Technical aspects of dental CBCT: state of the art

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Objective: To evaluate the effect of exposure parameters and voxel size on bone structure analysis in dental CBCT. Methods: 20 cylindrical bone samples underwent CBCT scanning (3D Accuitomo 170; J. Morita, Kyoto, Japan) using three combinations of tube voltage (kV) and tube currentexposure time product (mAs), corresponding with a CT dose index of 3.4 mGy: 90 kV and 62 mAs, 73 kV and 108.5 mAs, and 64 kV and 155 mAs. Images were reconstructed with a voxel size of 0.080 mm. In addition, the 90 kV scan was reconstructed at voxel sizes of 0.125, 0.160, 0.200, 0.250 and 0.300 mm. The following parameters were measured: bone surface (BS) and bone volume (BV) per total volume (TV), fractal dimension, connectivity density, anisotropy, trabecular thickness (Tb. Th.) and trabecular spacing (Tb. Sp.), structure model index (SMI), plateness, branches, junctions, branch length and triple points. Results: For most parameters, there was no significant effect of the kV value. For BV/TV, "90 kV" differed significantly from the other kV settings; for SMI, "64 vs 73 kV" was significant. For BS/TV, fractal dimension, connectivity density, branches, junctions and triple points values incrementally decreased at larger voxel sizes, whereas an increase was seen for Tb. Th., Tb. Sp., SMI and branch length. For anisotropy and plateness, no (or little) effect of voxel size was seen; for BV/TV, the effect was inconsistent. Conclusions: Most bone structure parameters are not affected by the kV if the radiation dose is constant. Parameters dealing with the trabecular structure are heavily affected by the voxel size. Dentomaxillofacial Radiology (2015Radiology ( ) 44, 20150078. doi: 10.1259 Cite this article as: Pauwels R, Faruangsaeng T, Charoenkarn T, Ngonphloy N, Panmekiate S. Effect of exposure parameters and voxel size on bone structure analysis in CBCT. Dentomaxillofac Radiol 2015; 44: 20150078.

Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 96%

Effect of exposure parameters and voxel size on bone structure analysis in CBCT

Pauwels¹,

Faruangsaeng²,

Charoenkarn³

et al. 2015

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“…These reports are consistent with our results. Pauwels et al 29 stated that image noise can be reduced by averaging multiple consecutive slices. Our results also showed that with thicker slices, the image noise was reduced (Figure 2).…”

Section: Discussionmentioning

confidence: 99%

Effects of exposure parameters and slice thickness on detecting clear and unclear mandibular canals using cone beam CT

Jasa

Shimizu

Okamura

et al. 2017

Objectives: The purpose of this study was to clarify the effects of exposure parameters and image-processing methods when using CBCT to detect clear and unclear mandibular canals (MCs). Methods: 24 dry half mandibles were divided into 2 groups with clear and unclear MCs based on a previous CBCT study. Mandibles were scanned using a CBCT system with varying exposure parameters (tube voltages 60 kV, 70 kV and 90 kV; and tube currents 2 mA, 5 mA, 10 mA and 15 mA) to obtain a total of 144 scans. The images were processed with different slice thicknesses using ImageJ software (National Institutes of Health, Bethesda, MD). Five radiologists evaluated the cross-sectional images of the first molar region to detect the MCs. The diagnostic accuracy of varying exposure parameters and image-processing conditions was compared with the area under the curve (Az) in receiver-operating characteristic analysis. Results:The Az values for clear MCs were higher than those for unclear MCs (p , 0.0001). With increasing exposure voltages and currents, Az values increased, but no significant differences were found with high voltages and currents in clear MCs (p 5 1.0000 and p 5 0.9340). The Az values of serial images were higher than those of overlaid images (p , 0.0001), and those for thicker slices were higher than those for thinner slices (p , 0.0001). Conclusions: Our findings indicate that detection of unclear MCs requires either higher exposure parameters or processing of the images with thicker slices. To detect clear MCs, lower exposure parameters can be used.

“…[26][27][28] The remainder of this section will focus on experimental findings related to the accuracy and clinical application of GV in CBCT. Studies on non-dental CBCTs will not be discussed, although the inherent issues and findings are similar, 29,30 and corrections have been proposed that may be applicable for dental CBCT as well.…”

Section: Applicability Of Hounsfield Units In Cbctmentioning

confidence: 99%

CBCT-based bone quality assessment: are Hounsfield units applicable?

Pauwels

Jacobs²,

Singer³

et al. 2015

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319

228

CBCT is a widely applied imaging modality in dentistry. It enables the visualization of highcontrast structures of the oral region (bone, teeth, air cavities) at a high resolution. CBCT is now commonly used for the assessment of bone quality, primarily for pre-operative implant planning. Traditionally, bone quality parameters and classifications were primarily based on bone density, which could be estimated through the use of Hounsfield units derived from multidetector CT (MDCT) data sets. However, there are crucial differences between MDCT and CBCT, which complicates the use of quantitative gray values (GVs) for the latter. From experimental as well as clinical research, it can be seen that great variability of GVs can exist on CBCT images owing to various reasons that are inherently associated with this technique (i.e. the limited field size, relatively high amount of scattered radiation and limitations of currently applied reconstruction algorithms). Although attempts have been made to correct for GV variability, it can be postulated that the quantitative use of GVs in CBCT should be generally avoided at this time. In addition, recent research and clinical findings have shifted the paradigm of bone quality from a density-based analysis to a structural evaluation of the bone. The ever-improving image quality of CBCT allows it to display trabecular bone patterns, indicating that it may be possible to apply structural analysis methods that are commonly used in micro-CT and histology.