A comparative evaluation of cone beam CT and micro-CT on trabecular bone structures in the human mandible

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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.

Section: Alternative Methods For Bone Evaluationmentioning

confidence: 78%

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

Pauwels

Jacobs²,

Singer³

et al. 2015

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319

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“…Secondly, a high correlation does not imply that the numerical values correspond between the two variables, and large differences between bone parameter values of CBCT and other modalities have been revealed. [27][28][29][30][31] As seen in Table 1, correlation coefficients could be reasonably high even if the values for CBCT were severely underor overestimated (as shown by the calibration coefficients). In other words, even if a bone parameter is found to have a high correlation coefficient, the value obtained from CBCT images may be far off the true value.…”

Section: Discussionmentioning

confidence: 92%

“…[23][24][25][26] Various other studies have measured morphometric and other parameters, correlating values from CBCT with those from mCT and dual-energy X-ray absorptiometry. [27][28][29][30][31] Correlation coefficients were typically interpreted as "high". However, when comparing the present results with previous studies, it is important to note that a correlation coefficient has limited value when evaluating the potential clinical applications of these bone parameters.…”

Section: Discussionmentioning

confidence: 99%

Comparison of mandibular bone microarchitecture between micro-CT and CBCT images

Panmekiate¹,

Ngonphloy²,

Charoenkarn³

et al. 2015

Objectives: To compare microarchitecture parameters of bone samples scanned using micro-CT (mCT) to those obtained by using CBCT. Methods: A bone biopsy trephine bur (3 3 10 mm) was used to remove 20 cylindrical bone samples from 20 dry hemimandibles. Samples were scanned using mCT (mCT 35; SCANCO Medical, Brüttisellen, Switzerland) with a voxel size of 20 mm and CBCT (3D Accuitomo 170; J. Morita, Kyoto, Japan) with a voxel size of 80 mm. All corresponding sample scans were aligned and cropped. Image analysis was carried out using BoneJ, including the following parameters: skeleton analysis, bone surface per total volume (BS/TV), bone volume per total volume (BV/TV), connectivity density, anisotropy, trabecular thickness and spacing, structure model index, plateness and fractal dimension. Pearson and Spearman correlation coefficients (R) were calculated. CBCT values were then calibrated using the slope of the linear fit with the mCT values. The mean error after calibration was calculated and normalized to the standard deviation of the mCT values. Results: R-values ranged between 0.05 (plateness) and 0.83 (BS/TV). Correlation was significant for both Spearman and Pearson's R for 8 out of 16 parameters. After calibration, the smallest normalized error was found for BV/TV (0.48). For other parameters, the error range was 0.58-2.10. Conclusions: Despite the overall correlation, this study demonstrates the uncertainty associated with using bone microarchitecture parameters on CBCT images. Although clinically relevant parameter ranges are not available, the errors found in this study may be too high for some parameters to be considered for clinical application.

“…Prior investigations have shown varying degrees of variability for a subset of bone structure parameters as a result of varying scan settings. 10,14,15 However, to our knowledge, an analysis of all available bone structure parameters on a larger (n . 8) sample has not yet been performed.…”

Section: Introductionmentioning

confidence: 98%

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

Pauwels¹,

Faruangsaeng²,

Charoenkarn³

et al. 2015

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.