1. An ultrasonic imaging method comprising the steps of: generating a reference image of a subject; storing the reference image and a scan condition used to acquire said reference image; reading said reference image and said scan condition, said reference image comprising a region of treatment encompassed by a region of interest before providing medical treatment to the subject; setting the scan condition as a current scan condition before providing medical treatment; acquiring a real-time image of the subject after providing medical treatment to the subject; automatically defining the region of interest in said real-time image encompassing the region of treatment after providing medical treatment to the subject; calculating a correlation coefficient between a portion outside of the region of interest in said reference image and a portion outside of the region of interest in the real-time image; displaying on an ultrasonic image display device said reference image and said real-time image side by side, the correlation coefficient, and in a hold manner, a maximum value of the correlation coefficient from a beginning of acquisition of said real-time image up to the present; and adjusting an orientation of an ultrasonic probe against the subject so that the correlation coefficient becomes equal to the maximum value.