Accuracy of dynamic navigation-assisted trephine method for bone harvesting

BackgroundThe emergence of robotic Cone Beam Computed Tomography (CBCT) imaging systems in trauma departments has enabled 3D anatomical assessment of musculoskeletal injuries, supplementing conventional 2D fluoroscopic imaging for examination, diagnosis, and treatment planning. To date, the primary focus has been on trauma sites in the extremities.PurposeTo determine if CBCT images can be used during the treatment planning process in spinal instrumentation and laminectomy procedures, allowing accurate 3D‐printed pedicle screw and laminectomy drill guides to be generated for the cervical and thoracic spine.MethodsThe accuracy of drill guides generated from CBCT images was assessed using animal cadavers (ovine and porcine). Preoperative scans were acquired using a robotic CBCT C‐arm system, the Siemens ARTIS pheno (Siemens Healthcare, GmbH, Germany). The CBCT images were imported into 3D‐Slicer version 4.10.2 (www.slicer.org) where vertebral models and specific guides were developed and subsequently 3D‐printed. In the ovine cadaver, 11 pedicle screw guides from the T1–T5 and T7–T12 vertebra and six laminectomy guides from the C2–C7 vertebra were planned and printed. In the porcine cadaver, nine pedicle screw guides from the C3–T4 vertebra were planned and printed. For the pedicle screw guides, accuracy was assessed by three observers according to pedicle breach via the Gertzbein–Robbins grading system as well as measured mean axial and sagittal screw error via postoperative CBCT and CT scans. For the laminectomies, the guides were designed to leave 1 mm of lamina. The average thickness of the lamina at the mid‐point was used to assess the accuracy of the guides, measured via postoperative CBCT and CT scans from three observers. For all measurements, the intraclass correlation coefficient (ICC) was calculated to determine observer reliability.ResultsCompared with the planned screw angles for both the ovine and porcine procedures (n = 32), the mean axial and sagittal screw error measured on the postoperative CBCT scans from three observers were 3.9 ± 1.9° and 1.8 ± 0.8°, respectively. The ICC among the observes was 0.855 and 0.849 for the axial and sagittal measurements, respectively, indicating good reliability. In the ovine cadaver, directly comparing the measured axial and sagittal screw angle of the visible screws (n = 14) in the postoperative CBCT and conventional CT scans from three observers revealed an average difference 1.9 ± 1.0° in axial angle and 1.8 ± 1.0° in the sagittal angle. The average thickness of the lamina at the middle of each vertebra, as measured on‐screen in the postoperative CBCT scans by three observes was 1.6 ± 0.2 mm. The ICC among observers was 0.693, indicating moderate reliability. No lamina breaches were observed in the postoperative images.ConclusionHere, CBCT images have been used to generate accurate 3D‐printed pedicle screw and laminectomy drill guides for use in the cervical and thoracic spine. The results demonstrate sufficient precision compared with those previously reported, generated from standard preoperative CT and MRI scans, potentially expanding the treatment planning capabilities of robotic CBCT imaging systems in trauma departments and operating rooms.

ObjectiveThe aim of this study was to evaluate the influence of cone-beam computed tomography (CBCT) resolution, 3D printing resolution, and drilling depth on drilling accuracy in guided endodontic access.MethodsFifty-six printed canines were designed, fabricated, and mounted in maxillary arch models. Preoperative CBCT and 3D surface scan were matched and used to design a surgical guide with different planning parameters: 1) reference (high-resolution CBCT (80 µm) and 3D printing (50 µm), shallow drilling (14 mm), 2) low-resolution CBCT (120 µm), 3) low-resolution 3D printing (100 µm) and 4) deep drilling (high-resolution CBCT (80 µm) and 3D printing (50 µm), deep drilling (21 mm). Guided access into the printed canines was performed in a simulated clinical setting. A postoperative CBCT was matched with the planning data in order to determine the angular and linear (total, mesiodistal, buccolingual and depth) deviation between the planned and performed cavities. Mann-Whitney test was used to analyse differences between the reference group and each test group.ResultsAngular, total linear and buccolingual deviations were significantly higher in the low-resolution CBCT group than in the reference group (median: 3.10° and 2.0° (p<0.01), 1.41 mm and 1.06 mm (p<0.05) and 0.77 mm and 0.41 mm (p<0.05), respectively). Depth deviation was significantly higher in the low-resolution 3D printing group than in the reference group (median: 0.90 mm and 0.45 mm (p<0.01), respectively). No other significant differences between the groups were noted (p>0.05).ConclusionHigher CBCT resolution resulted in lower angular and total linear deviation during guided endodontic access. Higher 3D printing resolution yielded lower vertical linear deviation.

