Image Evaluation Method for Digital Mammography with Soft-copy Reading Using a Digital Phantom

Abstract

Evaluation of mammograms has been done using films or hard copy. In Japan, there has been a rapid shift to soft―copy diagnosis, and facilities for this approach are necessary. Digital mammography has high resolution and a large matrix size. When a monitor displays the mammogram, the image is either displayed partially by １：１ pixel mapping or is narrowed to fit the monitor, resulting in loss of image quality. We have developed the digital phantom used for every mammographic detector sold in Japan. This phantom resembles the Contrast Detail Phantom and comprises group of １２ different shapes and group of eight different brightnesses. One group consists of９signals, and each signal is located at the prime number coordinate from a central signal coordinate. This phantom is able to evaluate the display system including the reduction function and monitor resolution, etc. This phantom is also useful for education and quality control.