Patient movement and motion artefacts in cone beam computed tomography of the dentomaxillofacial region: a systematic literature review

Low-dose CBCT protocols in implant dentistry: a systematic review

OBJECTIVE

To evaluate the state-of-the-art evidence for applying low-dose CBCT protocols in 3 stages of implant therapy (planning, insertion, and follow-up examination of peri-implantitis) and assess the overall body of evidence presented in the literature.

STUDY DESIGN

The search was conducted in the MEDLINE/Pubmed and Scopus databases. Studies comparing low-dose CBCT protocols to a relevant reference standard in relation to any stage of implant therapy were included. Data extraction and quality assessment were performed for all included studies.

RESULTS

Sixteen studies were included. Low-dose protocols were reported to result from reduction of the exposure parameters of kV, mA, resolution (through increased voxel size), exposure time, and scanning trajectory. The current literature suggests that low-dose CBCT protocols perform similarly in the 3 stages of implant therapy compared to higher resolution protocols regarding objective measurements, with adverse impacts mostly on subjective assessment of image quality. The results also suggest that CBCT-based bone measurements are similar to direct measurements, independent of the imaging protocol. Reduction in all parameters except kV seems feasible as the basis of low-dose CBCT protocols for implant therapy.

CONCLUSIONS

The use of low-dose CBCT protocols does not impact objective image quality assessment in any stage of implant therapy. Clinical studies are needed to indicate if the reported results can be extrapolated to improve patient care in relation to the responsible use of ionizing radiation.

The effect on the performance of a dynamic navigation system of superimposing a standard tessellation language (STL) file obtained with an intraoral scan on a cone beam computer tomograph (CBCT). An experimental in vitro study

OBJECTIVES

To compare the accuracy and operative time of implant placement using a dynamic computer assisted implant surgery (dCAIS) system based on a cone beam computer tomography (CBCT) image, with and without superimposing a standard tessellation language (STL) file of an intraoral scan of the patient.

METHODS

Ten identical resin models simulating an upper maxilla with posterior edentulism were assigned to two groups. In the CBCT+STL group, a CBCT file and an intraoral STL file were superimposed and used for registration; in the CBCT group, registration was performed using CBCT images. Six implants were placed in each model using the Navident® dynamic navigation system. Anatomy registration was performed by tracing fiducial points on the CBCT or STL image, depending on the group. Preoperative and postoperative CBCT images were overlaid to assess implant placement accuracy.

RESULTS

Sixty implants were analyzed (30 implants in each group). 3D platform deviation was significantly lower (mean difference (MD): 0.17 mm; 95 % confidence interval (CI): 0.01 to 0.23; P = 0.039) in the CBCT+STL group (mean: 0.71 mm; standard deviation (SD): 0.29) than in the CBCT group (mean: 0.88 mm; SD: 0.39). The remaining accuracy outcome variables (angular deviation MD: -0.01; platform lateral deviation MD: 0.08 mm; apex global MD: 0.01 mm; apex depth MD: 0.33 mm) and surgery time (MD: 3.383 min.) were similar in both groups (p > 0.05).

CONCLUSIONS

The introduction of an intraoral scan (STL) seems to reduce deviations slightly in dental implant placement with dCAIS systems. However, the clinical repercussion of this improvement is questionable.

CLINICAL SIGNIFICANCE

Superimposing an intraoral scan on the CBCT image does not seem to increase the accuracy of dCAIS systems but can be useful when radiographic artifacts are present.

Efficacy of the CALM® Algorithm in Reducing Motion-Induced Artifacts in CBCT Imaging: A Fractal Dimension Analysis of Trabecular Bone

OBJECTIVE

The primary goal of this investigation was to ascertain the efficacy of the CALM® motion artifact reduction algorithm in diminishing motion-induced blurriness in Cone Beam Computed Tomography [CBCT] images. The assessment was conducted through Fractal Dimension [FD] analysis of the trabecular bone.

METHODS AND MATERIALS

A desiccated human mandible was subjected to Planmeca ProMax 3D® scanning under eight distinct protocols, marked by variations in motion presence [at 5, 10, and 15 degrees] and the deployment of CALM®. In every scan, five distinct regions of interest [ROIs] were designated for FD analysis, meticulously avoiding tooth roots or cortical bone. The FD was computed employing the box-counting method with Image-J 1.53 software.

RESULTS

Our findings reveal that a 5-degree motion does not significantly disrupt FD analysis, while a 10-degree motion and beyond exhibit statistical differences and volatility among the sites and groups. A decreased FD value, signifying a less intricate or "rough" bone structure, correlated with amplified motion blurriness. The utilization of CALM® software seemed to counteract this effect in some instances, reconciling FD values to those akin to the control groups. Nonetheless, CALM®'s efficacy differed across sites and motion degrees. Interestingly, at one site, CALM® application in the absence of motion resulted in FD values considerably higher than all other groups.

CONCLUSION

The study indicates that motion, particularly at 10 degrees or more, can considerably impact the FD analysis of trabecular bone in CBCT images. In some situations, the CALM® motion artifact reduction algorithm can alleviate this impact, though its effectiveness fluctuates depending on the site and degree of motion. This underscores the necessity of factoring in motion and the employment of artifact reduction algorithms during the interpretation of FD analysis outcomes in CBCT imaging. More research is necessary to refine the application of such algorithms and to comprehend their influence on different sites under varying motion degrees.

A systematic review comparing the effective radiation dose of musculoskeletal cone beam computed tomography to other diagnostic imaging modalities

PURPOSE

Cone-Beam CT (CBCT) is well established in orofacial diagnostic imaging and is currently expanding into musculoskeletal applications. This systematic review sought to update the knowledge base on radiation dose comparisons between imaging modalities in MSK imaging and consider how research studies have reported dose measures.

METHODS

This review utilised a database search and an online literature tool. Studies with potential relevance were screened then before full text review, each performed by two independent reviewers, with a third independent reviewer available for conflicts. Data was extracted using a bespoke tool created within the literature tool.

RESULTS

21 studies were included in the review which compared CBCT with MSCT (13), conventional radiography (1), or both (7). 19 studies concluded that CBCT provided a reduced radiation dose when compared with MSCT: the factor of reduction ranging from 1.71 to 50 with an average of 12. Studies comparing CBCT to DR found DR to have an average dose reduction of 4.55.

CONCLUSIONS

The claims that CBCT produces a lower radiation dose than MSCT is borne out with most studies confirming doses less than half that of MSCT. Fewer studies include DR as a comparator but confirm that CBCT results in a higher effective dose on average, with scope for CBCT to provide an equivalent radiation dose. This review highlighted a need for consistency in methodology when conducting studies which compare radiation dose across different technologies. Potential solutions lie outside the scope of this review, likely requiring multi-discipline approach to ensure a cohesive outcome.

The current role and future potential of digital diagnostic imaging in implant dentistry: A scoping review

OBJECTIVES

Diagnostic imaging is crucial for implant dentistry. This review provides an up-to-date perspective on the application of digital diagnostic imaging in implant dentistry.

METHODS

Electronic searches were conducted in PubMed focusing on the question 'when (and why) do we need diagnostic imaging in implant dentistry?' The search results were summarised to identify different applications of digital diagnostic imaging in implant dentistry.

RESULTS

The most used imaging modalities in implant dentistry include intraoral periapical radiographs, panoramic views and cone beam computed tomography (CBCT). These are dependent on acquisition standardisation to optimise image quality. Particularly for CBCT, other technical parameters (i.e., tube current, tube voltage, field-of-view, voxel size) are relevant minimising the occurrence of artefacts. There is a growing interest in digital workflows, integrating diagnostic imaging and automation. Artificial intelligence (AI) has been incorporated into these workflows and is expected to play a significant role in the future of implant dentistry. Preliminary evidence supports the use of ionising-radiation-free imaging modalities (e.g., MRI and ultrasound) that can add value in terms of soft tissue visualisation.

