Accurately calibrated frequency domain diffuse optical spectroscopy compared against chemical analysis of porcine adipose tissue

Frequency domain diffuse optical spectroscopy (fdDOS) is a noninvasive technique to estimate tissue composition and hemodynamics. While fdDOS has been established as a valuable modality for clinical research, comparison of fdDOS with direct chemical analysis (CA) methods has yet to be reported. To compare the two approaches, we propose a procedure to confirm accurate calibration by use of liquid emulsion and solid silicone phantoms. Tissue fat (FAT) and water (H2O) content of two ex vivo porcine tissue samples were optically measured by fdDOS and compared to CA values. We show an average H2O error (fdDOS minus CA) and SD of 1.9 +/- 0.2% and -0.9 +/- 0.2% for the two samples. For FAT, we report a mean error of -9.3 +/- 1.3% and 0.8 +/- 1.3%. We also measured various body sites of a healthy human subject using fdDOS with results suggesting that accurate calibration may improve device sensitivity.