Abstract: [Problem] To provide a labeled fatty acid derivative for diagnostic imaging that enables the quantification of myocardial fatty acid metabolic activity. [Solution] The inventors, engaging in diligent research into methods that enable the quantification of fatty acid metabolic activity, discovered that a labeled fatty acid derivative represented by formula (1), in which [18F] has been substituted at a specific position of a long-chain carboxylic acid compound containing a sulfur atom, or a salt thereof, has good accumulation in the myocardium, and enables imaging of fatty acid metabolic activity via positron emission tomography (PET). Therefore, the labeled fatty acid derivative according to the present invention can be used as a radiotracer for swift and noninvasive quantification of myocardial fatty acid metabolic activity, diagnostic imaging of heart diseases such as ischemic heart disease, diagnostic imaging of the therapeutic effects yielded by a heart disease therapeutic agent, and so forth.

Abstract: [Problem] Provided is a labeled fatty acid derivative for diagnostic imaging that enables quantification of fatty acid metabolic activity in the heart muscle. [Means for Solution] The present inventors have conducted intensive investigations on a method that enables quantification of fatty acid metabolic activity and thus have found that a labeled fatty acid derivative typified by 3-{[(5Z)-3-[18F]fluorotetradeca-5-en-1-yl]sulfanyl}propanoic acid or a salt thereof has excellent accumulation to the heart muscle and thus enables imaging of fatty acid metabolic activity by positron emission tomography (PET). Therefore, the labeled fatty acid derivative of the present invention can be used as a radiolabeled tracer for rapid and non-invasive quantification of fatty acid metabolic activity in the heart muscle, diagnostic imaging of heart disease typified by an ischemic heart disease, diagnostic imaging of the therapeutic effect of a therapeutic drug for heart disease, and the like.