157 Automated Quantitative Perfusion CMR With Simplified Dual-Bolus Contrast Protocol false-positive conclusion, which can be verified by an experienced CMR reader. It has been shown that QP-derived stress MBF values in dark rim artifact are significantly higher than in true perfusion defects resulting from obstruction in coronary artery (2.17 ± 0.61 vs. 0.95 ± 0.43 ml/min/g, p < 0.001).39 However, since QP CMR has not yet been widely implemented in daily clinical practice, the readers may still need to use the conventional first-pass perfusion images to verify the results of color pixel maps and make a final diagnostic conclusion. Further, larger studies will be crucial to evaluate the diagnostic performance of color pixel QP maps in a daily clinical practice with patients referred for stress perfusion CMR. Limitations of the study The major limitation of the study is a small sample size and lack of inclusion of healthy volunteers. Therefore, larger validation studies are needed to confirm the presented results and establish cut-off values of stress MBF to detect obstructive CAD. Moreover, we did not perform a head-to-head comparison with the conventionally used GBCA administration schemes. In a young healthy population the blood flow may reach even 4 ml/g/min, therefore choosing the moderate infusion rate at 3 ml/s may cause a bias with underestimation of MBF in this population. In our study, the presented protocol was applied to patients suspected of having obstructive CAD, who had cardiovascular risk factors, and some of them already had a history of CAD. Therefore, a moderate infusion rate of 3 ml/s applied together with two concentrated boluses appears to be a reasonable compromise that can be implemented in daily clinical practice. After exclusion of coronary territories with LGE, the prevalence of coronary artery obstruction was relatively low. As a consequence, our approach yielded relatively low PPV. However, even based on such a small cohort, our simplified dual-bolus scanning protocol showed comparable results to other studies validating QP CMR on larger population of patients in an easy to implement approach in contemporary clinical practice. Nevertheless, larger studies involving simultaneously comprehensive assessment of coronary physiology and function of microcirculation are required to provide the precise (age- and sex-specific) cut-off values and propose a diagnostic algorithm to detect obstructive CAD and CMD using our workflow. It is also crucial to recognize the overall limitation of perfusion CMR, presence of dark rim artifact, which due to loss of SI may result in false-positive results in QP analysis and possibly affect the accuracy of this method. Finally, the fully-automated QP CMR software remains a research tool and further studies on its validation in clinical practice are warranted. CONCLUSIONS This study successfully implemented a ready-to-use QP CMR workflow with simplified GBCA administration scheme which provides good image quality and holds promise for high diagnostic accuracy for detection of obstructive CAD. The used dual-bolus protocol 7
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