Patent ID: 7471758

Claim:
An X-ray CT apparatus comprising: a first storage device configured to previously store therein a first table where a fat content and sample CT numbers for different irradiation conditions are associated with each other, the sample CT numbers having been obtained by irradiating water phantoms containing predetermined quantities of fats with X-rays under different irradiation conditions; a second storage device configured to previously store therein a second table of sample CT numbers for respective different water phantom sizes irradiated under different irradiation conditions; a CT number measurement unit configured to irradiate an object with X-rays under the different irradiation conditions, and to obtain actually-measured CT numbers for the different respective irradiation conditions; and a fat content obtaining unit configured to obtain a fat content corrected by a size of the object, based on the first table, the second table and the actually-measured CT numbers for the different respective irradiation conditions.