Several models for the quantitative analysis of myocardial blood flow (MBF) at stress and rest and myocardial flow reserve (MFR) with 13 N-ammonia myocardial perfusion PET have been implemented for clinical use. We aimed to compare quantitative results obtained from 3 software tools (QPET, syngo MBF, and PMOD), which perform PET MBF quantification with either a 2-compartment model (QPET and syngo MBF) or a 1-compartment model (PMOD). Methods: We considered 33 adenosine stress and rest 13 N-ammonia studies (22 men and 11 women). Average age was 54.5 6 15 y, and average body mass index was 26 6 4.2. Eighteen patients had a very low likelihood of disease, with no chest pain, normal relative perfusion results, and normal function. All data were obtained on a PET/CT scanner in list mode with CT attenuation maps. Sixteen dynamic frames were reconstructed (twelve 10-s, two 30-s, one 1-min, and one 6-min frames). Global and regional stress and rest MBF and MFR values were obtained with each tool. Left ventricular contours and input function region were obtained automatically in system QPET and syngo MBF and manually in PMOD. Results:The flow values and MFR values were highly correlated among the 3 packages (R 2 ranging from 0.88 to 0.92 for global values and from 0.78 to 0.94 for regional values. Mean reference MFR values were similar for QPET, syngo MBF, and PMOD (3.39 6 1.22, 3.41 6 0.76, and 3.66 6 1.19, respectively) by 1-way ANOVA (P 5 0.74). The lowest MFR in very low likelihood patients in any given vascular territory was 2.25 for QPET, 2.13 for syngo MBF, and 2.23 for PMOD. Conclusion: Different implementations of 1-and 2-compartment models demonstrate an excellent correlation in MFR for each vascular territory, with similar mean MFR values.

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Whether 18 F-FDG PET can detect inflammation in the coronary arteries remains controversial. We examined 18 F-FDG uptake at the culprit sites of acute myocardial infarction (AMI) after percutaneous coronary stenting (PCS) by coregistering PET and coronary CT angiography (CTA). Methods: Twenty nondiabetic patients with AMI (median age, 62 y; 16 men and 4 women) and 7 nondiabetic patients with stable coronary artery disease (CAD; median age, 67 y; 4 men and 3 women) underwent 18 F-FDG PET and coronary CTA 1-6 d after PCS of culprit stenoses. After a low-carbohydrate dietary preparation and more than 12 h of fasting, 480 MBq of 18 F-FDG were injected, and PET images were acquired 3 h later. Helical CTA was performed on a dual-source scanner. Stent position on attenuation-correction noncontrast CT and CTA was used to fuse PET and CTA. Two experienced readers masked to patient data independently quantified maximum target-to-background ratio (maxTBR) at each PCS site. A maxTBR greater than 2.0 was the criterion for significant uptake. Results: Compared with stable CAD patients, more AMI patients exhibited a PCS site maxTBR greater than 2.0 (12/20 vs. 1/7, P 5 0.04). More AMI patients were active smokers (9/20 vs. 0/7 in stable CAD, P 5 0.03). After adjusting for baseline demographic differences, stent-myocardium distance, and myocardial 18 F-FDG uptake, presentation of AMI was positively associated with a PCS site maxTBR greater than 2.0 (odds ratio, 31.6; P 5 0.044). Prevalence of excess myocardial 18 F-FDG uptake was similar in both populations (8/20 AMI vs. 3/7 stable CAD, P 5 0.89). Conclusion: Systematic fusion of 18 F-FDG PET and coronary CTA demonstrated increased culprit site 18 F-FDG uptake more commonly in patients with AMI than in patients with stable CAD. However, this approach failed to detect increased signal at the culprit site in nearly half of AMI patients, highlighting the challenging nature of in vivo coronary artery plaque metabolic imaging. Nonetheless, our findings suggest that imaging of coronary artery inflammation is feasible, and further work evaluating 18 F-FDG uptake in high-risk coronary plaques prior to rupture would be of great interest.

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