Fluoroscopy: Recording of fluoroscopic images and automatic exposure control

Some means of recording images is a necessary part of most fluoroscopic sys tems. Several methods are available for recording images during fluoroscopy . Screen-film recording methods such as use of spot film devices and automa tic film changers provide high-spatial-resolution images. Recording images by using the image intensifier (fluorography) provides film or digital imag es at relatively lower doses but with poorer spatial resolution. Digitally recorded images have better contrast resolution than analog images but lowe r spatial resolution and represent a compromise between dose and image qual ity. Motion picture (cine fluorographic) recording requires extremely high dose rates compared with those of lower-resolution videotape recording of m otion. Recording systems in fluoroscopy require automatic exposure control for optimum image quality. The same feedback system used to control fluorog raphic exposures can be used to control exposure rates during fluoroscopy a s well. Automatic brightness control maintains intensifier exposure rates o n the basis of subject thickness by adjusting various technique factors. Th e type of control mechanism depends on the imaging task and the complexity (age and cost) of the equipment. The operator can choose between better ima ge quality (higher contrast) or lower radiation dose.