title: Photothermolysis of sebaceous glands in human skin ex vivo with a 1,708 nm Raman fiber laser and contact cooling.
abstract: OBJECTIVE
  Wavelengths near ∼1,720 nm are of interest for targeting fat/lipid-rich tissues due to the high absorption coefficient of human fat and low water scattering and absorption. In this study, a 1,708 nm laser was built and shown to selectively target fat/lipid adjacent to porcine heart and dermis and then used to damage dermal sebaceous glands in human skin. STUDY DESIGN AND MATERIALS: An all-fiber 1,708 nm laser with ∼4 W maximum power was designed and built. Selectivity for targeting fat/lipid was studied by exposing porcine heart and skin tissue cross-sections to the 1,708 nm laser. Human skin treatments to damage sebaceous glands were performed both with and without cold window cooling. Histochemical evaluation on the frozen sections was performed using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay.
  
  
  RESULTS
  Histochemical analysis of porcine tissue cross-sections showed that 1,708 nm laser can selectively damage pericardial fat(heart) and subcutaneous fat(skin) with little to no damage to the myocardium and the dermis, respectively. In human skin, histochemical evaluation without contact cooling showed damage to both epidermis and dermis. With cooling, epidermis was spared and damage was observed in dermis extending ∼0.4-1.65 mm from the skin surface at an average laser fluence of ∼80 J/cm(2). Selective damage of sebaceous glands was suggested but not definitively demonstrated.
  
  
  CONCLUSIONS
  We have developed an all-fiber 1,708 nm laser capable of damaging majority of the sebaceous glands in the dermis and thus may have potential applications in the treatment of conditions such as acne vulgaris whose pathophysiology involves disorders of sebaceous glands.
authors.affiliation: Electrical and Computer Engineering Department, University of Michigan, Ann Arbor, Michigan 48109, USA. vinalex@umich.edu
authors.forename: Vinay V
authors.initials: VV
authors.lastname: Alexander
authors.forename: Kevin
authors.initials: K
authors.lastname: Ke
authors.forename: Zhao
authors.initials: Z
authors.lastname: Xu
authors.forename: Mohammed N
authors.initials: MN
authors.lastname: Islam
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Freeman
authors.forename: Bertram
authors.initials: B
authors.lastname: Pitt
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Welsh
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Orringer
mesh_terms: D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D007834:Lasers; D012627:Sebaceous Glands / Q000473:pathology / Q000528:radiation effects*; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D013059:Spectrum Analysis, Raman; D013552:Swine; D013696:Temperature