Scanning laser system for combined fluorescent diagnostics and photodynamic therapy: structural design, preliminary trials, and potentials

Photodynamic therapy (PDT) is commonly performed by administration of porphyrin photosensitizers selectively retained by malignant tumors. Subsequent photoexcitation with UV-blue light causes fluorescence useful for diagnosis. Excitation by red light destroys the cancer tissue. The use of high-speed scanning of laser light as an alternative to conventional PDT which employs dispersed light to achieve uniformity of treatment is proposed. It is shown that treatment with scanned light beams produces photochemical effects in malignant animal tissue that are virtually the same as those caused by comparable treatments with diffused light. It is argued that undesirable thermal effects can be reduced by the use of focused, scanned laser beams in lieu of diffused light. It is also shown how concurrent analysis and treatment can proceed using a system of two laser beams