Abstract
: Imaging blood flow or oxygenation changes using optical techniques is useful for monitoring cortical activity in healthy subjects as well as in diseased states such as stroke or epilepsy. However, in order to gain a better understanding of hemodynamics in conscious, freely moving animals, these techniques must be implemented in a small scale, portable design that is adaptable to a wearable format. We demonstrate a novel system which combines the two techniques of laser speckle contrast imaging and intrinsic optical signal imaging simultaneously, using compact laser sources, to monitor induced cortical ischemia in a full field format with high temporal acquisition rates. We further demonstrate the advantages of using combined measurements of speckle contrast and oxygenation to establish absolute flow velocities, as well as to statistically distinguish between veins and arteries. We accomplish this system using coherence reduction techniques applied to Vertical Cavity Surface Emitting Lasers (VCSELs) operating at 680, 795 and 850 nm. This system uses minimal optical components and can easily be adapted into a portable format for continuous monitoring of cortical hemodynamics.
Highlights
In the quantification of neural signals in healthy and diseased states, hemodynamic measurements have proven very valuable, giving signals which are well correlated with data collected from electrophysiology measurements [1]
The data garnered from combined imaging of blood flow, oxygenation and fluorescence can be applied to develop a better understanding of real time hemodynamics and other physiological changes
We have developed a system that uses coherence control of Vertical Cavity Surface Emitting Lasers (VCSELs) to produce illumination satisfying the needs of both Intrinsic Optical Signal Imaging (IOSI) and Laser Speckle Contrast Imaging (LSCI) from a single source in a specialized current sweep (SW) operation scheme
Summary
In the quantification of neural signals in healthy and diseased states, hemodynamic measurements have proven very valuable, giving signals which are well correlated with data collected from electrophysiology measurements [1]. With the use of fiber bundles to illuminate and collect fluorescent emission, very high-resolution images can be produced, but the field of view is limited and light collection efficiency is significantly reduced. For these reasons, fully integrated, wide-field imaging techniques are preferable in portable imaging. The data garnered from combined imaging of blood flow, oxygenation and fluorescence can be applied to develop a better understanding of real time hemodynamics and other physiological changes This provides a more complete picture of the numerous processes occurring along with neural activity in diseased and healthy states [11]
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