Simultaneous [18F]fluoride and gadobutrol enhanced coronary positron emission tomography/magnetic resonance imaging for in vivo plaque characterization

Aims ¹⁸F-sodium fluoride ([18F]fluoride) and gadobutrol are promising probes for positron emission tomography (PET) and magnetic resonance imaging (MRI) characterizing coronary artery disease (CAD) activity. Unlike [18F]fluoride-PET/ computed tomography (CT), the potential of PET/MR using [18F]fluoride and gadobutrol simultaneously, has so far not been evaluated. This study assessed feasibility and diagnostic potential of [18F]fluoride and gadobutrol enhanced dual-probe PET/MR in patients with CAD. Methods Twenty-one patients (age, 66.7 ± 6.7 years) with CAD scheduled for invasive coronary angiography (XCA) underwent and results simultaneous [18F]fluoride (mean activity/effective dose: 157.2 ± 29.7 MBq/3.77 ± 0.72 mSv) and gadobutrol enhanced PET/MR on an integrated PET/MRI (3 T) scanner. Optical coherence tomography (OCT) was used as reference. Target-to-background ratio (TBR, [18F]fluoride-PET) and contrast-to-noise ratio (CNR) values (MRI, gadobutrol) were calculated for each coronary segment. Previously suggested PET/CT-TBR thresholds for adverse coronary events were evaluated. High-risk plaques, i.e. calcified and non-calcified thin-cap fibroatheromas (TCFAs) were predominantly located in segments with a TBR >1.28 (P = 0.012). Plaques containing a lipid core on OCT, were more frequently detected in segments with a TBR >1.25 (P < 0.001). TBR values significantly correlated with maximum calcification thickness (P = 0.009), while fibrous cap thickness was significantly less in segments with a TBR >1.28 (P = 0.044). Above a TBR threshold of >1.28, CNR values significantly correlated with the presence of calcified TCFAs (P = 0.032). Conclusion Simultaneous [18F]fluoride and gadobutrol dual-probe PET/MRI is feasible in clinical practice and may facilitate the identification of high-risk patients. The combination of coronary MR-derived CNR values post gadobutrol and [18F]fluoride based TBR values may improve identification of high-risk plaque features.