PET Imaging of Peripheral Benzodiazepine Receptors in Patients With Carotid Atherosclerosis

Objective

Inflammation in the vascular wall plays an important role in the pathophysiology of atherosclerosis, including development of plaque, plaque destabilization and rupture. Clinical and basic scientific data demonstrate the importance of peripheral white blood cells in this process. Therefore, a noninvasive method to detect inflammatory activity in atherosclerosis may be of great value to help determine prognosis, direct therapy and perhaps assess novel therapies for stabilization of atherosclerotic plaque.

The peripheral benzodiazepine receptor (PBR) is distinct from central benzodiazepine receptors associated with GABAA receptors and has been associated with immune function. PBR is expressed in macrophages, therefore, they may be a clinically useful marker to detect inflammation. Our preliminary autoradiographic data demonstrate specific PBR binding in carotid atherosclerosis samples. Though PBR has been imaged in vivo with positron emission tomography (PET) using [(11)C]1-(2-chlorophenyl-N-methylpropyl)-3-isoquinoline carboxamide (PK11195), we developed a new ligand, [(11)C]N-acetyl-N-(2-methoxybenzyl)-2-phenoxy-5-pyridinamine (PBR28) that shows greater specific signal than [(11)C]PK11195 in non-human primates.

The objective of this protocol is to assess the utility of [(11)C]PBR28 PET to detect inflammation in unstable atherosclerosis plaques and large vessels with inflammation.

Study population