Mr. Anthony Young Profile

Anthony Young

at Miami Univ

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Proceedings Article | 9 March 2018 Paper

Investigating the depth-sensitivity of laser speckle contrast imaging in flow phantoms

Anthony Young, Karthik Vishwanath

Proceedings Volume 10573, 105732Z (2018) https://doi.org/10.1117/12.2294480

KEYWORDS: Laser speckle contrast imaging, Speckle, Scattering, Tissue optics

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Laser speckle contrast imaging (LSCI) is a wide-field, optical technique capable of assessing changes in flow rates of scattering fluids. In biomedical applications, LSCI has been used to quantify changes of blood perfusion in various tissue. One limitation of LSCI is its limited depth sensitivity- it can only sense blood flow in superficial layers of tissue. The goal of this study was to experimentally investigate the depth-sensitivity of LSCI for detecting fluid flow embedded in a turbid optical phantom. LSCI was used to image a flow channel buried by the scattering medium at incremental depths ranging from 0 mm to 2.4 mm. The flow measurements were successively repeated using two illumination wavelengths, 633 nm and 785 nm. Images were captured with and without flow present through the phantom for each wavelength and analyzed to develop a flow-sensitivity parameter. This provided a metric of LSCI’s ability for detecting flow as a function of channel depth. At a depth of 1.5 mm, the flow sensitivity decreased by 80% with the 633 nm illumination and 65% for the 785 nm illumination relative to a depth of 0 mm. The results demonstrate that the flow sensitivity of the 785 nm source diminished at a slower rate as the buried depth was increased than the sensitivity of the 633 nm source. This study suggests that the flow depth and illumination wavelength should be considered while using LSCI.

Proceedings Article | 17 March 2016 Paper

Quantitative assessment of reactive hyperemia using laser speckle contrast imaging at multiple wavelengths

Anthony Young, Karthik Vishwanath

Proceedings Volume 9707, 97071H (2016) https://doi.org/10.1117/12.2213179

KEYWORDS: Laser speckle contrast imaging, Tissues, Speckle, Hemodynamics, Coherence imaging, Laser tissue interaction, Image processing, In vivo imaging, Functional imaging, Cameras, Light sources, Particles, Scattering, Imaging systems

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Reactive hyperemia refers to an increase of blood flow in tissue post release of an occlusion in the local vasculature. Measuring the temporal response of reactive hyperemia, post-occlusion in patients has the potential to shed information about microvascular diseases such as systemic sclerosis and diabetes. Laser speckle contrast imaging (LSCI) is an imaging technique capable of sensing superficial blood flow in tissue which can be used to quantitatively assess reactive hyperemia. Here, we employ LSCI using coherent sources in the blue, green and red wavelengths to evaluate reactive hyperemia in healthy human volunteers. Blood flow in the forearms of subjects were measured using LSCI to assess the time-course of reactive hyperemia that was triggered by a pressure cuff applied to the biceps of the subjects. Raw speckle images were acquired and processed to yield blood-flow parameters from a region of interest before, during and after application of occlusion. Reactive hyperemia was quantified via two measures - (1) by calculating the difference between the peak LSCI flow during the hyperemia and baseline flow, and (2) by measuring the amount of time that elapsed between the release of the occlusion and peak flow. These measurements were acquired in three healthy human participants, under the three laser wavelengths employed. The studies shed light on the utility of in vivo LSCI-based flow sensing for non-invasive assessment of reactive hyperemia responses and how they varied with the choice source wavelength influences the measured parameters.

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