  In the hard X rays domain, the phase shift of the wave passing through the
soft materials like tissues is typically three orders of magnitude larger than
the absorption. Therefore the phase-sensitive X-ray imaging methods can obtain
substantially increased contrast over conventional absorption-based imaging. In
this paper, we present a detector system design for the computed tomography(CT)
prototype which based on the grating-based phase contrast imaging(GBPCI)
method. This system consists of 43 Hamamatsu silicon photodiode S12058(X)
modules including 16512 pixels. Each module can provide 384(16*24) pixels,
which the minimum pixel size is 0.75mm*1mm. The front-end readout
electronics(FEE) of each module complete the analog-to-digital conversion, the
digital processing, and the data transmission. All digitized data from 43
detector module are transmitted to the control system through the data
collection boards. The test result shows that the efficient resolution of the
detector system is up to 14.6bit. For all pixels, the integral nonlinearity is
no more than 0.1%.
