<title>X-ray tube voltage dependence of Rossmann's three factors in Wiener spectra of radiographic mottles of a low-speed screen/film system</title>

ABSTRACT We obtained the tube# voltage dependence of the Wiener spectra of the radiographic mottles of the front andback emulsions made using a low-speed screen and an anticrossover film. The Wiener spectral values of the frontemulsion are almost constant, while those of the back emulsion increase with the tube voltage. The spectral valuesof the front emulsion are greater than those of the back emulsion at most of densities. In order to investigate thereason of these phenomena, we separated the radiographic mottle into the three factors. As a result, we have foundthat the reason for the dependence of the radiographic mottle is that the contribution of the quantum mottle isless than that of the structure mottle. The Wiener spectral values of the structure mottle of the front screen aregreater than those of the back screen for most of the tube voltages. The Wiener spectral values of the front screendecrease and those of the back screen increase with the tube voltage , and the two curves cross at high voltage.These reasons were explained from the spatial fluctuation of the thickness of the screen due to the nonuniformscreen structure and the attenuation curve of the x-ray intensity. The tube voltage dependence of the quantimmottle was explained from that of the number of photons absorbed in the screen.