Automated analysis of phase-contrast magnetic resonance images in the assessment of endothelium-dependent flow-mediated dilation

Measurement of flow-mediated arterial dilation (FMAD) provides information regarding the status of peripheral arterial endothelial function. Although phase-contrast magnetic resonance imaging (PC-MRI) can be used to measure FMAD, the manual analysis of one study (tracing regions of interest and processing data on 100 images) can require six or more hours. To enhance the clinical utility of the PC-MRI assessment of FMAD, we hypothesized that an automated technique (Multi-Stage Intensity Thresholding or MSIT) for determining femoral arterial area and flow before and after cuff inflation over the thigh could be used to evaluate FMAD in a rapid, accurate, and reproducible manner. Compared with manual analysis, automated analysis detected a similar percentage change in peak FMAD between healthy individuals (17.2% vs. 16.5%) and patients with congestive heart failure (4.0% vs. 5.1%). The correlation between percentage changes in arterial area after cuff release derived manually and automatically was very good (r = 0.93). Analysis time for 100 images averaged 10 minutes with MSIT vs. 6 hours for manual analysis. In conclusion, rapid, accurate assessments of femoral artery FMAD can be obtained using Multi-Stage Intensity Thresholding. This methodology may prove useful for the rapid MRI assessment of peripheral arterial endothelial function in a clinical setting when studying patients with cardiovascular disease.