METHOD FOR DETECTING PROSPECTIVE CONTOUR POINTS OF AN IRRADIATION FIELD

摘要

A method for detecting a prospective contour point of an irradiation field comprises the steps of detecting an image signal representing a radiation image from a recording medium which has been exposed to radiation over a limited irradiation field in order to record the radiation image thereon, and obtaining digital image signal components corresponding to image information stored at respective positions on the recording medium from the image signal. A characteristic value which represents the characteristics of the distribution of the values of the digital image signal components representing image information stored on a single line on the recording medium is calculated. A predetermined threshold value is adjusted on the basis of the characteristic value, and differentiation processing of the digital image signal components is carried out along the line. A point, for which the absolute value of a corresponding differentiated value obtained by differentiation processing exceeds the threshold value, is detected as a prospective contour point of the irradiation field.