Optical Phantom Mimicking Cerebral Blood Flow for Validation of Speckle Contrast Optical Spectroscopy
Disciplines
Bioimaging and Biomedical Optics
Abstract (300 words maximum)
Monitoring cerebral blood flow (CBF) is essential for understanding and maintaining brain health. Non-invasive optical techniques such as Speckle Contrast Optical Spectroscopy (SCOS) offer a low-cost method for assessing CBF. However, evaluating the depth sensitivity of SCOS systems is limited by the lack of tissue phantoms. Many existing phantoms use bulk liquids or single-layer solids and model a uniform tissue type. To address this, we propose a multi-layer, multi-channel tissue phantom designed to better reflect the optical properties and flow patterns of the skin and skull.
A single-layer tissue phantom was fabricated using polydimethylsiloxane (PDMS) with embedded silicone tubing placed 4 mm below the surface to simulate superficial blood vessels. Titanium dioxide (TiO₂) was added to match brain-like reduced scattering properties. A lens system was used to magnify the speckle pattern, ensuring the speckle-to-pixel ratio exceeded 2. The source and detector fibers were placed on the phantom surface at varying source-detector separations.
An intralipid solution was circulated through the tubing using a syringe pump to simulate dynamic flow. Video data were recorded by the SCOS system, and speckle contrast (κ) was calculated as the ratio of the standard deviation to the mean intensity of pixels within each frame. Measurements were taken across different source-detector separations to examine depth sensitivity. At low flow, the speckle pattern appears sharp with high contrast; at high flow, it becomes blurred, indicating reduced contrast. A circular ROI was selected from each frame, and 1/κ² increased during flow-on periods and returned to baseline during flow-off periods, demonstrating sensitivity to dynamic flow.
While promising, these results are preliminary. A two-layer, two-channel phantom is being developed to further evaluate SCOS depth sensitivity and resolve layered flow. Upcoming experiments will assess the SCOS system’s ability to resolve depth-dependent flow changes and support its application for more physiologically relevant measurements.
Use of AI Disclaimer
no
Academic department under which the project should be listed
SPCEET – Electrical and Computer Engineering
Primary Investigator (PI) Name
Paul Lee
Optical Phantom Mimicking Cerebral Blood Flow for Validation of Speckle Contrast Optical Spectroscopy
Monitoring cerebral blood flow (CBF) is essential for understanding and maintaining brain health. Non-invasive optical techniques such as Speckle Contrast Optical Spectroscopy (SCOS) offer a low-cost method for assessing CBF. However, evaluating the depth sensitivity of SCOS systems is limited by the lack of tissue phantoms. Many existing phantoms use bulk liquids or single-layer solids and model a uniform tissue type. To address this, we propose a multi-layer, multi-channel tissue phantom designed to better reflect the optical properties and flow patterns of the skin and skull.
A single-layer tissue phantom was fabricated using polydimethylsiloxane (PDMS) with embedded silicone tubing placed 4 mm below the surface to simulate superficial blood vessels. Titanium dioxide (TiO₂) was added to match brain-like reduced scattering properties. A lens system was used to magnify the speckle pattern, ensuring the speckle-to-pixel ratio exceeded 2. The source and detector fibers were placed on the phantom surface at varying source-detector separations.
An intralipid solution was circulated through the tubing using a syringe pump to simulate dynamic flow. Video data were recorded by the SCOS system, and speckle contrast (κ) was calculated as the ratio of the standard deviation to the mean intensity of pixels within each frame. Measurements were taken across different source-detector separations to examine depth sensitivity. At low flow, the speckle pattern appears sharp with high contrast; at high flow, it becomes blurred, indicating reduced contrast. A circular ROI was selected from each frame, and 1/κ² increased during flow-on periods and returned to baseline during flow-off periods, demonstrating sensitivity to dynamic flow.
While promising, these results are preliminary. A two-layer, two-channel phantom is being developed to further evaluate SCOS depth sensitivity and resolve layered flow. Upcoming experiments will assess the SCOS system’s ability to resolve depth-dependent flow changes and support its application for more physiologically relevant measurements.