  We present the first evaluation of a recently developed silicon-strip
detector for photon-counting dual-energy breast tomosynthesis. The detector is
well suited for tomosynthesis with high dose efficiency and intrinsic scatter
rejection. A method was developed for measuring the spatial resolution of a
system based on the detector in terms of the three-dimensional modulation
transfer function (MTF). The measurements agreed well with theoretical
expectations, and it was seen that depth resolution was won at the cost of a
slightly decreased lateral resolution. This may be a justifiable trade-off as
clinical images acquired with the system indicate improved conspicuity of
breast lesions. The photon-counting detector enables dual-energy subtraction
imaging with electronic spectrumsplitting. This improved the detectability of
iodine in phantom measurements, and the detector was found to be stable over
typical clinical acquisition times. A model of the energy resolution showed
that further improvements are within reach by optimization of the detector.
