1. An image processing apparatus comprising: a storage unit configured to store corresponding information in which one or more images of one or more frame images included in a dynamic image and one or more calculation middle images generated from two or more frame images included in the dynamic image in which a pixel value is employed when a statistic regarding a single pixel region is obtained in the calculation, relative to the single pixel region for each pixel region including one or more pixels in a calculation result image having the statistic obtained by the calculation for a medical dynamic image as each pixel value; a specification unit configured to specify the one or more pixel regions in the calculation result image; and a determination unit configured to determine one or more output images based on one or more images corresponding to the one or more pixel regions specified by the specification unit in the corresponding information.