CONCLUSIONS

Digital diagnostic imaging is the sine qua non in implant dentistry. Image acquisition protocols must be tailored to the patient's needs and clinical indication, considering the trade-off between radiation exposure and needed information. growing evidence supporting the benefits of digital workflows, from planning to execution, and the future of implant dentistry will likely involve a synergy between human expertise and AI-driven intelligence. Transiting into ionising-radiation-free imaging modalities is feasible, but these must be further developed before clinical implementation.

Low-dose, standard, and high-resolution cone beam computed tomography for alveolar bone measurements related to implant planning: An ex vivo study in human specimens

AIM

To evaluate the performance of low-dose cone beam computed tomography (CBCT) protocols with regard to linear bone measurements in the posterior mandible for implant planning compared with higher dose protocols.

MATERIALS AND METHODS

Forty-two edentulous posterior sites in human cadaveric mandibles were imaged in three CBCT scanners using three or four protocols with varying exposure parameters to achieve lower dose. Co-registration was performed to generate sagittal and cross-sectional image sections representative of the implant site. Three observers measured bone height, from the alveolar crest to the mandibular canal, and width, three mm from the top of the alveolar crest. Intra- and interobserver reproducibility were assessed for the cases rated as nonmeasurable as well as for completed measurements. The measurements were analyzed using paired t-tests for differences among the CBCT protocols and the frequency distribution of nonmeasurable cases with a Pearson Chi-square test.

RESULTS

Reproducibility for registering nonmeasurable cases varied among observers; however, no consistent significant differences were found in the frequency distribution of these cases among observers, units, and protocols. Intraclass correlation coefficients (ICC) were >0.9 for all measurements of bone height and width. Mean differences of <0.5 mm were found regardless of protocol; however, one observer did in some cases produce larger differences.

CONCLUSION

Linear bone measurements did not differ significantly and could be performed with excellent reliability, using low-dose CBCT protocols compared with standard and high-resolution ones. Varying approaches for rating nonmeasurable cases were found, indicating differences in diagnostic strategies related to implant planning among observers.

The Utility of Cone Beam Computed Tomography Scans in Diagnosing and Treating Anterior Lesions of the Maxilla and Mandible

BACKGROUND

The standard screening protocol for radiographic examination in dentistry as per the American Dental Association recommendations is a panoramic radiograph (PAN) and four horizontal bitewings. PAN inherently suffers from several shortcomings like the superimposition of anatomic structures, especially of the cervical spine that obscures a significant portion of the anterior maxilla and mandible. This region has a significant amount of pathology that is not adequately imaged. Three-dimensional (3D) imaging provides circumferential information on the area of interest and adds value to the diagnosis and treatment planning of pathology, especially in the anterior maxilla and mandible. However, there is not an adequate number of well-designed studies that articulate the true value addition of 3D imaging for the evaluation of this region.

OBJECTIVES

The objective of this study is to evaluate the value addition of 3D imaging in diagnosing pathologies in the anterior maxilla and mandible when compared to two-dimensional PAN.

MATERIALS AND METHODS

A total of 25 cases that had a diagnosis of anterior pathology and had both a PAN and a cone beam computed tomography (CBCT) scan were collected for this study. An institutional review board approval to retrospectively evaluate these data was obtained. The PAN and CBCT scans were randomly evaluated by a second-year dental student, an oral and maxillofacial radiology resident in training, and a board-certified oral radiologist. The scans were evaluated using a three-point modified Likert scale, where 1 represents "not visible or clear," 2 represents "visible but not clear," and 3 represents "visible and clear." The lesions were evaluated for characteristics like lesion location, size & shape, internal contents, borders of the lesion, cortical integrity, locularity, and effect on adjacent structures like root resorption. After the evaluation was completed, a comparison of the lesion diagnosis was done with histopathology to confirm the diagnosis. The evaluators were also asked to comment on the specific feature that 3D imaging provided that added value to the case. Kappa analysis was done to evaluate inter-operator reliability.

RESULTS

PAN demonstrated significantly lower efficacy in identifying and diagnosing lesions. Only 56% of cases were analyzed using PAN, with 44% deemed undetectable or poorly visualized. These challenging cases necessitated CBCT scans for accurate diagnosis, which successfully diagnosed all 25 cases. The p-value of 0.0002 for PAN implies a highly significant difference from histopathology, suggesting the distinctions are not due to chance. Conversely, the p-value of 0.3273 for CBCT implies that observed differences may be random, lacking sufficient evidence to reject the null hypothesis. CBCT scans consistently outperformed PAN in visualizing various lesion characteristics, underscoring their superior diagnostic capabilities.

CONCLUSIONS

In this study, with a small sample size, 3D imaging provided a significant value addition to the diagnosis and treatment planning by providing additional information regarding the location, extent, internal content, and effect on adjacent structures. The practical implications for clinical settings, along with comparisons to current literature, underscore the study's distinctiveness.

Repetition Rate of Scanning Due to Motion Artefacts in Cone-Beam Computed Tomography: a Retrospective Study

Objectives

The objective of this retrospective study was to investigate the incidence of repeated cone-beam computed tomography scans due to motion artefacts in a Turkish subpopulation.

Material and Methods

A total of 6364 patients' cone-beam computed tomography data were analysed retrospectively to identify repeated scans due to motion artefacts. Patients were divided into eight age groups: 1) < 10-year-olds, 2) 10 to 19-year-olds, 3) 20 to 29-year-olds, 4) 30 to 39-year-olds, 5) 40 to 49-year-olds, 6) 50 to 59-year-olds, 7) 60 to 69-year-olds, and 8) > 70 year-olds. Chi-square test was applied to evaluate the repetition rate of scans by age and gender groups. Statistical significance was set at P < 0.05.

Results

Repeated scans due to motion artefacts were observed in 1.96% of the patients. The repetition rate of scans was significantly higher in males than in females (P = 0.006). Furthermore, the repetition rate of scans was significantly higher in patients < 10 years old compared to the other age groups. However, there was no significant difference in the repetition rate of scans due to motion artefacts among the other age groups (P > 0.05).

Conclusions

The present findings suggest that patient age and gender are associated with repeated cone-beam computed tomography scans due to motion artefacts. Males and children under the age of 10 had more common repeated scans due to motion artefacts.

Indications and use of cone beam computed tomography in children and young individuals in a university-based dental hospital

BACKGROUND

The aim of this study was to evaluate the indications of cone beam computed tomography (CBCT) in children and young individuals in a university-based dental hospital and their association with age, gender and field of view.

METHODS

7131 CBCT scans, taken during 3-year period, were reviewed and a total of 649 pediatric patients (0-18 years) with complete request forms were included. Data related to gender, age, referring department, CBCT indications, field of view (FOV), region of interest (ROI), need for re-exposure and patients received more than one CBCT examination were recorded.

RESULTS

The mean age was 13.57 ± 3.52 years and "malocclusion and dentofacial anomaly" (28.7%) was the most common clinical indication. Facial trauma, dental trauma and supernumerary tooth in males; "malocclusion and dentofacial anomaly" and implant planning in females were recorded more frequently compared to other gender. Maxilla was the most frequently monitored ROI (35.1%) for patients. Small (≤ 10 cm) FOV was preferred in 58.1% of all patients. Large FOV was selected in the majority of patients who underwent CBCT scan for "malocclusion and dentofacial anomaly" (89.6%). The repeated scans constituted 2.3% of patients and 105 patients (16.2%) underwent multiple CBCT scans on different dates for mainly orthodontic follow-up.

CONCLUSIONS

The justification of CBCT scans was not fully compatible with current guidelines and mainly larger FOV was preferred. The number of CBCT examination in children and young individuals tends to increase.

TRIAL REGISTRATION NUMBER

Not applicable.

Review and recommendations on deformable image registration uncertainties for radiotherapy applications

Deformable image registration (DIR) is a versatile tool used in many applications in radiotherapy (RT). DIR algorithms have been implemented in many commercial treatment planning systems providing accessible and easy-to-use solutions. However, the geometric uncertainty of DIR can be large and difficult to quantify, resulting in barriers to clinical practice. Currently, there is no agreement in the RT community on how to quantify these uncertainties and determine thresholds that distinguish a good DIR result from a poor one. This review summarises the current literature on sources of DIR uncertainties and their impact on RT applications. Recommendations are provided on how to handle these uncertainties for patient-specific use, commissioning, and research. Recommendations are also provided for developers and vendors to help users to understand DIR uncertainties and make the application of DIR in RT safer and more reliable.