Computed gray levels in multislice and cone-beam computed tomography

Is Panoramic Imaging Equivalent to Cone-Beam Computed Tomography for Classifying Impacted Lower Third Molars?

To assess and compare the accuracy of infrazygomatic crest screws (IZC) placed with and without a dynamic navigation system. Preoperative cone-beam computed tomography (CBCT) and intraoral scan of the maxillary arch were obtained for 12 patients requiring therapeutic first premolar extraction after leveling and alignment. Virtual planning of the final IZC screw position on both sides was done using Evalunav software. Maxillary left and right arches for each patient were randomized into experimental and control sides. A 12 × 2 mm dimension IZC screw was positioned with and without use of a dynamic navigation system randomly on either side. A postoperative CBCT was taken immediately to assess the final screw position. Preoperative and postoperative CBCTs were compared for deviation in the entry point, apical point, and angular point for experimental and control sides. Mean value deviations obtained were subjected to statistical analysis using SPSS 20.0 to describe the data. Paired t-tests were used to analyze the comparisons. Dynamic navigation showed a statistically significant difference in entry point and angular point compared to the freehand approach during implant placement. IZC screws implanted with the dynamic navigation system offered better control with less deviation and greater accuracy in all three planes of space. However, further studies are necessary to determine the stability and anchor value of implants placed with a dynamic navigation system.

Extraoral (EO) diagnostic radiography is an essential part of clinical dentistry. It is widely used as part of the clinical repertoire for diagnosis and treatment planning. Panoramic radiography (PR) is the mainstay of 2D EO imaging and cone beam computed tomography (CBCT) is now becoming widely adopted for 3D EO imaging.This research is composed of a literature review and special project investigations. The review focuses on the general development of extraoral radiography modalities, the diagnostic uses of such modalities, the medical and legal ramifications of ionising radiation, and summarises the legislations and regulations for operation of CBCT and PR machines across Australian jurisdictions. Project investigations were conducted to analyse the baseline number of PR and CBCT machines across Australian jurisdictions for the year ending 2014, and to examine the distribution of Medicare-rebated PR and CBCT scans after changes to the Medicare Benefits Schedule (MBS) in 2014 in limiting access to CBCT rebated scans. The main research results include:1. A total number of 1,913 EO X-ray machines made up of 1,681 PR machines and 232 CBCT machines were recorded nationally in 2014.2. Based on gross data, Queensland recorded the largest number of CBCT and PR machines, whereas NT recorded smallest number of CBCT and PR.3. The Australian Capital Territory had the highest accessibility to CBCT machines and Western Australia (WA) had the highest accessibility to PR machines relative to both the populationsize and the number of dental practitioners.4. The use-licensing regulations set out by each Radiation Regulator influences the adoption of CBCT and PR machines across Australian states and territories, particularly notable in WA.5. Increases in either the population size or the number of dentists could contribute to a positive growth in the adoption of PR and CBCT modalities.6. The underlying rationales imposed for restricting access to rebates for CBCT scans in the 2014 MBS were controversial, but were effective in reducing the number of rebated CBCT scans.7. During December 2014nNovember 2015 (under the new MBS), females received on average more Medicare-rebated CBCT and PR scans than males.8. Overall, the reduction in the number of Medicare-rebated CBCT scans provided significant cost savings for Medicare and also helped to reduce the ionisation load to the community during December 2014nNovember 2015.

