Optical integrating balloon device for photodynamic therapy

It is difficult to deliver light uniformly and efficiently over the complex shapes presented by various organs for photodynamic therapy (PDT). A balloon delivery device for photodynamic therapy was designed and tested for treatment of various anatomic tissues. The device uses the principle of optical integration by multiple internal diffuse reflections to achieve uniform output illumination.

Soft, white, medical-grade silicone balloons were made in various shapes and tested for optical output, uniformity, efficiency, and power capabilities. Balloons were cast to be approximately the shape of the target tissue surface, organ, or cavity. Laser power was introduced into the saline-filled balloon by one or more fiber optics. Devices were constructed and used to illuminate oral mucosa and uterine endometrium for PDT.

The balloon walls had low optical absorption, high diffuse reflectivity (80-95%), and low diffuse transmittance (5-20%) in the 500- to 900-nm wavelength region. Optical efficiencies of 65% were typical with emitted light over complex, nonspherical surfaces. Efficiency increased with inflation of the device, such that irradiance (power/area) at the balloon surface was nearly constant with inflation.

Optically integrating balloons can provide highly uniform, efficient light exposure over complex tissue surfaces. Uniformity and irradiance were not strongly affected by balloon inflation, and these robust devices are easy to produce in essentially any shape.