CBCT in contemporary endodontics

Cone-beam computed tomography (CBCT) is a three-dimensional imaging modality which can aid endodontic diagnosis and treatment planning. While there are guidelines available describing the indications, there are divergent philosophies on when this technology should be applied in clinical practice. This paper reviews the applications of CBCT including the clinical relevance of parameters which can be assessed, highlights the limitations of this technology, and provides guidance on how to maximise its clinical utility.

Effect of a Motion Artifact Correction System on Cone-Beam Computed Tomography Image Characteristics

OBJECTIVES

Determine the effect of the motion correction system on cone-beam computed tomography (CBCT) image quality parameters, artifacts, and contrast-to-noise ratio (CNR) using different motion settings.

MATERIALS AND METHODS

A customized phantom insert array was prepared using SEDENTEX CT IQ Phantom (Leeds Test Objects, Yorkshire, England) stabilized over a rotating electric turntable. Thirty baseline CBCT scans were acquired with standardized technique factors on the ProMax 3D (Planmeca, Helsinki, Finland) machine using combinations of different motion settings, including no motion, three- and six-degree motion, and with and without the use of a motion correction system. The standardized images were exported to ImageJ software. Image quality parameters, artifacts, and CNR values were evaluated and compared among the different acquisition settings.

RESULTS

The use of the motion correction system algorithm compared with the different motion settings showed a statistically significant difference for all the parameters (p<0.05) except for artifact values for six-degree motion (p<0.07). The effect of different motion settings on the parameters was not statistically significant.

CONCLUSION

The use of a motion correction system, a proprietary algorithm-based system incorporated in the ProMax 3D CBCT unit, deteriorates the image quality characteristics evaluated in this in vitro study, namely artifact value and CNR. Its use in clinical settings might be limited to situations where patient motion is expected and appropriate head stabilization is not possible due to age or disease.

Pipeline for Automated Processing of Clinical Cone-Beam Computed Tomography for Patient-Specific Temporal Bone Simulation: Validation and Clinical Feasibility

OBJECTIVE

Patient-specific simulation allows the surgeon to plan and rehearse the surgical approach ahead of time. Preoperative clinical imaging for this purpose requires time-consuming manual processing and segmentation of landmarks such as the facial nerve. We aimed to evaluate an automated pipeline with minimal manual interaction for processing clinical cone-beam computed tomography (CBCT) temporal bone imaging for patient-specific virtual reality (VR) simulation.

STUDY DESIGN

Prospective image processing of retrospective imaging series.

SETTING

Academic hospital.

METHODS

Eleven CBCTs were selected based on quality and used for validation of the processing pipeline. A larger naturalistic sample of 36 CBCTs were obtained to explore parameters for successful processing and feasibility for patient-specific VR simulation.Visual inspection and quantitative metrics were used to validate the accuracy of automated segmentation compared with manual segmentation. Range of acceptable rotational offsets and translation point selection variability were determined. Finally, feasibility in relation to image acquisition quality, processing time, and suitability for VR simulation was evaluated.

RESULTS

The performance of automated segmentation was acceptable compared with manual segmentation as reflected in the quantitative metrics. Total time for processing for new data sets was on average 8.3 minutes per data set; of this, it was less than 30 seconds for manual steps. Two of the 36 data sets failed because of extreme rotational offset, but overall the registration routine was robust to rotation and manual selection of a translational reference point. Another seven data sets had successful automated segmentation but insufficient suitability for VR simulation.

CONCLUSION

Automated processing of CBCT imaging has potential for preoperative VR simulation but requires further refinement.

Accuracy of intraoral real-time navigation versus static, CAD/CAM-manufactured pilot drilling guides in dental implant surgery: an in vitro study

Background

Nowadays, 3D planning and static for dynamic aids play an increasing role in oral rehabilitation of the masticatory apparatus with dental implants. The aim of this study is to compare the accuracy of implant placement using a 3D-printed drilling guide and an intraoral real-time dynamic navigation system.

Methods

A total of 60 implants were placed on 12 partially edentulous lower jaw models. 30 were placed with pilot drilling guides, the other half with dynamic navigation (DENACAM^®). In addition, implant placement in interdental gaps and free-end situations were investigated. Accuracy was assessed by cone-beam computed tomography (CBCT).

Results

Both systems achieved clinically acceptable results, yet more accurate results regarding the offset of implant base and tip in several spatial dimensions were achieved using drilling guides (each p < 0.05). With regard to angulation, real-time navigation was more precise (p = 0.0016). Its inaccuracy was 3°; the template-guided systems was 4.6°. Median horizontal deviation was 0.52 mm at base and 0.75 mm at tip using DENACAM^®. When using the pilot drill guide, horizontal deviation was 0.34 mm in the median and at the tip by 0.59 mm. Regarding angulation, it was found that the closer the drill hole was to the system's marker, the better navigation performed. The template did not show this trend (p = 0.0043; and p = 0.0022).

Conclusion

Considering the limitations of an in vitro study, dynamic navigation can be used be a tool for reliable and accurate implantation. However, further clinical studies need to follow in order to provide an evidence-based recommendation for use in vivo.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40729-022-00430-6.

Evaluation of the dosimetry and centralization of scout-view function in CBCT

This study evaluated the centralization of the region of interest (ROI) in acquisition of the CBCT images, when the freely positionable scout-view (SV) function is applied. Additionally, the dosimetry of the acquired images was assessed in the SV function alone as well as in complete tomographic image in two different fields of view (FOV) (50x50 and 78x150mm). A three-location device was created to accommodate the dosimeters and the specimens, in the right, middle and left location during image acquisition. For dose assessment, thermoluminescent dosimeters were irradiated within the FOV and analyzed in a portable reader. For ROI evaluation, three specimens of gutta-percha stick were placed on the same device and the CT scans were acquired (CBCT OP 300 Maxio device, 90kV, 13mA, 85 µm voxel size, FOV of 50X50mm), with and without the SV, in three positions (3-9, 1-7 and 5-11 o’clock), simulating different regions of the mouth. Two image evaluations were performed, an objective and subjective. There was a slight percentage increase (1.36% to 1.40%) of the radiation dose with the use of SV. The distances were significantly greater in the images acquired without SV (p < 0.05). Every image obtained with SV was classified as being at the FOV’s center. In conclusion, the results demonstrated that SVs function is effective to centralize the ROI in the FOV, increasing the scan precision and avoiding repetitions due to positioning errors.

Prevalence and morphology of C-shaped and non-C-shaped root canal systems in mandibular second molars

BACKGROUND

There are no cone-beam computed tomography (CBCT)-based data on the anatomy of mandibular second molars in an Australian population. This study investigated the prevalence and descending morphology of mandibular second molars with and without C-shaped canals using retrospective analysis of CBCT scans.

METHODS

Scans from 715 patients were screened for the presence of C-shaped canals and assessed for cross-sectional configuration at 5 axial levels. Non-C-shaped molars were assessed for other morphological characteristics. Data were modelled against patient, tooth and CBCT scan characteristics.

RESULTS

A total of 1278 teeth from 657 patients were evaluated. The overall prevalence of C-shaped canals was 13%. Cross-sectional configuration of C-shaped canals was variable, with an average of 2.8 unique cross-sections per tooth. Non-C-shaped teeth were predominantly Vertucci Type II (60%) and Type IV (29%) configurations in mesial roots, and Type I (91%) in distal roots. Additional roots occurred in 4.3% of teeth and there was a significant association between radix paramolaris and distal root bifurcation (P < 0.001).

CONCLUSIONS

Cross-sectional analysis confirmed the complexity and variability of C-shaped canals. Clinicians should be cognisant of the prevalence and variability of C-shaped root canal morphology and how this may affect endodontic treatment. © 2022 Australian Dental Association.

