title: Oxygen saturation and perfusion changes during dermatological methylaminolaevulinate photodynamic therapy.
abstract: BACKGROUND
  Methylaminolaevulinate (MAL)-photodynamic therapy (PDT) is a successful topical treatment for a number of (pre)cancerous dermatological conditions. In combination, light of the appropriate wavelength, the photosensitizer protoporphyrin IX (PpIX) and tissue oxygen result in the production of singlet oxygen and reactive oxygen species inducing cell death.
  
  
  OBJECTIVE
  This study investigates real-time changes in localized tissue blood oxygen saturation and perfusion in conjunction with PpIX fluorescence monitoring for the first time during dermatological MAL-PDT.
  
  
  METHODS
  Oxygen saturation, perfusion and PpIX fluorescence were monitored noninvasively utilizing optical reflectance spectroscopy, laser Doppler perfusion imaging and a fluorescence imaging system, respectively. Patients attending for standard dermatological MAL-PDT were recruited to this ethically approved study and monitored prior to, during and after light irradiation.
  
  
  RESULTS
  Significant reductions in mean blood oxygen saturation (P < 0·005) and PpIX fluorescence (P < 0·001) were observed within the first minute of irradiation (4·75 J cm(-2) ) while, in contrast, perfusion was observed to increase significantly (P < 0·01) during treatment. The changes in oxygen saturation and PpIX fluorescence were positively correlated during the initial phase of treatment (r(2) = 0·766).
  
  
  CONCLUSIONS
  Rapid reductions in the localized blood oxygen saturation have been observed for the first time to occur clinically within the initial minutes of light irradiation and positively correlate with the concurrent PpIX photobleaching. Furthermore, perfusion increases, suggesting that the microvasculature compensates for the PDT-induced oxygen depletion.
authors.affiliation: Clinical Photobiology, European Centre for Environment and Human Health, Peninsula Medical School, University of Exeter, Royal Cornwall Hospital, Truro TR1 3HD, UK.
authors.forename: J
authors.initials: J
authors.lastname: Tyrrell
authors.forename: C
authors.initials: C
authors.lastname: Thorn
authors.forename: A
authors.initials: A
authors.lastname: Shore
authors.forename: S
authors.initials: S
authors.lastname: Campbell
authors.forename: A
authors.initials: A
authors.lastname: Curnow
mesh_terms: D000369:Aged, 80 and over; D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation; D010100:Oxygen / Q000097:blood*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012867:Skin / Q000098:blood supply; D012871:Skin Diseases / Q000097:blood / Q000188:drug therapy*; D012881:Skin Temperature / Q000502:physiology
chemical_list: D017319:Photosensitizing Agents; C475457:methyl 5-aminolevulinate; D000622:Aminolevulinic Acid; D010100:Oxygen