title: Measurements of laser light attenuation following cryogen spray cooling spurt termination.
abstract: OBJECTIVE
  Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatological surgery. However, while CSC can protect the epidermis from non-specific thermal damage, the cryogen film on the skin surface may pose a potential problem of laser light attenuation due to optical scattering.
  
  
  METHODS
  This study is focused on measuring the light transmittance changes that occur following cryogen spurt termination. The wavelengths studied were chosen for their clinical relevance to treatment of hypervascular skin lesions (594 nm) and laser-assisted hair removal (785 nm). Following delivery of cryogen spurts to the surface of an epoxy skin phantom, continuous records of light transmittance for 594 and 785 nm were obtained using an integrating sphere-based light collection apparatus.
  
  
  RESULTS
  Shortly after spurt termination, there was negligible light attenuation by the cryogen film at the two wavelengths studied.
  
  
  CONCLUSIONS
  For the typical clinical use of a 30 milliseconds spurt duration and 30 milliseconds delay between spurt termination and delivery of the laser pulse, a minimum average transmittance value of approximately 97% was measured.
authors.affiliation: College of Medicine, University of California, Irvine, California 92697, USA.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Edris
authors.forename: Bernard
authors.initials: B
authors.lastname: Choi
authors.forename: Guillermo
authors.initials: G
authors.lastname: Aguilar
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Nelson
mesh_terms: D017679:Cryotherapy / Q000379:methods*; D004853:Epoxy Resins; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000008:administration & dosage; D008027:Light; D028022:Low-Level Light Therapy / Q000379:methods*; D008954:Models, Biological; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects*; D013057:Spectrum Analysis / Q000379:methods; D004980:Ethane / Q000031:analogs & derivatives; D005466:Fluorocarbons
chemical_list: D004853:Epoxy Resins; D006845:Hydrocarbons, Fluorinated; C063006:norflurane; D004980:Ethane; D005466:Fluorocarbons