A display technique determines the desired size of an object to be displayed, determines the distance between the display unit and a user, and adjusts the size of the displayed object based on the desired size and measured distance. The apparatus comprises a high voltage pulse generator and an intravascular catheter with electrodes adapted for delivery of electrical pulses to the media and adventitia of the treated segment of an artery. A coolant is disposed within the central passageway. The computer system assesses whether or not a rule of use has been violated, and will only permit the dispenser to dispense where the rule has not been violated.