title: Aorta and skin tissues welded by near-infrared Cr4+:YAG laser.
abstract: OBJECTIVE
  The aim of our study was to explore the wavelength dependence of welding efficacy. Ex vivo samples of human and porcine aorta and skin tissues were investigated using a tunable Cr(4+):yttrium aluminum garnet (YAG) laser.
  
  
  BACKGROUND
  Tissue welding is possible using laser light in the NIR spectral range. Collagen bonding in the tissue induced by thermal, photothermal, and photochemical reactions-or a combination of all of these-is thought to be responsible for tissue welding. Laser tissue welding (LTW) has gained success in the laboratory using animal models. Transition from laboratory to clinical application requires the optimization of welding parameters.
  
  
  METHODS
  A near-infrared (NIR) Cr(4+):YAG laser was used to weld ex vivo samples of human and porcine aorta and skin at wavelengths from 1430 to 1470 nm. Welding efficacy was monitored by measuring the tensile strength of the welded tissue and the extent of collateral tissue damage. Tensile strengths were measured using a digital force gauge. Changes in tissue morphology were evaluated using optical and scanning electron microscope (SEM). Fluorescence imaging of the welded areas was also used to evaluate molecular changes following tissue welding.
  
  
  RESULTS
  Full-thickness tissue bonding was observed with porcine aorta samples. No collateral damage of the aorta samples was observed. Tissue denaturation was observed with human aorta, human skin, and porcine skin samples. The optimum tensile strength for porcine and human aorta was 1.33 +/- 0.15 and 1.13 +/- 0.27 kg/cm2, respectively, at 1460 nm, while that for porcine and human skin was 0.94 +/- 0.15 and 1.05 +/- 0.19 kg/cm2, respectively, achieved at 1455 nm. The weld strength as a function of wavelength demonstrated a correlation with the absorption spectrum of water. Fluorescence imaging of welded aorta and skin demonstrated no significant changes in collagen and elastin emission at the weld site.
  
  
  CONCLUSIONS
  The observation that welding strength as a function of wavelength follows the absorption bands of water suggests that absorption of light by water plays a significant role in laser tissue welding.
authors.affiliation: The Department of Physics, New York State Center for Advanced Technology for Ultrafast Photonics, The City College of the City University of New York, New York, New York.
authors.forename: Tapan K
authors.initials: TK
authors.lastname: Gayen
authors.forename: A
authors.initials: A
authors.lastname: Katz
authors.forename: Howard E
authors.initials: HE
authors.lastname: Savage
authors.forename: Steven A
authors.initials: SA
authors.lastname: McCormick
authors.forename: M
authors.initials: M
authors.lastname: Al-Rubaiee
authors.forename: Yury
authors.initials: Y
authors.lastname: Budansky
authors.forename: John
authors.initials: J
authors.lastname: Lee
authors.forename: R R
authors.initials: RR
authors.lastname: Alfano
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology / Q000601:surgery*; D062109:Dermatologic Surgical Procedures; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D012879:Skin Physiological Phenomena / Q000528:radiation effects*; D013552:Swine; D013718:Tensile Strength / Q000528:radiation effects*