association between SOS and other variables (gender, skeletal class, and vertical pattern). Cohen's kappa analysis was used for reliability. RESULTS: A strong correlation was found between SOS maturation and CVM (r=0.852, P<001). Fisher's exact test indicated significant association only between gender and SOS in CVM stage 2 group, and between vertical pattern and SOS in CVM stage 4. Cohen's kappa analysis showed moderate inter and intra-rater reliability for CVM index (k=0.50 and 0.53 respectively, P<.001), strong inter-rater reliability (k=0.80, P<.001) and almost perfect intra-rater reliability (k=0.85, P<.001) for SOS index. CONCLUSIONS: SOS fusion correlates well with CVM and might be a reliable tool for skeletal maturation assessment. Girls seem to have an earlier fusion of SOS in relation to their respective CVM compared to boys, and the vertical pattern could influence the association between SOS and CVM stages.

Association between Anatomical Features of Petrotympanic Fissure and Tinnitus in Patients with Temporomandibular Joint Disorder Using CBCT Imaging: An Exploratory Study.

Mandible displacement is known to correlate with otological conditions such as pain in the ear canal, hearing loss, or tinnitus. The present work aimed to determine the association between the displacement of the condyle in a temporomandibular joint, the structure and position of the petrotympanic fissure (PTF), and comorbid tinnitus in patients affected by temporomandibular joint and muscle disorder (TMD). We enrolled 331 subjects with TMD (268 women and 63 men). The average age of women was 40.8 ± 16.8 years (range 13-88), whereas the average age of the examined men was 38 ± 14 years (range 13-74). We performed imaging studies of the facial part of the skull in the sagittal plane using a volumetric imaging method and a large imaging field (FOV) of 17 cm × 23 cm. The habitual position of the mandible was determined and used as a reference. Based on the imaging results, we developed a classification for the topography and the structure of the petrotympanic fissure. Thirty-three TMD patients (about 10% of the sample) reported having tinnitus. These patients had PTF configurations characterized by a rear (36.59%) or intracranial-cranial (63.41%) condylar displacement of the temporomandibular joint. Our findings imply that the TMJ- and tinnitus-positive group of patients possibly represents a distinct phenotype of tinnitus. We concluded that for such patients, the therapeutic approach for tinnitus should include TMD treatment.

Canal Transportation and Centring Ability of Reciproc and Reciproc Blue With or Without Use of Glide Path Instruments: A CBCT Study.

Objective: The objective of this ex vivo study was to evaluate canal transportation and centring ability of Reciproc and Reciproc blue systems in curved root canals with or without prior use of PathFile rotary system (PF) using Cone Beam Computed Tomography (CBCT). Methods: One hundred and twenty curved root canals from maxillary and mandibular premolars were selected. Canals were divided randomly into 4 groups (n=30): Reciproc 25 (R25), (PF+R25), Reciproc Blue 25 (RB25), (PF+RB 25). Specimens were scanned before and after root canal preparation. Using CBCT, root canal transportation and centring ability was assessed by measuring the shortest distance from the edge of uninstrumented canal to the periphery of the root (mesial and distal) before and after preparation. Data were analysed using a one-way analysis of variance and Tukey test. The p value was set at 0.05. Results: Less transportation and better centring ability occurred when PF was used before R25 or RB25 (P<0.0001). There was no significant difference between R25 and RB25 groups. Conclusion: Using PF before R25 and RB25 resulted in less root canal transportation and better centring ability. The specific thermo-mechanical treatment of RB25 did not provide better results when compared to R25.

Comparison of the collum angle of incisors and canines in skeletal malocclusions - A CBCT study.

INTRODUCTION: The collum angle that defines the crown root angulation of the single rooted teeth plays an important in treatment planning. OBJECTIVE: To compare the collum angle (crown root angulation) of maxillary and mandibular anterior teeth in different skeletal malocclusions using Cone Beam Computed Tomography (CBCT). MATERIALS AND METHODS: Sixty subjects were categorized into four groups (fifteen subjects in each group) Class I, Class II division 1, Class II division 2 malocclusion and Class III based on Angle classification, Wits and ANB. The collum angle of maxillary and mandibular anterior teeth was measured using CBCT. One way ANOVA, Post hoc comparison with Tukey HSD and Paired t-test were used to analyse the measured data. RESULTS: The collum angle of corresponding right and left side teeth were averaged. Thus, the mean and standard deviation of the collum angle (n-30) were generated for maxillary and mandibular central incisors, lateral incisors, and canines. A statistically significant increase was observed in the maxillary central incisors of Class II division 2 and mandibular lateral incisors of class III malocclusion. The collum angle was increased in mandibular canines of Class III malocclusion when compared with class I and Class II division 2 malocclusion. The collum angle was negative in mandibular central incisors of Class II division 2. No statistically significant difference was observed in the mean collum angle between the right and left side anterior teeth in all the four groups. CONCLUSION: A variation in Collum angle was observed between the maxillary and mandibular anterior teeth and malocclusions. The effect of these variations in collum angle in torque expression and biomechanics should be kept in mind by the orthodontist before treatment planning especially in Class II division 2 malocclusion.

