Doppler catheter

Claim 1

A steerable catheter which is operable to measure the fluid velocity in a fluid-carrying vessel, the catheter comprising: an elongated, flexible, tubular body having a distal end and being operably manipulable in the vessel; a channel structure operably received and generally longitudinally aligned within said body, said channel structure defining a lumen which, with the catheter inserted into the vessel, is isolated from the fluid within the vessel; a structure defining a passageway which, with the catheter inserted into the vessel, is adapted for operable communication with the fluid within the vessel and for receiving a wire steering guide to selectively position said distal end in the vessel; and Doppler means for measuring the velocity of the blood through the vessel including a Doppler crystal disposed adjacent said distal end, the Doppler crystal having a flat face oriented generally perpendicular to the longitudinal axis of said body, said flat face defining an acoustic axis generally aligned with the longitudinal axis of said body so that the acoustic axis is manipulable into linear alignment with the fluid flow axis in the vessel, and electrical leads connected to the crystal and disposed in said lumen in isolation from the fluid with the catheter inserted in the vessel.