Reference-free learning-based similarity metric for motion compensation in cone-beam CT

Purpose. Patient motion artifacts present a prevalent challenge to image quality in interventional cone-beam CT (CBCT). We propose a novel reference-free similarity metric (DL-VIF) that leverages the capability of deep convolutional neural networks (CNN) to learn features associated with motion artifacts within realistic anatomical features. DL-VIF aims to address shortcomings of conventional metrics of motion-induced image quality degradation that favor characteristics associated with motion-free images, such as sharpness or piecewise constancy, but lack any awareness of the underlying anatomy, potentially promoting images depicting unrealistic image content. DL-VIF was integrated in an autofocus motion compensation framework to test its performance for motion estimation in interventional CBCT.Methods. DL-VIF is a reference-free surrogate for the previously reported visual image fidelity (VIF) metric, computed against a motion-free reference, generated using a CNN trained using simulated motion-corrupted and motion-free CBCT data. Relatively shallow (2-ResBlock) and deep (3-Resblock) CNN architectures were trained and tested to assess sensitivity to motion artifacts and generalizability to unseen anatomy and motion patterns. DL-VIF was integrated into an autofocus framework for rigid motion compensation in head/brain CBCT and assessed in simulation and cadaver studies in comparison to a conventional gradient entropy metric.Results. The 2-ResBlock architecture better reflected motion severity and extrapolated to unseen data, whereas 3-ResBlock was found more susceptible to overfitting, limiting its generalizability to unseen scenarios. DL-VIF outperformed gradient entropy in simulation studies yielding average multi-resolution structural similarity index (SSIM) improvement over uncompensated image of 0.068 and 0.034, respectively, referenced to motion-free images. DL-VIF was also more robust in motion compensation, evidenced by reduced variance in SSIM for various motion patterns (σDL-VIF = 0.008 versusσgradient entropy = 0.019). Similarly, in cadaver studies, DL-VIF demonstrated superior motion compensation compared to gradient entropy (an average SSIM improvement of 0.043 (5%) versus little improvement and even degradation in SSIM, respectively) and visually improved image quality even in severely motion-corrupted images.Conclusion: The studies demonstrated the feasibility of building reference-free similarity metrics for quantification of motion-induced image quality degradation and distortion of anatomical structures in CBCT. DL-VIF provides a reliable surrogate for motion severity, penalizes unrealistic distortions, and presents a valuable new objective function for autofocus motion compensation in CBCT.

Valid 3D surface superimposition references to assess facial changes during growth

Currently, the primary techniques applied for the assessment of facial changes over time utilize 2D images. However, this approach has important limitations related to the dimensional reduction and the accuracy of the used data. 3D facial photography has been recently introduced as a risk-free alternative that overcomes these limitations. However, the proper reference areas that should be used to superimpose serial 3D facial images of growing individuals are not yet known. Here, we tested various 3D facial photo superimposition reference areas and compared their outcomes to those of a standard anterior cranial base superimposition technique. We found that a small rectangular area on the forehead plus an area including the middle part of the nose and the lower wall of the orbital foramen provided comparable results to the standard technique and showed adequate reproducibility. Other reference areas that have been used so far in the literature were less reliable. Within the limitations of the study, a valid superimposition reference area for serial 3D facial images of growing individuals is suggested. The method has potential to greatly expand the possibilities of this highly informative, risk free, and easily obtained 3D tool for the assessment of facial changes in growing individuals.

The effect of triangular cross-section neck design on crestal bone stability in the anterior mandible: A randomized, controlled, split-mouth clinical trial

OBJECTIVES

This randomized controlled trial aimed to compare crestal bone loss (CBL) and buccal bone thickness (BBT) around triangular cross-section neck (TN) to round neck (RN) implants retaining mandibular overdentures one year after loading, using cone beam computed tomography (CBCT).

MATERIAL AND METHODS

Twenty edentulous patients receiving 40 implants with similar diameters were randomly assigned to the RN and TN groups. Clinical buccal bone thickness (CBBT) around the implants was measured with a caliper at baseline. A resonance frequency analyzer was used to measure the implant stability quotient (ISQ) at the baseline and two months after insertion. Pocket probing depths (PPD), plaque index (PI), and gingival index (GI) were also recorded at postoperative months 2, 6, and 12. CBCT was used to evaluate proximal CBL and BBT at three levels (0, -2, and -4 mm) one year after loading.

RESULTS

No implant loss was observed during the follow-up period. No significant differences in CBBT, ISQ values, and scores for PPD, PI, and GI between the two groups were observed at any time (p > .05). BBT was also comparable one year after loading (p > .05). The mean ± SD proximal CBL one year after loading was 0.58 ± 0.36 mm for TN and 0.91 ± 0.59 mm for RN (p < .01).

CONCLUSIONS

This study found better crestal bone preservation in the implants with the novel neck design than conventional neck design in the anterior mandible after a follow-up of one year. However, it may not be clinically noticeable.

Reject Rates of Radiographic Images in Dentomaxillofacial Radiology: A Literature Review

This report surveyed the image reject rates of intra-oral, extra-oral, and cone-beam computed tomography (CBCT) imaging in the academic literature. PubMed, Web of Science, and Scopus databases were queried in mid-April 2021. Manual screening of the reference lists of the identified publications was performed to identify papers missed from the database search. All publications returned by the searches were initially included. Exclusion criteria included irrelevance, no reporting of reject rate, no access to the article, and not original article. The total number of images and the number of rejects were recorded for each type of radiographic images. Factors and commonest errors associated with the rejects were recorded. Twenty-six original articles were identified and reviewed. The average reject rate was 11.25% for bitewings, 16.38% for periapicals, 4.10% for panoramics, 6.08% for lateral cephalography, and 2.77% for CBCT. Positioning error and patient movement were two common reasons for the rejects. The average reject rates computed from data pooled across studies should form the reference values for quality assurance programs to follow. Future reject analysis studies should report more radiographic parameters such as type of collimation for intra-oral radiography and patient posture for CBCT.

Evaluation of the combined assessment of two digital enhancement filters in periapical radiographs obtained with different projection angles in the detection of simulated dental root fractures

OBJECTIVE

To evaluate the diagnostic efficacy of the combined assessment of the original radiographic image with the Invert or Emboss digital enhancement filters in periapical radiographs obtained with different horizontal projection angles in the detection of simulated dental root fracture.

MATERIALS AND METHODS

Thirty-four single-rooted teeth were selected, out of which 17 teeth were subjected to root fracture. Each tooth was individually placed in an empty socket of a dry human maxilla or mandible and X-rayed following the paralleling technique at three horizontal projections: mesial, right angle, distal. Then, the Invert and Emboss enhancement filters were applied. Five examiners independently evaluated all the images and rated the fractures using a 5-point scale. Weighted kappa test assessed the intra- and interexaminer agreements. Diagnostic values were calculated and the areas under the receiver operating characteristic curve (AUC) were compared using two-way ANOVA with Tukey test as post hoc (α = 0.05).

RESULTS

The inter- and intraexaminer agreement ranged from moderate to almost perfect and from substantial to almost perfect, respectively. Diagnostic values were considerably high for all conditions with no significant difference between the AUC values (p > 0.05).

CONCLUSIONS

The combined use of the original radiographic image with the Invert or Emboss digital enhancement filters in periapical radiographs obtained with different projection angles did not influence the detection of simulated dental root fracture.

Recent Advances in Cone-beam CT in Oral Medicine

BACKGROUND

The cone-beam computed tomography (CBCT) technology has continuously evolved since its appearance in oral medicine in the early 2000s.

OBJECTIVES

To present recent advances in CBCT in oral medicine: i) selection of recent and consensual evidence-based sources, ii) structured summary of the information based on an iterative framework and iii) compliance with ethical, public health and patient-centered concerns.

MAIN FINDINGS

We will focus on technological advances, such as sensors and reconstruction algorithms used to improve the constant quality of the image and dosimetry. CBCT examination is now performed in almost all disciplines of oral medicine: currently, the main clinical disciplines that use CBCT acquisitions are endodontics and oral surgery, with clearly defined indications. Periodontology and ear, nose and throat medicine are more recent fields of application. For a given application and indication, the smallest possible field of view must be used. One of the major challenges in contemporary healthcare is ensuring that technological developments do not take precedence over admitted standards of care. The entire volume should be reviewed in full, with a systematic approach. All findings are noted in the patient's record and explained to the patient, including incidental findings. This presupposes the person reviewing the images is sufficiently trained to interpret such images, inform the patient and organize the clinical pathway, with referrals to other medical or oral medicine specialties as needed.

