title: Comparison of laser-induced damage with forward-firing and diffusing optical fiber during laser-assisted lipoplasty.
abstract: OBJECTIVE
  Laser-assisted lipoplasty is made possible by using an optical fiber that delivers light endoscopically to subcutaneous fat tissue. Most optical fibers for laser-assisted lipoplasty are designed to be irradiated in a forward direction. In this study, we compared forward-firing fiber and diffusing fiber for use in laser-assisted lipoplasty. The effective parameters of the ablation pattern which resulted from the laser-induced damage are discussed for both systems. In particular, we note the effect resulting from the different beam emission patterns and the contours of laser fluence.
  
  
  METHODS
  We used two different laser delivery systems (a forward-firing fiber and a diffusing fiber) to examine how the beam emission pattern affects the laser-assisted coagulation and damage pattern of in vitro fat tissues. A porcine liver tissue (water-rich tissue) was used as a secondary laser target to investigate how the laser-assisted coagulation pattern depends on both the type of tissue (water-rich and lipid-rich tissue) as well as the delivery system. An evaluation using a digital camera and a thermal camera was conducted for the tissue ablation processes in order to observe the generated heat transfer in fat and liver.
  
  
  RESULTS
  The overall shape of the laser-assisted coagulation zone was different from the beam emission pattern in the case where a forward-firing fiber was used within fat tissue. The center of the laser-affected zone is characterized by the formation of a reservoir of melted fat. In the thermal image analysis, there existed a discrepancy between the temperature distribution of the fat tissue and the liver tissue during the forward-firing fiber irradiation. In the liver tissue ablation process, the temperature distribution during the laser ablation also demonstrated an elongated ellipse that matches well with the laser-induced damage zone. The temperature distribution in fat tissue adhered to a more discoid pattern that corresponded to the laser-induced damage zone.
  
  
  CONCLUSIONS
  Based on our findings, we have proposed mechanisms that can explain the laser-induced damage in both tissues when a forward firing fiber is employed as the delivery system. In the case of fat tissue, the ablation mechanism can be characterized by the reservoir formation of melted lipids while the ablation is characterized as the well-known drilling effect for liver tissue.
authors.affiliation: School of Mechanical Engineering, Kyungpook National University, Daegu, 702-701, Korea.
authors.forename: Changhwan
authors.initials: C
authors.lastname: Kim
authors.forename: Hoyong
authors.initials: H
authors.lastname: Park
authors.forename: Ho
authors.initials: H
authors.lastname: Lee
mesh_terms: D000818:Animals; D004724:Endoscopy; D066298:In Vitro Techniques; D007259:Infrared Rays; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D015187:Lipectomy / Q000295:instrumentation* / Q000379:methods; D008099:Liver / Q000473:pathology / Q000601:surgery; D055100:Optical Fibers; D050151:Subcutaneous Fat / Q000473:pathology / Q000601:surgery*; D013552:Swine
keywords: endoscopy surgery; fiber optics; laser-induced damage; lipoplasty