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

Significance: Spatial frequency domain imaging (SFDI) is a diffuse optical measurement technique that can quantify tissue optical absorption ([Formula: see text]) and reduced scattering ([Formula: see text]) on a pixel-by-pixel basis. Measurements of [Formula: see text] 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 [Formula: see text] and [Formula: see text] 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 [Formula: see text] and [Formula: see text] 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 [Formula: see text] in [Formula: see text] and [Formula: see text] in [Formula: see text] , compared to a commercial SFDI system. Bland–Altman analysis revealed the limits of agreement between the two systems to be [Formula: see text] for [Formula: see text] and [Formula: see text] to [Formula: see text] for [Formula: see text]. The openSFDI system had low drift with an average standard deviation of [Formula: see text] and [Formula: see text] in [Formula: see text] and [Formula: see text] , respectively. Conclusion: The openSFDI provides a customizable hardware platform for research groups seeking to utilize SFDI for quantitative diffuse optical imaging.