Tissue treatment

A catheter system comprising:

• a catheter shaft;
• an expandable member coupled to a distal region of the catheter shaft;
• an ultrasound emission element configured to emit ultrasound energy beyond the expandable member;
• and
• a controller configured to regulate a power level and duration of the ultrasound energy to thermally damage nerve tissue in or exterior of a body lumen in which the ultrasound emission element is positioned.

A catheter for intravascular ultrasound therapy comprising:

• a catheter shaft configured for insertion into a vessel;
• an expandable member coupled to a distal region of the catheter shaft, the expandable member defining an internal chamber configured to receive a fluid;
• and
• an ultrasound emission element configured to emit ultrasound energy through the fluid and beyond the expandable member.

A method of treating tissue surrounding a vessel comprising:

• inserting a catheter having an ultrasound emission element and an expandable member into a body lumen;
• expanding the expandable member to contact a wall of the body lumen and to define a space between the ultrasound emission element and the wall;
• introducing a fluid into the expandable member;
• and
• emitting ultrasound energy through the expandable member and toward the wall to heat a target tissue.