High-speed spatial frequency domain imaging with temporally modulated light.

Spatial frequency domain imaging (SFDI) is a wide-field diffuse optical technique used to obtain optical properties and chromophore concentrations in highly scattering media, such as biological tissue. Here, we present a method for rapidly acquiring multispectral SFDI data by modulating each illumination wavelength at a different temporal frequency. In the remitted signal, each wavelength is temporally demodulated and processed using conventional SFDI techniques. We demonstrate a proof-of-concept system capable of acquiring wide-field maps (2048×1536  pixels, 8.5×6.4  cm) of optical properties at three wavelengths in under 2.5 s. Data acquired by this method show a good agreement with a commercial SFDI imaging system (with an average error of 13% in absorption and 8% in scattering). Additionally, we show that this strategy is insensitive to ambient lighting conditions, making it more practical for clinical translation. In the future, this technique could be expanded to tens or hundreds of wavelengths without increasing acquisition time.