1. An image generating apparatus comprising: a determining unit configured to determine projection data collected a by scan of an imaging object using a radiation source and a detector; a first setting unit configured to set a plurality of first reconstruction planes in a body axis direction of the imaging object; a second setting unit configured to set one or more second reconstruction planes different from the first reconstruction planes in the body axis direction of the imaging object; a reconstruction unit configured to reconstruct a plurality of images corresponding to the first reconstruction planes and to be supplied to an operator and one or more images corresponding to the one or more second reconstruction planes and not to be supplied to the operator, based on the projection data, and a processing unit 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 plural first reconstruction planes and at least one of the one or more second reconstruction planes.