Simultaneous detection of multiple contrast agents with photoacoustic spectroscopy

Early detection of cancer is important for survival, and multiple targeted contrast agents can be used for advanced cellular profiling. Photoacoustic (PA) imaging is effective at imaging optically-absorbing contrast agents. In this study, we present simulated and experimental results using spectral decomposition to separate the PA absorption spectrum into components from individual contrast agents. The original colocalized concentration of each agent is then simultaneously reconstructed. Monte Carlo simulations were performed to estimate wavelength-dependent fluences in the sample. In phantom experiments, the concentration of two contrast agents (gold nanorods with different absorption spectra) and a background absorbing dye (India Ink) were reconstructed. Finally, we implemented our algorithm in a mouse after injections of gold nanorods with absorption peaks of 750 and 810 nm. The concentration of each nanoparticle was identified from the endogenous background signal with a signal-to-noise ratio of greater than 25 dB.