Marking device and implantation system

A marking device for implantation into a tissue, comprising:

• a support structure configured to transition between a radially compressed state and an axially compressed state, the support structure comprising a plurality of elongated segments bounded by first and second tubular ends, the plurality of elongated segments extending along a longitudinal axis of the marking device and each having a first end and a second end, at least one of the first ends and the second ends of the plurality of elongated segments terminating at one of the first and second tubular ends of the support structure,
• wherein:
• when the support structure is in the radially compressed state, each of the plurality of elongated segments is substantially parallel with the longitudinal axis of the marking device, and
• when the support structure is in the axially compressed state, at least two segments of the plurality of elongated segments arc outward to form an expanded central portion of the support structure, an exterior surface of the expanded central portion curving in a continuous arc between the first and second tubular ends to encompass an open center bounded by the first and second tubular ends.