title: Energy deposition profile in human skin upon irradiation with a 1,342 nm Nd:YAP laser.
abstract: OBJECTIVE
  Nd:YAP laser emitting at 1,342 nm appears promising for nonablative skin rejuvenation treatment, based on favorable absorption properties of water and melanin in this part of the spectrum. A quantitative determination of energy deposition characteristics of Nd:YAP in normal human skin should enable design of a safe and effective treatment protocol for future human studies.
  
  
  METHODS
  Energy deposition profile of a prototype Nd:YAP laser was determined using pulsed photothermal radiometry. This technique involves time-resolved measurement of mid-infrared emission from a sample after pulsed laser irradiation. The laser-induced temperature depth profile is reconstructed from the radiometric transients using a custom optimization algorithm, developed and tested earlier in our group. Measurements were performed on the extremities of four healthy volunteers at low radiant exposure (2.8 J/cm(2) ). For the purpose of comparison, energy deposition characteristics of commercial Nd:YAG and KTP lasers (at 1,064 and 532 nm, respectively), were also determined at the same test sites.
  
  
  RESULTS
  On average, the Nd:YAP laser deposits 50% of the absorbed energy within the top 0.36 mm of skin and 90% within 0.86 mm, which is significantly shallower than the Nd:YAG laser. The ratio between the dermal versus epidermal heating is more favorable and shows a smaller inter- and intra-patient variance as compared to both Nd:YAG and KTP laser.
  
  
  CONCLUSIONS
  Energy deposition characteristics of the 1,342 nm Nd:YAP laser are very suitable for controlled heating of the upper dermis, as required for nonablative skin rejuvenation. The risks of overheating the epidermis or subcutis should be significantly reduced in comparison with the 1,064 nm Nd:YAG laser.
authors.affiliation: Jožef Stefan Institute, Jamova 39, SI 1000 Ljubljana, Slovenia. matija.milanic@ijs.si
authors.forename: Matija
authors.initials: M
authors.lastname: Milanič
authors.forename: Boris
authors.initials: B
authors.lastname: Majaron
mesh_terms: D000328:Adult; D017610:Calcium Compounds; D005542:Forearm; D006801:Humans; D053685:Laser Therapy / Q000295:instrumentation*; D053844:Lasers, Solid-State; D008297:Male; D010087:Oxides; D012782:Shoulder; D012867:Skin / Q000528:radiation effects*; D012869:Skin Absorption / Q000528:radiation effects; D012881:Skin Temperature / Q000528:radiation effects; D014025:Titanium; D055815:Young Adult
chemical_list: D017610:Calcium Compounds; D010087:Oxides; C059910:perovskite; D014025:Titanium