A medical image processing device, method, and program that, when a plurality of past brain images are available, make it possible to select a past brain image that makes it possible to accurately calculate the atrophy rate of a brain. According to the present invention, an image acquisition unit 21 acquires, for the same subject: a target brain image Bt that is for diagnosis; and a plurality of past brain images Bpi that were captured before the target brain image Bt. A degree of similarity calculation unit 22 calculates the degree of similarity between each of the plurality of past brain images Bpi and a standard brain image Bs. A selection unit 23 selects, from the plurality of past brain images Bpi, a reference brain image B0 that serves as a reference for calculating the amount that a brain has changed.
MEDICAL IMAGE PROCESSING DEVICE, METHOD, AND PROGRAM