Large screen image amplification with closed-circuit television employing television tape-recorder.

Abstract

The ever increasing public emphasis on the hazards of radiation and the ever expanding fields of motion radiography present challenges to the radiologist and to the manufacturer of x-ray equipment. At the same time that more extensive use of motion studies is made, every effort must be concentrated on limiting the amount of radiation during any given examination. The recently opened x-ray department at the Children's Hospital of Pittsburgh utilizes television tape-recording of the fluoroscopic image, mediated through a newly developed image Orthicon television camera2 optically coupled to a 9-inch image amplifier. The system permits recording on television tape and simultaneous viewing on the closed-circuit television monitor at the same low levels of radiation as are required for closed-circuit television viewing alone. This paper will outline some of the considerations that went into the planning of the department. Image amplifiers with field diameters of 4 1/2 and 5 inches have been available for nine years. They have the disadvantages of limited field size and inconvenience of viewing by more than one observer. The optical coupling of Vidicon television cameras with these amplifiers to record the fluoroscopic image on closed-circuit television monitors solved the problem of viewing but necessitated increased amounts of radiation for adequate visualization of the field under observation. Satisfactory cineradiographic film recording of the fluoroscopic image on the amplifier requires a major increase in radiation. In the course of investigation of available systems of image amplification, particularly with reference to larger field size, the authors became interested in the General Electric TVX system, which employed closed-circuit television as an integral part of its operation. It offered the potential advantage of television viewing at diminished rates of radiation but raised the problem of recording the television image. Kinescopic movie-film recording of the image on the television screen is relatively difficult technically, moderately expensive, and attended by film problems inherent in other cineradiographic methods. Television tape-recording affords the ideal method for reproduction of the picture on the television monitor. The identity of an original picture with its television-taped reproduction is apparent to any home television viewer. Television tape also offers the advantages of immediate playback for review, and of availability to all fluoroscopic rooms. An additional cable run from the television camera to the tape-recorder allows recording from each fluoroscopic unit. Television tape-recording is possible at the level of radiation required for closed-circuit television monitor viewing.