Takahashi Mei, Ito Arisa, Miyoshi Shunichiro, Kimura Takehiro, Takatsuki Seiji, Fukumoto Kotaro, Fukuda Keiichi, Arai Tsunenori
School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Kohoku-ku, Yokohama 223-8522, Japan.
Lasers Surg Med. 2012 Aug;44(6):508-13. doi: 10.1002/lsm.22049. Epub 2012 Jul 5.
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.
接触式激光照射通常用于整形手术和激光导管导线移除等治疗性激光手术。然而，在血液环境中，它可能会在光学窗口表面诱导血液炭化，从而导致激光束被阻挡。已经提出了各种炭化检测方法，但它们都是在炭化发生后才检测到炭化。本研究调查了在血液环境中红色激光照射期间，光学窗口表面炭化之前红细胞（RBC）的瞬态行为。
连续测量背向散射光功率，以研究1毫米厚的猪血液模型（血细胞比容：40%）在连续激光照射（中心波长：663纳米；辐照度：81瓦/平方厘米）期间的瞬态行为。照射后对兔血液模型进行显微镜观察。使用双积分球装置和反向倍增法测量吸收系数（µ(a)）和约化散射系数（μ'(s)）。在猪心脏腔体内通过激光导管进行接触式激光照射期间，在体内连续测量背向散射光功率。
结果表明，从背向散射光功率随时间的变化过程中，有可能检测到炭化的前驱状态。在炭化发生之前，µ(a)单调增加了15%。μ'(s)在出现一个宽峰后下降了10%，直到炭化发生。这些光学性质的变化与红细胞形态的变化相对应。体内测量的背向散射光功率变化与体外测量的相似。
炭化之前血液中的瞬态光学变化可能是由光学窗口表面红细胞形态的变化引起的。背向散射光功率测量可能是检测炭化前驱状态的一种实用方法。
