149 Automated Quantitative Perfusion CMR With Simplified Dual-Bolus Contrast Protocol Using the color pixel QP maps, image readers were instructed to diagnose ischemia if two adjacent segments within a coronary territory each demonstrated stress MBF below the established study-specific cut-off value in the absence of LGE. Subsequently, the imaging experts viewed the conventional gray-scale first-pass perfusion images and assessed the image quality using a 5-point Likert scale, including assessment of artifacts, noise, overall impression of the image quality and certainty in diagnosis (Supplementary Figure S1). Finally, after viewing the gray-scale perfusion images, the image readers were asked again to classify the patient into the obstructive CAD or no obstructive CAD group. For the assessment of diagnostic accuracy of QP and gray-scale images, in cases of discordance between the two readers regarding diagnosis (obstructive CAD or no obstructive CAD), a third image reading expert experienced in QP analysis (S.B.J.) evaluated the scan and this assessment was used for the analysis. Statistical analysis Statistical analysis was performed with the SPSS software package (IBM SPSS Statistics 20.0, Chicago, IL, USA) and MedCalc (MedCalc Software 12.7.8.0, Mariakerke, Belgium). Continuous variables are expressed as mean ± standard deviation (SD) for normally distributed data or median with interquartile range (IQR) for non-normally distributed variables. One-way ANOVA was used to compare the MBF estimates between groups. A p-value < 0.05 was considered statistically significant. A receiver operating characteristics (ROC) curve per-vessel analysis was performed to assess the diagnostic accuracy of newly proposed dual-bolus QP workflow for detection of obstructive CAD. The Youden index was used to identify the optimal stress MBF cut-off value on a per-vessel basis using the mean stress MBF value of two lowest adjacent segments within a coronary territory. Coronary territories with presence of LGE were excluded from the analysis. Therefore, the study-specific calculated optimal cut-off value of stress MBF was used by the CMR expert readers to assign the patients into obstructive or no obstructive CAD groups based on QP CMR results. Ethics approval and consent to participate The study was approved by the Medical Ethics Review Committee of the Amsterdam UMC, location VUmc. Informed consents from all participants were obtained. RESULTS Baseline characteristics of the population studied according to the simplified dual-bolus protocol (n = 25) is presented in Table 1. The median age was 60 (IQR 54–71) years, and 64% of patients were male. All patients had sufficient response to adenosine based on the analysis of stress MBF, presence of splenic switch-off and heart rate increase (average heart rate increase from 66 ± 12 to 93 ± 15 bpm, p < 0.01) during stress perfusion. In total 23 patients underwent ICA, whereas 2 patients underwent CCTA (which was used only 7
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