An ultrasonic imaging system for indicating blood vessels of a human body includes an ultrasonic imaging module, a display module, a marking module, and processing module operatively coupled to the ultrasonic imaging module, the display module, and the marking module. The processing module is configured to obtain, using the ultrasonic imaging module, ultrasonic images corresponding to a portion of the human body； present, using the display module, the ultrasonic images, where the ultrasonic images depict one or more blood vessels of the human body； determine that the ultrasonic imaging system is aligned according to a particular blood vessel depicted in the ultrasonic images； and upon determining that the ultrasonic imaging system is aligned according to the particular blood vessel depicted in the ultrasonic images, apply, using the marking module, a marking substance to a surface of the human body. The marking substance is applied to a point immediately above the particular blood vessel.
