title: Plasma bubble formation induced by holmium laser: an in vitro study.
abstract: OBJECTIVE
  To use the elementary physical measurements of temperature and size to prove that the thermal effects produced by the holmium laser's pulses are due to the formation of a plasma bubble. The physical phenomenon related to high temperatures generated during procedures with the holmium laser (holmium:yttrium-aluminum-garnet) was the object of our interest.
  
  
  METHODS
  Using a double micrometric slide attached to a 550-microm optic fiber and two thermocouples submerged in water, a series of pulses of 0.8 J at 10 to 30 Hz was delivered from a holmium:yttrium-aluminum-garnet laser, and we recorded temperatures on both frontal and lateral planes. Subsequently, samples of prostatic tissue and small stones were treated with 1.5 J at 20 Hz on both frontal and lateral planes.
  
  
  RESULTS
  Treatment with 1.5 J at 30 Hz (frontal plane) and with 1.5 J at 20 Hz (lateral plane) produced the ablation of the structure of the thermocouple at 2 mm and 1 mm, respectively, indicating plasma formation. The dimensions of the bubble after the delivery of 1.5 J at 20 Hz was 2 x 1.5 mm. Coagulation of the prostatic tissue took place at 1 mm from the plasma bubble, on both frontal and lateral planes.
  
  
  CONCLUSIONS
  The plasma bubble that forms at the tip of the fiber connected to the holmium:yttrium-aluminum-garnet laser makes it possible to work on stones and soft tissues. The coagulation of the prostatic tissue is caused by the hot water-vapor bubble that forms on the edge of the plasma bubble. During lithotripsy, guidewires and baskets within the expansion area of the plasma bubble risk damage.
authors.affiliation: INFM, Department of Chemistry-Physics, Ca' Foscari University, Venice, Italy.
authors.forename: W
authors.initials: W
authors.lastname: Cecchetti
authors.forename: F
authors.initials: F
authors.lastname: Zattoni
authors.forename: F
authors.initials: F
authors.lastname: Nigro
authors.forename: A
authors.initials: A
authors.lastname: Tasca
mesh_terms: D000535:Aluminum; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology; D005740:Gases; D006695:Holmium; D006801:Humans; D066298:In Vitro Techniques; D017075:Laser Coagulation / Q000295:instrumentation*; D007834:Lasers; D017602:Lithotripsy, Laser / Q000295:instrumentation*; D008297:Male; D017319:Photosensitizing Agents / Q000737:chemistry; D011467:Prostate; D017640:Silicates; D013696:Temperature; D014545:Urinary Calculi; D014867:Water; D015019:Yttrium
chemical_list: D005740:Gases; D017319:Photosensitizing Agents; D017640:Silicates; D014867:Water; D015019:Yttrium; D000535:Aluminum; D006695:Holmium