Respiration-averaged CT versus standard CT attenuation map for correction of ¹⁸F-sodium fluoride uptake in coronary atherosclerotic lesions on hybrid PET/CT

Background: To evaluate the impact of respiratory-averaged computed tomography attenuation correction (RACTAC) compared to standard single-phase computed tomography attenuation correction (CTAC) map, on the quantitative measures of coronary atherosclerotic lesions of ¹⁸F-sodium fluoride (¹⁸F-NaF) uptake in hybrid positron emission tomography and computed tomography (PET/CT). Methods: This study comprised 23 patients who underwent ¹⁸F-NaF coronary PET in a hybrid PET/CT system. All patients had a standard single-phase CTAC obtained during free-breathing and a 4D cine-CT scan. From the cine-CT acquisition, RACTAC maps were obtained by averaging all images acquired over 5 seconds. PET reconstructions using either CTAC or RACTAC were compared. The quantitative impact of employing RACTAC was assessed using maximum target-to-background (TBR_MAX) and coronary microcalcification activity (CMA). Statistical differences were analyzed using reproducibility coefficients and Bland-Altman plots. Results: In 23 patients, we evaluated 34 coronary lesions using CTAC and RACTAC reconstructions. There was good agreement between CTAC and RACTAC for TBR_MAX (median [Interquartile range]): CTAC = 1.65 [1.23 to 2.38], RACTAC = 1.63 [1.23 to 2.33], p = 0.55), with coefficient of reproducibility of 0.18, and CMA: CTAC = 0.10 [0 to 1.0], RACTAC = 0.15 [0 to 1.03], p = 0.55 with coefficient of reproducibility of 0.17 Conclusion: Respiratory-averaged and standard single-phase attenuation correction maps provide similar and reproducible methods of quantifying coronary ¹⁸F-NaF uptake on PET/CT.