obtaining a plurality of brain-related images;

selecting one or more candidate images including information related to the ventricle region and the white matter hyperintensity (WMH) region among the plurality of images;

obtaining a disease index from the candidate images; and

selecting a target medical image corresponding to a disease index satisfying a predetermined condition among the plurality of disease indexes by considering the plurality of disease indexes calculated from the candidate images,

wherein the selecting one or more candidate images includes segmenting the brain-related images to obtain information on a plurality of brain regions in the images, detecting the brain regions corresponding to the ventricle region and the white matter hyperintensity region, and determining the image including both the ventricle region and the white matter hyperintensity region among the plurality of images as the candidate images,

wherein the obtaining the disease index includes determining at least one of a width or area of a white matter hyperintensity region included in the candidate image, determining a distance between the ventricle region and the white matter hyperintensity region, and calculating the disease index by considering the width or area of the white matter hyperintensity region and the distance between the ventricle region and the white matter hyperintensity region, and

wherein the target medical image corresponding to the disease index satisfying the predetermined condition is a medical image indicating the highest grade value of disease index.