Method for Measuring Contrast-to-Noise Ratio (CNR) in Non-uniform Image Area on Digital Radiography

Abstract

One of physical indices for evaluating the image quality of digital radiography is contrast-to-noise ratio (CNR). The CNR was reported to simulate the human perception. Thus, the CNR is a variable index for evaluating detectability for digital radiography. However, it is difficult to evaluate the CNR in non-uniform image area. In this study, we have devised a new method for measuring CNR in non-uniform image area on digital radiography using top-hat transform. Furthermore, we investigated the radiation dose dependence of CNR in the digital image of an anthropomorphic breast phantom containing a simulated calcification. We have shown that the CNR in non-uniform image area can be analyzed with high accuracy by our devised method for measuring CNR. In the radiation dose dependence of CNR, CNR increased with mAs values and reduced depending on the increase in the concentration of glandular in the anthropomorphic breast phantom.