Design and construction of a light-delivery system for photodynamic therapy

We have developed a device to divide the output from a dye laser into as many as eight beams of equal power with negligible total power loss. In this system, 630-nm s-plane polarized laser light was split by a series of highly polarization-sensitive plate beamsplitters. Each of the beams was coupled to a 200, 400, or 600 microm diameter optical fiber. Brewster-window-type attenuators allowed the power of each beam to be individually set. It was possible to reconfigure the device to produce four, two, or one output(s). We discuss the design requirements of the beamsplitter device and describe its construction from mostly commercially available components. An apparatus for positioning and stabilizing each optical fiber relative to the skin surface of a patient is also described. The illumination from the fiberoptic supported by such an apparatus strikes a defined surface area and is independent of patient movement. Both the beamsplitter device and the optical fiber positioner are used routinely in photodynamic therapy (PDT) of malignant tumors in the clinic and in the laboratory.