The effect of amorphous selenium thickness on imaging performance of contrast enhanced digital breast tomosynthesis

Abstract

Digital breast tomosynthesis (DBT) and contrast enhancement (CE) for both DBT (CEDBT) and planar mammography (CEDM) are being investigated to increase conspicuity of malignant lesions. To image above the k-edge of iodine (33 keV), CEDBT requires x-ray energies higher than those of typical mammograms (∼28 kVp). Increasing the thickness of the detector's amorphous selenium (a-Se) layer improves x-ray absorption and detective quantum efficiency (DQE), particularly at higher energies. For DBT, where systems are often designed with partially isocentric geometries, thicker a-Se layers may result in degradation of the modulation transfer function (MTF) for oblique views. We employed a cascaded linear system model to analyze the effect of oblique entry on MTF. Also, the model was experimentally validated using 200 and 300 μm a-Se flat panel imagers. Finally, we use an ideal-observer SNR model for projection and DBT imaging to optimize a-Se layer thickness for detectability of iodinated objects. © 2012 Springer-Verlag Berlin Heidelberg.