A diffusing sphere which delivers homogeneous laser light for use in photodynamic therapy

• Published in: Journal of dermatological science 1995-05, Vol.9 (3), p.195-202
• Main Authors: Bernstein, Eric F., Smith, Paul D., homas, Gunter F., Xie, Huchen, Mitchell, James B., Glatstein, Eli, Russo, Angelo
• Format: Article
• Language: English
• Subjects: Animals; Diffusion; Dihematoporphyrin; Dihematoporphyrin Ether - therapeutic use; Evaluation Studies as Topic; Fiber Optic Technology - instrumentation; Fiberoptic; Guinea Pigs; Hematoporphyrin; Laser; Laser Therapy; Photochemotherapy - instrumentation; Photodynamic; Photosensitizing Agents - therapeutic use; Skin - drug effects; Skin - radiation effects; Treatment
• ISSN: 0923-1811; 1873-569X
• DOI: 10.1016/0923-1811(94)00377-Q

Photodynamic therapy (PDT) exploits the selective uptake of a photosensitizer in tumors and other hyperproliferative target tissues, as well as the ability to direct the treatment light beam to a specific region. Since the photodynamic effect depends upon light dose, tissue optical properties and photosensitizer concentration, uniform delivery of light is crucial to attain optimal photodynamic effect. Many commonly used methods for delivering laser light during photodynamic therapy, such as a free fiber or microlens, require fiber and laser adjustments to obtain a highly uniform beam. In this study we test the ability of a diffusing sphere to improve the uniformity of a light field coming from an argon laser coupled to a free fiber, in which no attempt has been made to optimize beam characteristics. Light fields from the free fiber, a microlens and the diffusing sphere are compared for uniformity via light intensity readings. An in vivo comparison between the sphere and the free fiber is also made in guinea pigs given Photofrin-II. The diffusing sphere decreases problems with shielding, allows quick and easy application of light by simply applying the device over the desired treatment area, and optimizes the desired photodynamic effect by producing a highly uniform beam of light with no necessity to optimize light delivery by vibrating, looping or re-cleaving fibers.