Mei Takahashi

Publications (2)2.75 Total impact

• Article: Study of blood charring precursor states using backscattering at 663 nm from blood and optical window boundary.

  Mei Takahashi, Arisa Ito, Shunichiro Miyoshi, Takehiro Kimura, Seiji Takatsuki, Kotaro Fukumoto, Keiichi Fukuda, Tsunenori Arai
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  ABSTRACT: 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. 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. 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. 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.
  Lasers in Surgery and Medicine 07/2012; 44(6):508-13. · 2.75 Impact Factor
• Article: Basic study of charring detection at the laser catheter-tip using back scattering light measurement during therapeutic laser irradiation in blood.

  Mei Takahashi, Arisa Ito, Takuro Kajihara, Hiroki Matsuo, Tsunenori Arai
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  ABSTRACT: The purpose of this study is to investigate transient process of the charring at the laser catheter-tip in blood during therapeutic laser irradiation by the back scattering light measurement to detect precursor state of the charring. We took account of using photodynamic therapy for arrhythmia in blood through the laser catheter. We observed the influence of the red laser irradiation (λ=663 nm) upon the shape of red blood cells (RBCs). The RBCs aggregation, round formation, and hemolysis were took place sequentially before charring. With a model blood sandwiched between glass plates simulated as a catheter-tip boundary, we measured diffuse-reflected-light power and transmitted-light power simultaneously and continuously by a microscopic optics during the laser irradiation. We found that measured light power changes were originated with RBCs shape change induced by temperature rise due to the laser irradiation. A gentle peak following a slow descending was observed in the diffuse-reflected-light power history. This history might indicate the precursor state of the charring, in which the hemolysis might be considered to advance rapidly. We think that the measurement of diffuse-reflected-light power history might be able to detect precursor state of charring at the catheter-tip in blood.
  Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:2759-61.