<title>Simultaneous Objective Measurements Of Dose And Image Quality In Mammography</title>

Abstract

The performance of a radiological system can be evaluated on the one hand by an objective determination of the quality of the produced image and, on the other hand, by the dose delivered to the patient. In order to measure these two factors in a single exposure a Kodak breast phantom has been modified so as to simulate the breast absorption. The dose distribution is measured with thermoluminescent detectors. By consideration of a theoretical model of the X -ray imaging in mammography, a single quality factor is computed from the contrast, the spatial resolution and the noise measured on the phantom image. We present results obtained in various working conditions, i.e. variable X -ray tube voltages, use of different screen -film combinations, use of a grid.

Image quality index (IQI) for screen-film mammography

“…The image quality index is defined as the diameter of the smallest detectable object with a high probability of correct decision. In a previous approach (Pochon et a1 1982, Pochon 1983, Hessler et al 1985 the following simplifying assumptions were made:…”

“…A quality index can be naturally taken as the diameter of the smallest perceptible spherical object. This quantity has been called the image quality index, IQI (Pochon 1983). Such a definition has already been applied (Pochon er a/ 1982, Hessler ef a/ 1985); its validity for the evaluation of image quality has been checked by a rank correlation test on 10 films representative of different operating conditions in mammography.…”