Robust flow measurement with multi-exposure speckle imaging

Abstract

Laser Speckle Contrast Imaging (LSCI) is a minimally invasive full field optical technique used to generate blood flow maps with high spatial and temporal resolution. The lack of quantitative accuracy and the inability to predict flows in the presence of static scatterers such as an intact or thinned skull have been the primary limitation of LSCI. We present a new Multi-Exposure Speckle Imaging (MESI) instrument that has potential to obtain quantitative baseline flow measures. We show that the MESI instrument extends the range over which relative flow measurements are linear. We also present a new speckle model which can discriminate flows in the presence of static scatters. We show that in the presence of static scatterers the new model used along with the new MESI instrument can predict correlation times of flow consistently to within 10% of the value without static scatterers compared to an average deviation of more than 100% from the value without static scatterers using traditional LSCI. We also show that the new speckle model used with the MESI instrument can maintain the linearity of relative flow measurements in the presence of static scatterers.

Chronic Monitoring of Vascular Progression after Ischemic Stroke Using Multiexposure Speckle Imaging and Two-Photon Fluorescence Microscopy

“…[10][11][12][13][14] Recent advances in LSCI termed multiexposure speckle imaging (MESI) have allowed for the technique to move from primarily acute experiments to chronic studies through improvements in its quantitative accuracy of blood flow measurements. 15 By using multiple camera exposures spanning almost three decades in duration and improved mathematical models, MESI is able to more precisely sample and map the flow distributions prevalent in the rodent vasculature. 16 Studies have shown MESI to accurately estimate a wide range of flows in vivo, including complete flow reduction during middle cerebral artery occlusions, 17 and also shows the ability to determine spatially integrated perfusion measurements from unresolvable microvasculature within the parenchyma.…”

‘Go with the flow ’: A review of methods and advancements in blood flow imaging

“…Progress has been made in establishing a flow decorrelation time using laser speckle contrast techniques [117]; however, issues still remain of how to relate this time constant to the flow velocity [118]. Although accurate absolute measurements RBC V cannot be calculated, perfusion changes can be successively monitored and tracked.…”

Understanding and Augmenting Collateral Blood Flow During Ischemic Stroke

“…While LSCI permits sensitive mapping of blood flow in surface vessels, the exact quantitative relationship between speckle contrast and blood flow velocity remains undefined (Duncan & Kirkpatrick, 2008). LSCI is susceptible to experimental artifacts that can vary between animals and imaging sessions (Parthasarathy et al, 2008;Ayata et al, 2004) and is best restricted to describing relative changes in the pattern of blood flow rather than quantifying blood flow velocity (Parthasarathy et al, 2008;Ayata et al, 2004).…”