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 being configured to generated an ultrasonic image of the target on the display based on the signals transmitted by the ultrasonic sensor, the image processor being further configured to generate 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, a beam icon to mark an area scanned by the ultrasonic image sensor and an orientation icon in a same orientation as the ultrasonic image of the target depicted on the display; wherein the image processor depicts in real-time the generated ultrasound image and the beam icon on the 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.