Mordon Serge, Maunoury Vincent
INSERM IFR 114 bDepartment of Gastroenterology, Lille University Hospital, Lille, France.
Eur J Gastroenterol Hepatol. 2006 Jul;18(7):765-71. doi: 10.1097/01.meg.0000223910.08611.79.
Photodynamic therapy (PDT) involves selective uptake and retention of a photosensitizer in a tumor, followed by irradiation with light (usually a 630 nm diode laser), initiating tumor necrosis through formation of oxidized products or singlet oxygen. Successful PDT of early cancers of the esophagus and of Barrett's esophagus with severe dysplasia has been reported. However, side effects (edema, stricture, etc.) and treatment failure have been observed. This study aims to evaluate the possible photodynamic effect induced by illumination from the endoscope on the PDT effect, since a photon emitted to see the lesion can potentially be a photon to treat it!
Two fiber endoscopes (Olympus GIFPQ20 and Pentax FG34X) and one videoendoscope (Olympus GIFQ140) were evaluated. Output power, irradiance and emission spectrum were measured. Using the molar extinction coefficient of Photofrin and optical coefficients of the esophagus, the relative photodynamic reaction yield, determined as a function of depth, was compared with that obtained with a 630 nm diode laser.
The irradiance at 1 and 2 cm was, respectively, 18.4 and 4.6 mW/cm (Pentax FG34X), 10.6 and 2.65 mW/cm (Olympus GIFPQ20), and 2.7 and 3.2 mW/cm (Olympus GIFQ140). The highest irradiance could lead to a relative photodynamic reaction yield at the surface of the esophagus similar to (Olympus GIFPQ20) or greater than (Pentax FG34X) that obtained using a diode laser alone.
Our results could explain side effects sometimes observed when performing PDT. 'Endoscopic' illumination, however, could also represent an interesting alternative to the 630 nm diode laser. When using white light, superficial efficacy of PDT could be reinforced and transmural necrosis leading to perforation or stenoses reduced, since there is less red light in depth compared with a diode laser.
光动力疗法（PDT）包括光敏剂在肿瘤中的选择性摄取和潴留，随后用光照（通常为630nm二极管激光）照射，通过形成氧化产物或单线态氧引发肿瘤坏死。已报道光动力疗法成功治疗早期食管癌和重度不典型增生的巴雷特食管。然而，也观察到了副作用（水肿、狭窄等）和治疗失败的情况。本研究旨在评估内镜照明所诱导的可能光动力效应，因为用于观察病变而发射的光子有可能成为用于治疗病变的光子！
对两台纤维内镜（奥林巴斯GIFPQ20和宾得FG34X）和一台视频内镜（奥林巴斯GIFQ140）进行评估。测量输出功率、辐照度和发射光谱。利用卟吩姆钠的摩尔消光系数和食管的光学系数，将作为深度函数测定的相对光动力反应产率与用630nm二极管激光获得的相对光动力反应产率进行比较。
在1cm和2cm处的辐照度分别为：宾得FG34X为18.4和4.6mW/cm²，奥林巴斯GIFPQ20为10.6和2.65mW/cm²，奥林巴斯GIFQ140为2.7和3.2mW/cm²。最高辐照度可导致食管表面的相对光动力反应产率与单独使用二极管激光时相似（奥林巴斯GIFPQ20）或更高（宾得FG34X）。
我们的结果可以解释在进行光动力疗法时有时观察到的副作用。然而，“内镜”照明也可能是630nm二极管激光的一种有趣替代方法。使用白光时，由于与二极管激光相比，深部的红光较少，光动力疗法的浅表疗效可能会增强，导致穿孔或狭窄的透壁坏死减少。
