Implantable embolization device

An embolization device configured to be positioned within a body lumen of a patient, the embolization device comprising:

• an elongated primary structure formed of a coiled wire, wherein the primary structure forms a secondary structure when unconstrained in which the primary structure forms an anchor portion and a trailing portion, and wherein:
• the anchor portion comprises at least one loop configured to be in contact with and press radially outwardly against an inner surface of the body lumen at a treatment site such that the anchor portion is configured to anchor the embolization device at the treatment site, and
• the trailing portion is configured to fill space in the body lumen to reduce or block flow into and/or through the body lumen, wherein the trailing portion is more flexible than the anchor portion,
• wherein the primary structure has a first length corresponding to the trailing portion and a second length corresponding to the anchor portion, and wherein a sidewall of the primary structure comprises a first number of coil layers along the first length and a second number of coil lavers along the entire second length, the second number greater than the first number, and
• wherein the wire comprises a first wire length comprising a first cross-sectional dimension and a second wire length comprising a second cross-sectional dimension greater than the first cross-sectional dimension, each of the first and second cross-sectional dimensions measured perpendicular to a longitudinal axis of the wire, and wherein the first length of the wire extends along at least a portion of the first length of the primary structure and the second length of the wire extends along at least a portion of the second length of the primary structure.