A system for treating a vascular malformation has an expandable device and a heating device for heating and shrinking the malformation. The expandable device may have deformable elements which plastically deform in the expanded position. The balloon may be self-expanding, balloon expanded or expanded with an actuating rod. A fluid, such as saline, may be introduced during heating when using RF heating. A sealant may also be introduced into the expandable device to further seal the aneurysm.