Physical and psychophysical evaluation of a new digital specimen radiography system for use in mammography

The goal of this project was to physically and psychophysically evaluate a new digital detector for surgical breast specimen radiography. It is an optical imaging system with a 1K × 1K CCD detector with 24 micron pixels and a 2:1 fiber reducer. Physical evaluation of linearity, noise and spatial resolution were conducted. To measure observer performance, two contrast-detail phantoms were imaged and displayed in four conditions: plain film, CR printed to film, CR displayed on a monitor, and the new digital images displayed on a monitor. Images were acquired at 25 and 30 kV at high, medium and low exposures. 10 observers participated. The system is linear, noise goes as the square-root of exposure, and resolution is in excess of 10 1p/mm. Observer performance was significantly higher with the new digital system (average 74% detections) than all other conditions at all exposure levels, both kVs and for both phantoms (film average 28%, CR film average 61%, CR monitor 50%). The digital specimen radiography system outperformed all other detectors. The system is compact and can easily be used in the operating room. The two versions of the contrast-detail phantoms used in the study are essentially comparable, although some differences were noted.