Sodium-fluoride PET-CT for the non-invasive evaluation of coronary plaques in symptomatic patients with coronary artery disease: a cross-correlation study with intravascular ultrasound

Objectives The aim of this study was to evaluate the 18 F-sodium fluoride ( 18 F-NaF) coronary uptake compared to coronary intravascular ultrasound (IVUS) in patients with symptomatic coronary artery disease. Background 18 F-NaF PET enables the assessment of vascular osteogenesis by interaction with surface hydroxyapatite, while IVUS enables both identification and quantification of intra-plaque components. Methods Forty-four patients with symptomatic coronary artery disease were included in this prospective controlled trial, 32 of them (30 patients with unstable angina and 2 patients with stable angina), representing the final study cohort, got additional IVUS. All patients underwent cardiac 18 F-NaF PET/CT and IVUS within 2 days. 18 F-NaF maximum tissue-to-blood ratios (TBR max ) were calculated for 69 coronary plaques and correlated with IVUS plaque classification. Results Significantly increased 18 F-NaF uptake ratios were observed in fibrocalcific lesions (meanTBR max = 1.42 ± 0.28), thin-cap atheroma with spotty calcifications (meanTBR max = 1.32 ± 0.23), and thick-cap mixed atheroma (meanTBR max = 1.28 ± 0.38), while fibrotic plaques showed no increased uptake (meanTBR max = 0.96 ± 0.18). The 18 F-NaF uptake ratio was consistently higher in atherosclerotic lesions with severe calcification (meanTBR max = 1.34 ± 0.22). The regional 18 F-NaF uptake was most likely localized in the border region of intensive calcification. Coronary lesions with positive 18 F-NaF uptake showed some increased high-risk anatomical features on IVUS in comparison to 18 F-NaF negative plaques. It included a significant severe plaque burden (70.1 ± 13.8 vs. 61.0 ± 13.8, p = 0.01) and positive remodeling index (1.03 ± 0.08 vs. 0.99 ± 0.07, p = 0.05), as well as a higher percentage of necrotic tissue (37.6 ± 13.3 vs. 29.3 ± 15.7, p = 0.02) in positive 18 F-NaF lesions. Conclusions 18 F-NaF coronary uptake may provide a molecular insight for the characterization of coronary atherosclerotic lesions. Specific regional uptake is needed to be determined by histology.