CONCLUSION

A close collaboration between dentists, medical physicists, radiologists, radiographers and engineers is critical for all aspects of CBCT technology.

A motion correction approach for oral and maxillofacial cone-beam CT imaging

Patient movement affects image quality in oral and maxillofacial cone-beam computed tomography imaging. While many efforts are made to minimize the possibility of motion during a scan, relatively little attention has been given to motion correction after acquisition. We propose a novel method which can improve the image quality after an oral and maxillofacial scan. The proposed method is based on our previous work and is a retrospective motion estimation and motion compensation (ME/MC) approach that iteratively estimates and compensates for rigid pose change over time. During motion estimation, image update and motion update are performed alternately in a multi-resolution scheme to obtain the motion. We propose use of a feature-based motion update and patch-based image update in the iterative estimation process, to alleviate the effect of limited scan field of view on estimation. During motion compensation, a fine-resolution image reconstruction was performed with compensation for the estimated motion. The proposed ME/MC method was evaluated with simulations, phantom and patient studies. Two experts in dentomaxillofacial radiology assessed the diagnostic importance of the resulting motion artifact suppression. The quality of the reconstructed images was improved after motion compensation, and most of the image artifacts were eliminated. Quantitative analysis by comparison to a reference image and by calculation of a sharpness metric agreed with the qualitative observation. The results are promising, and further evaluation is required to assess the clinical value of the proposed method.

Effects of Groove Sealing of the Posterior Occlusal Surface and Offset of the Internal Surface on the Internal Fit and Accuracy of Implant Placements Using 3D-Printed Surgical Guides: An In Vitro Study

This study evaluated the internal fit and the accuracy of the implant placement position in order to determine how the surface shape of the tooth and the offset influence the accuracy of the surgical guide. The acquired digital data were analyzed in three dimensions using 3D inspection software. The obtained results confirmed that the internal fit was better in the groove sealing (GS) group (164.45 ± 28.34 μm) than the original shape (OS) group (204.07 ± 44.60 μm) (p < 0.001), and for an offset of 100 μm (157.50 ± 17.26 μm) than for offsets of 30 μm (206.48 ± 39.12 μm) and 60 μm (188.82 ± 48.77 μm) (p < 0.001). The accuracy of implant placement was better in the GS than OS group in terms of the entry (OS, 0.229 ± 0.092 mm; GS, 0.169 ± 0.061 mm; p < 0.001), apex (OS, 0.324 ± 0.149 mm; GS, 0.230 ± 0.124 mm; p < 0.001), and depth (OS, 0.041 ± 0.027 mm; GS, 0.025 ± 0.022 mm; p < 0.001). In addition, the entries (30 μm, 0.215 ± 0.044 mm; 60 μm, 0.172 ± 0.049 mm; 100 μm, 0.119 ± 0.050 mm; p < 0.001) were only affected by the amount of offset. These findings indicate that the accuracy of a surgical guide can be improved by directly sealing the groove of the tooth before manufacturing the surgical guide or setting the offset during the design process.

Two decades of research on CBCT imaging in DMFR - an appraisal of scientific evidence

OBJECTIVE

This article aims to appraise how scientific evidence related to CBCT has changed over the years, based on levels of evidence and diagnostic efficacy.

METHODS

A general search strategy was used in different databases (Pubmed, Embase, and Web of Science) to identify systematic reviews (SRs) on CBCT until November of 2020. The SRs included were divided according to different specialties of dentistry. A critical review of the articles was made, describing the level of evidence and efficacy.

RESULTS

In total, 75 articles were selected. There was an increase in the number of SRs on CBCT from 2014 onwards, as 83% of the SRs on this topic were published after 2013, and 72% between 2016 and to date. Twenty SRs (27%) performed meta-analysis. Only 28% of the SRs provided a detailed description of CBCT protocols. According to SR evidence, almost all specialties of dentistry have advanced concomitantly with the introduction of CBCT. The majority of SRs were related to clinical applications (level 2 of efficacy), followed by technical parameters (level 1 of efficacy). Only some CBCT models were mentioned in the SRs selected.

CONCLUSION

Over the course of 20 years, SRs related to CBCT applications for a broad range of dental specialties have been published, with the vast majority of studies at levels 1 and 2 of diagnostic efficacy. Not all CBCT models available on the market have been scientifically validated. At all times, one should remain cautious as such not to simply extrapolate in vitro results to the clinical setting. Also, considering the wide variety of CBCT devices and protocols, reported results should not be overstated or generalized, as outcomes often refer to specific CBCT devices and protocols.

Objective assessment of the combined effect of exomass-related- and motion artefacts in cone beam CT

OBJECTIVES

To assess quantitatively the combined effect of exomass-related- and motion artefacts on voxel value parameters in cone beam CT (CBCT).

METHODS

A cylindrical phantom was manufactured, containing 21 tubes filled with a radiopaque solution, allowing the inclusion of three titanium implants in the periphery to induce exomass-related artefacts. The phantom was mounted on a robot simulating 0.75-, 1.5-, and 3 mm movements (nodding/lateral rotation/tremor). CBCT images with/without exomass and with/without movements were acquired in duplicate in three units: Cranex 3Dx, Orthophos SL-3D, and X1 (with motion-artefact correction). A cylindrical volume of interest was defined in each tube and voxel value mean and standard deviation were assessed. For each CBCT volume, the 21 mean voxel values were averaged providing the overall mean voxel value (MVV), and the standard deviation (among the 21 values) was calculated providing overall voxel value inhomogeneity (VVI). The standard deviation from each of the 21 volumes-of-interest were averaged, providing overall image noise (IN). The effect of the diverse tested situations was inferred from a repeated-measures analysis of variance, followed by Sidak's test (α = 0.05).

RESULTS

Overall, images acquired with exomass showed significantly (p ≤ 0.05) lower MVV, and higher VVI and IN. Motion artefacts aggravated exomass-related alterations. MVV and VVI were mostly affected by 3 mm nodding movements. Motion-artefact correction eliminated the deleterious effect of movement.

CONCLUSIONS

CBCT voxel-value parameters are altered by exomass-related artefacts, and this finding is aggravated in the presence of motion artefacts. Motion-artefact correction effectively eliminated the deleterious impact of movement.

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.

Head motion and perception of discomfort by young children during simulated CBCT examinations

OBJECTIVES

To assess the frequency and characteristics (number, complexity, and distance) of head movements, and the perception of discomfort during simulated CBCT examinations in children, considering units with different patient positioning method and head immobilization device combinations.

METHODS

Forty children (20 boys/20 girls, age range 10-14 years) were video-recorded during simulated CBCT examinations. Children were randomly allocated to a sequence of five CBCT units: Newtom-5G, Orthophos-SL, Cranex-3Dx (patient standing/sitting), and X1. The child scored his/her discomfort perception (visual scale) and the preferred/ill-favored unit. Three observers scored the videos (20% in duplicate): child movement (yes/no), number (<3/≥3/continuous), complexity (uniplanar/multiplanar) and distance (<3 mm/≥3 mm). κ statistics provided intra-/interobserver reproducibility. Severe/extreme motion was defined based on movement characteristics. Chi-square tests assessed the frequency differences of severe/extreme motion among the units, age and operator. Logistic regression analyses with severe/extreme motion as outcome were performed.

RESULTS

The range of intra- and inter-observer reproducibility for movement observation was 0.78-0.89 and 0.61-0.64, respectively. Between 60% (Newtom-5G) and 100% (X1) of children moved during the examination. Severe/extreme motion was significantly related to unit and age. There was significantly less severe/extreme motion, when the child was in the supine position with a foam headrest as head support. The younger the child, the higher the risk for severe/extreme motion. The majority of the children preferred the unit with the supine position and a foam headrest.

CONCLUSIONS

The prevalence of severe and extreme motion was associated with the unit's patient positioning method and head immobilization devices combined, and child age.

