Loubele M, Jacobs R, Maes F, Denis K, White S, Coudyzer W, Lambrichts I, van Steenberghe D, Suetens P
ESAT-PSI, Katholieke Universiteit Leuven, Belgium.
Dentomaxillofac Radiol. 2008 Sep;37(6):309-18. doi: 10.1259/dmfr/16770531.
To evaluate image quality by examining segmentation accuracy and assess radiation dose for cone beam CT (CBCT) scanners.
A skull phantom, scanned by a laser scanner, and a contrast phantom were used to evaluate segmentation accuracy. The contrast phantom consisted of a polymethyl methacrylate (PMMA) cylinder with cylindrical inserts of air, bone and PMMA. The phantoms were scanned on the (1) Accuitomo 3D, (2) MercuRay, (3) NewTom 3G, (4) i-CAT and (5) Sensation 16. The structures were segmented with an optimal threshold. Thicknesses of the bone of the mandible and the diameter of the cylinders in the contrast phantom were measured across lines at corresponding places in the CT image vs a ground truth. The accuracy was in the 95th percentile of the difference between corresponding measurements. The correlation between accuracy in skull and contrast phantom was calculated. The radiation dose was assessed by DPI(100,c) (dose profile integral (100,c)) at the central hole of a CT dose index (CTDI) phantom.
The results for the DPI(100,c) were 107 mGy mm for (1), 1569 mGy mm for (2), 446 mGy mm for (3), 249 mGy mm for (4) and 1090 mGy mm for (5). The segmentations in the contrast phantom were submillimeter accurate in all scanners. The segmentation accuracy of the mandible was 2.9 mm for (1), 4.2 mm for (2), 3.4 mm for (3), 1.0 mm for (4) and 1.2 mm for (5). The correlation between measurements in the contrast and skull phantom was below 0.37 mm.
The best radiation dose vs image quality was found for the i-CAT.
通过检查分割准确性来评估图像质量，并评估锥形束CT（CBCT）扫描仪的辐射剂量。
使用经激光扫描仪扫描的头颅模型和对比模型来评估分割准确性。对比模型由一个聚甲基丙烯酸甲酯（PMMA）圆柱体以及内部的空气、骨骼和PMMA圆柱形插入物组成。这些模型在以下设备上进行扫描：（1）Accuitomo 3D、（2）MercuRay、（3）NewTom 3G、（4）i-CAT和（5）Sensation 16。采用最佳阈值对结构进行分割。在CT图像的相应位置，测量下颌骨的骨厚度以及对比模型中圆柱体的直径，并与真实值进行比较。准确性以相应测量值之间差异的第95百分位数表示。计算头颅模型和对比模型测量结果之间的相关性。通过CT剂量指数（CTDI）模型中心孔处的DPI(100,c)（剂量分布积分(100,c)）评估辐射剂量。
（1）的DPI(100,c)结果为107 mGy·mm，（2）为1569 mGy·mm，（3）为446 mGy·mm，（4）为249 mGy·mm，（5）为1090 mGy·mm。在所有扫描仪中，对比模型的分割精度均在亚毫米级别。（1）中下颌骨的分割精度为2.9 mm，（2）为4.2 mm，（3）为3.4 mm，（4）为1.0 mm，（5）为1.2 mm。对比模型和头颅模型测量结果之间的相关性低于0.37 mm。
i-CAT在辐射剂量与图像质量方面表现最佳。
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