Patient movement characteristics and the impact on CBCT image quality and interpretability.

OBJECTIVES: To assess the impact of patient movement characteristics and metal/radiopaque materials in the field-of-view (FOV) on CBCT image quality and interpretability. METHODS: 162 CBCT examinations were performed in 134 consecutive (i.e. prospective data collection) patients (age average: 27.2 years; range: 9-73). An accelerometer-gyroscope system registered patient's head position during examination. The threshold for movement definition was set at ≥0.5-mm movement distance based on accelerometer-gyroscope recording. Movement complexity was defined as uniplanar/multiplanar. Three observers scored independently: presence of stripe (i.e. streak) artefacts (absent/"enamel stripes"/"metal stripes"/"movement stripes"), overall unsharpness (absent/present) and image interpretability (interpretable/not interpretable). Kappa statistics assessed interobserver agreement. χ2 tests analysed whether movement distance, movement complexity and metal/radiopaque material in the FOV affected image quality and image interpretability. Relevant risk factors (p ≤ 0.20) were entered into a multivariate logistic regression analysis with "not interpretable" as the outcome. RESULTS: Interobserver agreement for image interpretability was good (average = 0.65). Movement distance and presence of metal/radiopaque materials significantly affected image quality and interpretability. There were 22-28 cases, in which the observers stated the image was not interpretable. Small movements (i.e. <3 mm) did not significantly affect image interpretability. For movements ≥ 3 mm, the risk that a case was scored as "not interpretable" was significantly (p ≤ 0.05) increased [OR 3.2-11.3; 95% CI (0.70-65.47)]. Metal/radiopaque material was also a significant (p ≤ 0.05) risk factor (OR 3.61-5.05). CONCLUSIONS: Patient movement ≥3 mm and metal/radiopaque material in the FOV significantly affected CBCT image quality and interpretability.

Accuracy of video observation and a three-dimensional head tracking system for detecting and quantifying robot-simulated head movements in cone beam computed tomography.

OBJECTIVES: To assess the accuracy of detecting robot-simulated head movements using video observation (VO) and 3-dimensional head tracking (HT) in a cone beam computed tomography examination setup. STUDY DESIGN: A mannequin head was mounted on a robot that was programmed to simulate patient head movements. Six types of movement (tremor, nodding, lateral rotation, lifting, swallowing, and anteroposterior translation), 3 distances (0.25, 1, and 5 mm), and 2 speeds (1 and 5 mm/s) were tested in triplicate (108 examinations). An additional 18 videos and HT of no-motion served as controls for a total of 126 examinations. Three blinded observers viewed video recordings of the examinations, scoring whether the head moved and the movement type. HT provided quantitative measures of movement distance. Accuracy, sensitivity, and specificity for movement detection by VO and HT were calculated, related to true type, distance, and speed of movement. Differences between the true and the measured movement distances were assessed for HT. RESULTS: VO movement detection presented accuracy of 0.86, sensitivity of 0.85, and specificity of 0.94. Anteroposterior translation (33.3%) and 0.25 mm movements (41.7%) were often not detected by VO. HT correctly detected all cases (accuracy = 1). HT presented small differences between the true and the measured movement distances (average 20-54 µm). CONCLUSIONS: VO missed 41.7% of the 0.25 mm movements. HT correctly detected all movements and quantified movements with an average error <55 µm.

Detection of patient movement during CBCT examination using video observation compared with an accelerometer-gyroscope tracking system.

