PROBLEM TO BE SOLVED: To provide a ring-knot structure capable of easily grasping a posture around an axis when fluoroscopy is performed. SOLUTION: This is a nodal ring structure in which a plurality of nodal rings are sequentially adjacent to each other along the axial direction and are arranged so as to extend from a base end to a tip end. Each nodal ring 5 has four through holes 53a to 53d arranged at a pitch of approximately 90 ° each other including a pair of mountain portions forming a swing center and a pair of through holes 53a and 53b formed in the mountain portions. To be equipped. The tip is engaged with each of the most advanced knots, and is inserted into four passages 54a to 54d composed of through holes 53a to 53d of each of the knots, and the base end is the base end of the knot structure. The four wires W1 to W4 leading to the above were provided. The knots and wires W1 and W2 were formed of an X-ray permeable material, and the wires W3 and W4 were formed of an X-ray opaque material. [Selection diagram] FIG. 2A【課題】Ｘ線透視した際に軸心周りの姿勢を容易に把握できる節輪構造体を提供すること。【解決手段】複数の節輪を軸心方向に沿って順次隣接して基端から先端にわたって延在するように配設してなる節輪構造体である。各節輪５は、揺動中心を構成する一対の山部と、該山部に形成された一対の貫通孔５３ａ，５３ｂを含む互いに略９０°ピッチで配置された４つの貫通孔５３ａ～５３ｄを備える。それぞれ最先端の節輪に先端部が係合し、複数の節輪の各貫通孔５３ａ～５３ｄにより構成される４つの通路５４ａ～５４ｄに挿通され、基端部が節輪構造体の基端に至る４本のワイヤＷ１～Ｗ４を設けた。各節輪、ワイヤＷ１，Ｗ２をＸ線透過性の材料で形成し、ワイヤＷ３，Ｗ４をＸ線不透過性の材料で形成した。【選択図】図２Ａ
