Abstract
Before laser speckle contrast imaging (LSCI) can be used reliably and quantitatively in a clinical setting, there are several theoretical and practical issues that still must be addressed. In order to address some of these issues, an electro-optical system that utilizes a nematic liquid crystal spatial light modulator (SLM) to mimic LSCI experiments was assembled. The focus of this paper is to address the issue of how incident intensity affects LSCI results. Using the SLM-based system, we systematically adjusted incident intensity on the SLM and assessed the resulting first- and second-order statistics of the imaged speckle to explain the corresponding spatial contrast values in both frozen and time-integrated speckle patterns. The SLM-based system was used to generate speckle patterns with a controlled minimum speckle size, probability intensity distribution, and temporal decorrelation behavior. By eliminating many experimental parameters, this system is capable of serving as a useful intermediary tool between computer simulation and physical experimentation for further developing LSCI as a quantitative imaging modality.
Highlights
Laser speckle contrast imaging (LSCI) is a simple, noninvasive, low-cost method that allows for the assessment of blood flow and perfusion in near-real time
Since a single polarization state was observed, the speckle patterns produced from these phase screens should exhibit a negative exponential intensity probability distribution function (PDF)
The highest contrast values were seen in the cases where both the calculated PDF and quantized intensities follow the theoretical negative exponential
Summary
Laser speckle contrast imaging (LSCI) is a simple, noninvasive, low-cost method that allows for the assessment of blood flow and perfusion in near-real time. It has become common place for LSCI and its variations to be used in full-field qualitative visualization of blood flow.[1,2] there are numerous experimental challenges, as well as theoretical and practical limitations, that remain unresolved in using LSCI to make quantitative measurements of flow and perfusion.[3] for both quantitative and qualitative assessment of blood flows, there are compounding issues such as changes in hematocrit that manifest as changes in bulk blood optical properties that appear identical to relative changes in blood flow. Because scatterer density has been shown to affect the measured contrast in LSCI,[4] when we refer to flow and perfusion, we are implying a volume movement of scatterers in time
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