OpenSFDI: an open-source guide for constructing a spatial frequency domain imaging system.

Matthew Applegate, Kavon Karrobi, Joseph Angelo, Wyatt Austin, Syeda Tabassum, Enagnon Aguénounon, Karissa Tilbury, Rolf Saager, Sylvain Gioux, Darren Roblyer

Journal of biomedical optics 2020 Jan

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Significance: Spatial frequency domain imaging (SFDI) is a diffuse optical measurement technique that can quantify tissue optical absorption (μa) and reduced scattering (μs') on a pixel-by-pixel basis. Measurements of μa at different wavelengths enable the extraction of molar concentrations of tissue chromophores over a wide field, providing a noncontact and label-free means to assess tissue viability, oxygenation, microarchitecture, and molecular content. We present here openSFDI: an open-source guide for building a low-cost, small-footprint, three-wavelength SFDI system capable of quantifying μa and μs' as well as oxyhemoglobin and deoxyhemoglobin concentrations in biological tissue. The companion website provides a complete parts list along with detailed instructions for assembling the openSFDI system.

Aim: We describe the design of openSFDI and report on the accuracy and precision of optical property extractions for three different systems fabricated according to the instructions on the openSFDI website.

Approach: Accuracy was assessed by measuring nine tissue-simulating optical phantoms with a physiologically relevant range of μa and μs' with the openSFDI systems and a commercial SFDI device. Precision was assessed by repeatedly measuring the same phantom over 1 h.

Results: The openSFDI systems had an error of 0 ± 6 % in μa and -2 ± 3 % in μs', compared to a commercial SFDI system. Bland-Altman analysis revealed the limits of agreement between the two systems to be ± 0.004 mm - 1 for μa and -0.06 to 0.1 mm - 1 for μs'. The openSFDI system had low drift with an average standard deviation of 0.0007 mm - 1 and 0.05 mm - 1 in μa and μs', respectively.

Conclusion: The openSFDI provides a customizable hardware platform for research groups seeking to utilize SFDI for quantitative diffuse optical imaging.

Citation

Matthew Applegate, Kavon Karrobi, Joseph Angelo, Wyatt Austin, Syeda Tabassum, Enagnon Aguénounon, Karissa Tilbury, Rolf Saager, Sylvain Gioux, Darren Roblyer. OpenSFDI: an open-source guide for constructing a spatial frequency domain imaging system. Journal of biomedical optics. 2020 Jan;25(1):1-13