An image generation method of an interior computed tomography, CT, comprising the following steps: a step for obtaining interior CT projection data by measuring quantum beams passing only through a region of interest, ROI, in an inside of a photographing object in a geometrical system for a CT measurement; a step for obtaining partial entire projection data by measuring quantum beams passing through an entire of said photographing object; and a processing step for reconstructing said ROI on the basis of said interior CT projection data obtained and said partial entire projection data, characterized in that reconstructing said ROI uses only partial entire projection data from a partial orbit around an outside of said photographing object in said geometrical system for the CT measurement; wherein the interior CT projection data includes a truncation therein, and the partial entire projection data does not include a truncation therein; and wherein inability of calculation of Hilbert transform in said interior CT projection data including said truncation therein is brought into ability of calculation by using said partial entire projection data not including said truncation therein, comprising: • calculating a differentiation from the partial entire projection data and calculating a Hilbert transform on the differentiation and applying a symmetry that filter correct projection data of two positions opposing each other are equal to establish a prior information with an enlarged angular range where the Hilbert transform can be made; • calculating filter correct projection data from the prior information and from differentiation filtered interior CT projection data; • conducting back projecting on the filter correct projection data; and thereby reconstructing said ROI. a step for obtaining interior CT projection data by measuring quantum beams passing only through a region of interest, ROI, in an inside of a photographing object in a geometrical system for a CT measurement; a step for obtaining partial entire projection data by measuring quantum beams passing through an entire of said photographing object; and a processing step for reconstructing said ROI on the basis of said interior CT projection data obtained and said partial entire projection data, characterized in that reconstructing said ROI uses only partial entire projection data from a partial orbit around an outside of said photographing object in said geometrical system for the CT measurement; wherein the interior CT projection data includes a truncation therein, and the partial entire projection data does not include a truncation therein; and wherein inability of calculation of Hilbert transform in said interior CT projection data including said truncation therein is brought into ability of calculation by using said partial entire projection data not including said truncation therein, comprising: • calculating a differentiation from the partial entire projection data and calculating a Hilbert transform on the differentiation and applying a symmetry that filter correct projection data of two positions opposing each other are equal to establish a prior information with an enlarged angular range where the Hilbert transform can be made; • calculating filter correct projection data from the prior information and from differentiation filtered interior CT projection data; • conducting back projecting on the filter correct projection data; • calculating a differentiation from the partial entire projection data and calculating a Hilbert transform on the differentiation and applying a symmetry that filter correct projection data of two positions opposing each other are equal to establish a prior information with an enlarged angular range where the Hilbert transform can be made; • calculating filter correct projection data from the prior information and from differentiation filtered interior CT projection data; • conducting back projecting on the filter correct projection data; and thereby reconstructing said ROI.