The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 09, 1991
Filed:
Apr. 05, 1989
Michitaka Honda, Yaita, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
An estimating circuit estimates the thickness of the subject appearing on a mask image, by using the value of the thickness of a uniform material equivalent to a subject, with respect to each pixel of the mask image, based on radiographic conditions and pixel density of each pixel. A correction coefficient table has correction coefficients corresponding to the thickness of the uniform material. One of the correction coefficients is selected from the correction coefficient table, based on the estimated thickness obtained from the estimating circuit. The selected correction coefficient and each pixel of the mask image are subjected to an arithmetic operation, thereby to produce a mask image in which influence due to beam-hardening effect is corrected. On the other hand, a suitable correction coefficient is selected from a correction coefficient table having correction coefficients corresponding to the thickness of the contrast medium, based on the estimated thickness of the image and on a subtraction image obtained by subtracting the mask image from a contrast image produced by irradiating radioactive rays onto the subject in which the contrast medium is injected. The selected correction coefficient and each pixel of the subtraction image are subjected to an arithmetic operation, thereby to obtain a mask image in which influence due to beam-hardening effect is corrected.