In vitro light distributions from intracranial PDT balloons

Background: Optical fibres can be placed in balloons to deliver light for intracranial photodynamic therapies. Method: A series of fibres, with either cleaved ends or terminating in cylindrical diffusers, housed in two different balloons, containing various solutions were investigated. The aim of the experiments performed was to assess which equipment produced the most uniform illumination field. A balloon manufactured by Medlight (ML) was compared to one adapted from a Rush Silkomed (RS) paediatric urinary catheter. Measurements were made at regular angular intervals, within parallel horizontal planes surrounding the balloons. Results: The inter-planar and intra-planar variability of the illumination field was assessed. Experimental combinations with high intra-planar variability included those using a cleaved optical fibre, without a linear diffuser. Experimental combinations with high inter-planar variability included those using cleaved optical fibres, and some of the balloons inflated with solutions not containing optical scattering media. Conclusions: The best experimental combination, from those assessed in this paper, would include a diffuser and either the RS balloon inflated with a liquid containing some Intralipid, or the ML balloon which was required to be filled only with saline. (C) 2007 Elsevier B.V. All rights reserved.