Phase contrast digital mammography using molybdenum X-ray: Clinical implications in detectability improvement

We have applied phase imaging on digital mammography to investigate adequate contrast of printed images for digital phase contrast mammography using a practical molybdenum X-ray tube. Phase contrast mammography procedures were performed with defined air gap (e.g., 0.6 m) configuration using customized mammography equipment and a computed radiography (CR) system. Magnified (x2) phase contrast images acquired with 0.0875mm per pixel were mapped onto the laser imager resolution at 0.04375mm per pixel for printing life-size object on wet processing silver halide recording film. For contact mammography of screen-film system, we used MinR2000 system as a baseline method. ACR 156 phantom printed images with contrasts of 2.8, 3.7, 4.9 5.7 and 6.7 were evaluated by five radiologists. The ACR scores for the life-size image based on the 2 times magnified phase contrast image acquired by the computed radiography were higher than the scores of MinR2000 image, when-the contrast of printed images for both methods was 3.7. The ACR scores were lower in the low contrast images (i.e., 2.8) than its higher contrast counterparts (i.e., greater than or equal to 3.7) for all techniques used. The detectability improvement should be due to higher spatial resolution and lower noise in the phase contrast images.