Ruptured coronary atherosclerotic plaques commonly cause acute myocardial infarction. It has been recently shown that active microcalcification in the coronary arteries, one of the features that characterizes vulnerable plaques at risk of rupture, can be imaged using (18)F-sodium fluoride ((18)F-NaF) PET. We aimed to determine whether a motion correction technique applied to gated (18)F-NaF PET images could enhance image quality and improve uptake estimates.
METHODS: Seventeen patients with myocardial infarction (n = 7) and stable angina (n = 10) underwent (18)F-NaF PET and prospective coronary CT angiography (CCTA). PET data were reconstructed in 4 different ways: (i) one gated bin (end-diastolic phase with 25% of the counts), (ii) 4 gated bins (consecutive 25% segments), (iii) 10 gated bins (consecutive 10% segments), and (iv) ungated. Subsequently, gated PET images were registered using a local and non-linear motion correction method guided by the extracted coronary arteries from CT angiography using either 4 or 10 bins. Global noise levels and target-to-background ratios (TBR) defined on manually delineated coronary plaque lesions were compared to assess image quality and uptake estimates.
RESULTS: Compared to the reference standard of using only one bin of PET data, motion correction using the 10 bins of PET data reduced image noise (-46%, p<0.0001). TBR in positive lesions was 11% higher using 10-bin motion corrected data, compared to one-bin data (1.98 [IQR 1.70-2.37] vs 1.78 [IQR 1.58-2.16], P = 0.0027), and 33% higher compared to ungated data (1.98 [IQR 1.70-2.37] vs 1.48 [IQR 1.39-1.88], p<0.0001).
CONCLUSION: Motion correction of gated (18)F-NaF PET/CCTA is feasible, reduces image noise and increases TBR. This improvement may allow more reliable identification of vulnerable coronary artery plaques using (18)F-NaF PET.