Spot Film Devices
The aforementioned image recording methods merely store the image recorded by the TV camera, which is of lower quality than a radiographic image and has even poorer resolution than the image appearing on the output phosphor of the image-intensifier tube because of the limita-tions of the TV imaging process. In order to record higher quality images during a fluoroscopic examination, spot film devices are used. The most common device transports a conventional radiographic screen/film cassette to a posi-tion in front of the image intensifier at the push of a button on the fluoroscopic carriage. The x-ray tube is then switched into a radiographic mode (ie, the milliamperage is increased from low mA to 200 to 400 mA to shorten expo-sure time), and a conventional radiographic image is obtained on film. Digital spot films can be obtained by dig-itizing a TV frame from the image intensifier acquired with a short exposure burst at a higher exposure value than that of a single continuous fluoroscopic frame. These produce an image of higher quality (lower noise) than that obtained from the fluoroscopic image.
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