Imaging of inflamed and vulnerable plaque in coronary arteries with 18F-FDG PET/CT in patients with suppression of myocardial uptake using a low-carbohydrate, high-fat preparation

PET/CT imaging with (18)F-FDG has been used to detect inflammation in carotid and aortic plaque; its use in detecting coronary plaque has been limited by avid (18)F-FDG uptake by the myocardium. We investigated whether (18)F-FDG PET/CT could be used to image inflammation in coronary arteries as a potential noninvasive method to detect vulnerable plaque.

METHODS

We retrospectively studied 32 patients treated for malignancy who underwent (18)F-FDG PET/CT and concomitant cardiac catheterization. As part of the recently described protocol, all patients were instructed to eat a low-carbohydrate, high-fat meal the night before and drink a vegetable oil drink the morning of the study. We reviewed the patients' baseline characteristics and their (18)F-FDG PET/CT scans for adequacy of myocardial uptake suppression and correlated the presence of angiographically apparent plaque with (18)F-FDG uptake in the major coronary arteries. Two independent observers assessed the angiographic images and (18)F-FDG PET scans.

RESULTS

A total of 95% of patients had 2 or more coronary disease risk factors, and 25% had unstable symptoms; 30% of index catheterizations resulted in intervention. In 20 of 32 patients (63%), myocardial suppression was good (12) or adequate (8). Inadequate suppression was due to self-reported dietary nonadherence. Patients with good, adequate, and poor suppression had maximal myocardial standardized uptake values of 2.8 +/- 0.7, 5.0 +/- 1.3, and 17.0 +/- 9.7, respectively. We identified (18)F-FDG uptake in 15 patients in 1 or more coronary segments. A trend to significance in correlation between presence of angiographic disease and signal in the vessel was observed (P = 0.07; 80 vessels examined). A total of 7 patients with significant coronary artery disease had aortic (18)F-FDG uptake.

CONCLUSION

In this retrospective study, we demonstrated the potential use of (18)F-FDG PET in imaging of inflammation in coronary arteries. The potential of (18)F-FDG PET is also being investigated in a prospective study.

Asymmetric 18F-FDG Uptake in the Infradiaphragmatic Brown Adipose Tissue (BAT) Mimicking Adrenal Metastasis: A Relatively Rare Site of Brown Fat and a Potential Source for False Positive FDG-PET Study

FDG uptake in the metabolically active brown adipose tissue (BAT) is a source of significant concern while interpreting FDG-PET studies. It is also of great interest due to its potential implications for obesity research. In this communication, we describe hitherto unreported asymmetric BAT uptake in the abdomen, persisting after diazepam intervention in the repeat PET study on a separate day. The patient did not have any evidence of disease even at 24 months' follow up. The present case is a useful addition to the current body of literature of false positive FDG-PET due to BAT uptake in unusual location and underscores the importance of high index of suspicion and careful correlation, whenever one comes across an unusual PET finding in a given clinical situation. This assumes important diagnostic value particularly when it coexists in the setting of malignancy where the disease can be falsely upstaged by misinterpretation. The literature relevant to the report is discussed and a schema is suggested for correct interpretation.

Best practices in PET/CT: consensus on performance of positron emission tomography-computed tomography

Positron emission tomography-computed tomography (PET-CT) using the glucose metabolism tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) has become a widespread and preferred imaging modality for evaluating most cancers. Since commercial PET-CT scanners became available in 2001, there has been rapid dissemination of this hybrid imaging modality and PET-CT scanners have largely replaced stand-alone PET scanners. How PET-CT scans are performed and applied to cancer management has varied considerably, in part reflecting the varied background of the practice settings and training experience of the physicians performing and interpreting the PET-CT studies. Combined PET/CT with FDG has become the gold standard in oncologic imaging by accurately defining anatomy and function of many tumors. From April 2-4, 2008, a focus group composed of physicians and technologists from different practice settings and training backgrounds entitled "Best Practices in PET/CT Symposium" was held in Sonoma, California. The symposium focused on optimization of PET-CT protocols but also included other pertinent topics related to PET-CT imaging in oncology. This article summarizes areas of consensus reached by the group regarding many of the discussion topics. The summary consensus covered in this article is meant to provide direction for future discussions on how to improve the application of this hybrid modality to patient care.