In vivoisolation of the effects of melanin from underlying hemodynamics across skin types using spatial frequency domain spectroscopy

Abstract

In vivo isolation of the effects of melanin from underlying hemodynamics across skin types using spatial frequency domain spectroscopy," J. Abstract. Skin is a highly structured tissue, raising concerns as to whether skin pigmentation due to epidermal melanin may confound accurate measurements of underlying hemodynamics. Using both venous and arterial cuff occlusions as a means of inducing differential hemodynamic perturbations, we present analyses of spectra limited to the visible or near-infrared regime, in addition to a layered model approach. The influence of melanin, spanning Fitzpatrick skin types I to V, on underlying estimations of hemodynamics in skin as interpreted by these spectral regions are assessed. The layered model provides minimal cross-talk between melanin and hemodynamics and enables removal of problematic correlations between measured tissue oxygenation estimates and skin phototype. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Noninvasive mesoscopic imaging of actinic skin damage using spatial frequency domain imaging

“…We acknowledge that the use of fewer wavelengths may result is less stable fitting and therefore the quantification of physiological parameters such as oxy-, deoxy-hemoglobin and melanin may suffer. Melanin in particular can be a difficult absorber to quantify due to its featureless absorption spectrum and uneven distribution in the skin [18,22]. Although hemodynamic parameters may not show as much difference as the optical properties for these patients, these are useful physiological parameters related to disease progression and may show differences for other patients, each parameter and the combination thereof can show different sensitivity and specificity for individual patient.…”

Separating melanin from hemodynamics in nevi using multimode hyperspectral dermoscopy and spatial frequency domain spectroscopy

“…In a separate study, SFDS was also able to demonstrate that this two-layer model approach was able to significantly decouple and isolate melanin from induced hemodynamic events in healthy subjects (n ¼ 9) across a distribution of skin pigmentation. 33 This study not only illustrated how interpretation of results using a layer model can be insensitive to crosstalk errors induced by depth-specific sources of optical contrast (i.e., melanin and hemoglobin), but also demonstrated how significantly these errors can affect the estimation of underlying hemoglobin concentrations when high concentrations of melanin might be present (e.g., pigmented lesions).…”

Two-layer inverse model for improved longitudinal preclinical tumor imaging in the spatial frequency domain

“…This model was tested for top layer thicknesses of 2 to 4 mm, which are substantially larger than the 312.5 μm top layer thickness used in this work. Saager et al 20,21 utilized Hankel-transformed conventional (i.e., spatially resolved) MC simulations to develop a two-layer model of human epidermis (containing melanin) and dermis (containing melanin and hemoglobin). This model also provides estimates for top layer thickness constrained within a range of 80 to 300 μm.…”

“…11 However, tissue geometry is complex, and in the case of subcutaneous tumors in mice, a thin skin layer is located above the tumor, which remains unaccounted for in a homogeneous model. Although there are several prior studies that have described inversion algorithms that utilize a layered-tissue structure [17][18][19][20][21] or utilize tomographic reconstructions with SFDI, 22,23 we describe, in this work, the first use of MC simulations conducted natively in the spatial frequency domain to make a two-layer LUT inversion algorithm that closely matches the true physiology and optical characteristics of preclinical tumor models.…”