A newly developed a-Se mammography flat panel detector with high-sensitivity and low image artifact

Abstract

A novel amorphous selenium (a-Se) detector with the hexagonal pixel has been developed for full-field digital mammography. The pixel area of the detector was designed to be same as that of the 68 μm square pixel detector, while the pixel pitch between neighboring pixels was set to be 73-75 μm in six directions. By applying the hexagonal pixels, the sensitivity of the detector has improved by 18% compared with a conventional square pixel. A simulation showed that the hexagonal pixel provided a more uniform electric field in the a-Se layer than the square pixel, which has lead to higher sensitivity. The modulation transfer function of the detector was 92 % at 2 mm^-1 and 62 % at 5 mm^-1. These values were as high as that of a conventional a-Se detector with 50 μm square pixels. As a result, the detective quantum efficiency of this detector achieved 75 % with 5 mR and 72 % with 2.5mR at 2 mm^-1. The exposure conditions were 28 kV W/Rh with a 2 mm aluminum filter. Therefore, the new detector can reduce the exposure dose while maintaining a high image quality.