Spatial frequency domain spectroscopy imaging using a snap-shot filter mosaic camera compared to a multi-camera system with band-pass filters (Conference Presentation)

Spectroscopic imaging of human tissue analyzes backscattered light intensity separated by wavelength. We used a DLP-projector illuminating sinusoidal patterns with varying phase and varying spatial frequency on forearm skin. Detection was done with: 1) a snap-shot filter mosaic camera with 16 wide-band sensitive pixels; 2-3) a four cameras setup with narrow and wide bandwidth optical bandpass filters in the 450-700 nm range, respectively. The detected images were processed with a demodulation scheme, assessing tissue optical parameters, involving light absorption. Calibration was done using an optical phantom with known optical properties. From the absorption coefficient the concentration of skin blood and its oxygenation was determined. We will present results from forearm arterial occlusion and release experiments using the three setups above. Specifically, the effect of the filter bandwidth will be evaluated using data from the multi-camera setups. Furthermore, the snap-shot filter mosaic camera data may be explained by the calculation of modulation using an illumination and detector setup with a broad spectral transmission bandwidth, with considerable variation in μ_a of included chromophores. Approaches for either reducing the effective bandwidth of the filters or by including their characteristic in a light transport model for SFDI modulation, will be proposed.