OBJECTIVES: To compare video observation (VO) with a novel three-dimensional registration method, based on an accelerometer-gyroscope (AG) system, to detect patient movement during CBCT examination. The movements were further analyzed according to complexity and patient age. METHODS: In 181 patients (118 females/63 males; age average 30 years, range: 9-84 years), 206 CBCT examinations were performed, which were video-recorded during examination. An AG was, at the same time, attached to the patient head to track head position in three dimensions. Three observers scored patient movement (yes/no) by VO. AG provided movement data on the x-, y- and z-axes. Thresholds for AG-based registration were defined at 0.5, 1, 2, 3 and 4 mm (movement distance). Movement detected by VO was compared with that registered by AG, according to movement complexity (uniplanar vs multiplanar, as defined by AG) and patient age (≤15, 16-30 and ≥31 years). RESULTS: According to AG, movement ≥0.5 mm was present in 160 (77.7%) examinations. According to VO, movement was present in 46 (22.3%) examinations. One VO-detected movement was not registered by AG. Overall, VO did not detect 71.9% of the movements registered by AG at the 0.5-mm threshold. At a movement distance ≥4 mm, 20% of the AG-registered movements were not detected by VO. Multiplanar movements such as lateral head rotation (72.1%) and nodding/swallowing (52.6%) were more often detected by VO in comparison with uniplanar movements, such as head lifting (33.6%) and anteroposterior translation (35.6%), at the 0.5-mm threshold. The prevalence of patients who move was highest in patients younger than 16 years (64.3% for VO and 92.3% for AG-based registration at the 0.5-mm threshold). CONCLUSIONS: AG-based movement registration resulted in a higher prevalence of patient movement during CBCT examination than VO-based registration. Also, AG-registered multiplanar movements were more frequently detected by VO than uniplanar movements. The prevalence of patients who move was highest in patients younger than 16 years.

Movement characteristics in young patients and the impact on CBCT image quality.

OBJECTIVES: To assess patient movement characteristics in children and young adults and the impact on CBCT image quality. METHODS: During 33 CBCT examinations, the patients (age: average, 14 years; range, 9-25 years) who had moved were identified by video observation [movement group (MG)]. The CBCT data sets were matched with those of 33 non-moving patients according to age, diagnostic task, examined region, field of view and voxel resolution [non-movement group (N-MG)]. Three observers scored the videos of MG, regarding motional state second by second (moving/non-moving), and movement characteristics: duration (in seconds), complexity (uniplanar or multiplanar) and distance (<3/≥3 ≤ 10/>10 mm). The observers blindly assessed axial sections of the 66 examinations individually, categorizing the image quality (appropriate/acceptable/inappropriate). Next, the observers blindly assessed axial sections of the matched-pairs images simultaneously, deciding which image in the pair had the highest image quality or if it was impossible to decide. The relationship between image quality and movement/movement characteristics was evaluated. RESULTS: When the 66 CBCT images were evaluated individually, no relationship between image quality and movement was found. However, based on the matched-pairs assessment, accumulated number (≤2 vs ≥3, p = 0.039), duration (≤5 s vs ≥6 s, p = 0.024) and complexity (uniplanar vs multiplanar, p = 0.046) of movements had an impact on image quality; the more severe the movement, the more often the image quality was assessed lower in the MG. CONCLUSIONS: Axial CBCT images of young patients who moved during examination did not always present lower quality than images originating from non-moving patients. Image quality was, however, significantly lower in the moving patients when movement occurred several times, had a long duration or was multiplanar.

Factors affecting patient movement and re-exposure in cone beam computed tomography examination.

OBJECTIVE: To assess operator-, examination-, and patient-related factors, affecting patient movement and re-exposure in cone beam computed tomography (CBCT) examination. STUDY DESIGN: The sample consisted of 248 CBCT examinations in 190 patients video-recorded during examination. Three observers scored the videos; the patient moved or did not move. Operator-, examination-, and patient-related factors were evaluated separately (chi-square test) and by multivariate regression analyses (patient movement and re-exposure as separate outcomes). RESULTS: The prevalence of movement was 21%. Cotton roll stabilizing patient's jaws, CBCT unit touching patient's hair, and patient's age 15 years or greater were related to movement. Age 15 years or greater had a significant impact on movement (P < .001; odds ratio [OR] 11.0). There were 16 re-exposures (6.4%). Age 15 years or greater, presence of a cotton roll, and field of view (FOV) were related to re-exposure. Use of a large FOV had significant impact on re-exposure (P = .04; OR 5.8). CONCLUSIONS: Operator-, examination-, and patient-related factors may affect patient movement and re-exposure in CBCT examination.

Immediate placement and provisionalization of single-tooth implants involving a definitive individual abutment: a clinical and radiographic retrospective study.

