Information Capacity of Radiographic Images for the Random Signal and Continuous Objects

Abstract

Some of the results in a previous paper, JJAP 7 (1968) 414, which deals with the random signal are considered again. The capacity is roughly proportional to the square bandwidth of the equipment. The reason is explained. To investigate the decrease of the capacity of actual continuous object from the random signal, capacities for three kinds of object spectrum, including that of bones in human bodies, are estimated using numerical examples. For wide object spectra, the wider bandwidth of a radio-graphic or inspecting equipment produces the greater capacity. For narrow object spectra or for low frequency objects, the capacity is proportional to the square spread of the object spectrum and the insertion of a low pass filter improves the capacity. The reasons are discussed in detail. Since eyes and an intensifying screen act as low pass filters, for low frequency objects, the capacity of the film directly exposed is increased by exposing with the screen or by inspecting by eyes.