title: Bioimpedance for pain monitoring during cutaneous photodynamic therapy: Preliminary study.
abstract: BACKGROUND
  Pain is a well-known problem associated with light exposure during topical photodynamic therapy (PDT). Different methods for dealing with the pain have been developed over the past years, ranging from cooling with air or water to nerve blocking. However, the mechanisms responsible for the pain induction have not yet been fully understood.
  
  
  OBJECTIVE
  This study aims to evaluate bioimpedance in situ measurements of human skin as a method to shed light on pain-inducing real-time changes during light exposure during topical PDT.
  
  
  METHODS
  Cream containing 20% aminolevulinic acid (ALA) was applied on forearms of ten healthy human volunteers. After 24h incubation, the cream was removed and the spots were exposed to red laser light (636nm, 300mW/cm(2)). During light exposure bioimpedance measurements with a 4-electrode set-up were taken at two frequencies (10Hz and 100kHz).
  
  
  RESULTS
  A significant drop in skin impedance at high and low frequencies coincided with onset of pain during light exposure of spots treated with ALA. A similar drop was not observed for controls.
  
  
  CONCLUSIONS
  Bioimpedance spectroscopy can provide valuable data for real-time observation of changes in skin, and may contribute to an increased understanding of the mechanisms responsible for induction of pain during topical PDT. Future studies are needed.
authors: Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway. patrycja.mikolajewska@rr-research.no
authors: Patrycja
authors: P
authors: Mikolajewska
authors: Ola Taarud
authors: OT
authors: Rømoen
authors: Orjan G
authors: OG
authors: Martinsen
authors: Vladimir
authors: V
authors: Iani
authors: Johan
authors: J
authors: Moan
authors: Sverre
authors: S
authors: Grimnes
authors: Asta
authors: A
authors: Juzeniene
mesh_terms: D000328:Adult; D001676:Biofeedback, Psychology / Q000379:methods; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D010146:Pain / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology* / Q000517:prevention & control; D010147:Pain Measurement / Q000379:methods*; D010778:Photochemotherapy / Q000009:adverse effects* / Q000379:methods; D010865:Pilot Projects; D010992:Plethysmography, Impedance / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012867:Skin / Q000503:physiopathology* / Q000528:radiation effects*