Role of FDG PET/CT in investigating the mechanisms underlying atherosclerotic plaque formation and evolution

Prediction of coronary artery calcium progression by FDG uptake of large arteries in asymptomatic individuals

PURPOSE

The purpose of this study is to evaluate whether fluorodeoxyglucose (FDG) uptake of the large arteries can predict coronary artery calcium (CAC) progression in asymptomatic individuals.

METHODS

Ninety-six asymptomatic individuals who underwent FDG positron emission tomography (PET) and CAC scoring on the same day for health screening and follow-up CAC scoring ≥1 year after baseline studies (mean 4.3 years) were included. Vascular FDG uptake was measured and corrected for blood pool activity to obtain peak and average target-to-blood pool ratios (TBRpeak and TBRavg, respectively) for the carotid arteries, and ascending and abdominal aorta. CAC scores at baseline and follow-up of each individual were measured and absolute CAC change (ΔCAC), annual CAC change (ΔCAC/year), and annual CAC change rate (ΔCAC%/year) were calculated. CAC progression was defined as ΔCAC >0 for individuals with negative baseline CAC; ΔCAC/year ≥10 for those with baseline CAC of 0<x<100; ΔCAC%/year ≥10 % for those with baseline CAC ≥100. Vascular FDG uptake and other clinical risk factors were compared between CAC-progressors and non-CAC-progressors. Multivariate analysis was performed to evaluate whether vascular FDG uptake can independently predict CAC progression.

RESULTS

Thirty-one subjects showed CAC progression. CAC-progressors showed significantly higher TBRpeak and TBRavg as compared to non-CAC-progressors for all three arteries. TBRpeak of the abdominal aorta was significantly associated with CAC progression in multivariate analysis, with age and baseline CAC. A higher TBRpeak of the abdominal aorta (≥2.11) was associated with CAC progression among subjects with negative baseline CAC only. In subjects with positive baseline CAC, only the amount of baseline CAC was significantly associated with CAC progression. However, the positive predictive value of the TBRpeak of the abdominal aorta was <40 % when age was <58 or baseline CAC was negative.

CONCLUSIONS

Higher FDG uptake of the large arteries is associated with an increased risk of CAC progression in asymptomatic subjects with negative baseline CAC. But its clinical application needs further validation.

Current and future trends in multimodality imaging of coronary artery disease

Nowadays, there is a wide array of imaging studies available for the evaluation of coronary artery disease, each with its particular indications and strengths. Cardiac single photon emission tomography is mostly used to evaluate myocardial perfusion, having experienced recent marked improvements in image acquisition. Cardiac PET has its main utility in perfusion imaging, atherosclerosis and endothelial function evaluation, and viability assessment. Cardiovascular computed tomography has long been used as a reference test for non-invasive evaluation of coronary lesions and anatomic characterization. Cardiovascular magnetic resonance is currently the reference standard for non-invasive ventricular function evaluation and myocardial scarring delineation. These specific strengths have been enhanced with the advent of hybrid equipment, offering a true integration of different imaging modalities into a single, simultaneous and comprehensive study.