Abstract: An ultrasound imaging apparatus is provided. The apparatus comprises an ultrasound probe configured to perform ultrasound sweeping of a region of interest including a target location and a target vessel in a real time volume ultrasound scan mode, an image acquiring unit configured to acquire three-dimension scan data of the target location and the target vessel, and a controlling unit configured to calculate the target vessel centerline length based on the acquired three-dimension scan data. The apparatus further comprises an image processing unit configured to automatically mark distance scales from the critical line located at the target location along the target vessel centerline at predetermined intervals based on the calculated centerline length, and a displaying unit configured to displaying the target location and the target vessel centerline marked with distance scales in real time.