Wikner Johannes, Friedrich Reinhard E, Rashad Ashkan, Schulze Dirk, Hanken Henning, Heiland Max, Gröbe Alexander, Riecke Björn
1 Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
2 Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Dentomaxillofac Radiol. 2016;45(4):20150436. doi: 10.1259/dmfr.20150436. Epub 2016 Mar 9.
Conventional panoramic radiography (cPR) underlines procedure-related limitations in the display of objects. CBCT is presumed to overcome these constraints. To virtualize a cPR view, reformatted panoramic images (rPIs) can be generated. This study evaluated the rPI with regard to its susceptibility to sterical object deposition in comparison with cPR.
A specially developed implant model with dental implants each of 4.0-mm diameter and 11.0-mm length was depositioned by shift, rotation and tilt of 5.00 mm (±0.01 mm) of horizontal shift and 5.0° (±0.167°), respectively, on a highly precise goniometer rotation table, and cPRs and rPIs were generated. Automated evaluation of the cPRs was carried out using a specially developed software. rPIs were processed and analyzed by a semi-automated image analysis.
Object deposition lead to distortive effects in the rPI analogue to cPR, but they appear in display only. Objects illustrated in the rPI were dimensionally correct, but sterical relations are elusive. Results are obtained for the horizontal shift, declination and reclination, lateral tilt and rotation.
Distortions within the rPI represent the illustration of the hyperbolic-shaped layer out of the three-dimensional data set. With this study, we demonstrated these procedure-related inherent but practically underestimated consequences. Effects of sterical object malpositioning must be compensated by the observer by adequate virtual adjustment of the processed layer. Accurate virtual adjustment leads to vertical dimensions. Sterical relations, e.g. angulation of two objects, are irretraceable unless precisely referenced.
传统全景放射摄影（cPR）突显了在显示物体方面与程序相关的局限性。锥形束计算机断层扫描（CBCT）被认为可以克服这些限制。为了虚拟出cPR视图，可以生成重新格式化的全景图像（rPI）。本研究评估了rPI与cPR相比在空间物体沉积敏感性方面的情况。
在高精度测角仪旋转台上，通过分别平移、旋转和倾斜5.00毫米（±0.01毫米）的水平位移和5.0°（±0.167°），放置一个专门开发的植入模型，其中每个牙种植体的直径为4.0毫米，长度为11.0毫米，然后生成cPR和rPI。使用专门开发的软件对cPR进行自动评估。rPI通过半自动图像分析进行处理和分析。
物体沉积在rPI中产生了与cPR类似的扭曲效应，但仅出现在显示中。rPI中显示的物体尺寸正确，但空间关系难以捉摸。获得了水平位移、偏斜和倾斜、侧向倾斜和旋转的结果。
rPI内的扭曲代表了从三维数据集中双曲线形层的图示。通过本研究，我们证明了这些与程序相关的固有但实际被低估的后果。空间物体位置不当的影响必须由观察者通过对处理层进行适当的虚拟调整来补偿。精确的虚拟调整可得出垂直尺寸。除非精确参照，否则空间关系，例如两个物体的角度，是无法追溯的。
