Abstract: Since the shape of the target objects may be very different during industrial computed tomography testing,conventional CT image reconstruction algorithms usually assume a rectangular region as the reconstruction domain.A fast image reconstruction method based on minimal region is proposed in this paper.Firstly,the envelope of the minimal projection region of the target object is obtained by using a line scan conversion algorithm on the scanned projection data.Then,a fast region filling algorithm is applied to generate the minimal region for reconstruction.This method limits the reconstruction domain to a minimal region,hence reducing unnecessary computation and accelerating the reconstruction process.Experimental results show the effectiveness of the proposed method compared with the conventional methods.