A system and method for imaging a target in a patient's body uses a pre-acquired image of the target and a catheter having a position sensor and an ultrasonic imaging sensor. The catheter is placed in the patient's body and positional information of a portion of the catheter in the patient's body is determined using the position sensor. The catheter is used to generate an ultrasonic image of the target using the ultrasonic imaging sensor. An image processor is used for determining positional information for any pixel of the ultrasonic image of the target and registering the pre-acquired image with the ultrasonic image; and a display is used for displaying the registered pre-acquired image and ultrasonic image.