An intravenous ultrasound (IVUS) system can include a catheter which can include memory. Because portions of the catheter are in intimate contact with the patient, electrical signals are isolated for safety. The IVUS system or catheter can thus comprise a catheter interface which provides bidirectional isolation circuitry for coupling the catheter to additional components of the IVUS system. Such circuitry allows for memory operation and communication from within the catheter while remaining electrically isolated. Catheter memory can contain information specific to the catheter such as the type of catheter, information regarding catheter components, information regarding catheter use, and other information useful for catheter operation.