Patent ID: 7056276

Claim:
A catheter for radiation therapy for treating part of a body vessel with ionizing radiation, the catheter for radiation therapy having a long catheter having a tip end part and a base end part, comprising an expandable part positioned on the tip end side of said catheter, and means for passing a radiation source through said catheter in a longitudinal direction to dispose said radiation source in said expandable part, wherein said expandable part has a two-layer structure in a radial direction of an inner layer and an outer layer, at least the inner layer is formed from an elastic substance, the bend elastic constant as measured using a measurement method based on ASTM-D790 is set to be at least 20% higher for the outer layer than for the inner layer, one or a plurality of voids are present in said outer layer, said expandable part has no protruding parts on the surface thereof when not expanded, and parts of the inner layer protrude from said voids of said outer layer when said expandable part is expanded, whereby when said expandable part is expanded, perfusion of a body fluid in the vicinity of said expandable part is made possible, and the protruding parts of said expandable part are disposed such that, when a radiation source is disposed inside the expandable part, the radiation source is always positioned in the center of said expandable part in the radial direction.