1. An image generating apparatus comprising: a determiner configured to determine projection data collected by a scan of an imaging object using a radiation source and a detector; a first setter configured to set a plurality of first reconstruction planes in a body axis direction of the imaging object; a second setter configured to set one or more second reconstruction planes different from the plurality of first reconstruction planes in the body axis direction of the imaging object, wherein the plurality of first reconstruction planes are located at different locations along the body axis direction from the one or more second reconstruction planes; a reconstructor configured to reconstruct a plurality of images corresponding to the plurality of first reconstruction planes and to be supplied to an operator and one or more images corresponding to the one or more second reconstruction planes, based on the projection data; and a processor configured to perform an artifact reduction process on an image corresponding to a given first reconstruction plane using a plurality of images corresponding to a plurality of reconstruction planes including the plurality of first reconstruction planes and at least one of the one or more second reconstruction planes, wherein the processor is further configured to: calculate a probability that a pixel in the image corresponding to the given first reconstruction plane represents an artifact based on pixel value variations in the plurality of images corresponding to the plurality of reconstruction planes, the pixel value variations are variations in the body axis direction; and perform the artifact reductions process on the pixel based on the probability.