1. An X-ray CT apparatus comprising: an X-ray generating means; an X-ray detector disposed opposing to the X-ray generating means; a rotating means for rotating the X-ray generating means and the X-ray detector in a circular orbit of a same rotation center; a control means for controlling the X-ray generating means so as to irradiate X-rays from the X-ray generating means to an object to be examined laid along the rotation center and controlling the X-ray detector to detect X-ray dose penetrated through the object, while controlling the rotating means to rotate the X-ray generating means and the X-ray detector; and a reconstruction computing means for performing reconstruction computation by making use of the data of the penetrated X-ray dose obtained under the control of the control means and acquiring a tomographic image; the X-ray CT apparatus further comprising an input means configured for input of information with respect to a target tissue of the object to be discriminated with a specific recognition rate in the tomographic image, and for input of an index with respect to the specific recognition rate of the discrimination; and a scanning condition determining means for determining scanning conditions for discriminating the target tissue based on the index inputted by the input means.