Schulze R, Schalldach F, d'Hoedt B
Poliklinik für Zahnärztliche Chirurgie, Johannes Gutenberg-Universität Mainz.
Mund Kiefer Gesichtschir. 2000 May;4(3):164-70. doi: 10.1007/s100060050190.
Magnification factors (VF) in relation to various head positions were evaluated for a digital panoramic radiography machine (Orthophos DS, Sirona) by means of a dry skull phantom. Six metallic objects were attached to the facial layer of the mandible. A set of 170 digital radiographs (program 1) was produced, with defined positioning errors within the vertical and horizontal plane. Repeated digital measurements of the object images were performed by one reader, applying the mouse-driven measurement tool integrated in the proprietary software. In addition, the central layer of the radiographic device was experimentally determined and its location compared to that of the accurately positioned dry mandible. All objects were located on the outside of the central layer of minimum distortion and therefore placed towards the sensor. One- and two-way analysis of variance was applied for the statistical evaluation of the data, with VF as dependent variable and the positions as factors, respectively. Vertical inclinations of the skull affected horizontal VF only in the premolar region (p = 0.0069). However, when the skull was rotated within the horizontal plane, VF was significantly influenced in all anatomical regions of the mandible (p = 0.0001). This was particularly obvious in the premolar region, with a maximum variation of 10.3%. Fluctuations of VF were more pronounced in the premolar region than at the mandibular angle. We conclude from this study that, as expected, digital panoramic radiographs exhibit identical distortion effects as compared to conventional panoramic x-rays. Exact quantification of regional magnification requires (spherical) reference objects with known dimensions. Horizontal magnification is quite unreliable and far less reproducible than vertical magnification. Whenever several panoramic radiographs of one patient are to be compared quantitatively, accurate positioning of the patients' head is a necessary prerequisite.
通过一个干燥颅骨模型，对一台数字全景X射线摄影设备（Orthophos DS，西诺德公司）在不同头部位置时的放大系数（VF）进行了评估。在下颌骨的面部层面附着了六个金属物体。生成了一组170张数字射线照片（程序1），在垂直和水平平面内有规定的定位误差。由一名读者使用集成在专用软件中的鼠标驱动测量工具，对物体图像进行重复的数字测量。此外，通过实验确定了射线摄影设备的中心层面，并将其位置与精确定位的干燥下颌骨的位置进行比较。所有物体都位于最小失真中心层面的外侧，因此朝向传感器放置。对数据进行统计评估时应用了单向和双向方差分析，分别将VF作为因变量，将位置作为因素。颅骨的垂直倾斜仅在前磨牙区域影响水平VF（p = 0.0069）。然而，当颅骨在水平面内旋转时，下颌骨的所有解剖区域的VF均受到显著影响（p = 0.0001）。这在前磨牙区域尤为明显，最大变化为10.3%。VF的波动在前磨牙区域比在下颌角处更为明显。我们从这项研究中得出结论，正如预期的那样，与传统全景X射线相比，数字全景射线照片表现出相同的失真效果。区域放大率的精确量化需要尺寸已知的（球形）参考物体。水平放大率相当不可靠，且远不如垂直放大率可重复。每当要对一名患者的多张全景射线照片进行定量比较时，患者头部的精确定位是必要的前提条件。
