High resolution and high contrast noninvasive photoacoustic imaging of neovascularization in tumor angiogenesis

Photoacoustic tomography (PAT) was presented to in vivo monitor neovascularization in tumor angiogenesis with high resolution and high contrast images in a rat. With a circular scan system, the photoacoustic signal, generated by laser pulses at a wavelength of 532 nm from a Q-switched Nd:YAG laser, is captured through of a hydrophone with a diameter of 1 mm and a sensitivity of 850 nV/Pa. The vascular structure around the rat tumor was imaged clearly, with optimal contrast, because blood has strong absorption near this wavelength. Serial noninvasive photoacoustic images of neovascularization in tumor angiogenesis were also obtained consecutively from a growing tumor implanted under the skin of a rat over a period of two weeks. This work demonstrates that PAT can potentially provide a powerful tool for tumor angiogenesis detection in cancer research. It will bring us closer to clinical application of the technique for tumor diagnosis and treatment monitoring.