title: Study of blood charring precursor states using backscattering at 663 nm from blood and optical window boundary.
abstract: OBJECTIVE
  Contact laser irradiation is generally used in therapeutic laser procedures such as plastic surgery and laser catheter lead removal. However, it may induce blood charring on the surface of the optical window in blood circumstance so that the laser beam might be blocked. Various charring detection methods have been proposed, but they detect charring only after charring has occurred. This study investigates the transient behavior of red blood cells (RBCs) prior to the charring on the surface of an optical window during red laser irradiation in blood circumstance.
  
  
  METHODS
  The backscattering light power was continuously measured to investigate the transient behavior of a 1-mm-thick porcine blood model (hematocrit: 40%) during continuous laser irradiation (center wavelength: 663 nm; irradiance: 81 W/cm(2)). A rabbit blood model was microscopically observed after irradiation. The absorption coefficient (µ(a)) and the reduced scattering coefficient (μ'(s)) were measured using a double integrating sphere setup and the inverse adding-doubling method. The backscattering light power was continuously measured in vivo during contact laser irradiation via a laser catheter in a porcine heart cavity.
  
  
  RESULTS
  The results reveal that it may be possible to detect a precursory state of charring from a time course of the backscattering light power. µ(a) increased monotonically by 15% until charring occurred. μ'(s) decreased by 10% followed a broad peak until charring occurred. These changes in the optical property correspond to changes in the morphology of RBCs. Changes in the backscattering light power measured in vivo were similar to those measured ex vivo.
  
  
  CONCLUSIONS
  The transient optical changes in blood prior to charring may be caused by changes in the morphology of RBCs on the optical window surface. Backscattering light power measurements may be a practical method to detect the precursor state of charring.
authors: School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kohoku-ku, Yokohama 223-8522, Japan. mei.60613195@a3.keio.jp
authors: Mei
authors: M
authors: Takahashi
authors: Arisa
authors: A
authors: Ito
authors: Shunichiro
authors: S
authors: Miyoshi
authors: Takehiro
authors: T
authors: Kimura
authors: Seiji
authors: S
authors: Takatsuki
authors: Kotaro
authors: K
authors: Fukumoto
authors: Keiichi
authors: K
authors: Fukuda
authors: Tsunenori
authors: T
authors: Arai
mesh_terms: D000818:Animals; D004912:Erythrocytes / Q000528:radiation effects*; D066298:In Vitro Techniques; D007834:Lasers; D055620:Optical Phenomena; D011817:Rabbits; D012542:Scattering, Radiation; D034421:Sus scrofa