To grasp positional relationships between two or more arbitrary objects of a bone and an indwelling device such as a pedicle screw or of a bone and the like to which the indwelling device is fixed properly and in real time even if the bone is not under direct vision.SOLUTION: When a body surface is traced with an ultrasonic probe 21 in which a marker of a navigation system is attached to the ultrasonic probe, a three-dimensional model of a bone surface can be constructed from the position of the ultrasonic probe 21, an ultrasonic wave irradiation angle, and echo data. A three-dimensional model of an indwelling device or the like such as a pedicle screw is obtained and superposed on the three-dimensional model of the bone surface so that an image from a desired direction is displayed.SELECTED DRAWING: Figure 1【課題】骨と椎弓根スクリューのような体内留置用機器あるいは体内留置用機器を固定した骨等の任意の２つ以上の対象物に関する位置関係を直視下に無くても的確かつリアルタイムに把握する。【解決手段】超音波プローブにナビゲーションシステムのマーカーを取り付けた超音波プローブ２１で体表面をなぞると、超音波プローブ２１の位置と超音波の照射角度およびエコーデータから、骨表面の３次元モデルを構築できる。椎弓根スクリューのような体内留置用機器等の３次元モデルを得て、骨表面の３次元モデルに重ねて、所望方向からの画像を表示するようにする。【選択図】図１
