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Biomedical Imaging and Instrumentation

Biomedical Imaging and Instrumentation - Poster Session B

Poster G7 - Experimental comparison of speckle contrast optical spectroscopy with different detection configurations for assessing deep-tissue blood flow

Thursday, October 24, 2024

2:45 PM - 3:45 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Athar Awan

Student
Kennesaw State University
Woodstock, Georgia, United States

Co-Author(s)

Seoeun Cho

Student
Kennesaw State University, United States

Last Author(s)

SL

Seung Yup Lee, PHD

Assistant Professor
Kennesaw State University
Marietta, Georgia, United States

Introduction: Speckle contrast optical spectroscopy (SCOC) is an emerging optical technique assessing deep-tissue blood flow. Typically, SCOS illuminates a near-infrared (NIR) laser light into tissues and captures the interference pattern, i.e. speckle pattern at the surface using a camera system. This speckle pattern is related to the movement of scatterers, e.g., red blood cells, inside the tissues, allowing for quantification of blood flow. The different detection configurations, including the use of lenses to couple with a detection fiber and different quality of cameras, would significantly affect the SCOS performance. In this project, we have systematically analyzed the performance of SCOS with different detection setups (fiber-coupled lens-focused vs. direct imaging) with two different camera systems (CMOS vs. scientific CMOS sensor). This work investigates the technical feasibility of optimizing the SCOS system for further cost-reduction while maintaining comparable system performance.

Materials and

Methods: We built four different versions of the SCOS benchtop system with: 1) two detection schemes—fiber-optic coupled lens system versus direct imaging of speckle contrast without a lens—and 2) two different cameras—a compact, cheaper CMOS camera (CMOSIS 4000, XIMEA) and an expensive sCMOS camera (CS2100M, Thorlabs). These four setups were tested on a bulk liquid phantom consisting of Intralipid 20% I.V. fat emulsion and water. The temperature of the phantoms was controlled at 6, 20, and 40 degrees Celsius to vary the flow rate. Light from a long-coherence 850 nm laser (IBEAM-SMART, TOPTICA Photonics) was delivered to the phantom through a multimode fiber-optic probe. For the detection scheme using a fiber-optic coupled lens system, the detection fiber was located 2.5 cm away from the source fiber. A total of 100 images were taken with exposure times of 0.5, 1, 2, and 5 ms at each temperature for each setup. Dark and shot noise were accounted for to obtain accurate speckle contrast values from the raw data. The signal-to-noise ratio was characterized, and the estimated flow index was compared to the reference values measured by standard diffuse correlation spectroscopy.

Results, Conclusions, and Discussions: The experimental verification is ongoing. We hypothesize that, among the four setups, the one using an sCMOS camera to capture a focused speckle pattern imaging through a detection fiber has the highest SNR and accuracy. However, we also expect that the results from the compact CMOS camera will not be significantly inferior to those from the sCMOS camera. An SNR of >25 dB and an accuracy of >75% are acceptable for clinical studies of brain or muscle blood flow. Considering cost and size, the SCOS system with the compact camera has potential as a low-cost, portable optical flowmeter. We will report the results in detail during the poster session in October.

Acknowledgements (Optional):