A motion detection scheme is described which periodically sends a plurality of pulsed ultrasonic signals from a transducer to a particular range cell to receive a series of backscattered signals from the particular range cell. The time interval between any two pulses is greater than a largest dimension of the range cell divided by a slowest velocity of motion at the particular range cell. A temporal variation between the envelopes of the signals is then determined to detect motion at the particular range cell. This scheme may be applied at all points in an image, to produce images that depict regions undergoing motion.