Enhanced optical scattering by microbubbles

Optical properties of microbubbles (EchoGen, Sonus Pharmaceuticals, WA) have been evaluated using a 200 MHz phase modulation system. Studies have shown that the mean optical pathlength has been increased at 754 nm by an average of 1.5 mm (std. 0.46 mm) when EchoGen was administered to 11 fischer rats at the dose of 100 mu l or 150 mu l. As a comparison, the mean pathlength has been decreased at the same wavelength by an average of 4.2 mm (std. 3.66 wm) when Indocyanine Green (ICG) was administered at the dose of 100 mu l. The mean pathlength change at 816 nm is very small and the possible reasons are discussed. Potential applications of using microbubbles to provide a co-registration of ultrasound and light images of growing tumors are discussed.