Determination of subsurface tumor localization in animal models with near-infrared (NIR) fluorescence imaging

We have developed a novel imaging system for determining the localization of tumors labeled by fluorescent contrast agents and embedded several centimeters inside the highly scattering medium. This frequency-domain system utilizes the phased cancellation configuration with a goniometric probe. The instrumentation performance on the phantom test can detect 3 mm diameter sphere filled with 1 nM fluorescent dye, Indocyanine Green (ICG), and 3 cm deep inside the scattering medium with similar optical properties as human breast tissue within a 1 mm localization confidence. Mouse tumor model immersed in appropriate scattering/absorbing medium is used for animal test. Intra-tumor injection of ICG demonstrates the localization of the tumor (5 mm in diameter) submerged 3 cm deep inside the highly scattering medium with 2 mm position error. Results with NIR804-D-Glucosamide on the AR42J tumor bearing nude mouse are also presented with 3 mm localization error. The accuracy of the localization suggests that this system would be helpful to guide the clinical fine-needle biopsy for early breast cancer detection.