1. A medical imaging system for imaging a patient's body, the system comprising: a catheter comprising a position sensor and an ultrasonic imaging sensor, the position sensor transmitting electrical signals indicative of positional information of a portion of the catheter in a patient's body and the ultrasonic imaging sensor transmitting ultrasonic energy at a target in the patient's body, receiving ultrasonic echoes reflected from the target in the patient's body and transmitting signals relating to the ultrasonic echoes reflected from the target in the patient's body; a positioning processor operatively connected to the catheter for determining positional information of the portion of the catheter based on the electrical signals transmitted by the position sensor; a display; and an image processor operatively connected to the catheter, the positioning processor and the display, the image processor displaying on the display a catheter icon in a same orientation as an orientation of the portion of the catheter in the patient's body based on positional information derived from the position sensor, the image processor also generating an ultrasonic image of the target based on the signals transmitted by the ultrasonic sensor and depicting in real-time the generated ultrasound image on a display in a same orientation as the orientation of the portion of the catheter in the patient's body based on positional information derived from the position sensor.