Imaging properties of digital magnification mammography

Imaging properties of magnification mammography with a computed radiography (CR) system were measured to investigate the potential utility under the conditions of a matched average glandular dose (AGD). The AGD in each magnification mammography was matched to that of conventional contact mammography with 4 cm breast thickness. A dedicated mammographic unit with nominal focal spot sizes of 0.1 mm and 0.3 mm, molybdenum anode and 0.03 mm molybdenum filter, was used in this study. The magnification factor varied from 1.2 to 1.8, including contact radiography. The basic physical imaging parameters were evaluated by measuring scatter fraction, modulation transfer function (MTF) including geometric unsharpness of focal spot and presampled MTF of detector, and noise power spectrum (NPS) for the various magnification factors. In the no grid technique, the scatter fraction of the magnification radiography decreases considerably with increasing magnification factor, and was comparable to magnification radiography in the grid technique. The MTF of magnification mammography improved with an increasing magnification factor. The resolution properties of the digital magnification mammography depend upon focal spot size, pixel size, and magnification factor. The noise level for the digital magnification radiography was significantly increased. This result was caused by the reduced entrance exposure to the phantom, and thus reduced incident radiation to the detector.