Prevalence and risk factors of root resorption of adjacent teeth in maxillary canine impaction, among untreated children and adolescents

OBJECTIVES

The aim of this retrospective study was to assess in maxillary canine impaction cases both the prevalence of root resorption of adjacent teeth among untreated children and adolescents, and its associated risk factors.

SUBJECTS AND METHODS

Sixty subjects (mean age 12.2 years; SD 1.9; range 8-17 years) with 83 displaced maxillary canines and without any past or ongoing orthodontic treatment were included in this study. The presence of root resorption was evaluated on images from a single cone beam computed tomography (CBCT) unit. Potential risk factors were measured on the CBCT images and on panoramic reconstructions of the 3D data sets. The sample was characterized by descriptive statistics and multiple logistic regressions were performed to predict root resorption.

RESULTS

Root resorption of at least one adjacent tooth was detected in 67.5 per cent of the affected quadrants. It was found that 55.7 per cent of the lateral incisors, 8.4 per cent of the central incisors, and 19.5 per cent of first premolars were resorbed. Of the detected resorptions, 71.7 per cent were considered slight, 14.9 per cent moderate, and 13.4 per cent severe. Contact between the displaced canine(s) and the adjacent teeth roots was the only identified statistically significant risk factor, all teeth being considered (odds ratio [OR] = 18.7, 95% confidence interval: 2.26-756, P < 0.01). An enlarged canine dental follicle, a peg upper lateral, or an upper lateral agenesis were not significantly associated with root resorption of adjacent teeth, nor were age nor gender.

CONCLUSIONS

Root resorption of adjacent teeth was detected in more than two-thirds of a sample of sixty untreated children and adolescents.

Comparison of radiographical characteristics and diagnostic accuracy of intraosseous jaw lesions on panoramic radiographs and CBCT

OBJECTIVE

To investigate the differences in imaging characteristics and the diagnostic accuracy of 225 intraosseous jaw lesions on panoramic radiographs (PAN) versus cone beam computed tomography (CBCT).

METHODS

225 sets of PAN and CBCT images with biopsy-proven histopathological diagnoses were retrospectively compared in terms of radiographic features and diagnostic accuracy. The imaging characteristics of PAN and CBCT were independently evaluated by two oral and maxillofacial radiologists who were required to answer 12 questions and provided up to three differential diagnoses with their confidence scores.

RESULTS

Odds ratios (ORs) were statistically significant for border cortication (OR = 1.521; p = .003) and border continuity (OR = 0.421; p = .001), involvement on neurovascular canals (OR = 2.424; p < .001), expansion (OR = 7.948; p < .001), cortical thinning (OR = 20.480; p < .001) as well as its destruction (OR = 25.022; p < .001) and root resorption (OR = 2.477; p < .001). Furthermore, imaging features in the posterior and mandibular regions showed better agreement than those in the anterior and maxillary regions, respectively. The diagnostic accuracy of the first differential diagnosis was higher on CBCT than on PAN (Observer 1:78.7 vs 64.4%; Observer 2: 78.7 vs 70.2% (p < .001)). The observers' confidence scores were also higher at CBCT interpretation compared with PAN.

CONCLUSIONS

CBCT demonstrated a greater number of imaging characteristics of intraosseous jaw lesions compared with PAN, especially in the anterior regions of both jaws and in the maxilla. Diagnostic accuracy is improved with CBCT compared to PAN, especially for lesions in the maxilla. Radiologists have greater confidence when using CBCT.

Head motion during cone-beam computed tomography: Analysis of frequency and influence on image quality

Purpose

Image artifacts caused by patient motion cause problems in cone-beam computed tomography (CBCT) because they lead to distortion of the 3-dimensional reconstruction. This prospective study was performed to quantify patient movement during CBCT acquisition and its influence on image quality.

Materials and Methods

In total, 412 patients receiving CBCT imaging were equipped with a wireless head sensor system that detected inertial, gyroscopic, and magnetometric movements with 6 dimensions of freedom. The type and amplitude of movements during CBCT acquisition were evaluated and image quality was rated in 7 different anatomical regions of interest. For continuous variables, significance was calculated using the Student t-test. A linear regression model was applied to identify associations of the type and extent of motion with image quality scores. Kappa statistics were used to assess intra- and inter-rater agreement. Chi-square testing was used to analyze the impact of age and sex on head movement.

Results

All CBCT images were acquired in a 10-month period. In 24% of the investigations, movement was recorded (acceleration: >0.10 [m/s²]; angular velocity: >0.018 [°/s]). In all examined regions of interest, head motion during CBCT acquisition resulted in significant impairment of image quality (P<0.001). Movement in the horizontal and vertical axes was most relevant for image quality (R²>0.7).

Conclusion

Relevant head motions during CBCT imaging were frequently detected, leading to image quality loss and potentially impairing diagnosis and therapy planning. The presented data illustrate the need for digital correction algorithms and hardware to minimize motion artefacts in CBCT imaging.

Through the quality kaleidoscope: reflections on research in dentomaxillofacial imaging

The REduce research Waste And Reward Diligence statement has highlighted how weaknesses in health research can produce misleading results and waste valuable resources. Research on diagnostic efficacy in the field of dentomaxillofacial radiology (DMFR) is no exception to these criticisms and could be strengthened by more robust study designs, consistent use of a core set of outcome measures and completeness in reporting. Furthermore, we advocate that everyone participating in collaborative research on clinical interventions subscribes to the importance of methodological quality in how imaging methods are used. The aim of this paper, therefore, is to present a guide to conducting high-quality research on diagnostic efficacy in DMFR.We initially propose a framework inspired by the hierarchical model of efficacy of Fryback and Thornbury, highlighting study designs, measures of analysis, completeness of reporting and established guidelines to assist in these aspects of research. Bias in research, and measures to prevent or limit it, are then described.It is desirable to climb the Fryback and Thornbury "ladder" from technical efficacy, via accuracy and clinical efficacy, to societal efficacy of imaging methods. Efficacy studies on the higher steps of the ladder may be difficult to perform, but we must strive to answer questions of how useful our methods are in patient management and assess benefits, risks, costs, ethical and social issues. With the framework of six efficacy levels as the structure and based on our experience, we present information that may facilitate quality enhancement of diagnostic efficacy research in DMFR.

Correlation between magnetic resonance imaging and cone-beam computed tomography for maxillary sinus graft assessment

Purpose

Little is known regarding the accuracy of clinical magnetic resonance imaging (MRI) protocols with acceptable scan times in sinus graft assessment. The aim of this study was to evaluate the correlations between MRI and cone-beam computed tomographic (CBCT) measurements of maxillary sinus grafts using 2 different clinical MRI imaging protocols.

Materials and Methods

A total of 15 patients who underwent unilateral sinus lift surgery with biphasic calcium phosphate were included in this study. CBCT, T1-weighted MRI, and T2-weighted MRI scans were taken 6 months after sinus lift surgery. Linear measurements of the maximum height and buccolingual width in coronal images, as well as the maximum anteroposterior depth in sagittal images, were performed by 2 trained observers using CBCT and MRI Digital Imaging and Communication in Medicine files. Microcomputed tomography (micro-CT) was also performed to confirm the presence of bone tissue in the grafted area. Correlations between MRI and CBCT measurements were assessed with the Pearson test.

Results

Significant correlations between CBCT and MRI were found for sinus graft height (T1-weighted, r=0.711 and P<0.05; T2-weighted, r=0.713 and P<0.05), buccolingual width (T1-weighted, r=0.892 and P<0.05; T2-weighted, r=0.956 and P<0.05), and anteroposterior depth (T1-weighted, r=0.731 and P<0.05; T2-weighted, r=0.873 and P<0.05). The presence of bone tissue in the grafted areas was confirmed via micro-CT.

Conclusion

Both MRI pulse sequences tested can be used for sinus graft measurements, as strong correlations with CBCT were found. However, correlations between T2-weighted MRI and CBCT were slightly higher than those between T1-weighted MRI and CBCT.

