使用窄垂直探测器口腔锥形束 CT 进行图像质量优化。
Image quality optimization using a narrow vertical detector dental cone-beam CT.
机构信息
1 Department of Oral Diagnosis, Division of Oral Radiology, Piracicaba Dental School, University of Campinas (UNICAMP) , Piracicaba , Brazil.
2 Department of Imaging and Pathology, Faculty of Medicine, Catholic University of Leuven , Leuven , Belgium.
出版信息
Dentomaxillofac Radiol. 2019 Mar;48(3):20180357. doi: 10.1259/dmfr.20180357. Epub 2019 Jan 31.
OBJECTIVES
: To determine the optimized kV setting for a narrow detector cone-beam CT (CBCT) unit.
METHODS
: Clinical (CL) and quantitative (QUANT) evaluations of image quality were performed using an anthropomorphic phantom. Technical (TECH) evaluation was performed with a polymethyl methacrylate phantom. Images were obtained using a PaX-i3D Green CBCT (Vatech, Hwaseong, Korea) device, with a large 21 × 19 and a medium 12 × 9 cm field of view (FOV), and high-dose (HD-ranging from 85 to 110 kV) and low-dose (LD-ranging from 75 to 95 kV) protocols, totaling four groups (21 × 19 cm HD, 21 × 19 cm LD, 12 × 9 cm HD, 12 × 9 cm LD). The radiation dose within each group was fixed by adapting the mA according to a predetermined dose-area product. For CL evaluation, three observers assessed images based on overall quality, sharpness, contrast, artefacts, and noise. For QUANT evaluation, mean gray value shift, % increase of standard deviation (SD), % of beam hardening and contrast-to-noise ratio (CNR) were calculated. For TECH evaluation, segmentation accuracy, CNR, metal artefact SD, metal object area, and sharpness were measured. Representative parameters were chosen for CL, QUANT, and TECH evaluations to determine the optimal kV based on biplot graphs. kV values of the same protocol were compared by the bootstrapping approach. The ones that had statistical differences with the best kV were considered as worse quality.
RESULTS
: Overall, kV values within the same group showed similar quality (p > 0.05), except for 110 kV in 21 × 19 cm HD and 85 kV in 12 × 9 cm HD of CL score; also 85, 90 kV in 21 × 19 cm HD and 75, 80 kV in 21 × 19 cm LD of QUANT score which were worse (p < 0.05).
CONCLUSION
: At a constant dose, low and high kV protocols yield acceptable image quality for a narrow-detector CBCT unit.
目的
确定窄探测器锥形束 CT（CBCT）的优化千伏设置。
方法
使用体模对图像质量进行临床（CL）和定量（QUANT）评估。使用聚甲基丙烯酸甲酯体模进行技术（TECH）评估。使用 PaX-i3D Green CBCT（Vatech，韩国华城）设备获取图像，视场（FOV）分别为 21×19cm 和 12×9cm，高剂量（HD-85-110kV）和低剂量（LD-75-95kV）方案，共 4 组（21×19cm HD、21×19cm LD、12×9cm HD、12×9cm LD）。根据预定的剂量面积乘积，通过调整 mA 使每个组内的辐射剂量保持固定。对于 CL 评估，三位观察者根据整体质量、清晰度、对比度、伪影和噪声对图像进行评估。对于 QUANT 评估，计算平均灰度值偏移、标准差（SD）增加百分比、束硬化和对比噪声比（CNR）。对于 TECH 评估，测量分割准确性、CNR、金属伪影 SD、金属物体面积和锐度。根据双标图选择 CL、QUANT 和 TECH 评估的代表性参数，以确定最佳千伏值。使用 bootstrap 方法比较相同方案的千伏值。与最佳千伏值具有统计学差异的被认为是质量较差的。
结果
总体而言，同一组内的千伏值显示出相似的质量（p>0.05），但在 CL 评分中，21×19cm HD 中的 110kV 和 12×9cm HD 中的 85kV 除外；在 QUANT 评分中，21×19cm HD 中的 85、90kV 和 21×19cm LD 中的 75、80kV 也较差（p<0.05）。
结论
在恒定剂量下，窄探测器 CBCT 单元的低千伏和高千伏方案可获得可接受的图像质量。
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