The effect of threshold level on bone segmentation of cranial base structures from CT and CBCT images.

The use of a single grey intensity threshold is one of the most straightforward and widely used methods to segment cranial base surface models from a 3D radiographic volume. In this study we used thirty Cone Beam Computer Tomography (CBCT) scans from three different machines and ten CT scans of growing individuals to test the effect of thresholding on the subsequently produced anterior cranial base surface models. From each scan, six surface models were generated using a range of voxel intensity thresholds. The models were then superimposed on a manually selected reference surface model, using an iterative closest point algorithm. Multivariate tests showed significant effects of the machine type, threshold value, and superimposition on the spatial position and the form of the created models. For both, CT and CBCT machines, the distance between the models, as well as the variation within each threshold category, was consistently increasing with the magnitude of difference between thresholds. The present findings highlight the importance of accurate anterior cranial base segmentation for reliable assessment of craniofacial morphology through surface superimposition or similar methods that utilize this anatomical structure as reference.

CBCT of Swedish children and adolescents at an oral and maxillofacial radiology department. A survey of requests and indications.

Objectives: This retrospective study investigated requests and indications for cone-beam computed tomography (CBCT) in children and adolescents over a 3-year period at one oral and maxillofacial radiology department. Specific aims were to determine what technical settings were used, which caregivers write the referrals, and how often and for what reasons re-exposure was necessary.Materials and methods: Patients <19 years of age who had been referred to the department and undergone a CBCT scan during 2015-2017 were included in the study.Results: CBCT were made in 617 of the 3847 eligible referrals. The most common referral was from general practice dentists (GPD) (43%). Mean age of the patients was 12.5 years (range: 6-18). Nineteen different types of requests were identified. The most common request was assessment of an ectopic canine with a question about potential resorption of adjacent teeth (38.6%). Forty (6.5%) of the CBCT needed to be re-taken due to patient motion artefacts.Conclusions: The most common request and indication for CBCT examination of children and young adults were to assess an ectopic canine and determine the presence of resorption of adjacent teeth. Referrals from GPDs were the most frequent and the largest age group was the 11- to 15-year olds. The reason for re-exposures was motion artefacts. High scanning speed to reduce motion artefacts and a half rotation (180°) to reduce the radiation dose to the patient should be preferred. The need for continuous work with quality and systematic monitoring of radiographic procedures at any radiology department should be given high priority.

In vivo comparison of MRI- and CBCT-based 3D cephalometric analysis: beginning of a non-ionizing diagnostic era in craniomaxillofacial imaging?

OBJECTIVES: To evaluate whether magnetic resonance imaging (MRI) can serve as an alternative diagnostic tool to the "gold standard" cone-beam computed tomography (CBCT) in 3D cephalometric analysis. METHODS: In this prospective feasibility study, 12 patients (8 males, 4 females; mean age ± SD, 26.1 years ± 6.6) underwent 3D MRI and CBCT before orthognathic surgery. 3D cephalometric analysis was performed twice by two independent observers on both modalities. For each dataset, 27 cephalometric landmarks were defined from which 35 measurements (17 angles, 18 distances) were calculated. Statistical analyses included the calculation of Euclidean distances, intraclass correlation coefficients (ICCs), Bland-Altman analysis, and equivalence testing (linear mixed effects model) with a predefined equivalence margin of ± 1°/1 mm. RESULTS: Analysis of reliability for CBCT vs. MRI (intra-rater I/intra-rater II/inter-rater) revealed Euclidean distances of 0.86/0.86/0.98 mm vs. 0.93/0.99/1.10 mm for landmarks, ICCs of 0.990/0.980/0.986 vs. 0.982/0.978/0.980 for angles, and ICCs of 0.992/0.988/0.989 vs. 0.991/0.985/0.988 for distances. Bland-Altman analysis showed high levels of agreement between CBCT and MRI with bias values (95% levels of agreement) of 0.03° (- 1.49; 1.54) for angles and 0.02 mm (- 1.44; 1.47) for distances. In the linear mixed effects model, the mean values of CBCT and MRI measurements were equivalent. CONCLUSION: This feasibility study indicates that MRI enables reliable 3D cephalometric analysis with excellent agreement to corresponding measurements on CBCT. Thus, MRI could serve as a non-ionizing alternative to CBCT for treatment planning and monitoring in orthodontics as well as oral and maxillofacial surgery. KEY POINTS: • Clinically established 3D cephalometric measurements performed on MRI are highly reliable and show an excellent agreement with CBCT (gold standard). • The MRI technique applied in this study could be used as a non-ionizing diagnostic tool in orthodontics as well as oral and maxillofacial surgery. • Since most patients benefiting from 3D cephalometry are young in age, the use of MRI could substantially contribute to radiation protection and open up new possibilities for treatment monitoring.