Comparison of Selected Anatomical and Treatment-related Diagnostic Parameters Estimated by Cone-Beam Computed Tomography and Digital Periapical Radiography in Teeth with Apical Periodontitis

Objectives

To compare selected anatomical and treatment-related diagnostic parameters estimated by cone-beam computed tomography and by digital periapical radiography in teeth with apical periodontitis, and to evaluate reliability of different examiners in interpretation of images obtained by both methods.

Material and Methods

Teeth with apical periodontitis were evaluated independently by 2 endodontists and 1 radiologist based on 128 cone-beam computed tomography (CBCT) and 162 digital periapical radiography (DPR) images. Anatomical (size, relation with root, location of periapical radiolucency) and treatment-related (canal obturation length, homogeneity, coronal seal) parameters were assessed. Fleiss kappa reflected inter-observer agreement while intra-examiner agreement was estimated by Cohen’s kappa. McNemar and McNemar-Bowker tests served for evaluation of differences between CBCT- and DPR-based estimates.

Results

Cohen’s kappa ranged from 0.62 to 1 for all examiners. Fleiss kappa values were nearly perfect for majority of parameters. Diagnostic discrepancy between methods was found for size of radiolucency that in 15 - 17% cases was larger, and in 25 - 28% smaller in DPR than in CBCT images. DPR revealed 20% of root canals scored as non-obturated while in CBCT - obturation present. Canal obturation was rated as homogenous by CBCT, while absent or non-homogenous by DPR, in 17 - 23%, and 11 - 14% of cases, respectively. Radiologist detected more root perforations in CBCT than in DPR images.

Conclusions

Good intra- and inter-examiner agreement for anatomical and treatment-related diagnostic parameters was achieved using cone-beam computed tomography and digital periapical radiography methods and demonstrated similar diagnostic capability, although variation regarding root perforations and canal obturation quality was observed.

An investigation into dose optimisation for imaging root canal anatomy using cone beam CT

OBJECTIVES

To identify a dose as low as diagnostically acceptable and a threshold level of image quality for cone beam CT (CBCT) imaging root canals, using maxillary first molar (M1M) second mesiobuccal (MB2) canals of varying complexity for two CBCT scanners.

METHODS

Dose-area product (DAP) and contrast-to-noise ratio (CNR) were measured for two scanners at a range of exposure parameters. Subjective-image-quality assessment at the same exposures was performed for three M1Ms of varying MB2 complexity, positioned in an anthropomorphic phantom. Nine raters (three endodontists, three dental radiologists and three junior staff) assessed canal visibility, using a 5-point confidence scale rating.

RESULTS

Identification of simple-moderate MB2 canal complexity was achieved at a range of protocols, with DAP values of ≥209.3 and ≥203.2 mGy cm² and CNRs of 3 and 7.6 for Promax^®3D and Accuitomo-F170^® respectively. For complex canal anatomy, target subjective image quality was not achieved, even at the highest DAP values for both scanners. Junior staff classified significantly more images as undiagnostic compared with senior staff (p = 0.043).

CONCLUSIONS

In this first study to address optimisation of CBCT imaging of root canal anatomy, a similar threshold dose for both scanners was identified for M1Ms with simple-moderate MB2 canal complexity. Increasing dose to enhance visualisation of more complex canal anatomy was ineffective. Selection of standard protocols (while avoiding lower kV/mA protocols) instead of high-resolution scans was a practical means of reducing patient dose. CNR is not a transferable measure of image quality.

Cone beam computed tomography in dentomaxillofacial radiology: a two-decade overview

OBJECTIVES

The aim of this study was to evaluate and summarise features of currently and formerly available cone beam CT (CBCT) devices from 1996 to 2019. Additionally, a recommendation for standardised reporting of CBCT characteristics was provided.

METHODS AND MATERIALS

Information about the features of all available CBCT devices was obtained from the manufacturers' available data. Moreover, site visits to newly developed CBCT machines' manufacturers were performed in order to obtain relevant information.

RESULTS

A total of 279 CBCT models from 47 manufacturers located in 12 countries (Brazil, China, Denmark, Finland, France, Germany, Italy, Japan, Republic of Korea, Slovakia, Thailand, and USA) could be listed. Overall, wide variations in CBCT features and technical specifications were identified.

CONCLUSIONS

CBCT in dentomaxillofacial radiology is a generic term applicable to a broad range of CBCT machines and features. Experimental outcomes and literature statements regarding radiation doses, imaging performance and diagnostic applicability of dental CBCT cannot be simply transferred from one CBCT model to another considering a wide variation in technical characteristics and clinical diagnostic performance. The information tabulated in the present study will be later provided on the International Association of DentoMaxilloFacial Radiology website (www.iadmfr.one).

Cone-beam computed tomography and its applications in dental and maxillofacial radiology

Cone-beam computed tomography (CBCT) was first used in dental and maxillofacial radiology (DMFR) at the end of the 1990s. Since then, it has been successfully established as the standard three-dimensional radiographic imaging technique in DMFR, with a wide variety of applications in this field. This manuscript briefly reviews the background information on the technology and summarises available data on effective dose and dose optimisation. In addition, typical clinical applications and indications of the technique in DMFR are presented.

Image-stitching artefacts and distortion in CCD-based cephalograms and their association with sensor type and head movement: ex vivo study

OBJECTIVES

To assess presence and severity of image-stitching artefacts and distortion in lateral cephalograms acquired by CCD-based sensors and their association with movement.

METHODS

A human skull was mounted on a robot simulating five head movement types (anteroposterior translation/lifting/nodding/lateral rotation/tremor), at three distances (0.75/1.5/3 mm), based on two patterns (skull returning/not returning to the initial position, except for tremor). Three cephalometric units, two ProMax-2D (Planmeca Oy, Finland), one with Dimax-3 (D-3) and one with Dimax-4 (D-4) sensor, and one Orthophos-SL (ORT, Dentsply-Sirona, Germany), acquired cephalograms during the predetermined movements, in duplicate (54 with movement and 28 controls with no movement per unit). One observer assessed the presence of an image-stitching line (none/thin/thin with vertical stripes or thick), misalignment between the anatomical structure display (none/<1/1-3/>3 mm), and distortion in each image quadrant (present/absent), in duplicate. Severe image-stitching artefacts were defined for images scored with a thin line with vertical stripes or thick line and/or misalignment between anatomical structure display ≥1 mm. Severe distortion was defined for images scored with distortion in both anterior quadrants of the skull. κ-statistics provided intraobserver agreement.

RESULTS

Intraobserver reproducibility was >0.8 (all assessed parameters). Severe image-stitching artefacts were scored in 70.4 and 18.5% of D-3 and D-4 movement images, respectively. Severe distortion was scored in 64.8% of D-3, 5.6% of D-4 and 37% of ORT movement images. Neither severe image-stitching artefacts nor severe distortion were observed in control images.

CONCLUSION

Sensor type, movement type, distance and pattern affected presence and severity of image-stitching artefacts and distortion in CCD-based cephalograms.

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.

Primary oral manifestation of Langerhans cell histiocytosis refractory to conventional therapy but susceptible to BRAF-specific treatment: a case report and review of the literature

Langerhans cell histiocytosis (LCH) is a diagnostic and therapeutic challenge. We report on a rare case of its primary oral manifestation that was treated successfully with the BRAF-specific agent, vemurafenib, after insufficient standard LCH treatment. This case underlines the importance of proper diagnosis and the evaluation of targeted therapy as a valuable tool in LCH treatment. Furthermore, the close collaboration of surgeons, oncologists, and dentists is mandatory to ensure adequate treatment, restore the stomatognathic system in debilitating post-treatment situations, improve quality of life, and ensure effective disease control in infants and young patients.

Impact of movement and motion-artefact correction on image quality and interpretability in CBCT units with aligned and lateral-offset detectors

OBJECTIVES

To evaluate the impact of movement and motion-artefact correction systems on CBCT image quality and interpretability of simulated diagnostic tasks for aligned and lateral-offset detectors.

