Department of Oral and Maxillofacial Radiology, The Sahlgrenska Academy at the University of Gothenburg, and Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden.
Eur J Radiol. 2011 Nov;80(2):483-8. doi: 10.1016/j.ejrad.2010.09.018. Epub 2010 Oct 20.
To evaluate subjective image quality for two diagnostic tasks, periapical diagnosis and implant planning, for cone beam computed tomography (CBCT) using different exposure parameters and fields of view (FOVs).
Examinations were performed in posterior part of the jaws on a skull phantom with 3D Accuitomo (FOV 3 cm×4 cm) and 3D Accuitomo FPD (FOVs 4 cm×4 cm and 6 cm×6 cm). All combinations of 60, 65, 70, 75, 80 kV and 2, 4, 6, 8, 10 mA with a rotation of 180° and 360° were used. Dose-area product (DAP) value was determined for each combination. The images were presented, displaying the object in axial, cross-sectional and sagittal views, without scanning data in a random order for each FOV and jaw. Seven observers assessed image quality on a six-point rating scale.
Intra-observer agreement was good (κw=0.76) and inter-observer agreement moderate (κw=0.52). Stepwise logistic regression showed kV, mA and diagnostic task to be the most important variables. Periapical diagnosis, regardless jaw, required higher exposure parameters compared to implant planning. Implant planning in the lower jaw required higher exposure parameters compared to upper jaw. Overall ranking of FOVs gave 4 cm×4 cm, 6 cm×6 cm followed by 3 cm×4 cm.
This study has shown that exposure parameters should be adjusted according to diagnostic task. For this particular CBCT brand a rotation of 180° gave good subjective image quality, hence a substantial dose reduction can be achieved without loss of diagnostic information.
评估两种诊断任务（根尖诊断和种植体规划）的主观图像质量，使用不同的曝光参数和视野（FOV）的锥形束计算机断层扫描（CBCT）。
在颅骨模型的后牙区进行检查，使用 3D Accuitomo（FOV 3cm×4cm）和 3D Accuitomo FPD（FOVs 4cm×4cm 和 6cm×6cm）。使用 60、65、70、75、80kV 和 2、4、6、8、10mA 的所有组合，旋转 180°和 360°。为每个组合确定剂量面积乘积（DAP）值。图像以轴向、横截面和矢状面显示物体，每个 FOV 和颌骨以随机顺序显示无扫描数据。7 名观察者在 6 分制评分量表上评估图像质量。
观察者内一致性良好（κw=0.76），观察者间一致性中等（κw=0.52）。逐步逻辑回归显示 kV、mA 和诊断任务是最重要的变量。根尖诊断，无论颌骨如何，都需要比种植体规划更高的曝光参数。与上颌相比，下颌的种植体规划需要更高的曝光参数。FOV 的总体排名为 4cm×4cm、6cm×6cm，其次是 3cm×4cm。
本研究表明，应根据诊断任务调整曝光参数。对于这种特殊的 CBCT 品牌，180°的旋转可获得良好的主观图像质量，因此可以在不损失诊断信息的情况下大幅减少剂量。