AIM: To assess with a mean follow-up period of 33 months (median: 31 month, range: 11-89 month) the treatment outcome after immediate placement and provisionalization of single-tooth oral implants involving a definitive individual abutment and a provisional crown followed by later placement of a definitive crown. MATERIALS AND METHODS: 68 patients with 68 single-tooth implants in the esthetic zone were consecutively treated; 55 of these patients were included in the study. The treatment involved tooth extraction, implant placement, placement of a definitive individual abutment, and a provisional crown in the same visit in private practice. The definitive crown was placed after a mean period of 7 months. The primary outcome measures included implant survival, definitive implant crown survival, and overall treatment survival. The secondary outcome measures included probing depth, bleeding on probing, peri-implant marginal bone level, marginal bone level of the neighboring tooth surfaces, biological complications, and technical complications. RESULTS: Of the inserted implants 98% survived and of the definitive crowns mounted a survival of 100% was observed. Consequently, the overall treatment survival was 98%. The mean probing depth was 2.9 mm at implant level and 63% of the implants were characterized by no bleeding on probing. The mean peri-implant marginal bone level was 2 mm. A significant mean peri-implant marginal bone level gain of 0.5 mm was observed from implant placement to the follow-up (95% CI: 0.07-0.89 mm, P = 0.022). No significant changes of the marginal bone level at the neighboring tooth surfaces were seen. Four episodes of peri-implant inflammation were identified in three patients, while 46 incidents of loosening of the provisional crown occurred in 33 patients. One abutment screw loosened before placement of the definitive crown. Finally, loosening of four definitive crowns occurred in four patients. CONCLUSIONS: Immediate placement and provisionalization of single-tooth oral implants involving a definitive individual abutment and a provisional crown followed by later placement of a definitive crown were characterized by high survival of the implant crowns and implants as well as healthy peri-implant tissues, after a mean follow-up period of 33 months. Loss of retention of the provisional crown occurred frequently.

Impact of voxel size variation on CBCT-based diagnostic outcome in dentistry: a systematic review.

The objective of this study was to make a systematic review on the impact of voxel size in cone beam computed tomography (CBCT)-based image acquisition, retrieving evidence regarding the diagnostic outcome of those images. The MEDLINE bibliographic database was searched from 1950 to June 2012 for reports comparing diverse CBCT voxel sizes. The search strategy was limited to English-language publications using the following combined terms in the search strategy: (voxel or FOV or field of view or resolution) and (CBCT or cone beam CT). The results from the review identified 20 publications that qualitatively or quantitatively assessed the influence of voxel size on CBCT-based diagnostic outcome, and in which the methodology/results comprised at least one of the expected parameters (image acquisition, reconstruction protocols, type of diagnostic task, and presence of a gold standard). The diagnostic task assessed in the studies was diverse, including the detection of root fractures, the detection of caries lesions, and accuracy of 3D surface reconstruction and of bony measurements, among others. From the studies assessed, it is clear that no general protocol can be yet defined for CBCT examination of specific diagnostic tasks in dentistry. Rationale in this direction is an important step to define the utility of CBCT imaging.

Exploring CBCT-based DICOM files. A systematic review on the properties of images used to evaluate maxillofacial bone grafts.

Previous studies suggests that cone beam computerized tomography (CBCT) images could provide reliable information regarding the fate of bone grafts in the maxillofacial region, but no systematic information regarding the standardization of CBCT settings and properties is available, i.e., there is a lack of information on how the images were generated, exported, and analyzed when bone grafts were evaluated. The aim of this study was to (1) do a systematic review on which type of CBCT-based DICOM images have been used for the evaluation of the fate of bone grafts in humans and (2) use a software suggested in the literature to test DICOM-based data sets, exemplifying the effect of variation in selected parameters (windowing/contrast control, plane definition, slice thickness, and number of measured slices) on the final image characteristics. The results from review identified three publications that used CBCT to evaluate maxillofacial bone grafts in humans, and in which the methodology/results comprised at least one of the expected outcomes (image acquisition protocol, image reconstruction, and image generation information). The experimental shows how the influence of information that was missing in the retrieved papers, can influence the reproducibility and the validity of image measurements. Although the use of CBCT-based images for the evaluation of bone grafts in humans has become more common, this does not reflect on a better standardization of the developed studies. Parameters regarding image acquisition and reconstruction, while important, are not addressed in the proper way in the literature, compromising the reproducibility and scientific impact of the studies.

Comparison of panoramic and conventional cross-sectional tomography for preoperative selection of implant size.

