Combined photoacoustic and molecular fluorescence imaging in vivo.

Because of the overwhelming scattering of light in biological tissues, the spatial resolution and imaging depth of conventional fluorescent imaging is unsatisfactory. Therefore, we present a dual modality imaging technique by combining fluorescence imaging with high-resolution noninvasive photoacoustic tomography (PAT) for the study of an animal tumor model. PAT provides high-resolution structural images of tumor angiogenesis, and fluorescence imaging offers high sensitivity to molecular probes for tumor detection. Coregistration of the PAT and fluorescence images was performed on nude mice with M21 human melanoma cell lines with ..v..3 integrin expression. An integrin ..v..3-targeted peptide-ICG conjugated NIR fluorescent contrast agent was used as the molecular probe for tumor detection. PAT was employed to noninvasively image the brain structure and the angiogenesis associated with tumors in mice. The coregistration between the PAT and fluorescence images was used to visualize tumor location, angiogenesis, and brain structure simultaneously.