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X-ray image intensification (XRII) is discussed from a historical perspective in terms of the input scintillator, the electron optics, and the output phosphor screen. The basic concept and physical appearance of XRII has changed little since its introduction nearly 30 years ago. It is characterized by a minified output image. The minified output image was chosen so that additional brightness gain of approximately 100 times could be obtained. However, this design choice of obtaining additional brightness gain through the minification of the output image size has locked the XRII to inverting-type electrostatic-focused electron optics which require cylindrical symmetry, long electron trajectories, weak cathode field strength, and curved input screen. Nevertheless, significant improvements in the preformance of XRII have been made in the past 10 years. Primarily, these improvements were made through the use of improved X-ray-sensitive input screen phosphors, electron optics, and output screens. The improvements have led to the consideration, design, and construction of a novel proximity-type XRII. This device has the main advantage of fewer sources of unsharpness so that this advantage can be traded for higher MTF performance or dose reduction performance. In addition, the size and shape of this device are not restricted as in the case of current minifying-type X-ray image intensifier tubes. Various systems applications employing this device, such as in simple direct-view intensified panel-like fluoroscopy, low-dose TV fluoroscopy, and direct radiographic miniaturization, are discussed.
X-ray, image intensification, scintillator, electrostatic focused, proximity focused, MTF, dose, conversion factor, radiography
Professor, Stanford University, Stanford, Calif.