OBJECTIVE: To compare panoramic and conventional cross-sectional tomography for preoperative selection of implant size for three implant systems (Brånemark, Straumann(®), 3i). MATERIAL AND METHODS: Presurgical panoramic (Pan) and cross-sectional tomograms (Tomo) of 121 implant sites in 121 patients scheduled for single-tooth implant treatment were recorded; in 70 of the Pans (Pan-B), a metal ball was placed in the edentulous area. By means of dedicated software, an implant with subjectively determined proper dimensions for the respective site was outlined by manually placing four reference points in each image by three observers. Additionally, four reference points corresponding to the margins of the metal ball were manually placed in Pan-Bs. The length and width of the implant were calculated after calibration to the reference ball (true magnification) in Pan-Bs and to a "standard" calibration method in all images (magnification factor 1.25 in Pans and 1.7 in Tomos). Based on the corrected dimensions, the nearest, smaller implant size was selected among those available in each of the three implant systems. RESULTS: When comparing Pans with Tomos, selected implant size differed in on average 89% of the cases. The length differed in 69% and the width in 66%. Implants planned on Tomos were longer than those planned on Pans in 47% and narrower in 30% (<10% in posterior regions). The Straumann(®) system, with the smallest range of available implant sizes was significantly less affected by the radiographic method compared with the other two systems. CONCLUSION: The selected implant size differed considerably when planned on panoramic or cross-sectional tomographs.

Calibration of radiographs by a reference metal ball affects preoperative selection of implant size.

The aim was to evaluate the impact of a reference ball for calibration of periapical and panoramic radiographs on preoperative selection of implant size for three implant systems. Presurgical digital radiographs (70 panoramic, 43 periapical) from 70 patients scheduled for single-tooth implant treatment, recorded with a metal ball placed in the edentulous area, were evaluated by three observers with the intent to select the appropriate implant size. Four reference marks corresponding to the margins of the metal ball were manually placed on the digital image by means of computer software. Additionally, an implant with proper dimensions for the respective site was outlined by manually placing four reference marks. The diameter of the metal ball and the unadjusted length and width of the implant were calculated. Implant size was adjusted according to a "standard" calibration method (SCM; magnification factor 1.25 in panoramic images and 1.05 in periapical images) and according to a reference ball calibration method (RCM; true magnification). Based on the unadjusted as well as the adjusted implant dimensions, the implant size was selected among those available in a given implant system. For periapical radiographs, when comparing SCM and RCM with unadjusted implant dimensions, implant size changed in 42% and 58%, respectively. When comparing SCM and RCM, implant size changed in 24%. For panoramic radiographs, comparing SCM and RCM changed implant size in 48%. The use of a reference metal ball for calibration of periapical and panoramic radiographs when selecting implant size during treatment planning might be advantageous.

Influence of spatial resolution and bit depth on detection of small caries lesions with digital receptors.

OBJECTIVE: The aim of this study was to compare the caries diagnostic accuracy among intraoral digital receptor systems that provide images in more than one resolution and bit depth. STUDY DESIGN: Eighty noncavitated extracted human teeth were radiographed and analyzed by the following digital systems: Digora Optime (Soredex) 8-bit high- and 8-bit super-resolution, VistaScan (Dürr) 8-bit high- and 8-bit max-resolution and 16-bit high- and 16-bit max-resolution, Dixi2 (Planmeca) 8-bit and 12-bit depths. Insight Film was included as a reference. Six observers scored caries lesions in each tooth surface. The teeth were sectioned and microscopy served as validation. Two-way analysis of variance tested differences in sensitivity, specificity, positive and negative predictive values, and overall accuracy (true positives + true negatives) between the modalities. RESULTS: There were 160 approximal surfaces examined, and histology showed 63% sound, 31% enamel, and 6% dentinal lesions. Sensitivity was not significantly different within each brand except for VistaScan 8-bit max-resolution, which showed higher sensitivity than the 2 VistaScan high-resolution modalities (P = .003). Digora super-resolution showed higher sensitivity than almost all the other modalities (P < .02), but had lower specificity than all other systems, among which there were no differences. Overall accuracy was significantly lower for Digora high-resolution than for Dixi2 and VistaScan max-resolution modalities (P < .03); there were no differences among the other modalities. CONCLUSION: Caries diagnostic accuracy seems to be little influenced by an increase in spatial resolution and bit depth from 8-bit to 12- or 16-bit within digital radiographic system brands. Between systems, the Digora super-resolution images provided higher sensitivity, but lower specificity than most of the other receptors.