Evaluation of Performance of Image Orthicon, Vidicon and Permachon Television Camera Tubes in Conjunction with Fluoroscopic Image Intensifiers

Abstract

Television systems are now widely used in conjunction with image intensifiers to display fluoroscopic information. The relative merits of Orthicon vs. Vidicon systems in fluoroscopic practice have not been clearly defined. An opportunity to compare the two in a laboratory was provided by a research project involving image Orthicons with a 9-inch image intensifier for stereoscopic fluoroscopy. A storage Vidicon (Westinghouse “Permachon”), which will retain a still picture for several minutes, was also evaluated in conjunction with an image intensifier. In a preliminary study, immediate display of planigraphy was made possible by mounting the intensifier with TV camera at the film level in the cassette-transport mechanism. An image Orthicon (R.C.A. 6489) and a Vidicon (Westinghouse 7325) tube have been compared at 85 kvp (2 mm. A1 filter) with use of the Burger (1) test plate with several thicknesses of phantom. With 1.2 mr per minute at the face of the image intensifier (equivalent to a 25 cm. abdomen with conventional fluoroscopy) the image Orthicon picks up detailcontrast (5 mm. diameter hole 5 mm. deep) equal to conventional fluoroscopy at 360 mr per minute while the Vidicon is unable to show any detail. At 14 mr per minute (equivalent to about a 15 cm. thick part) the detail-contrast (3 mm. hole 3 mm. deep) is the same on the image Orthicon as it is on the Vidicon. At 95 mr per minute on the image intensifier the image Orthicon is “flooded” with light and the Vidicon gives better results. At this intensity the limit of visibility for the Vidicon is a 2 mm. diameter hole 2 mm. deep. In regard to motion of an object in the x-ray beam it is found that there is much more afterimage or “trailing” with the Vidicon than with the image Orthicon, especially at low x-ray intensities. This is well demonstrated when a rotating lead disk with a rectangular hole is placed in the x-ray beam just in front of the image intensifier.