Modelling topical photodynamic therapy treatment including the continuous production of Protoporphyrin IX
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Most existing theoretical models of photodynamic therapy (PDT) assume a uniform initial distribution of the photosensitive molecule, Protoporphyrin IX (PpIX). This is an adequate assumption when the prodrug is systematically administered; however for topical PDT this is no longer a valid assumption. Topical application and subsequent diffusion of the prodrug results in an inhomogeneous distribution of PpIX, especially after short incubation times, prior to light illumination. In this work a theoretical simulation of PDT where the PpIX distribution depends on the incubation time and the treatment modality is described. Three steps of the PpIX production are considered. The first is the distribution of the topically applied prodrug, the second in the conversion from the prodrug to PpIX and the third is the light distribution which affects the PpIX distribution through photobleaching. The light distribution is modelled using a Monte Carlo radiation transfer model and indicates treatment depths of around 2 mm during daylight PDT and approximately 3 mm during conventional PDT. The results suggest that treatment depths are not only limited by the light penetration but also by the PpIX distribution
Campbell , C L , Brown , C T A , Wood , K & Moseley , H 2016 , ' Modelling topical photodynamic therapy treatment including the continuous production of Protoporphyrin IX ' Physics in Medicine and Biology , vol 61 , no. 21 , pp. 7507-7521 . DOI: 10.1088/0031-9155/61/21/7507
Physics in Medicine and Biology
© 2016, Institute of Physics and Engineering in Medicine. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at iopscience.iop.org / https://dx.doi.org/10.1088/0031-9155/61/21/7507
C L Campbell acknowledges financial support from an UK EPSRC PhD studentship (EP/K503162/1) and the Alfred Stewart Trust.
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