Brain heating induced by near-infrared lasers during multiphoton microscopy
Brain heating induced by near-infrared lasers during multiphoton microscopy
复制标题
DOI：
10.1152/jn.00275.2016
复制
发表时间：
2016-09-01
影响因子：
2.5
通讯作者：
Ranganathan, Gayathri
中科院分区：
文献类型：
--
作者：
Podgorski, Kaspar;Ranganathan, Gayathri
双光子成像和光遗传刺激依赖于高照明功率，特别是对于最先进的应用，目标更深的结构，实现更快的测量，或探测更大的大脑区域。然而，关于高功率照明对大脑造成的加热和损伤的信息很少。在本研究中，我们使用热电偶探针和量子点纳米温度计来测量双光子显微镜下清醒和麻醉小鼠新皮层的温度变化。我们将加热表征为波长，曝光时间和距离照明中心的距离的函数。虽然总功率在大脑表面附近最高，但由于热量通过颅窗散失，在焦平面以下数百微米处加热最为严重。1毫米(2)面积的连续照明产生的峰值温度增加类似于1.8摄氏度/100兆瓦。功率在250 mW以上的持续照明诱导持久损伤，免疫组化检测Iba1、胶质纤维酸性蛋白、热休克蛋白和活化的caspase-3。在有限占空比的实验中，更高的功率是可用的，这表明了一种减轻高倍显微镜实验损伤的方法。
Two-photon imaging and optogenetic stimulation rely on high illumination powers, particularly for state-of-the-art applications that target deeper structures, achieve faster measurements, or probe larger brain areas. However, little information is available on heating and resulting damage induced by high-power illumination in the brain. In the current study we used thermocouple probes and quantum dot nanothermometers to measure temperature changes induced by two-photon microscopy in the neocortex of awake and anaesthetized mice. We characterized heating as a function of wavelength, exposure time, and distance from the center of illumination. Although total power is highest near the surface of the brain, heating was most severe hundreds of micrometers below the focal plane, due to heat dissipation through the cranial window. Continuous illumination of a 1-mm(2) area produced a peak temperature increase of similar to 1.8 degrees C/100 mW. Continuous illumination with powers above 250 mW induced lasting damage, detected with immunohistochemistry against Iba1, glial fibrillary acidic protein, heat shock proteins, and activated caspase-3. Higher powers were usable in experiments with limited duty ratios, suggesting an approach to mitigate damage in high-power microscopy experiments.