Leroy M. Wood

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.

A Beam-splitting Device for Use with Fiber-coupled Laser Light Sources for Photodynamic Therapy¶

A device that divides light into eight, four or two beams of equivalent power with only minor total power loss was designed, built and tested. The apparatus accepts light from a 200 μm diameter, 0.16 numerical aperture, silica–silica multimode optical fiber connected to one of several laser light sources for photodynamic therapy (PDT) of cancer. The incorporation of a variable iris diaphragm into the optical couplers allows the power of the beams to be independently set. Each of the beams can be coupled to a 400 or 600 μm diameter optical fiber to deliver the therapeutic light to the patient. This device is used in our institute for PDT of patients with either numerous small malignant tumors or single tumors with large surface area.

Factors effecting the light distribution of cylindrical diffusers

Th space irradiance produced by a fiber with a cylindrical diffusing tip was measured under a variety of launch and mode miling conditions. The aim of these measurements was to determine the extent to which conditions of use would effect the light distribution and to assess the impact these variations in light distribution would have on the therapeutic effect when the fibers were used in Photodynamic therapy treatments.