1. A method for generating a medical image of a subject including functional information, the steps of the method comprising: a) acquiring a first medical image weighted based on functional information reflecting physiological functions of the subject and a second medical image weighted based on anatomic information of the subject; b) generating a difference image between the first medical image and the second medical image; c) generating a local similarity image by subjecting the difference image and the second medical image to a localized kernel; d) generating an improved difference image using the local similarity image; and e) generating an enhanced medical image by subtracting the improved difference image from the first medical image to retain the functional information reflecting physiological functions of the subject.