title: Feed-forward active contour analysis for improved brachial artery reactivity testing.
abstract: The object of this study was to utilize a novel feed-forward active contour (FFAC) algorithm to find a reproducible technique for analysis of brachial artery reactivity. Flow-mediated dilation (FMD) is an important marker of vascular endothelial function but has not been adopted for widespread clinical use given its technical limitations, including inter-observer variability and differences in technique across clinical sites. We developed a novel FFAC algorithm with the goal of validating a more reliable standard. Forty-six healthy volunteers underwent FMD measurement according to the standard technique. Ultrasound videos lasting 5-10 seconds each were obtained pre-cuff inflation and at minutes 1 through 5 post-cuff deflation in longitudinal and transverse views. Automated segmentation using the FFAC algorithm with initial boundary definition from three different observers was used to analyze the images to measure diameter/cross-sectional area over the cardiac cycle. The %FMD was calculated for average, minimum, and maximum diameters/areas. Using the FFAC algorithm, the population-specific coefficient of variation (CV) at end-diastole was 3.24% for transverse compared to 9.96% for longitudinal measurements; the subject-specific CV was 15.03% compared to 57.41%, respectively. For longitudinal measurements made via the conventional method, the population-specific CV was 4.77% and subject-specific CV was 117.79%. The intraclass correlation coefficient (ICC) for transverse measurements was 0.97 (95% CI: 0.95-0.98) compared to 0.90 (95% CI: 0.84-0.94) for longitudinal measurements with FFAC and 0.72 (95% CI: 0.51-0.84) for conventional measurements. In conclusion, transverse views using the novel FFAC method provide less inter-observer variability than traditional longitudinal views. Improved reproducibility may allow adoption of FMD testing in a clinical setting. The FFAC algorithm is a robust technique that should be evaluated further for its ability to replace the more limited conventional technique for measurement of FMD.
authors.affiliation: Department of Internal Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA daniel.pugliese@uphs.upenn.edu.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Pugliese
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Chandra M
authors.initials: CM
authors.lastname: Sehgal
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Laith R
authors.initials: LR
authors.lastname: Sultan
authors.affiliation: Department of Medicine, Division of Cardiovascular Medicine, Section of Vascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Courtney B
authors.initials: CB
authors.lastname: Reamer
authors.affiliation: Department of Medicine, Division of Cardiovascular Medicine, Section of Vascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Emile R
authors.initials: ER
authors.lastname: Mohler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013997:Time Factors; D014463:Ultrasonography / Q000379:methods*; D014664:Vasodilation; D055815:Young Adult
keywords: active contour; brachial artery reactivity; endothelial function; flow-mediated dilation; ultrasound segmentation