DIFFERENCES BETWEEN REAL-TIME RADIOGRAPHY AND FILM RADIOGRAPHY
There are a number of differences between film radiograph and real-time radiograph. The four most significant differences are the speed at which an inspection can be accomplished, quality of the image, the equipment used and its related cost and, the method of image analysis and storage.
One advantage of RTR is inspection speed. With film radiography, film is placed behind the area of interest and exposed to radiation for a certain length of time. Exposure time can range from seconds to several minutes. A snapshot or a still image, i.e., the way the area looked at a certain point in time is the result. The film must be developed before viewing, a requirement that involves additional time. With RTR, the image is available almost simultaneously as the radiation passes through the part. Lag time is less than one second and, for all practical purposes, not really a consideration. This feature allows for greatly increased inspection speed. For example, lengths of a welded joint a few feet long can be inspected in less than a minute.
With sample positioning equipment, the part can be moved, e.g., rotated or tilted, so that the inspection area can be shifted and an entire part inspected in seconds. In film radiography, a single panoramic shot can be used to obtain complete coverage (a shot for which film is wrapped around the object); this can require radioactive isotope usage, and there is still the time required for the exposure plus the time to develop and dry the film before viewing. Nonetheless, the region(s) of interest (ROIs) can be viewed and reviewed much more quickly for RTR than for film radiography.