Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors arising in the digest tract. It brings a challenge to diagnosis because it is asymptomatic clinically. It is well known that tumor development is often accompanied by the changes in the morphology of collagen fibers. Nowadays, an emerging optical imaging technique, second-harmonic generation (SHG), can directly identify collagen fibers without staining due to its noncentrosymmetric properties. Therefore, in this study, we attempt to assess the feasibility of SHG imaging for detecting GISTs by monitoring the morphological changes of collagen fibers in tumor microenvironment. We found that collagen alterations occurred obviously in the GISTs by comparing with normal tissues, and furthermore, two morphological features from SHG images were extracted to quantitatively assess the morphological difference of collagen fibers between normal muscular layer and GISTs by means of automated image analysis. Quantitative analyses show a significant difference in the two collagen features. This study demonstrates the potential of SHG imaging as an adjunctive diagnostic tool for label-free identification of GISTs.

The tumor microenvironment (TME) is now recognized as an important participant of tumor progression. As the most abundant extracellular matrix component in TME, collagen plays an important role in tumor development. The imaging study of collagen morphological feature in TME is of great significance for understanding the state of tumor. Multiphoton microscopy (MPM), based on second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF), can be used to monitor the morphological changes of biological tissues without labeling. In this study, we used MPM for large-scale imaging of early invasive breast cancer from the tumor center to normal tissues far from the tumor. We found that there were significant differences in collagen morphology between breast cancer tumor boundary, near tumor transition region and normal tissues far from the tumor. Furthermore, the morphological feature of eight collagen fibers was extracted to quantify the variation trend of collagen in three regions. These results may provide a new perspective for the optimal negative margin width of breast-conserving surgery and the understanding of tumor metastasis.

利用高速摄像技术检测脉冲CO2激光诱导液体气穴通道形成、发展和坍塌的动态过程，考察不同聚焦辐照条件对气穴效应的影响。实验获得了气穴通道脉动过程的序列图像，得到了表征气穴通道特性的参数（如最大穿透深度等）。实验结果表明，不同聚焦条件对气穴通道的动力学过程有显著影响。正离焦及焦点位置条件下，气穴通道在最大纵深时，整体形态类似于漏斗状，而负离焦条件下，则呈U 形。研究结果对激光医疗、激光水下加工、能源等领域的研究具有一定的参考价值。

We evaluate the ablation thresholds of Er:YAG and Er,Cr:YSGG laser for enamel and dentin. A total of 140 dental slices is evenly divided into two groups: the dentin group and the enamel group. Dental tissues are irradiated with either an Er:YAG laser or an Er,Cr:YSGG laser with pulse widths in the order of 100 \mu s. The laser fluence is increased gradually until the ablation crater is formed. The laser ablation threshold is calculated using probit analysis. The ablation thresholds of the Er:YAG laser for dentin and enamel range from 2.88 to 3.36 J/cm2 and from 2.94 to 3.8 J/cm2, respectively, and the ablation thresholds of the Er,Cr:YSGG laser for dentin and enamel range from 2.92 to 4.2 J/cm2 and from 4.93 to 5.66 J/cm2, respectively.

回顾了“激光钻”的发展历程，归纳总结了牙硬组织的光学性质及牙硬组织与激光的相互作用方式和机制，综述了激光在牙釉质、牙本质、牙结石和牙槽骨等硬组织上的应用研究动态和最新进展，并对其存在的问题及发展趋势进行了探讨。分析表明：硬组织激光消融技术在牙科存在广阔的应用前景。

激光辐照生物组织消融过程中由于工作距离的变化引起的离焦现象对消融效果具有重要影响。以新鲜离体牛胫骨组织为实验样品，置于一维电动平移台上，移动速度为5.5 mm/s；脉冲CO2激光（10.64 μm）平行光束经一可移动聚焦透镜后垂直辐照样品表面，光斑直径为200 μm。实验时通过移动聚焦透镜位置改变焦点位置，实现消融过程动态聚焦。激光辐照功率为6 W，脉冲频率为420 Hz，水喷雾协同工作，喷水速度为5.5 mL/min。辐照后，利用扫描电镜观察消融凹槽微结构，用光学相干层析成像（OCT）技术测量消融凹槽深度。结果表明，动态聚焦条件可显著提高消融速率，消融深度随等效脉冲数增加而增加，消融速率呈减小趋势；在动态聚焦条件下获得的消融凹槽的表面形貌和微结构较离焦条件下更不规则。

比较了Er:YAG激光辐射对不同类型牙本质粘结效果的影响。选用正常牙本质(ND)和龋病影响牙本质(CAD)，经Er:YAG激光辐射后，分别以不同方式处理牙本质表面：质量分数为38%的磷酸酸蚀(磷酸组)，低剂量Er:YAG激光辐射(激光组) 和空白处理(对照组)。应用激光共聚焦扫描显微镜观察牙本质粘结界面超微结构。结果表明，Er:YAG激光辐射后，不同方式处理同种牙本质和相同方式处理不同牙本质后粘结层厚度均无差别(显著性水平p>0.05)，粘结树脂突长度有差别(p<0.05)，其中ND组大于CAD组，质量分数为38%的磷酸酸蚀组的最大，低剂量激光辐射组的居中，对照组的最小。所以Er:YAG激光辐射正常牙本质后，经质量分数为38%的磷酸酸蚀处理，牙本质粘结界面的渗透性最好，可形成理想的树脂突。

评估组织表面附着水膜层对激光骨硬组织消融效果的影响。以新鲜离体牛胫骨组织为实验样品，置于速度为12 mm/s的一维电动平移台上，分别在有附着和无附着水膜层情况下使用脉冲CO2激光进行垂直照射，来回扫描5次。激光波长10.64 μm，脉冲频率60 Hz，能量密度范围18～84 J/cm2，光斑直径400 μm，水膜层厚度0.4 mm。辐照后，利用体视显微镜和扫描电镜(SEM)观察消融凹槽表面形貌改变和微结构变化，利用光学相干层析成像(OCT)技术测量消融凹槽深度。结果表明，组织表面附着水膜层可减少激光骨消融过程产生的碳化和热损伤，有利于清洁消融凹槽，且辐射曝光量为50 J/cm2和70 J/cm2时附着水膜层可提高消融速率。