Patent ID: 7330609

Claim:
An MTF measuring method comprising the steps of: detecting a center of an LSF (line spread function) image contained in a tomographic image produced by an X-ray CT system; and working out a two-dimensional Fourier transform of the LSF image with the center as a reference so as to thus calculate an MTF (modulation transfer function), wherein: in order to detect the center, an enlarged image of a portion of the tomographic image containing the LSF image is created; the enlarged image is binary-coded based on a threshold; a morphological operation is performed on the binary-coded image; coordinates representing points that define the contour of the image resulting from the morphological operation are sampled; the coordinates representing points that define the contour are used to work out coordinates representing the center of a circle through Hough transform; and the coordinates representing the center are transformed into coordinates representing a point in the tomographic image.