1-(1-Phenylethyl)-1H-imidazole-5-carboxylic acid [11C]methyl ester

Excerpt

In the adrenocortex, 11β-hydroxylase is a key enzyme in the biosynthesis of cortisol and aldosterone. This enzyme can be overexpressed in adrenocortical carcinomas, which secrete excessive amounts of catecholamines and cortical hormone (1). However, some adrenal tumors appear unexpectedly as incidentalomas in computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound scans in 1-4% of patients (2). Most of these incidentalomas consist of benign, cortical, nonhypersecretory adenomas (3). Therefore, it is important to identify the malignant lesions in the incidentalomas for appropriate clinical treatments. Ketoconazole, etomidate and metomidate are potent inhibitors of 11β-hydroxylase (4, 5). [¹¹C]Metomidate introduced as an adrenocortical imaging tracer by Bergstrom et al. (6) has proven to be useful in distinguishing adrenocortical from non-cortical lesions and identifying incidentalomas of adrenocortical origin (7-10).