Interstitial tissue structure is treated with a flowable liquid agent by: providing a delivery cannula having a proximal end and a distal end and an external surface with at least one expandable member located on the external surface of at least one catheter or needle. The delivery cannula is inserted into live tissue, creating a hole in the tissue surrounding the delivery cannula. Contact is made against an inner surface of the hole with contact pressure from the at least one expandable member, said contact pressure establishing a first level of stress in tissue surrounding the hole in the tissue. The expandable member is expanded to increase the contact pressure and provide a second level of stress in the tissue surrounding the hole in the tissue to a second level of stress that is greater than the first level of stress.