X-rays are one way for a doctor to see problems in the chest area.
Radiographic cassettes are the plastic covers that hold X-ray film. Starting around 1948 the cassette was tweaked and improved upon in order to find the best combination of absorption time and clearest captured images. In the earliest days a person would stay exposed to the X-rays for 11 minutes, but now it takes mere milliseconds, which is about 2 percent of the overall exposure time from before.
Process
X-ray film can capture any part of the body that is safe in X-ray exposure.
The cassette is a thin rectangular prism-shaped container that opens like a book. In the center, the X-ray film is placed and the book is closed. The container is then placed underneath the section of the body, known as posterior-anterior or PA, so the X-rays can pass through the body and then the image is displayed on the film. Much like taking a photograph it is important for the subject to be as still as possible and the resulting photo to be as clear and crisp as possible.
Capturing the image
X-rays and photos use similar capturing processes.
The difference between a photograph and the X-ray image is the process of capturing the image. Basically, they are moments captured onto the film. A camera lets in light and burns that image onto the film. The X-ray film works similarly, but the cassette is much more complicated. To block free rays from distorting the image, the cassette needs to have multiple layers to deflect free rays from hitting random spots on the film, thus distorting the resulting image.
Cassette exterior
The prism is typically 14 mm thick, but the length and width are dependent on the situation. There are cassettes and films as small as 5 inches by 7 inches, or as big as 14 inches by 51 inches. The frame can be made out of aluminum, stainless steel, and more recently carbon fiber.
Casette interior
The inside needs to harness the rays and ensure that a clear image is captured from the exposure. This is achieved by the harmony of many layers. There is an initial grid that absorbs the rays and is built to deflect free rays that would distort the clarity of the image. Under that is a fluorescent intensifying screen, and an emulsion layer, before finally the film base. This is the structure on both sides of the "book" design of the cassette.
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