title: A quantitative study of in vivo protoporphyrin IX fluorescence build up during occlusive treatment phases.
abstract: BACKGROUND
  Topical photodynamic therapy (PDT) is a non-invasive light based therapy used to treat non-melanoma skin cancer (NMSC) and dysplasia. During PDT, the light sensitive molecule protoporphyrin IX (PpIX) is activated, resulting in the production of singlet oxygen, which subsequently leads to cell death. PpIX is metabolised from a topically applied pro-drug and the strong fluorescence signal associated with PpIX can be utilised as an indicator of the amount of PpIX present within the tumour tissue. In this work we measure the build up PpIX during the occlusive treatment phase and investigate how the PpIX production rate is affected by different lesion and patient characteristics.
  
  
  METHODS
  Fluorescence measurements were used to investigate the build up of PpIX within the tumour tissue during the 3h long occlusive treatment prior to irradiation. The study included in vivo measurements of 38 lesions from 38 individual patients. Actinic keratosis (AK) and basal cell carcinoma (BCC) were the lesion types included in this study. The resulting data from the study was analysed using generalised linear mixed effects models.
  
  
  RESULTS
  It was found that the surface fluorescence signal linearly increased with occlusive treatment time. The predictive models suggest that there is a significant difference in PpIX production between lesion location, however no significant difference is demonstrated between different lesion types, gender and skin type.
  
  
  CONCLUSIONS
  The study extends and supports previous knowledge of PpIX production during the occlusive treatment phase.
authors.affiliation: SUPA, School of Physics and Astronomy, University of St Andrews, UK.
authors.forename: C Louise
authors.initials: CL
authors.lastname: Campbell
authors.affiliation: SUPA, School of Physics and Astronomy, University of St Andrews, UK.
authors.forename: C Tom A
authors.initials: CTA
authors.lastname: Brown
authors.affiliation: SUPA, School of Physics and Astronomy, University of St Andrews, UK.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wood
authors.affiliation: Skin Department of Amaral Carvalho Hospital, Brazil.
authors.forename: Ana Gabriela
authors.initials: AG
authors.lastname: Salvio
authors.affiliation: São Carlos Institute of Physics, University of São Paulo, Brazil.
authors.forename: Natalia M
authors.initials: NM
authors.lastname: Inada
authors.affiliation: São Carlos Institute of Physics, University of São Paulo, Brazil.
authors.forename: Vanderlei S
authors.initials: VS
authors.lastname: Bagnato
authors.affiliation: Photobiology Unit, Ninewells Hospital and Medical School, UK. Electronic address: h.moseley@dundee.ac.uk.
authors.forename: Harry
authors.initials: H
authors.lastname: Moseley
mesh_terms: D000287:Administration, Topical; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001458:Bandages; D005260:Female; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D011524:Protoporphyrins / Q000008:administration & dosage / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014018:Tissue Distribution; D016896:Treatment Outcome
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; C028025:protoporphyrin IX