High-resolution quantification of stress perfusion defects by cardiac magnetic resonance

Quantitative stress perfusion cardiac magnetic resonance (CMR) is becoming more widely available, but it is still unclear how to integrate this information in clinical decision making. Typically, pixel-wise perfusion maps are generated but diagnostic and prognostic studies have summarised perfusion as just one value per-patient or in 16 myocardial segments. In this study, the reporting of quantitative perfusion maps is extended from the standard 16 segments to a high-resolution bullseye. Cut-off thresholds are established for the high-resolution bullseye and the identified perfusion defects are compared versus visual assessment. 34 patients with known or suspected coronary artery disease were retrospectively analysed. Visual perfusion defects were contoured on the CMR images and pixel-wise quantitative perfusion maps were generated. Cut-off values were established on the high-resolution bullseye consisting of 1800 points and compared to the per-segment, per-coronary, and per-patient resolution thresholds. Quantitative stress perfusion was significantly lower in visually abnormal pixels 1.11 (0.75-1.57) versus 2.35 (1.82-2.9) ml/min/g (Mann-Whitney U test p < 0.001), with an optimal cut-off of 1.72 ml/min/g. This was lower than the segment-wise optimal threshold of 1.92 ml/min/g. Bland-Altman analysis showed visual assessment underestimated large perfusion defects compared to the quantification with good agreement for smaller defect burdens. A Dice overlap of 0.68 (0.57-0.78) was found. This study introduces a high-resolution bullseye consisting of 1800 points, rather than 16, per patient for reporting quantitative stress perfusion which may improve sensitivity. Using this representation, the threshold required to identify areas of reduced perfusion is lower than for segmental analysis.