INTERNAL TWO PHOTON EXCITATION DEVICE FOR DELIVERY OF PDT TO DIFFUSE ABNORMAL CELLS

A plurality of light sources that emit light having a long wavelength are energized for an extended period of time to increase the likelihood of two photon absorption by cells that have preferentially absorbed a photoreactive agent such as psoralen. The cells are preferably microscopic metastatic cancer cells that are diffusely distributed throughout a treatment site, for example, within an organ. The plurality of light sources are arranged in a spaced-apart array, mounted on a support plate that includes a plurality of conductive traces. A plurality of such arrays are preferably mounted to a flexible sheet that can conform to an outer surface of an organ being treated. Because the light emitted by the light sources is in the infrared or near infrared waveband, it penetrates deeply into the tissue at the treatment site. The duration of the treatment and the number of light sources employed for administering the therapy increases the likelihood of two photon absorption by the metastatic cancer cells, which has been shown to activate the photoreactive agent to destroy cancer cells in a tumor, even though the characteristic light absorption waveband of the photoreactive agent is in the ultraviolet waveband.