X-ray ct apparatus and image calculating device for x-ray ct apparatus

An image calculating device for an X-ray CT apparatus, comprising:

• a signal processing device that obtains measured data, including signal values of 0 or less by processing a signal obtained by detecting X-rays passed through an object, and performs a logarithmic conversion on the measured data by using a predefined function so as to generate projection data;
• and
• a reconstruction calculating device that performs a reconstruction process on the projection data so as to generate an image,
• wherein the predefined function is a function of which an inverse function is present for values of a predetermined negative number or more, and the measured data including signal values of 0 or less within a predetermined range is restored by applying the inverse function to the projection data.

An X-ray CT apparatus comprising:

• an X-ray generation device that irradiates an object with X-rays;
• a data acquisition system that detects the X-rays passed through the object;
• a signal processing device that obtains measured data including signal values of 0 or less by processing an output, signal from the data acquisition system, and performs a conversion process on the measured data by using a predefined function including a logarithmic function so as to generate projection data;
• a reconstruction calculating device that performs a reconstruction process on the projection data so as to generate an image;
• and
• a storage device that stores the projection data,
• wherein the signal processing device includes a restorer that reads the projection data stored in the storage device, and that restores the measured data including the signal values of 0 or less within a predetermined range.