METHODS

A human skull simulating three diagnostic tasks (implant planning in the anterior maxilla, implant planning in the left-side-mandible and mandibular molar furcation assessment in the right-side-mandible) was mounted on a robot performing six movement types. Four CBCT units were used: Cranex 3Dx (CRA), Ortophos SL (ORT), Promax 3D Mid (PRO), and X1. Protocols were tested with aligned (CRA, ORT, PRO, and X1) and lateral-offset (CRA and PRO) detectors and two motion-artefact correction systems (PRO and X1). Movements were performed at one moment-in-time (t₁), for units with an aligned detector, and three moments-in-time (t₁-first-half of the acquisition, t₂-second-half, t₃-both) for the units with a lateral-offset detector. 98 volumes were acquired. Images were scored by three observers, blinded to the unit and presence of movement, for motion-related stripe artefacts, overall unsharpness, and interpretability. Fleiss' κ was used to assess interobserver agreement.

RESULTS

Interobserver agreement was substantial for all parameters (0.66-0.68). For aligned detectors, in all diagnostic tasks a motion-artefact correction system influenced image interpretability. For lateral-offset detectors, the interpretability varied according to the unit and moment-in-time, in which the movement was performed. PRO motion-artefact correction system was less effective for the offset detector than its aligned counterpart.

CONCLUSION

Motion-artefact correction systems enhanced image quality and interpretability for units with aligned detectors but were less effective for those with lateral-offset detectors.

Re-exposure in cone beam CT of the dentomaxillofacial region: a retrospective study

METHODS:

In a retrospective cohort study CBCT images of 4986 patients from the patient database from the Department of Oral Radiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany were included and the rate of re-exposures was counted. Patients were stratified into those who received a scan with the small field-of-view CBCT or the large field-of-view CBCT. The effect of patient-related parameters as age and gender was implicated. As a further device-specific parameter, the statistical analysis included whether the selection of the field of view due to the device type had a significant influence on the occurrence of re-exposures. Furthermore, the rescans were analyzed with regard to their causes.

RESULTS:

In total, CBCT images of 82 (1.6%) patients had to be repeated. Looking at the two different devices, in 42 (1.3%) patients that received a scan with the large field-of-view CBCT and in 40 (2.3%) patients that received a scan with the small field-of-view CBCT respectively needed a retake. There was no statistically significant correlation between age and gender to retakes. For the small field-of-view-size significantly more retakes were observed than for the large one. With 46% motion artifacts were the most frequent causes for a re-exposure of the patient.

CONCLUSIONS:

Gender and age did not have an impact on the occurrence of re-exposures. Patients who received a scan with the small field-of-view CBCT were significantly more often rescanned than those with the large field-of-view CBCT.

Optimization of exposure parameters in dental cone beam computed tomography using a 3-step approach

OBJECTIVE

The aim of this study was to find the optimal balance among tube voltage (kV), tube current (mA), and exposure time (s) in cone beam computed tomography (CBCT).

STUDY DESIGN

Three human hemimandibles were scanned by using the 3D Accuitomo 170 scanner (J. Morita, Kyoto, Japan). First, 3 combinations of kilovolt (kV) and milliampere (mA) were used at a constant radiation dose. Seven observers evaluated the images; the kV of the highest-scoring scan was considered optimal. Second, the lowest acceptable mA for visualizing different anatomic structures was determined. Finally, the samples were scanned by using 3 combinations of tube current and exposure time; the observers determined the combination with the highest image quality.

RESULTS

At a constant radiation dose, the highest available voltage (i.e., 90 kV) resulted in the highest image quality in terms of general impression, sharpness, noise, and artefacts. Depending on the anatomic structure, mA reductions of 20% to 40% compared with the default setting were possible. Fast-scan protocols showed equal or slightly better image quality compared with the standard-scan mode.

CONCLUSIONS

For the CBCT model used in this study, optimization implies the use of the highest kV along with the shortest exposure time and a task-specific mA. The proposed stepwise optimization approach could be applied to any CBCT unit, preferably during commissioning.

Uses of cone-beam computed tomography in San José, Costa Rica

Purpose

To analyze cone-beam computed tomography (CBCT) use, indications, and exposure parameters in San José, Costa Rica.

Materials and Methods

A cross-sectional study was performed. All CBCT examinations over a period of 6 months at 2 radiological centers in San José, Costa Rica were evaluated. The examinations were performed with Veraview EPOC X550 and Veraviewepocs 3D R100 equipment. The patients' age and sex, clinical indication for CBCT, region of interest (ROI), repeat examinations, specialty of the referring dentist, field-of-view (FOV), tube voltage (kV), tube current (mA), and radiation dose (µGy) were evaluated. Patients were classified by age as children (≤12 years), adolescents (13–18 years), and adults (≥19 years).

Results

The mean age of the 526 patients was 49.4 years. The main indications were implant dentistry and dental trauma. The most frequent ROIs were posterior, while anterior ROIs were much less common. The highest percentage of repeat examinations was in children. Fifty-six percent of the referring dentists were specialists. The most commonly used FOV was small. The mean tube voltage and current were 79.8 kV and 7.4 mA for Veraview EPOC X550 and 89.9 kV and 6 mA for Veraviewepocs 3D R100, respectively. The mean doses for children, adolescents, and adults were 6.9 µGy, 8.4 µGy, and 7.8 µGy, respectively.

Conclusion

Although CBCT was most commonly used in adults for implant dentistry, most repeat examinations were in children, and the highest mean dose was in adolescents. Additional dose optimization efforts should be made by introducing low-dose protocols for children and adolescents.

An ex vivo study of automated motion artefact correction and the impact on cone beam CT image quality and interpretability

OBJECTIVES

To assess the impact of head motion artefacts and an automated artefact-correction system on cone beam CT (CBCT) image quality and interpretability for simulated diagnostic tasks.

METHODS

A partially dentate human skull was mounted on a robot simulating four types of head movement (anteroposterior translation, nodding, lateral rotation, and tremor), at three distances (0.75, 1.5, and 3 mm) based on two movement patterns (skull returning/not returning to the initial position). Two diagnostic tasks were simulated: dental implant planning and detection of a periapical lesion. Three CBCT units were used to examine the skull during the movements and no-motion (control): Cranex 3Dx (CRA), Orthophos SL 3D (ORT), and X1 without (X1wo) and with (X1wi) an automated motion artefact-correction system. For each diagnostic task, 88 examinations were performed. Three observers, blinded to unit and movement, scored image quality: presence of stripe artefacts (present/absent), overall unsharpness (present/absent), and image interpretability (interpretable/non-interpretable). κ statistics assessed interobserver agreement, and descriptive statistics summarized the findings.

RESULTS

Interobserver agreement for image interpretability was good (average κ = 0.68). Regarding dental implant planning, X1wi images were interpretable by all observers, while for the other units mainly the cases with tremor were non-interpretable. Regarding detection of a periapical lesion, besides tremor, most of the 3 mm movements based on the "not returning" pattern were also non-interpretable for CRA, ORT, and X1wo. For X1wi, two observers scored 1.5 mm tremor and one observer scored 3 mm tremor as non-interpretable.

CONCLUSIONS

The automated motion artefact-correction system significantly enhanced CBCT image quality and interpretability.

Comparison of the accuracy of full head cone beam CT images obtained using a large field of view and stitched images

OBJECTIVE:

The aim of this study was to investigate the accuracy of the new stitching feature of the Morita 3D Accuitomo device by comparing it with the I-CAT device and real measurements.

METHODS:

Eight dry skulls were used in this study. The full scan mode of an I-CAT device and the new stitching feature of the Morita 3D Accuitomo device were used to obtain full head cone beam CT (CBCT) images, and the linear distances between the selected anatomical sites were measured by two observers. The real distances were measured directly on the skulls using digital calipers. Statistical analyses were performed using the intraclass correlation coefficient and Bland-Altman Limits of Agreement.

RESULTS:

High or perfect agreement was detected between the CBCT images and real measurements. The Bland-Altman Limits of Agreement analysis revealed that the stitched coronal and sagittal images of the Morita might differ by >1.54-1.67 or <0.01 mm from the real measurements.

CONCLUSIONS:

The stitched images of the Morita CBCT device showed perfect agreement with both real measurements and the images of an I-CAT full head scan. After the evaluation of the radiation doses received from stitching sectional images, this device may be used to obtain full head images.