Patent ID: 7054406

Claim:
An X-ray computer tomography apparatus comprising: an X-ray source configured to irradiate X-rays onto an object to be examined from plural directions; an X-ray detection unit configured to detect X-rays transmitted through the object; a driving unit configured to rotate at least one of the X-ray source and the X-ray detection unit around the object; a moving unit configured to move the object in a given direction; an image data generation unit configured to generate image data on the basis of projection data from the object collected from the X-ray detection unit plural times while moving the object by the moving unit; an ROI setting unit configured to set a region of interest in the image data generated by the image data generation unit; a CT value calculating unit configured to calculate CT values, in pixels, in the region of interest of the image data, while generating the image data by the image data generation unit; a range setting unit configured to set a range of the CT values; a pixel number measuring unit configured to measure the number of pixels providing CT values which are calculated by the CT value calculating unit and which are contained within the range set by the range setting unit; a threshold setting unit configured to set a threshold value for the number of pixels; and a pixel number comparing unit configured to keep comparing the number of pixels obtained by the pixel number measuring unit with the threshold value of the number of pixels set by the threshold setting unit and to generate an instruction signal for stopping X-ray irradiation when both substantially agree.