Modelling topical photodynamic therapy treatment including the continuous production of Protoporphyrin IX

C. L. Campbell, C. T A Brown, K. Wood, H. Moseley

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9 Citations (Scopus)
239 Downloads (Pure)


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.

Original languageEnglish
Pages (from-to)7507-7521
Number of pages15
JournalPhysics in Medicine and Biology
Issue number21
Publication statusPublished - 7 Oct 2016


  • Monte Carlo modeling
  • photodynamic therapy
  • Protoporhyrin IX
  • tissue optics

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging


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