title: Laser-mediated cartilage reshaping with feedback-controlled cryogen spray cooling: biophysical properties and viability.
abstract: OBJECTIVE
  Recent studies have indicated that chondrocyte viability decreases with prolonged or repeated laser irradiation. To optimize laser-mediated cartilage reshaping, the heating process must be finely controlled. In this study, we use high-power Nd:YAG laser irradiation (lambda = 1.32 microm) combined with cryogen spray cooling (CSC) in an attempt to reshape porcine septal cartilage while enhancing chondrocyte viability.
  
  
  METHODS
  Chondrocyte viability was determined after high-power (50 W/cm2) Nd:YAG-mediated cartilage reshaping with and without cryogen spray cooling (CSC) and correlated with dynamic measurements of tissue optical and thermal properties.
  
  
  RESULTS
  After 1.5 to 2.0 seconds of laser exposure, characteristic changes in diffuse reflectance (indicating the onset of accelerated stress relaxation) was observed in both laser only and laser with CSC specimens. After 2 seconds of laser exposure, specimens in both groups retained the curved shape for up to 14 days. After one laser exposure, chondrocyte viability was 94.35 +/- 6.1% with CSC and 68.77 +/- 20.1% (P < 0.05) without CSC. After two laser exposures, a similar trend was observed with CSC (70.18 +/- 16.44%) opposed to without CSC (28 +/- 45%; P < 0.05).
  
  
  CONCLUSIONS
  CSC during high-power laser irradiation allows rapid heating while minimizing extreme front surface temperature elevations and axial thermal gradients. Laser irradiation with CSC can be used to effectively reshape cartilage tissue with the additional advantage of increasing chondrocyte viability.
authors: Beckman Laser Institute and Medical Clinic, University of California Irvine, 92697, USA.
authors: A M
authors: AM
authors: Karamzadeh
authors: A
authors: A
authors: Rasouli
authors: B S
authors: BS
authors: Tanenbaum
authors: T E
authors: TE
authors: Milner
authors: J S
authors: JS
authors: Nelson
authors: B J
authors: BJ
authors: Wong
mesh_terms: D000335:Aerosol Propellants; D000818:Animals; D002356:Cartilage / Q000637:transplantation; D019902:Chondrocytes / Q000502:physiology; D006845:Hydrocarbons, Fluorinated; D053685:Laser Therapy; D009300:Nasal Septum / Q000601:surgery* / Q000637:transplantation; D019651:Plastic Surgery Procedures / Q000379:methods*; D013552:Swine; D004980:Ethane / Q000031:analogs & derivatives; D005466:Fluorocarbons
chemical_list: D000335:Aerosol Propellants; D006845:Hydrocarbons, Fluorinated; C063006:norflurane; D004980:Ethane; D005466:Fluorocarbons