Monte Carlo simulations for optimal light delivery in photodynamic therapy of non-melanoma skin cancer

摘要

The choice of light source is important for the efficacy of photodynamic therapy (PDT) of non-melanoma skin cancer. We simulated the photodynamic dose (PDD) delivered to a tumour during PDT using theoretical radiation transfer simulations performed via our 3D Monte Carlo radiation transfer (MCRT) model for a range of light sources with light doses up to 75 J cm 2. The PDD delivered following superficial irradiation from (A) non-laser light sources, (B) monochromatic light, (C) alternate beam diameters and (D) re-positioning of the tumour within the tissue was computed. (A) The final PDD deposited to the tumour at a depth of 2mm by the Paterson light source was 2.75, 2.50 and 1.04× greater than the Waldmann 1200, Photocure and Aktilite, respectively. (B) Tumour necrosis occurred at a depth of 2.23mm and increased to 3.81mm for wavelengths 405 and 630nm, respectively. (C) Increasing the beam diameter from 10 to 50mm had very little effect on depth of necrosis. (D) As expected, necrosis depths were reduced when the tumour was re-positioned deeper into the tissue. These MCRT simulations show clearly the importance of choosing the correct light source to ensure optimal light delivery to achieve tumour necrosis.