Reduction of patient dose on medical radiographs using scattered X-rays

摘要

We propose a new method for reduction of the patient dose by using scattered X-rays in order to achieve the same density as without scattered rays. The minimum perceptible thickness difference Δ_(min) of the object was calculated using psychophysical analysis for various radiographic densities, scatter fractions and luminous exitances of the viewer. The mAs values to obtain many densities were measured using four kinds of anti-scattered X-ray grid with their scatter fractions. The measured values were applied to above calculated psychophysical results to obtain the reduction ratio by using the scattered X-rays in actual radiography. The perceptibility of human eyes is influenced by luminous exitance of the viewer. As a result, the patient dose reduced 33 percent in maximum under the same perceptibility of Δ_(min) by increasing the luminous exitance from 1500 1m·m~(-2) to 8000 lm·m~(-2). The method of changing grid will be considered.