Conventional CT reconstruction algorithm, filtered-backprojection (FBP), requires the projection data acquired within the angular range from 0 to 2pi. However, for an irregular object, the data acquired at some projection views may be not available due to the detector saturation. In this work, we proposed a method to optimize the current patterns for obtaining two sets of complementary attenuation data and to employ an iterative method based on equation and inequality to improve the reconstruction quality. The simulation results obtained from the projection data, which are generated by use of the GEANT toolkit, show that the uses of optimal current scanning method and the corresponding iterative reconstruction method can yield the accuracy images with lower noise level.