Quantitative Analysis of the Image Layer in Rotational Panoramic Radiography

为了分析三维图像层，我们测量了旋转全景X线片中TMJ区域前面的调制传递函数(MTF)，这些MTF使我们能够确定McDavid等人引入的信息传递因子(ITF)，并定义了层厚。DuPont HiPlus/Kodak X-Omat RP胶片以1.1 mm的狭缝宽度曝光，在固定的千伏和毫安下拍摄狭缝X射线图像。在每个区域的膜层中心放置一条宽0.1 mm、厚0.1 mm的铅缝，每隔一段时间向膜侧和管侧移动。用Doi等人的方法测得NTF，以ITF为75时，测得前牙层厚为5.74 mm，尖牙为7.35 mm，磨牙为15.1 mm，TMJ为20.7 mm。实验得到的图像层与计算得到的图像层基本一致。

To analyze the three dimensional image layer, we measured the modulation transfer function (MTF) at the anterior to TMJ region in rotational panoramic radiography.These MTFs enabled us to determine the information transfer factor (ITF) introduced by McDavid et al, and defined the layer thickness.Veraview (J. Morita Corp. Japan) was used as a panoramic x-ray unit. Dupont HiPlus/ Kodak X-OMAT RP film was exposed with 1.1mm slit width to gives slit x-ray image at the fixed kV and mA. A lead slit, 0.1mm wide and 0.1mm thick was positioned at the center of the layer in each region.The slit was moved toward the film side and the tube side at given intervals. The NTF was obtained by the method of Doi et al.When we defined the limit of the layer by the ITF of 75, the measured layer thickness was 5.74mm in the anterior, 7.35mm in the canine, 15.1mm in the molar and 20.7mm in the TMJ region, respectively. The image layer obtained by our experiment was in fair agreement with the calculated one.