X-ray CT device and processing device

An X-ray CT device comprising:

• an X-ray generation unit for generating X-ray;
• an X-ray detection unit for detecting the X-ray after transmitting through a subject to acquire measured projection data;
• an image-taking unit that includes a mechanism provided with the X-ray generation unit and the X-ray detection unit, and rotates around the subject;
• and
• an image generation unit that includes an iterative approximation reconstruction unit for iteratively correcting a CT image generated by the image-taking unit from the measured projection data so as to substantially equalize a difference between calculated projection data acquired by a forward projection calculation from the CT image and the measured projection data, wherein
• the image generation unit includes a table unit that stores a relationship between a noise or an X-ray reduction ratio of the CT image and a parameter used for iterative correction,
• the iterative approximation reconstruction unit determines the parameter from the table unit in accordance with the noise or the X-ray reduction ratio of the CT image,
• the iterative approximation reconstruction unit includes a weight calculation unit for calculating a weight used for iteratively correcting the CT image from the measured projection data, and determines the parameter from the table unit in accordance with the weight calculated by the weight calculation unit,
• the weight calculation unit calculates a ratio between a reference weight Wb as a value derived from summing the weight of at least one of a plurality of detection elements which constitute the X-ray detection unit under at least one image-taking condition, at least one reconstruction condition, and at least one reference position, and a weight WI as a value derived from summing the weight of at least one detection element under conditions other than the image-taking condition, the reconstruction condition, or at a position other than the reference position, and
• the iterative approximation reconstruction unit determines the parameter under conditions other than the image-taking condition, the reconstruction condition, or at the position other than the reference position from a parameter of the reference weight Wb and the calculated ratio between the weights Wb and WI.