| 摘要 |
<p>A radiographic film cassette exposes a sheet of film to X-rays projected along an X-ray path by an X-ray tube. The cassette has an inner surface defining a recess for receiving the film sheet. A base having an inner surface is adapted to close upon the cover for securing the film sheet. A key is permanently mounted to the cover and disposed within the recess to provide the recess with chiral asymmetry. The sheet of film has a cutout adapted to engage the key. A marker is permanently fixed along at least on edge of the film. The key is so mounted that its disposition within the recess permits engagement with the cutout in only one orientation of the film sheet therein. The marker has chiral asymmetry and cooperates with the key and the cutout to identify the side of the film sheet facing the X-ray tube during exposure.</p> |