Objective: The aim of this study was to compare the horizontal dimensional changes of split-bone block and cortico-cancellous block graft in horizontal ridge augmentation using Cone Beam Computed Tomography (CBCT). The quality of the regenerated bone in both groups was compared histologically and histomorphometrically. Material and methods: Twenty patients were randomly divided in two equal groups (n= 10): Split-bone block group which was harvested from the external oblique ridge or cortico-cancellous block graft group which was harvested from the mandibular symphysis. Pre-augmentation crestal ridge width was measured using bone caliper. CBCT scans were taken on the 2nd week and 4th month post-operatively to measure crestal and total horizontal ridge dimensions. A biopsy was collected from the regenerated ridge immediately before implant insertion on the 4th month post-operatively. Results: Pre-augmentation crestal bone widths of both groups were comparable (P= 0.870). On the 2nd week and 4th month post-operatively, split-bone block showed a significantly wider crestal (P= 0.028 and P= 0.001 respectively) and total horizontal ridge dimension (P= 0.025 and P= 0.002 respectively), and on the 4th month post-operatively, it showed significantly lesser resorption at crest (P= 0.040) and in total horizontal ridge dimension (P= 0.017) than cortico-cancellous block. Histologically, the regenerated bone quality was similar in both groups. Histomorphometric analysis showed a non-significant difference in percentage of mature (P= 0.365) and immature collagen (P= 0.531) between both groups. Conclusion: Split-bone block maintained a significantly wider ridge and experienced less resorption after 4 months than the cortico-cancellous block graft, with no difference in regenerated bone quality between both groups. Keywords Dental implants; CBCT; Cortico-cancellous block graft; Histomorphometric analysis; Split-bone block technique.

To assess the accuracy of five different computed tomography (CT) scanners for the evaluation of the oropharynx morphology. An existing cone-beam computed tomography (CBCT) data set was used to fabricate an anthropomorphic phantom of the upper airway volume that extended from the uvula to the epiglottis (oropharynx) with known dimensions (gold standard). This phantom was scanned using two multi-detector row computed tomography (MDCT) scanners (GE Discovery CT750 HD, Siemens Somatom Sensation) and three CBCT scanners (NewTom 5G, 3D Accuitomo 170, Vatech PaX Zenith 3D). All CT images were segmented by two observers and converted into standard tessellation language (STL) models. The volume and the cross-sectional area of the oropharynx were measured on the acquired STL models. Finally, all STL models were registered and compared with the gold standard. The intra- and inter-observer reliability of the oropharynx segmentation was fair to excellent. The most accurate volume measurements were acquired using the Siemens MDCT (98.4%; 14.3 cm3) and Vatech CBCT (98.9%; 14.4 cm3) scanners. The GE MDCT, NewTom 5G CBCT, and Accuitomo CBCT scanners resulted in smaller volumes, viz., 92.1% (13.4 cm3), 91.5% (13.3 cm3), and 94.6% (13.8 cm3), respectively. The most accurate cross-sectional area measurements were acquired using the Siemens MDCT (94.6%; 282.4 mm2), Accuitomo CBCT (95.1%; 283.8 mm2), and Vatech CBCT (95.3%; 284.5 mm2) scanners. The GE MDCT and NewTom 5G CBCT scanners resulted in smaller areas, viz., 89.3% (266.5 mm2) and 89.8% (268.0 mm2), respectively. Images of the phantom were acquired using the vendor-supplied default airway scanning protocol for each scanner. Significant differences were observed in the volume and cross-sectional area measurements of the oropharynx acquired using different MDCT and CBCT scanners. The Siemens MDCT and the Vatech CBCT scanners were more accurate than the GE MDCT, NewTom 5G, and Accuitomo CBCT scanners. In clinical settings, CBCT scanners offer an alternative to MDCT scanners in the assessment of the oropharynx morphology.

