The present invention relates to an ultrasound system and a method of forming an ultrasound image. The ultrasound system includes: a transmit/receive unit operable to transmit ultrasound signals to a target object and receive ultrasound echo signals to form receive signals based on the received ultrasound echo signals a signal processing unit operable to form Doppler signals based on the receive signals and an image processing unit operable to obtain information on a plurality of blood flow velocities at the target object from the Doppler signals, set a reference velocity, compute a dispersion of the plurality of the blood flow velocities with respect to the reference velocity, and form a 3-dimensional image indicating velocity changes at the respective locations in the target object by using the reference velocity and the dispersion.
