Quantitative color analysis for capillaroscopy image segmentation

Multivariate Parametric Study of Nailfold Capillary Images for Disease Detection

Nailfold capillaroscopy is a tool which is non-invasive in nature and can be useful for diagnosis, research, therapeutic study and prognosis. Research shows that specific capillary morphology patterns are identified for diabetic subjects, hypertensive subjects and normal controls. In this study, we have proposed RATHEW approach of classifying these three classes of subjects. RATHEW approach employs a three step process for classifying nailfold images: one, identify six abnormality parameters from the image dataset; two, score these abnormality parameters based on the defined scoring rules; and three, combine them mathematically to segregate them into three classes. This technique can be further enhanced to grade the severity of disease and organ involvement. This can bring in a paradigm shift to the disease detection and therapeutic study mechanism.

Effect of skin phototype on quantitative nailfold capillaroscopy

Objectives

To determine the impact of Fitzpatrick scale-based skin phototype on visualization of capillary density using nailfold capillaroscopy in healthy Indian adults.

Methods

In this cross-sectional study, healthy adults were examined for nailfold capillaroscopy findings utilizing a portable capillary microscope at 800× magnification. Photographs of two contiguous areas measuring 1 mm2 each of the distal row of capillaries were captured. Images were captured from the central area of all fingers except thumb in both hands. Capillary density and morphology of nailfold capillaroscopies were assessed by two blinded assessors. The nailfold capillaroscopy parameters were compared between the Standard Fitzpatrick scale-based skin phototypes.

Results

A total of 118 healthy adults were enrolled in the study. Type III, IV, V, and VI skin phototypes were seen in 27 (22.90%), 32 (27.19%), 29 (24.58%), and 30 (25.42%) participants, respectively. All participants (100%) had normal nailfold capillaroscopy morphology and architecture. Zero capillaries were visible in 11 fingers among 5 patients (4.24%) and all of them had Type VI phototype. The median capillary density per mm was 5.19 (interquartile range = 4.37-6.75) with 90 (76.27%) participants having less than seven capillaries. The median average capillary density was significantly different (p-value < 0.0001) across Type III (8.13, interquartile range = 6.44-8.88), Type IV (5.67, interquartile range = 4.41-6.98), Type V (4.94, interquartile range = 4.19-5.38), and Type VI (4.53, interquartile range = 3.72-4.91) phototypes (p < 0.05).

Conclusion

The number of capillaries visualized during nailfold capillaroscopy decreases as the skin pigmentation increases. There is a need to redefine the nailfold capillaroscopy density and avascularity by taking skin phototype as one of the determinants before labeling a nailfold capillaroscopy finding with less visualized capillaries as abnormal.

Quantitative nailfold capillaroscopy-update and possible next steps

We review the exciting potential (and challenges) of quantitative nailfold capillaroscopy, focusing on its role in systemic sclerosis. Quantifying abnormality, including automated analysis of nailfold images, overcomes the subjectivity of qualitative/descriptive image interpretation. First we consider the rationale for quantitative analysis, including the potential for precise discrimination between normal and abnormal capillaries and for reliable measurement of disease progression and treatment response. We discuss nailfold image acquisition and interpretation, and describe how early work on semi-quantitative and quantitative analysis paved the way for semi-automated and automated analysis. Measurement of red blood cell velocity is described briefly. Finally we give a personal view on 'next steps'. From a clinical perspective, increased uptake of nailfold capillaroscopy by general rheumatologists could be achieved via low-cost hand-held devices with cloud-based automated analysis. From a research perspective, automated analysis could facilitate large-scale prospective studies using capillaroscopic parameters as possible biomarkers of systemic sclerosis-spectrum disorders.

Contrast Ratio Quantification During Visualization of Microvasculature

INTRODUCTION

Visualization and monitoring of capillary loops in dermis and mucosa are of interest for a number of clinical applications, such as capillaroscopy, early cancer, or shock detection. For historical reasons, an unaided eye is still a primary aide to diagnostics in visual examinations for many medical specializations. However, the ability to make an early diagnosis using the unaided eye has remained poor. New optical modalities can significantly improve the accuracy of anomaly detection. To compare the image quality of various optical schemes, a systematic way to quantify it is required. The goal of this work is to develop an analytical approach for assessment of a contrast ratio as a single number quantitative metric image quality during optical imaging of capillary network.

METHODS

Based on skin layers geometry, we developed a two-layer optical tissue model. Then, we extended a two-layer Kubelka-Munk model to calculate the contrast ratio of a subsurface defect (absorption or scattering) imaging.

RESULTS

We have obtained an explicit expression for the contrast ratio in the two-layer model. Then, we investigated how the contrast ratio is affected by the tissue optical parameters and depth of the inhomogeneity. Based on this analysis we identified two important cases: (a) the top layer with negligible absorption, and (b) the 'optically thick' top layer. The contrast ratio deteriorates differently with the inhomogeneity depth in these two cases.

CONCLUSIONS

The contrast ratio can be used for quantification of image quality of subsurface inhomogeneities in the skin. The developed approach can be employed for estimation of interrogating depth of various tissue inhomogeneities and optimization of imaging techniques.

A quantitative study of nanoparticle skin penetration with interactive segmentation

In the last decade, the application of nanotechnology techniques has expanded within diverse areas such as pharmacology, medicine, and optical science. Despite such wide-ranging possibilities for implementation into practice, the mechanisms behind nanoparticle skin absorption remain unknown. Moreover, the main mode of investigation has been qualitative analysis. Using interactive segmentation, this study suggests a method of objectively and quantitatively analyzing the mechanisms underlying the skin absorption of nanoparticles. Silica nanoparticles (SNPs) were assessed using transmission electron microscopy and applied to the human skin equivalent model. Captured fluorescence images of this model were used to evaluate degrees of skin penetration. These images underwent interactive segmentation and image processing in addition to statistical quantitative analyses of calculated image parameters including the mean, integrated density, skewness, kurtosis, and area fraction. In images from both groups, the distribution area and intensity of fluorescent silica gradually increased in proportion to time. Since statistical significance was achieved after 2 days in the negative charge group and after 4 days in the positive charge group, there is a periodic difference. Furthermore, the quantity of silica per unit area showed a dramatic change after 6 days in the negative charge group. Although this quantitative result is identical to results obtained by qualitative assessment, it is meaningful in that it was proven by statistical analysis with quantitation by using image processing. The present study suggests that the surface charge of SNPs could play an important role in the percutaneous absorption of NPs. These findings can help achieve a better understanding of the percutaneous transport of NPs. In addition, these results provide important guidance for the design of NPs for biomedical applications.