Abstract
A new X-ray image intensifier(Toshiba J-type I.I.)has been developed in response to the digital X-ray image requirements of recent diagnostic systems. In the J-type I.I., the input phosphor screen(450-μm thick, CsI)has been deposited directly on the input window. Since there is no space between the input window and phosphor screen, the scattering of X-rays at the input window is reduced. Consequently, the X-ray detection efficiency over a wide range of X-ray tube operating voltages is also improved. Our studies have shown that the 10-mm contrast ratio is 24(for a 9 inch I.I.). Using International Electrotechnical Commission(IEC)Standard methods, we have concluded that the detective quantum efficiency(DQE)is 70%. We have also compared the characteristics of the J-type I.I.with those of the conventional G-type I.I. using the DFP-2000A DF system(TOSHIBA). The main results are enumerated below. (1)The veiling-glare fraction(VGF)was about 5% less for the J-type I.I. (2)The resolution quality was the same for both types of I.I. (3)Noise was less for the J-type I.I.because of the improvement in DQE. (4)The signal to noise ratio was higher for the J-type I.I.because of the reduction of noise. (5)Receiver operating characteristic(ROS)analysis showed that signal detectability was better for the J-type I.I.
