Sewerin I
Københavns Tandlaegehøjskoles Afdeling for Radiologi.
Tandlaegebladet. 1990 Sep;94(12):483-6.
The lead foil of dental x-ray film packets may cause a number of artifacts; especially well known are the "tractor treads" and "herringbone patterns" following a backward filmpositioning in the patient's mouth. In the present paper a specific and seldomly occurring lead foil artifact is described which is caused by bending of the film packet. Four cases collected over a 5-year period are presented. Although different the four cases show a number of similarities. They appear as radiopaque areas covering the upper or lower halves of the films. Their borders show the characteristic "sandbar-pattern" previously described by the author. The explanation of their origin is that the patient has been occluding on a part of the film packet which has been bent to a nearly horizontal position. The x-rays directed against the edge of the lead foil will be absorbed causing irregular radiopaque areas on the film lined by "sandbar-pattern". When the film packet is bent, the lead foil will be stretched and drawn a little away from the edges of the films. Consequently the x-rays will be able to expose the edges of the films. Irregularities of the foil will give rise to concentric "bars". The lead foil is only of limited radiopacity, but due to the oblique direction of the x-rays through the foil the absorbing effect is intensified.
牙科X线胶片包的铅箔可能会导致一些伪影;尤其是在患者口腔中胶片向后放置时出现的“拖拉机胎痕”和“人字形图案”广为人知。本文描述了一种由胶片包弯曲引起的特殊且罕见的铅箔伪影。介绍了在5年期间收集的4个病例。尽管这4个病例有所不同,但有一些相似之处。它们表现为覆盖胶片上半部分或下半部分的不透射线区域。其边界呈现出作者先前描述的特征性“沙洲图案”。其成因是患者咬合在已弯曲至接近水平位置的部分胶片包上。对准铅箔边缘的X线会被吸收,从而在胶片上形成由“沙洲图案”勾勒出的不规则不透射线区域。当胶片包弯曲时,铅箔会被拉伸并从胶片边缘略微拉开。因此,X线能够使胶片边缘曝光。箔片的不规则会产生同心“条带”。铅箔的射线不透性有限,但由于X线穿过箔片的倾斜方向,吸收效果会增强。