X-ray Image Detection by Electronic Methods.

In diagnostic radiology, the excellence of the conventional radiographic screen-film combination as a means of detecting and displaying the X-ray pattern (the radiation image) is qualified by its inability to show movement. The technique of fluoroscopy, in which the light image on the fluorescent screen is viewed by the dark-adapted but otherwise unaided eye, has long been employed in an attempt to overcome this disadvantage. Unfortunately, because of restricted optical aperture and low retinal efficiency, the eye responds to only a very small fraction of the light emitted by the screen, and only about one-fifth of the information inherent in the screen image is transmitted to the brain. This inefficiency of information transfer also renders it necessary in clinical work to use dose-rates which are higher than appear at present to be desirable. These fundamental deficiencies, together with the inconvenience of the darkened room which can be a great handicap in complex techniques such as cardiac catheterization, seriously limit the clinical applications of fluoroscopy.