This study aims to study the accuracy of cone beam computed tomography (CBCT) for measuring peri-implant bone thickness in living patients via a novel visualization method (NVM). The validity of the NVM was verified ex vivo by measuring the same peri-implant bone thicknesses in bovine ribs by using raw postoperative CBCT (clinical measurement, CM), the visualized fused images obtained using the NVM (visualized fused measurement, VF), and hard tissue sections (gold standard measurement, GS). The NVM was applied by deconstructing the postoperative CBCT model into the Modelpost-bone and Modelimplant and replacing it with bone from preoperative CBCT and standard implant models, respectively. In vivo, 52 implants were included, and the VF of each implant was obtained using data processing methods similar to those used ex vivo. Then, we compared the results of CM and VF. Ex vivo, the VF was similar to GS, while CM usually underestimated the peri-implant bone thickness, especially at the implant shoulder (P < 0.01). In vivo, on CBCT, areas with a peri-implant bone thickness of 0-0.50mm were not visible, while those with a thickness of 0.50-1.00mm were occasionally visible. There was less underestimation of bone along the implant long axis. Thin peri-implant bones could be completely underestimated on CBCT. CBCT scans alone are insufficient to warrant surgical intervention. Our NVM facilitates the accurate visual assessment of implant dimensions. The thickness of peri-implant bone could be completely underestimated when thinner than 1.0mm inlivingpatients. Familiarity with these confusing CBCT results may help clinicians and patients avoid further unnecessary evaluation, misdiagnosis, and invasive treatment.

The aim of this study was to investigate the accuracy of cone-beam computed tomography (CBCT) to assess the volume of bone graft in alveolar cleft patients. Twelve patients of unilateral alveolar cleft were included in this study. All patients were taken CBCT preoperative and 1 week postoperative. The digital imaging and communications in medicine (DICOM) files were imported into Simplant software and three-dimensional (3D) reconstruction of the alveolar defect was achieved. With 3D volumetric measurements module, the volume of alveolar cleft was calculated preoperatively. During operation, the syringe compression method was adopted to calculate the actual amount of bone graft. One week postoperative, CBCT scan was performed again to measure the bone volume grafted to the defect. The volumetric ratio of the syringe compression method to preoperative CBCT assessment and the volume difference between syringe compression method and postoperative CBCT assessment were analyzed to evaluate the accuracy of CBCT measurement. The 3D structure of the alveolar cleft and the boundary of bone graft was clear from CBCT images. The estimated volume of alveolar cleft by preoperative CBCT scans was 1.06 ± 0.09 cm, and the actual amount of bone graft determined by the syringe compression method was 1.51 ± 0.12 cm. The ratio between the latter to the former was 1.43 ± 0.07. The calculated volume of bone graft by 1-week postoperative CBCT scans was 1.53 ± 0.11 cm, with no significant difference compared with the actual amount of bone graft (P > 0.05). CBCT was an accurate measurement to calculate the volume of alveolar defect and bone graft in alveolar cleft patients. Preoperative scans could aid in quantitatively determining the bone amount needed to adequately fill the bone defect, and the postoperative scans give accurate follow-up evaluation after surgery.

