Impact of dose reduction strategies on image quality of coronary cta in real-world clinical practice : A subanalysis of PROTECTION VI registry data

BACKGROUND. Dose reduction strategies for coronary CTA (CCTA) have been underused in clinical practice given concern that the strategies may lower image quality. OBJECTIVE. The purpose of this study was to explore associations between dose reduction strategies and CCTA image quality in real-world clinical practice. METHODS. This subanalysis of the international Prospective Multicenter Registry on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice in 2017 (PROTECTION VI) study included 3725 patients (2109 men, 1616 women; median age, 59 years) who underwent CCTA for coronary artery evaluation performed at 55 sites in 32 countries. CCTA image sets were reviewed at a core laboratory. A range of patient and scan characteristics, including use of three dose reduction strategies (prospective ECG triggering, low tube potential, and iterative image reconstruction) and image dose, were recorded. A single core laboratory member reviewed all examinations for quantitative image quality measures, including signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), and reviewed 50% of examinations to assign a qualitative CCTA image quality score and a semiquantitative coronary calcification measure. Multivariable logistic regression models were used to identify predictors of image quality. A second core laboratory member repeated quantitative measures for 100 examinations and the qualitative measure for 383 (approximately 20%) examinations to assess interreader agreement. RESULTS. Independent predictors (p < .05) of SNR were female sex (effect size, 2.70), lower body mass index (0.38 per 1-unit decrease), stable sinus rhythm (1.71), and scanner manufacturer (variable effect across manufacturers). These factors were also the only independent predictors of CNR. Independent predictors (p < .05) of CCTA image quality were heart rate (0.17 per 10 beats/min reduction) and coronary calcification (0.15 per coronary calcification grade). None of the three dose-saving strategies or dose-length product was an independent predictor of any image quality measure. Interreader agreement analysis showed intraclass correlation coefficients of 0.874 for SNR and 0.891 for CNR and a kappa value of 0.812 for the qualitative score. CONCLUSION. This large international multicenter study shows that three dose reduction strategies were not associated with decreased CCTA image quality. CLINICAL IMPACT. The dose reduction strategies should be routinely implemented in clinical CCTA