Douplik Alexandre, Chen Dean, Akens Margarete K, Zanati Simon, Cirocco Maria, Bassett Nancy, Marcon Norman E, Fengler John, Wilson Brian C
Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, ON, Canada.
Lasers Surg Med. 2010 Mar;42(3):224-31. doi: 10.1002/lsm.20892.
In autofluorescence endoscopy, the difference in the fluorescence of intrinsic fluorophores is imaged to help visualize pre-malignant lesions, as in the system evaluated here. In this, blue light is used for excitation and the green autofluorescence is normalized by the red diffuse reflectance and presented using a false color scale. The present study was designed to quantify the degree of fluorescence photobleaching induced by the excitation light during use in the colon, since significant photobleaching could lead to false interpretation of the images, particularly false-positive lesions.
Measurements were made ex vivo and in vivo, both using the endoscopic imaging system and a separate fiberoptic spectroscopy probe in externalized rat jejunum and in patients undergoing routine colonoscopy, using exposures typical of autofluorescence endoscopic examination.
Photobleaching could be potentially caused at blue light exposure. However, at light intensities and exposure times that are typically used in clinical practice, the average photobleaching (% loss of peak fluorescence intensity) was <1% and <6% in the rat and human tissues, respectively. Nevertheless, the range was large: from -17% to +18% in rats and -33% to +43% in patients, where negative values denote an apparent increase in fluorescence. Both the large positive and negative deviations are believed in part to be due to a measurement artifact caused by uncontrollable tissue motility.
It is concluded that, using exposures typically encountered in clinical practice, there is minimal photobleaching during fluorescence endoscopy at exposure such as are used in the Onco-LIFE and comparable systems. The small changes in fluorescence intensity and spectral shift that do occur are not likely to be detectable by eye, and so should not impact significantly on the diagnostic accuracy of the technique.
在自体荧光内镜检查中，对固有荧光团的荧光差异进行成像，以帮助可视化癌前病变，如下文所评估的系统。在此系统中，蓝光用于激发，绿色自体荧光通过红色漫反射进行归一化处理，并使用伪彩色标尺呈现。本研究旨在量化在结肠检查过程中激发光引起的荧光光漂白程度，因为显著的光漂白可能导致图像的错误解读，尤其是假阳性病变。
采用内窥镜成像系统以及外置大鼠空肠中的单独光纤光谱探头，对大鼠进行离体和在体测量，并对接受常规结肠镜检查的患者进行测量，采用自体荧光内镜检查的典型曝光量。
蓝光照射可能会导致光漂白。然而，在临床实践中通常使用的光强度和曝光时间下，大鼠和人体组织中的平均光漂白（峰值荧光强度损失百分比）分别<1%和<6%。尽管如此，范围很大：大鼠中为-17%至+18%，患者中为-33%至+43%，其中负值表示荧光明显增加。较大的正负偏差部分被认为是由于无法控制的组织运动引起的测量假象。
得出的结论是，在临床实践中通常遇到的曝光条件下，如在Onco-LIFE及类似系统中使用的曝光，荧光内镜检查期间的光漂白极小。确实发生的荧光强度和光谱偏移的微小变化不太可能被肉眼检测到，因此不应显著影响该技术的诊断准确性。
