Oral Radiology, Department of Dentistry, Aarhus University, Denmark.
Dentomaxillofac Radiol. 2013;42(2):32310645. doi: 10.1259/dmfr/32310645. Epub 2012 Jul 27.
The aim of this study was to assess artefacts and their impact on cone beam CT (CBCT) image quality (IQ) after head motion simulated by a robot skull.
A fully dentate human skull incorporated into a robot simulated pre-determined patient movements. Ten head motion patterns were selected based on the movement of the C-arm of the CBCT units (no motion as reference). Three CBCT units were used [a three-dimensional eXam (K) (KaVo Dental GmbH, Biberach, Germany), a Promax 3D MAX (P) (Planmeca Oy, Helsinki, Finland) and a Scanora(®) 3D (S) (Soredex Oy, Tuusula, Finland)]. Axial images were qualitatively assessed at three levels: mental foramen (MF), infraorbital foramen and supraorbital foramen, and artefacts characterized as stripe-like, double contours, unsharpness or ring-like. A 100 mm visual analogue scale (VAS) was used to quantitatively assess IQ. Cross-sectional images of the lower third molar and MF bilaterally were also evaluated by VAS. Four blinded examiners assessed the images.
For all units and motion patterns, stripe-like artefacts were the most common. The four observers agreed on the presence of at least one artefact type in 90% of the images. Axial images showed lower overall IQ after motion (VAS = 72.4 ± 24.0 mm) than reference images (VAS = 97.3 ± 2.6 mm). The most severe artefacts were seen at the MF level. For cross-sectional images, IQ was lowest after tremor. The mean IQ range was 74-89 and 57-90 for isolated (tilting, rotation and nodding) and combined (nodding + tilting and rotation + tilting) movements, respectively. IQ for MF was lower than for third molar for any movement except tremor.
Head motion of any type resulted in artefacts in CBCT images. The impact on IQ depended on the region and level in the skull.
本研究旨在评估机器人颅骨模拟头部运动后锥形束 CT（CBCT）图像质量（IQ）的伪影及其影响。
将一个完全有牙的人类颅骨整合到机器人中，以模拟预定的患者运动。根据 CBCT 单元 C 臂的运动选择了 10 种头部运动模式（无运动作为参考）。使用了三个 CBCT 单元[三维 eXam（K）（KaVo Dental GmbH，Biberach，德国）、Promax 3D MAX（P）（Planmeca Oy，赫尔辛基，芬兰）和 Scanora(®)3D（S）（Soredex Oy，图苏拉，芬兰）]。在三个水平上对轴向图像进行定性评估：下颌孔（MF）、眶下孔和眶上孔，并将伪影特征化为条纹状、双轮廓、不清晰或环状。使用 100 毫米视觉模拟量表（VAS）对 IQ 进行定量评估。还通过 VAS 评估双侧下第三磨牙和 MF 的横截面图像。四名盲法检查者评估图像。
对于所有单元和运动模式，条纹状伪影最为常见。四名观察者一致认为，90%的图像中至少存在一种伪影类型。与参考图像（VAS=97.3±2.6mm）相比，运动后的轴向图像总体 IQ 较低（VAS=72.4±24.0mm）。MF 水平的伪影最严重。对于横截面图像，震颤后的 IQ 最低。孤立（倾斜、旋转和点头）和组合（点头+倾斜和旋转+倾斜）运动的平均 IQ 范围分别为 74-89 和 57-90。除震颤外，MF 的 IQ 低于第三磨牙的 IQ。
任何类型的头部运动都会导致 CBCT 图像出现伪影。对 IQ 的影响取决于颅骨的区域和水平。
