title: ED50 study of femtosecond terawatt laser pulses on porcine skin.
abstract: OBJECTIVE
  Terawatt (TW) lasers have become commonplace since the development of the chirped-pulse amplification method using Ti:sapphire and Nd:glass laser rods. We have measured the minimum visible lesion (MVL) thresholds for porcine1The animals involved in this study were procured, maintained, and used in accordance with the Federal Animal Welfare Act and the "Guide for the Care and Use of Laboratory Animals" prepared by the Institute of Laboratory Animal Resources-National Research Council. Brooks City-Base, TX has been fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care, International (AAALAC) since 1967. (Yucatan mini-pig) skin using TW laser pulses.
  
  
  METHODS
  Our system produced laser pulses at 810 nm and sub-50 femtoseconds. These 1-2 TW laser pulses created multiple self-focusing (SF) filaments during propagation and were directed on the flanks of mini-pigs under anesthesia. We measured the pulse energies necessary to determine the ED(50) skin damage thresholds.
  
  
  RESULTS
  The MVL ED(50) threshold at 1 hour was 8 mJ and increased to 21 mJ after 24 hours. Histological sections were obtained after 1-hour and 24-hour readings.
  
  
  CONCLUSIONS
  The damage patterns on the skin indicated the number of filaments in the laser pulse. Many of the pulses produced only superficial damage that disappeared in 24 hours and that nearly three times the pulse energy was required to cause subdural or cellular damage. With further research, non-thermal tissue ablation using TW laser pulses could provide a viable alternative to current techniques of laser use in dermatology.
authors.affiliation: U.S. Air Force Research Laboratory, USAFRL/HEDO, 2624 Louis Bauer Drive, Brooks City-Base, TX 78235, USA. semih.kumru@brooks.af.mil
authors.forename: Semih S
authors.initials: SS
authors.lastname: Kumru
authors.forename: Clarence P
authors.initials: CP
authors.lastname: Cain
authors.forename: Gary D
authors.initials: GD
authors.lastname: Noojin
authors.forename: Mary F
authors.initials: MF
authors.lastname: Cooper
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Imholte
authors.forename: David J
authors.initials: DJ
authors.lastname: Stolarski
authors.forename: Duane D
authors.initials: DD
authors.lastname: Cox
authors.forename: Carrie C
authors.initials: CC
authors.lastname: Crane
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Rockwell
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D028022:Low-Level Light Therapy / Q000379:methods*; D023421:Models, Animal; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D013552:Swine; D013556:Swine, Miniature