Image reconstruction using EM method in X-ray CT

Computed tomography (CT) is a technique for imaging cross-sections of an object using a series of X-ray measurements taken from different angles around the object. It has been widely applied in diagnostic medicine and industrial non-destructive testing. Traditional CT reconstructions are limited by many kinds of artifacts, and they give dissatisfactory image. To reduce image noise and artifacts, the theory of maximum likelihood estimation is extended to X-ray scan in this paper, and expectation maximization (EM) algorithm is studied and implemented for image reconstruction of X-ray CT (XCT). Then the point spread function and modulation transfer function of the EM algorithm is analyzed. Last experimental results with computer simulated data and real CT data are presented to verify our method is effective.