Patent ID: 7263398

Claim:
Microwave apparatus for measuring blood flow rate in a patient's blood vessel, said apparatus comprising, an intravascular catheter having proximal and distal ends and containing an inner coaxial cable forming a first antenna and an outer cable coaxial with the inner cable and forming a second antenna, said first antenna extending axially beyond the second antenna a selected distance; an extracorporeal control unit including a microwave transmitter which transmits signals to the catheter, a microwave receiver which receives signals from the catheter, and a processor controlling the transmitter and receiver, said processor including means responsive to the timing of the transmitted and received signals for measuring said blood flow rate, and a diplexer connected between said first and second antennas and the control unit for coupling signals from the transmitter to one of the antennas but not to the receiver and for coupling signals from the other of the antennas to the receiver but not to the transmitter.