Open AccessThe AAPM/RSNA Physics Tutorial for Residents
Author(s) -
Van Lysel
Publication year - 2000
Publication title -
radiographics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.866
H-Index - 172
eISSN - 1527-1323
pISSN - 0271-5333
DOI - 10.1148/radiographics.20.6.g00nv201769
Subject(s) - image intensifier , image sensor , optics , image noise , computer vision , image resolution , aperture (computer memory) , frame rate , noise (video) , artificial intelligence , time delay and integration , image quality , computer science , physics , image (mathematics) , acoustics
In fluoroscopic/fluorographic systems, an image intensifier is optically coupled to recording cameras. The optical distributor is responsible for transmitting a focused image from the output phosphor of the image intensifier to the focal planes of the cameras. Each camera has an aperture, which is used to control the level of light reaching its focal plane. The aperture setting determines the patient x-ray exposure level and the image noise level. Increasing the x-ray exposure reduces image noise; reducing the x-ray exposure increases image noise. Fluoroscopic/fluorographic systems always include a video camera. The functions of the video system are to provide for multiple observers and to facilitate image recording. The camera head contains an image sensor, which converts the light image from the image intensifier into a voltage signal. The device used to generate the video signal is a pickup tube or a charge-coupled device sensor. The method used is raster scanning, of which there are two types: progressive and interlaced. The vertical resolution of the system is primarily determined by the number of scan lines; the horizontal resolution is primarily determined by the bandwidth. Frame rate reduction can be a powerful tool for exposure reduction.