Time-gated Cherenkov emission spectroscopy from linear accelerator irradiation of tissue phantoms.

Radiation from a linear accelerator induces Cherenkov emission in tissue, which has recently been shown to produce biochemical spectral signatures that can be interpreted to estimate tissue hemoglobin and oxygen saturation or molecular fluorescence from reporters. The Cherenkov optical light levels are in the range of 10(-6) to 10(-9) W/cm2, which limits the practical utility of the signal in routine radiation therapy monitoring. However, due to the fact that the radiation is pulsed, gated-acquisition of the signal allows detection in the presence of ambient lighting, as is demonstrated here. This observation has the potential to significantly increase the value of Cherenkov emission spectroscopy during radiation therapy to monitor tissue molecular events.