title: Characterization of tissue ablation with a continuous wave holmium laser.
abstract: OBJECTIVE
  The pulsed holmium laser is a promising tool for tissue ablation but possesses some limitations. For example, it is capable of producing significant mechanical damage in certain tissues in the form of fissures and fractures. Because longer pulse durations should reduce mechanical damage, this study examined the tissue effects produced by a prototype continuous wave holmium laser.
  
  
  METHODS
  A prototype liquid nitrogen cooled holmium operating at 2.12 microns was used. The heat of ablation and ablation threshold were determined using a mass loss technique. Fresh pig skin was irradiated in air or under saline, and prepared for histologic analysis. Hemostasis was qualitatively assessed in vivo during incisions made in the skin, liver, and small intestine.
  
  
  RESULTS
  Threshold radiant exposure and heat of ablation were calculated from the mass loss measurements to be 191 J/cm2 with a 95% confidence interval of -80-440 J/cm2. Residual thermal damage in skin ranged from 390 to 690 microns in saline and from 390 to 490 microns in air. Excellent hemostasis was achieved in all incisions.
  
  
  CONCLUSIONS
  Using appropriate irradiation parameters, the continuous wave holmium laser produces tissue effects suitable for a general use surgical instrument. In addition, the laser source could become compact and inexpensive when diode-pumped and direct diode devices become available.
authors.affiliation: Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Domankevitz
authors.forename: K
authors.initials: K
authors.lastname: McMillan
authors.forename: N S
authors.initials: NS
authors.lastname: Nishioka
mesh_terms: D000388:Air; D000818:Animals; D002645:Chickens; D016001:Confidence Intervals; D062109:Dermatologic Surgical Procedures; D004867:Equipment Design; D006488:Hemostasis, Surgical; D006695:Holmium; D006358:Hot Temperature / Q000009:adverse effects; D007101:Immersion; D007421:Intestine, Small / Q000601:surgery; D053685:Laser Therapy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D016014:Linear Models; D008099:Liver / Q000601:surgery; D009584:Nitrogen; D012867:Skin / Q000033:anatomy & histology / Q000293:injuries; D012965:Sodium Chloride; D013552:Swine
chemical_list: D012965:Sodium Chloride; D009584:Nitrogen; D006695:Holmium