title: Photocoagulation of dermal blood vessels with multiple laser pulses in an in vivo microvascular model.
abstract: OBJECTIVE
  Current laser therapy of port wine stain (PWS) birthmarks with a single laser pulse (SLP) does not produce complete lesion removal in the majority of patients. To improve PWS therapeutic efficacy, we evaluated the performance of an approach based on multiple laser pulses (MLP) to enhance blood vessel photocoagulation.
  
  
  METHODS
  The hamster dorsal window chamber model was used. Radiant exposure (RE), pulse repetition rate (f(r)), total number of pulses (n(p)), and length of vessel irradiated were varied. Blood vessels in the window were irradiated with either SLP with RE of 4-7 J/cm(2) or MLP with RE per pulse of 1.4-5.0 J/cm(2), f(r) of 0.5-26.0 Hz, and n(p) of 2-5. The laser wavelength was 532 nm and pulse duration was 1 ms. Either a 2 mm vessel segment or entire vessel branch was irradiated. Digital photographs and laser speckle images of the window were recorded before and at specific time points after laser irradiation to monitor laser-induced blood vessel structural and functional changes, respectively.
  
  
  RESULTS
  We found that: (1) for a SLP approach, the RE required to induce blood vessel photocoagulation was 7 J/cm(2) as compared to only 2 J/cm(2) per pulse for the MLP approach; (2) for MLP, two pulses at a repetition rate of 5 Hz and a RE of 3 J/cm(2) can induce photocoagulation of more than 80% of irradiated blood vessel; and (3) irradiation of a longer segment of blood vessel resulted in lower reperfusion rate.
  
  
  CONCLUSIONS
  The MLP approach can induce blood vessel photocoagulation at much lower RE per pulse as compared to SLP. The 5 Hz f(r) and the need for two pulses are achievable with modern laser technology, which makes the MLP approach practical in the clinical management of PWS birthmarks.
authors.affiliation: Beckman Laser Institute and Medical Clinic, Department of Surgery, University of California, Irvine, California 92617-3010, USA. wjia@uci.edu
authors.forename: Wangcun
authors.initials: W
authors.lastname: Jia
authors.forename: Nadia
authors.initials: N
authors.lastname: Tran
authors.forename: Victor
authors.initials: V
authors.lastname: Sun
authors.forename: Marko
authors.initials: M
authors.lastname: Marinček
authors.forename: Boris
authors.initials: B
authors.lastname: Majaron
authors.forename: Bernard
authors.initials: B
authors.lastname: Choi
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Nelson
mesh_terms: D000818:Animals; D001777:Blood Coagulation / Q000528:radiation effects; D006224:Cricetinae; D017075:Laser Coagulation / Q000379:methods*; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008297:Male; D055806:Microvessels / Q000528:radiation effects; D019339:Port-Wine Stain / Q000601:surgery*; D012867:Skin / Q000098:blood supply / Q000528:radiation effects; D016896:Treatment Outcome