Mitsuaki Tatsumi, MD, PhD, and colleagues from the Johns Hopkins University School of Medicine looked at combined PET/CT scans from 85 patients who had been imaged with fluorodeoxyglucose, FDG, a radiopharmaceutical for diagnosis and staging of tumors. Fifty patients (58.8%) showed at least one positive focus of FDG uptake in the thoracic aortic wall, and 45 patients showed calcifications. In general, the site of FDG uptake in the patients was distinct from the site of calcifications.
"Our analysis hypothesizes that a certain percentage of the FDG uptake sites potentially corresponds to high risk or vulnerable atherosclerotic lesions that could lead to future cardiovascular events," said Dr. Tatsumi. "The aortic wall FDG uptake finding may be useful for detection of patients at increased risk for future cardiovascular events."
"We believe that the aortic wall FDG uptake may be a sign of ‘vulnerable' plaque, and it clearly did not correspond to calcification in general," said co-author Richard L. Wahl, MD, Director of Nuclear Medicine, Vice Chair of Technology and New Business Development, Russell H. Morgan Department of Radiology at Hopkins. "Since the aortic wall FDG uptake was shown to be a very common finding, we do not know if this early finding is a significant risk factor, but the fact that the frequency of FDG uptake increased with age and the uptake sites were distinct from the calcification sites is of concern for early atherosclerosis."
Atherosclerosis, along with cancer, is the leading cause of world deaths. Atherosclerosis occurs when arteries become narrow and hardened as a result of cholesterol plaque build-up. More than 500,000 American die each year of coronary artery disease, and more than 90% of sudden deaths occur in individuals with two or more arteries narrowed by atherosclerosis. Yet, if identified early, atherosclerosis is reversible with medications and dietary and lifestyle changes.
FDG is already a mainstay of nuclear medicine diagnosis because, when injected, it is "taken up" more rapidly by tissue with higher glucose metabolic activity. Not only is this of benefit in cancer imaging, but more studies like those of Dr. Tatsumi and colleagues indicate that with PET/CT, this tracer may be useful in a wide range of clinical settings. Most promising is its use in identifying "vulnerable" tissue and, therefore, assisting physicians in monitoring and proactively treating patients.
"It is too early to know with certainty, but we believe this increased FDG uptake is a marker of early atherosclerosis," concluded Dr. Wahl. "However, follow-up clinical and pathological studies are needed to prove our hypothesis."
The Society of Nuclear Medicine Annual Meeting is being held June 15–19 at the Los Angeles Convention Center, Los Angeles, CA. In addition to educational sessions, the meeting will focus on leading medical developments in the field of nuclear medicine, including radioimmunotherapy with a new class of drugs that target cancer, diagnostic breakthroughs with PET, and other topics. More than 5,000 specialists in the field of nuclear medicine, including scientists, technologists, researchers, and representatives from the medical industry, are expected to attend. The Society of Nuclear Medicine is an international scientific and professional organization with more than 13,000 members dedicated to promoting the science, technology, and practical applications of nuclear medicine. The SNM is based in Reston, VA.
For late-breaking news about the world of nuclear medicine and events at the 49th Annual Society of Nuclear Medicine meeting, visit www.snm.org
Abstract 10. Sunday, June 16, 2:50–3:05 p.m. Room 410
Evaluation of Thoracic Aortic Wall Metabolic Activity and Calcification with FDG-PET/CT: A Preliminary Study to Identify "Vulnerable Plaque"
M. Tatsumi, C. Cohade, Y. Nakamoto, R.L. Wahl
The Johns Hopkins Medical Institutions
The Johns Hopkins University School of Medicine
Baltimore MD 21287 USA
Abstract No. 10
EVALUATION OF THORACIC AORTIC WALL METABOLIC ACTIVITY AND CALCIFICATION WITH FDG-PET/CT: A PRELIMINARY STUDY TO IDENTIFY "VULNERABLE PLAQUE" M. Tatsumi*, C. Cohade, Y. Nakamoto, R. L. Wahl, The Johns Hopkins Medical Institutions, Baltimore, MD. (200361) Glucose metabolism can be increased in many non-malignant processes including active plaque in arteries. Combined PET and CT scanners (PET/CT) have recently emerged as a promising imaging modality. Objectives: To evaluate for the presence, location, and intensity of FDG uptake (F) in the thoracic aortic wall (aw) using the PET/CT and to compare F with aw calcification (C), a common correlate of aging or atherosclerosis on CT, to determine if F was increased in calcified plaque. Methods: 85 consecutive patients (pts) having clinical tumor FDG-PET/CT studies were evaluated retrospectively (46 M and 39 F, mean: 55 ± 16 y.o.). All pts had information regarding diabetes and obesity, and 67 pts regarding smoking, hypertension, and hyperlipidemia. 1 hr after injection of 555 MBq of FDG, whole-body CT images were acquired for 37 sec without contrast media. A whole-body emission PET scan was performed with 5 min acquisition per each bed position (PET/CT: Discovery LS, GE). CT, PET, and fused PET/CT images were generated for review, and F and C were evaluated visually and semiquantitatively. Results: 50 pts (58.8 %) exhibited at least one positive focus of F in the thoracic aw. Weak F tended to be observed in the ascending aorta, whereas intermediate to strong F in the descending aorta. 45 pts (52.9 %) had at least one measurable C. Dense C was mostly observed at the aortic arch. 12 pts (14.1 %) had 13 positive F foci at the site of C. Positive pts were older on average (P < 0.005) and higher incidence was shown in the older patient group (P < 0.05) both in F and C. The size of the largest C and the number of C sites in each pt correlated with age (r = 0.49 and r = 0.47, P < 0.005, respectively) in contrast to the highest F intensity and the number of positive F sites. Women and hyperlipidemia tended to have relationship with F (P = 0.073 and 0.080, respectively), whereas diabetes had significant relationship with C (P < 0.05). Conclusion: PET/CT demonstrated F commonly occurred in the thoracic aw. The F site was generally distinct from the location of C site. FDG-PET/CT may be promising in stratification of high-risk pts for future cardiovascular events.