The objective of this study was to model the optical profile of a proprietary light source in various simulated biological tissues using Monte Carlo based raytracing software. The proprietary light source, built by Light Sciences Corporation, has an LED array at its distal end and is being evaluated for use as an intratumoral PDT treatment device. The light source was scanned in a goniometer to characterize its optical geometry in air and this data provided the basis for an optical model of the device. The bulk scattering effect of the model in biological tissue was then simulated using the raytracing software. The simulated results were further verified with experimental measurements in phantom medium. The simulated results indicated a non-uniform light distribution along the LED array axis in air. In addition, the light distribution at cross section normal to the LED array axis is "butterfly" in shape with the differences of the peak to average approximately ±42%. However, the optical profile of the light source in a bulk scattering tissue became much more uniform than those in air, with a peak to average spread in cross section of ±15%.
Light Sciences Corporation has developed a novel LED array that was designed and manufactured to treat large bulky tumors. We describe our LED design process, culminating in the manufacture of a flexible silicone catheter currently under investigation in a Phase 1 clinical trial. The performance characteristics of the wire-bonded die to a flexible polyimide substrate forming a linear array are discussed. The LED array consists of 100 die arranged asymmetrically on the substrate with 50 LED's on either side producing up to 60mW total optical power at 38°C (500mA) over a spectral bandwidth 645-670nm FWHM. The LED's are encapsulated within biocompatible silicon for interstitial placement within the treatment tissue. The effect of time, temperature and humidity on the device performance was investigated. Optical power ranged from −2.5% to +0.5% of the normalized original power over 50 hours in 100% RH within the control group. Over a temperature range of 35°C to 50°C the optical power decreased at a rate of 0.56% per °C. Preliminary non-clinical experiments carried out in normal swine muscle demonstrate a significant treatment zone and are consistent with threshold models for photodynamic effect.