Xu Tao, Li Yingxing, Wu Xing
School of Precision Instruments and Opto-Engineering, Tianjin University, 235# Tianjin, 300072, China.
Lasers Med Sci. 2004;19(3):150-4. doi: 10.1007/s10103-004-0310-1. Epub 2004 Oct 26.
During the process of photodynamic therapy (PDT), problems arise such as stasis or occlusion of microvasculature, tumor oxygen depletion, and photosensitizer bleaching. This study shows that the first problem could be reduced by using a lower fluence rate light source in PDT. Microvasculature damage was studied experimentally in hematoporphyrin derivative-mediated PDT against light fluence rate, and, to some extent, less microvasculature damage was induced under 75 mW/cm(2) illumination than under 150 mW/cm(2). Histology of vessels at the end of PDT showed that vessel damage could be observed in both groups, indicating that the microvasculature would eventually be damaged as long as the administration of light fluence was sufficient and regardless of the illuminating fluence rates. Thus microvasculature damage induced by low fluence rate illumination could also be effective in tumor control after PDT. The cell-killing experiment was performed in vitro and designed so that cell-killing rate was influenced only by light characteristics. The higher cell-killing rate caused by 75 mW/cm(2) illumination indicated that lower fluence rate light could enhance the light absorbency or decrease the bleaching of photosensitizer.
在光动力疗法（PDT）过程中，会出现诸如微血管停滞或阻塞、肿瘤缺氧以及光敏剂漂白等问题。本研究表明，在PDT中使用较低光通量率的光源可减少第一个问题。针对光通量率，在血卟啉衍生物介导的PDT中对微血管损伤进行了实验研究，在某种程度上，75 mW/cm²光照下诱导的微血管损伤比150 mW/cm²光照下的要少。PDT结束时血管的组织学检查表明，两组均能观察到血管损伤，这表明只要给予足够的光通量，微血管最终都会受到损伤，而与光照通量率无关。因此，低通量率光照诱导的微血管损伤在PDT后控制肿瘤方面也可能有效。体外进行了细胞杀伤实验，其设计使得细胞杀伤率仅受光特性影响。75 mW/cm²光照导致的较高细胞杀伤率表明，较低通量率的光可增强光吸收或减少光敏剂的漂白。
