A processing unit is configured perform an image process upon an ultrasound image to thereby detect a center of a blood vessel from the ultrasound image. The processing unit is configured to set the center of the blood vessel as an optimal focal point position. The processing unit is configured to calculate a plurality of steering angles, a plurality of transmit (Tx) frequencies and a plurality of sound speeds. The processing unit is further configured to form a plurality of ultrasound images corresponding to each of the steering angles, the Tx frequencies and the sound speeds based on the ultrasound data, detect a signal to noise ratio (SNR), a number of edge points of the blood vessel and a contrast difference between pixels for each of the second ultrasound images to thereby detect an optimal steering angle, an optimal Tx frequency and an optimal sound speed.
