Abstract: Methods and apparatus for creating and delivering a medical agent into an isolated vein segment, the isolated vein segment not having any communicating vein branches, the apparatus comprising a catheter having at least expandable vein occlusion devices to engage and expand the inside wall of a vein, thereby blocking the interior of the vein and preventing fluid located in the isolated segment from flowing between the occlusion devices and the wall of the vein at a pressure within the isolated vein segment of at least 100, and preferably 200, millimeters of mercury, the catheter including one or more lumens for directing a fluid into the isolated vein segment at a pressure of at least 100 millimeters of mercury.