Compact tissue oximeter based on dual-wavelength multichannel time-resolved reflectance

We developed a compact dual-wavelength multichannel tissue oximeter based on the time-correlated single-photon counting (TCSPC) technique. The light sources are two pulsed diode lasers (output wavelengths of 672 and 818 nm, an average power of 1 mW, a pulse duration of 100 ps, and a pulse-repetition rate as high as 80 MHz). The time-resolved reflectance photons are detected by a multianode photomultiplier, and the output signals are redirected by a router to different memory blocks of the TCSPC personal computer board. The system's accuracy in determining the absorption microa and the reduced-scattering micros' coefficients and in reconstructing absorber concentrations in diffusive media was tested on phantoms. Preliminary in vivo tissue-oxygenation measurements were performed on healthy volunteers under different physiological conditions with a minimum acquisition time of 100 ms and an injected power of less than 100 microW.