PROBLEM TO BE SOLVED: To provide a contrast medium for optical acoustic imaging that has a high signal per concentration of organic dye.SOLUTION: A contrast medium for optical acoustic imaging has a plurality of complexes each of which has at least one organic dye covalently bonding to albumin, the organic dye being a compound represented by the formula (1) or salt thereof [R1-R8 independently represent H, a C1-3 alkyl group, or sulfonic acid group R9-R12 independently represent H or a C1-3 alkyl group R13 and R14 independently represent a substituted/unsubstituted C1-5 alkyl group, where the substituent is a carboxyl group, a sulfonic acid group or a phosphonic acid group n1 and n2 independently represent 0 or 1 L1-L7 are a methine group, where L1-L7 may form a 4 membered-6 membered ring R100 is a phenyl group, a pyridyl group or a substituted/unsubstituted C1-5 alkyl group, where the substituent is an aryl group and the like].SELECTED DRAWING: NoneCOPYRIGHT: (C)2017,JPO&INPIT【課題】有機色素の濃度当りの信号が大きい、光音響イメージング用造影剤の提供。【解決手段】アルブミンに少なくとも1つの有機色素が共有結合してなる複合体を複数有する光音響イメージング用造影剤であって、該有機色素が下記式(1)で表わされる化合物又はその塩である光音響イメージング用造影剤。[R1~R8は各々独立にH、C1~3のアルキル基、スルホン酸基;R9~R12は各々独立にH、C1~3のアルキル基;R13及びR14は各々独立に置換/非置換のC1~5のアルキル基、前記置換基はカルボキシル基、スルホン酸基或いはホスホン酸基;n1及びn2は各々独立に0又は1;L1~L7はメチン基、L1~L7は4員~6員の環を形成していてもよい;R100は、フェニル基、ピリジル基又は置換/非置換のC1~5のアルキル基、前記置換基はアリール基等]【選択図】なし