ObjectivesThis study aims to evaluate the accuracy of cone beam computed tomography (CBCT) in predicting the exposure of inferior alveolar nerve (IAN) during complicated mandibular third molars (M3M) extraction.Methods115 M3Ms with canal cortical defect signs on preoperative CBCT were extracted. Candidate variables included sex, age, types of CBCT machine, the Winter classification of M3Ms, the size of root entering the canal on CBCT, the size of cortical defect on CBCT. The primary outcome was the exposure of IAN and the exposed neurovascular bundle size which was recorded measured under endoscope. The independent sample t-test, Bland-Altman analysis was performed to assess the agreement between the CBCT and endoscopic measurements. The regression analysis was performed to determine if there was a correlation between the measurements of CBCT and endoscope. The Chi-square test was used to evaluate whether the proportion of IAN exposure in different impacted M3M types were consistent. ANOVA was used to test the correlation between the actual size of exposed IAN and (1) Winter classification types; (2) types of CBCT machine.Results85/115 (73.9%) M3Ms with canal cortical defect signs on preoperative CBCT had intraoperative exposure of IAN. The average length and width of the exposed IAN were 5.89 ± 1.72 mm and 2.48 ± 0.79 mm, which were significantly smaller than the size of root entering the canal on CBCT (9.69 ± 3.05 mm and 3.26 ± 0.87 mm, P < 0.001) but larger than the cortical defect size (5.06 ± 2.05 mm and 2.10 ± 0.54 mm, P < 0.05). The regression analysis showed that IAN exposure was significantly associated with the cortical defect length (0.1 mm) on CBCT (OR = 1.38, P = 0.001). The probability of intraoperative IAN exposure was statistically different among different Winter classifications of M3M and the probability of IAN exposure was higher in non-horizontal impacted type according to Chi-square test results. ANOVA showed statistical difference between exposed IAN length and Winter classification types (p = 0.001).ConclusionsNot all M3Ms with tooth-IAN contact signs on preoperative CBCT indicated intraoperative IAN exposure. The size of root entering the canal on CBCT were mostly larger than the intraoperative endoscopic measurements. IAN exposure can be accurately predicted by the length of cortical defect on CBCT. Non-horizontal impaction predisposed the M3M to a higher risk of intraoperative IAN exposure.Clinical relevanceEndoscope provides the possibility to observe and record the IAN exposure directly. IAN exposure can be accurately predicted by the length of cortical defect instead of the size of root entering the canal on CBCT. Non-horizontal impaction predisposed the M3M to a higher risk of intraoperative IAN exposure.Clinical trial numberNot applicable

Accuracy of a calibration method based on cone beam computed tomography and intraoral scanner data registration for robot-assisted implant placement: A single arm clinical study.

To evaluate the validity and reliability of cone-beam computed tomography (CBCT) masseter muscle segmentation by comparing with the magnetic resonance imaging (MRI) masseter muscle segmentation of the same patients. Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations. Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations. Paired t-test showed that there was no significant difference in CSA between CBCT and MRI masseter segmentations. The ICCs were all larger than 0.95 and the SEM was less than 4.85 mm2 for CSA. The DSC was all larger than 0.95 showing over 95% of similarity between CBCT and MRI masseter segmentations. The aHD was all smaller than 0.09mm showing great consistency of the contour of CBCT and MRI segmentations. Masseter muscle segmentation from CBCT scans was not significantly different from the segmentation from MRI scans. CBCT muscle segmentation showed great validity compared with MRI scans, and great reliability in retests.

Usefulness of Cone-Beam Volume CT with Flat Panel Detectors in Conjunction with Catheter Angiography for Transcatheter Arterial Embolization

For prostate cancer patients, large organ deformations occurring between radiotherapy treatment sessions create uncertainty about the doses delivered to the tumor and surrounding healthy organs. Segmenting those regions on cone beam CT (CBCT) scans acquired on treatment day would reduce such uncertainties. In this work, a 3D U-net deep-learning architecture was trained to segment bladder, rectum, and prostate on CBCT scans. Due to the scarcity of contoured CBCT scans, the training set was augmented with CT scans already contoured in the current clinical workflow. Our network was then tested on 63 CBCT scans. The Dice similarity coefficient (DSC) increased significantly with the number of CBCT and CT scans in the training set, reaching 0.874 ± 0.096 , 0.814 ± 0.055 , and 0.758 ± 0.101 for bladder, rectum, and prostate, respectively. This was about 10% better than conventional approaches based on deformable image registration between planning CT and treatment CBCT scans, except for prostate. Interestingly, adding 74 CT scans to the CBCT training set allowed maintaining high DSCs, while halving the number of CBCT scans. Hence, our work showed that although CBCT scans included artifacts, cross-domain augmentation of the training set was effective and could rely on large datasets available for planning CT scans.