PROBLEM TO BE SOLVED: To improve operability in measurement of the Cobb angle of a vertebral column image, and to prevent an erroneous diagnosis.SOLUTION: The vertebral column image indicating a vertebral column in which a plurality of curved parts exist is displayed on the monitor screen of a display part, and auxiliary lines are drawn along the axial direction upper end of the upper end vertebra and the axial direction lower end of the lower end vertebra of each of the plurality of curved parts of the vertebral column image displayed on the monitor screen on the basis of operations from an operation part. At the time, the drawing of the respective auxiliary lines is permitted only in a craniocaudal order in the extending directions of the vertebral column of the vertebral column image displayed on the monitor screen. Then, an angle formed by the two auxiliary lines adjacent to each other in the drawing order (craniocaudal direction) of the respective drawn auxiliary lines is measured as the Cobb angle.COPYRIGHT: (C)2010,JPO&INPIT【課題】脊椎画像のコブ角の計測における操作性を向上させるとともに、誤診を防止する。【解決手段】複数の湾曲部が存在する脊椎を示す脊椎画像を表示部のモニタ画面に表示させ、操作部からの操作に基づいて、モニタ画面に表示された脊椎画像の複数の湾曲部のそれぞれの上位終椎の軸方向上端及び下位終椎の軸方向下端に沿って補助線を描画する。その際、モニタ画面に表示された脊椎画像の脊椎の延在方向のうち、頭尾方向に沿う順序でのみ各補助線の描画を許可する。そして、描画された各補助線の描画順(頭尾方向)において相隣る二つの補助線同士が互いになす角度をコブ角として計測する。【選択図】図8