To easily calculate a coronary blood flow spare quantity ratio from information on a structure of a coronary artery.SOLUTION: A calculation method of a coronary blood flow spare quantity ratio includes: a first calculation procedure for calculating a coronary blood flow spare ability based on a normal coronary artery area which is a cross-section area of a normal part, and a lesion coronary artery area which is a cross-section area of a narrow part of the cross-section area of the coronary artery, and predetermined blood viscosity, blood specific gravity, and lesion length； a second calculation procedure for calculating pressure loss of the coronary artery in the narrow part based on the coronary blood flow spare ability calculated in the first calculation procedure, and a predetermined resting coronary blood flow velocity； and a third calculation procedure for calculating the coronary blood flow spare quantity ratio based on the pressure loss calculated in the second calculation procedure.SELECTED DRAWING: Figure 1【課題】冠動脈の構造の情報から簡便に冠血流予備量比を算出する。【解決手段】冠血流予備量比の算出方法は、冠動脈の断面積のうち、正常部の断面積である正常冠動脈面積と、狭窄部の断面積である病変冠動脈面積と、予め定められた血液粘度、血液比重及び病変長とに基づいて、冠血流予備能を算出する第１の算出手順と、第１の算出手順において算出される冠血流予備能と、予め定められた安静時冠血流速度とに基づいて、狭窄部における冠動脈の圧力損失を算出する第２の算出手順と、第２の算出手順において算出される圧力損失に基づいて、冠血流予備量比を算出する第３の算出手順とを有する。【選択図】図１
