Visualization and Quantitative Evaluation of Arterial Inflammatory Plaque of Carotid, Coronary, and Aorta in Patients with Coronary Artery Disease Using a SiPM PET/CT System

1675 Introduction: In patients with lifestyle-related diseases, atherosclerotic plaque progresses, and stenosis is accelerated. This process leads to plaque collapse, causing cerebral infarction and/or myocardial infarction. One of the major causes of unstable plaque is its inflammation. The silicon photomultiplier (SiPM) PET/CT system has improved the spatial resolution, making it possible to visualize and evaluate the inflammatory activity of the plaque that is as small as 5 mm. To identify patients with a high risk of cardiovascular events non-invasively and to intervene early in their treatment, we planned this pioneering clinical study. The purpose of this study is to develop an image analysis method for the visualization of whole body arterial inflammatory lesions in patients suspected of coronary artery disease. Methods: This study is a prospective, observational, IRB-approved study. The subjects were those with lifestyle-related diseases and were either attending or hospitalized at Hokkaido University Hospital or related facilities because of suspected coronary artery disease. Written consent was obtained from all subjects. 18F-FDG was administered intravenously at a dose of 4.5 MBq/kg after at least 18 hours of fasting with a low carbon diet to suppress physiological myocardial uptake, and PET/CT imaging was started 70 min later. Scanning was performed in the following order: 15 min emission scanning at the neck, 90 sec/bed emission scanning from the base of the skull to mid-thigh, and 15 min emission scanning at heart using a SiPM PET/CT scanner (Vereos, Philips Healthcare). To measure the maximum standardized uptake value (SUVmax) in each artery as an index of active inflammation, a 5-mm and a 10-mm spherical volume of interest (VOI) were defined for the coronary arteries and the internal carotid arteries, respectively. To evaluate the aorta, the spherical VOI was set on ascending, descending, abdominal aorta, and aortic arch at 3~4 cm. A 5-mm spherical VOI was set within the lumen of the descending aorta at the LMT level as a blood pool. The targeted blood ratio (TBR) of each artery and clinical parameters were compared with the clinically diagnosed acute coronary syndrome (ACS), stable angina (SA), and non-coronary arterial disease (non-CAD) groups. Results: Based on coronary artery angiography, the subjects were classified into the following three groups; ACS (n=8), SA (n=6), and non-CAD group (n=5) (Table). In the ACS group, FDG PET/CT was scanned within one month after urgent revascularization; in the SA and non-CAD groups, FDG PET/CT was performed before medical treatment. In this study, the normal of each artery TBR was defined as the maximum of those for 5 non-CAD subjects. The percentage of ACS and SA patients with TBR values above normal in the carotid artery was 50% (4/8) and 33% (2/6) (Fig.1). In the coronary artery, abnormal uptake was visualized in ACS and SA patients with 38% (3/8) and 50% (3/6), 63% (6/8) and 67% (4/6), 38% (3/8) and 33% (2/6), and 50% (4/8) and 17% (1/6) in the left coronary trunk, left anterior descending branch, left circumflex branch, and right coronary artery, respectively. Abnormal FDG accumulation was observed in the aorta as follows in ACS and SA patients; 13% (1/8) and 17 % (1/6) in ascending aorta, 38% (3/8) and 17 % (1/6) in the aortic arch, 75% (1/8) and 33 % (1/6) in descending aorta, and 13% (1/8) and 17 % (1/6) in the abdominal aorta (Fig.2). Conclusion: In this study, we were able to clearly visualize and quantitatively evaluate the vascular inflammation in the whole body. In comparison with non-CAD subjects, about 33~50% of patients with CAD had been considered carotid artery inflammation. Similarly, in the aorta, abnormal accumulation was observed in up to 75% of patients. This study focuses on the visualization of arterial plaque inflammation and advances personalized medicine from the viewpoint of identifying high-risk atherosclerosis.