Pauwels R, Faruangsaeng T, Charoenkarn T, Ngonphloy N, Panmekiate S
1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.
2 OMFS-IMPATH Research Group, Oral Imaging Center, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
Dentomaxillofac Radiol. 2015;44(8):20150078. doi: 10.1259/dmfr.20150078. Epub 2015 Jun 9.
To evaluate the effect of exposure parameters and voxel size on bone structure analysis in dental CBCT.
20 cylindrical bone samples underwent CBCT scanning (3D Accuitomo 170; J. Morita, Kyoto, Japan) using three combinations of tube voltage (kV) and tube current-exposure 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.
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.
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.
评估牙科锥形束计算机断层扫描（CBCT）中曝光参数和体素大小对骨结构分析的影响。
20个圆柱形骨样本接受CBCT扫描（3D Accuitomo 170；日本京都森田公司），使用三种管电压（kV）与管电流-曝光时间乘积（mAs）的组合，对应的CT剂量指数为3.4 mGy：90 kV和62 mAs、73 kV和108.5 mAs以及64 kV和155 mAs。图像以0.080 mm的体素大小重建。此外，90 kV扫描以0.125、0.160、0.200、0.250和0.300 mm的体素大小重建。测量以下参数：每总体积（TV）的骨表面（BS）和骨体积（BV）、分形维数、连通性密度、各向异性、小梁厚度（Tb.Th.）和小梁间距（Tb.Sp.）、结构模型指数（SMI）、板状度、分支、节点、分支长度和三点。
对于大多数参数，kV值没有显著影响。对于BV/TV，“90 kV”与其他kV设置有显著差异；对于SMI，“64与73 kV”有显著差异。对于BS/TV、分形维数、连通性密度、分支、节点和三点值，在较大体素大小时逐渐降低，而Tb.Th.、Tb.Sp.、SMI和分支长度则增加。对于各向异性和板状度，未观察到（或几乎未观察到）体素大小的影响；对于BV/TV，影响不一致。
如果辐射剂量恒定，大多数骨结构参数不受kV影响。处理小梁结构的参数受体素大小的影响很大。
