A temporal and spatial analysis approach to automated segmentation of microbubble signals in contrast-enhanced ultrasound images: application to quantification of active vascular density in human lower limbs

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Title: A temporal and spatial analysis approach to automated segmentation of microbubble signals in contrast-enhanced ultrasound images: application to quantification of active vascular density in human lower limbs
Authors: Cheung, WK
Williams, KJ
Christensen-Jeffries, K
Dharmarajah, B
Eckersley, RJ
Davies, AH
Tang, M-X
Item Type: Journal Article
Abstract: Contrast-enhanced ultrasound (CEUS) using microbubble contrast agents has shown great promise in visualising and quantifying active vascular density. Most existing approaches for vascular density quantification using CEUS are calculated based on image intensity and are susceptible to confounding factors and imaging artefact. Poor reproducibility is a key challenge to clinical translation. In this study, a new automated temporal and spatial signal analysis approach is developed for reproducible microbubble segmentation and quantification of contrast enhancement in human lower limbs. The approach is evaluated in vitro on phantoms and in vivo in lower limbs of healthy volunteers before and after physical exercise. In this approach, vascular density is quantified based on the relative areas microbubbles occupy instead of their image intensity. Temporal features of the CEUS image sequences are used to identify pixels that contain microbubble signals. A microbubble track density (MTD) measure, the ratio of the segmented microbubble area to the whole tissue area, is calculated as a surrogate for active capillary density. In vitro results reveal a good correlation (r(2) = 0.89) between the calculated MTD measure and the known bubble concentration. For in vivo results, a significant increase (129% in average) in the MTD measure is found in lower limbs of healthy volunteers after exercise, with excellent repeatability over a series of days (intra-class correlation coefficient = 0.96). This compares to the existing state-of-the-art approach of destruction and replenishment analysis on the same patients (intra-class correlation coefficient ≤0.78). The proposed new approach shows great potential as an accurate and highly reproducible clinical tool for quantification of active vascular density.
Issue Date: 8-Jul-2017
Date of Acceptance: 21-May-2017
URI: http://hdl.handle.net/10044/1/49954
DOI: https://dx.doi.org/10.1016/j.ultrasmedbio.2017.05.021
ISSN: 0301-5629
Publisher: Elsevier
Start Page: 2221
End Page: 2234
Journal / Book Title: Ultrasound in Medicine and Biology
Volume: 43
Issue: 10
Copyright Statement: © 2017 World Federation for Ultrasound in Medicine & Biology Printed in the USA. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords: Contrast-enhanced ultrasound
Image segmentation
Lower limb
Peripheral arterial disease
Reproducibility
Temporal analysis
Vascular density quantification
1103 Clinical Sciences
Acoustics
Publication Status: Published
Conference Place: England
Appears in Collections:Faculty of Engineering
Bioengineering
Division of Surgery
Faculty of Medicine



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