Toward handheld real time frequency domain diffuse optical spectroscopy

Frequency domain diffuse optical spectroscopy (fd-DOS) uses modulated laser light to image tissue and extract quantitative chromophore information. Currently no fd-DOS systems are completely handheld and only one is capable of displaying chromophore data in real time, which could allow for real-time studies of tissue hemodynamics, spatial chromophore (e.g. water, lipid, and hemoglobin) concentrations, greater ease of use by clinicians, and more generally, a simple platform for quantitative tissue spectroscopy. We present progress towards a handheld, real time fd-DOS system based upon an all-digital FPGA coupled hardware approach that includes data collection and processing and can attain imaging speeds of >30Hz. Quantitative optical scattering and absorption measurements are found to be within 10% agreement as compared to a reference system. We conclude that high speed quantitative tissue chromophore assessments are possible with this system-on-a-chip fd-DOS approach, which will enable real time handheld monitoring of rapid physiological changes.