Coronary 18F-sodium fluoride (18F-NaF) PET identifies ruptured plaques in patients with recent myocardial infarction and localizes to atherosclerotic lesions with active calcification. Most studies to date have performed the PET acquisition 1 h after injection. Although qualitative and semiquantitative analysis is feasible with 1-h images, residual blood-pool activity often makes it difficult to discriminate plaques with 18F-NaF uptake from noise. We aimed to assess whether delayed PET performed 3 h after injection improves image quality and uptake measurements. Methods: Twenty patients (67 ± 7 y old, 55% male) with stable coronary artery disease underwent coronary CT angiography (CTA) and PET/CT both 1 h and 3 h after the injection of 266.2 ± 13.3 MBq of 18F-NaF. We compared the visual pattern of coronary uptake, maximal background (blood pool) activity, noise, SUVmax, corrected SUVmax (cSUVmax), and target-to-background (TBR) ratio in lesions defined by CTA on 1-h versus 3-h 18F-NaF PET. Results: On 1-h PET, 26 CTA lesions with 18F-NaF PET uptake were identified in 12 (60%) patients. On 3-h PET, we detected 18F-NaF PET uptake in 7 lesions that were not identified on 1-h PET. The median cSUVmax and TBRs of these lesions were 0.48 (interquartile range [IQR], 0.44–0.51) and 1.45 (IQR, 1.39–1.52), respectively, compared with −0.01 (IQR, −0.03–0.001) and 0.95 (IQR, 0.90–0.98), respectively, on 1-h PET (both P, 0.001). Across the entire cohort, 3-h PET SUVmax was similar to 1-h PET measurements (1.63 [IQR, 1.37–1.98] vs. 1.55 [IQR, 1.43–1.89], P 5 0.30), and the background activity was lower (0.71 [IQR, 0.65–0.81] vs. 1.24 [IQR, 1.05–1.31], P, 0.001). On 3-h PET, TBR, cSUVmax, and noise were significantly higher (respectively: 2.30 [IQR, 1.70–2.68] vs. 1.28 [IQR, 0.98–1.56], P, 0.001; 0.38 [IQR, 0.27–0.70] vs. 0.90 [IQR, 0.64–1.17], P, 0.001; and 0.10 [IQR, 0.09–0.12] vs. 0.07 [IQR, 0.06–0.09], P 5 0.02). Median cSUVmax and TBR increased by 92% (range, 33%–225%) and 80% (range, 20%–177%), respectively. Conclusion: Blood-pool activity decreases on delayed imaging, facilitating the assessment of 18F-NaF uptake in coronary plaques. Median TBR increases by 80%, leading to the detection of more plaques with significant uptake than are detected using the standard 1-h protocol. A greater than 1-h delay may improve the detection of 18F-NaF uptake in coronary artery plaques.
Bibliographical noteFunding Information:
This research was supported in part by grant R01HL135557 from the National Heart, Lung, and Blood Institute/National Institutes of Health (NHLBI/NIH). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The study was also supported by a grant (‘‘Cardiac Imaging Research Initiative’’) from the Miriam & Sheldon G. Adelson Medical Research Foundation. No other potential conflict of interest relevant to this article was reported.
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All Science Journal Classification (ASJC) codes
- Radiology Nuclear Medicine and imaging