An acoustic catheter (10) has a shaft (18) driven by a rotary motor (60). The shaft drives a rotary-to-axial motion converter (30) near the distal end (14) of the catheter. The converter (30) includes a rotary driver (42) with a wavy or sinusoidal bearing surface (36) facing a similarly wavy face (38)...http://www.google.se/patents/US5593415?utm_source=gb-gplus-sharePatent US5593415 - Acoustic catheter with reduced friction drive
