Development of MTF measurement algorithm for CT images with high noise by a radial edge method

In order to remove high noise of the CT image reconstructed by a hard kernel efficiently and to minimize the number of images to be added, we constructed the system to fit the discrete data to a continuous function and developed the algorithm which calculate the MTF through a curve fitting technique with two steps. From the results, we found that the MTF obtained by this algorithm in CT images scanned under same conditions had converged to 0 at the same spatial frequency regardless of noise levels. In other words, regardless of the number of images to be added, the cut-off frequency of the MTF had a substantially the same value. In addition, we confirmed that resolution properties of the nonlinear CT images, depended on noise levels, and the usefulness of this algorithm was shown. Therefore, we made it possible to evaluate a spatial resolution of a nonlinear CT image with high noise quantitatively.