Method Article

A Reproducible Computerized Method for Quantitation of Capillary Density using Nailfold Capillaroscopy

DOI:

10.3791/53088

October 27th, 2015

In This Article

Summary

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Capillaroscopy is a non-invasive, efficient, relatively inexpensive and easy-to-learn methodology for directly visualizing capillaries in the microcirculation. However, only one publication to date describes the reliability of a complex software program available for quantitating capillaroscopy data. Here, we present a simple, reliable protocol for quantitating capillaries using a standardized algorithm.

Abstract

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Capillaroscopy is a non-invasive, efficient, relatively inexpensive and easy to learn methodology for directly visualizing the microcirculation. The capillaroscopy technique can provide insight into a patient’s microvascular health, leading to a variety of potentially valuable dermatologic, ophthalmologic, rheumatologic and cardiovascular clinical applications. In addition, tumor growth may be dependent on angiogenesis, which can be quantitated by measuring microvessel density within the tumor. However, there is currently little to no standardization of techniques, and only one publication to date reports the reliability of a currently available, complex computer based algorithms for quantitating capillaroscopy data.1 This paper describes a new, simpler, reliable, standardized capillary counting algorithm for quantitating nailfold capillaroscopy data. A simple, reproducible computerized capillaroscopy algorithm such as this would facilitate more widespread use of the technique among researchers and clinicians. Many researchers currently analyze capillaroscopy images by hand, promoting user fatigue and subjectivity of the results. This paper describes a novel, easy-to-use automated image processing algorithm in addition to a reproducible, semi-automated counting algorithm. This algorithm enables analysis of images in minutes while reducing subjectivity; only a minimal amount of training time (in our experience, less than 1 hr) is needed to learn the technique.

Introduction

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Microvascular imaging is a rapidly growing field with many potential clinical applications.2 For example, oncologists are using microvessel imaging to determine the extent of tumor angiogenesis, yielding valuable information concerning the state of the tumor and insight into possible treatment options. 34 However, nailfold capillaroscopy is perhaps the most cost efficient and widely applicable form of microvascular imaging. Researchers are using video nailfold capillaroscopy to study blood flow rates and investigate capillary morphology.5 6 Both video and still-picture nailfold capillaroscopy are adjuncts to care ....

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Protocol

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Note: The acquisition process for obtaining capillary images has previously been published and is accomplished using a still digital camera with a corresponding image acquisition and analysis computer program. 1121 This lab utilizes still images for analysis, not videos, simplifying image acquisition for analysis. The following describes the new technique for quantitating the capillaries from the images.

1. Image Enhancement Process

  1. Obtain digital images with a monochrome digital camera. Calibrate the images to an object of known size by taking a picture of an object of known length such as a ruler ....

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Results

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The goal of this image processing procedure is to differentiate the capillaries from the background image so they can be accurately quantified. Both incomplete image processing and excessive image processing are detrimental to the program's ability to quantify the capillaries. As seen in Figure 3, incomplete image processing makes the capillaries difficult to distinguish from the background. It is critical that the user be able to readily distinguish the border of a capillary since the counting method de.......

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Discussion

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Nailfold capillaroscopy shows promise as a clinically useful tool in the future for various oncology, cardiovascular, and rheumatologic disease applications. The image acquisition process is fairly consistent among researchers, yet there are currently multiple methods for image processing and analysis. Methods currently include computerized and manual capillary counts. Manual counts are problematic as they are time-consuming, and subject to user subjectivity and fatigue. Current computer based methods require a high leve.......

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Disclosures

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The authors have no conflicts of interest.

Acknowledgements

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This project was supported by Grant Numbers HL96593 from NIH and D56HP20783 from HRSA/ HHS. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH or HRSA / HHS.

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Image-Pro PremierMedia Cybernetics, Inc9.1Image processing software

References

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  1. Gronenschild, E. H., et al. Semi-automatic assessment of skin capillary density: proof of principle and validation. Microvasc Res. 90, 192-198 (2013).
  2. Allen, J., Howell, K. Microvascular imaging: techniques and opportunities f....

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Tags

Capillary Density QuantitationNailfold CapillaroscopyImage Processing AlgorithmCapillary Counting MethodMicrocirculation AnalysisImage Manipulation TechniqueRegion of Interest PlacementHistogram Adjustment ProtocolAutomated Image AnalysisCapillary Morphology Assessment

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