Evaluation of upper airway volume and craniofacial volumetric structures in obstructive sleep apnoea adults: A descriptive CBCT study.

OBJECTIVE: The aim of this investigation was to assess, with a descriptive three-dimensional evaluation, the volume of upper airway (UAWV) and the volume of craniofacial structures in adult patients suffering from obstructive sleep apnoea (OSA) and compare them to the corresponding findings in adults with no sleep disorders. MATERIALS AND METHODS: The sample consisted of 54 adult males, 27 suffering from OSA diagnosed by means of the Apnoea Hypopnea Index and 27 with no history of sleep disorders. All subjects had a cone beam computerized tomography scan performed with the same head position. UAWV was assessed with the Amira® software, and craniofacial volumes by means of a specially developed data-processing program, which allowed the construction of tetrahedrons using anatomical landmarks. Assessed volumes were naso-maxillary, cranium upper anterior, oral cavity, post-oral cavity, hyoid to mandible, and post-hyoid. SPSS (version 19.0) was used for the statistical analysis. The Levene's test for Equality of Variance, the t-test for Equality of Means and the Mann-Whitney test were used to evaluate the variables. The level of significance was set at P ≤ 0.05. RESULTS: The mean value of UAWV was smaller in the OSA group. The post-hyoid volume, the calculated posterior volume, and the ratio of posterior to total volume showed differences between the groups. CONCLUSIONS: Craniofacial structures did not show significant differences between the groups, but in the OSA group the posterior space released for upper airway was significantly bigger and UAWV was significantly smaller.

Accuracy of CBCT images in the volumetric assessment of residual root canal filling material: Effect of voxel size.

AIMS: Our aim was to compare three different voxel sizes of CBCT images for the determination of residual filling material volume in root canals when compared with micro CT. MATERIAL AND METHODS: Forty-two root canals of 14 extracted human maxillary molar teeth were retreated by using ProFile® instruments. Images were obtained after retreatment by using ProMax 3D Max CBCT at 3 different voxel sizes (1) High resolution (0.1 mm); (2) High definition (0.15 mm); and (3) Normal resolution (0.2 mm). Two observers measured volumes of residual filling materials in exported CBCT images by means of 3D Doctor Software. Micro CT measurements were served as gold standard. Mann-Whitney U test and Wilcoxon Test were used for the comparison of CBCT and micro CT measurements. Statistical significance was set at P < 0.05. RESULTS: No statistically differences were found between the two observers for all measurements (P > 0.05). There were no significant differences among different CBCT voxel sizes used (0.1 mm, 0.15 mm, and 0.2 mm) (P > 0.05). The Spearman correlation coefficients between CBCT at different voxel sizes significantly highly correlated with micro CT measurements for each observer (P < 0.05). Furthermore, no significant differences were found between the measurements obtained by the two observers in consideration to root canal location (P > 0.05). CONCLUSION: CBCT images may provide useful information in the volumetric assessment of the amount of residual filling material in root canals for retreatment procedures.

Variations of the Dose Distribution Between CT- and CBCT-based Plans for Oropharyngeal Cancer.

BACKGROUND/AIM: The parotid glands in the head and neck are organs at risks (OARs) adjacent to high dose region and dose of OARs might be increased during the course of radiotherapy. The influence factors of the dose distribution for the parotid glands were investigated in terms of weight loss and mandibular rotation for head and neck cancers treated with volumetric modulated arc therapy (VMAT). PATIENTS AND METHODS: Ten oropharyngeal cancer patients (OPC) who underwent VMAT were enrolled. The dose volume histogram (DVH) parameters of the parotid glands and planning target volume (PTV) were compared between the planning computed tomography (CT) and the on board imager (OBI) at 1, 5, 10, 15, and 20 fractions. RESULTS: The variation of dose distribution in PTV was not observed in both factors. The relationship between the mandibular rotation and dose difference for the right and left parotid glands (linear regression, r2=0.1577 and -0.689) showed a slighty stronger correlation with dose difference than the weight loss (linear regression, r2=-0.079 and -0.547). CONCLUSION: The mandibular rotation tends to have a large influence on dose distribution of the parotid glands for head and neck cancers treated with VMAT.