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Introduction: Photodynamic therapy (PDT) is a promising adjunctive treatment for high grade brain tumors. However, early clinical trials have utilized significant variations in the conditions of light delivery, including the type of fibre and diffusing fluid. Our goal of this study was to sweep these conditions to determine optimal parameters for light delivery to the tumor resection cavity using a 3D model. Method: A 3D model to mimic an intracranial cavity was created and a PDT device was assembled using multiple 2W output lasers connected to cylindrical diffusing fibres. A variety of light delivery conditions were tested, including the use of bare fibres versus fibres placed inside balloon catheters, with deionized water or intralipid solutions. India ink was utilized to mimic blood products in the resection cavity. Light intensity at the edge of the model, signifying incident intensity at the tissue surface, was measured in multiple axes to assess for strength and uniformity. Light intensity and uniformity were compared between groups using Kruskal-Wallis analysis of variance. Results: Light delivery was significantly higher with the bare fibre compared to the balloon catheter across all types of circulating fluid (34.2 ± 3.54 vs. 30.8 ± 1.31 mV/cm2, p<0.05), but less uniform. The light uniformity increased as the concentration of intralipid increased. In conditions with the addition of india ink, the bare fibre performed better than the balloon catheter. Conclusion: In this phantom model assessment, bare fibres with 0.1% or 0.5% intralipid solution led to improved light delivery compared to other parameters. Photodynamic therapy of the cavity following surgical resection of HGG should be performed with optimal light delivery parameters to ensure treatment efficacy.
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