Umetani K, Fukushima K
Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
Rev Sci Instrum. 2013 Mar;84(3):034302. doi: 10.1063/1.4795830.
An X-ray intravital microscopy technique was developed to enable in vivo visualization of the coronary, cerebral, and pulmonary arteries in rats without exposure of organs and with spatial resolution in the micrometer range and temporal resolution in the millisecond range. We have refined the system continually in terms of the spatial resolution and exposure time. X-rays transmitted through an object are detected by an X-ray direct-conversion type detector, which incorporates an X-ray SATICON pickup tube. The spatial resolution has been improved to 6 μm, yielding sharp images of small arteries. The exposure time has been shortened to around 2 ms using a new rotating-disk X-ray shutter, enabling imaging of beating rat hearts. Quantitative evaluations of the X-ray intravital microscopy technique were extracted from measurements of the smallest-detectable vessel size and detection of the vessel function. The smallest-diameter vessel viewed for measurements is determined primarily by the concentration of iodinated contrast material. The iodine concentration depends on the injection technique. We used ex vivo rat hearts under Langendorff perfusion for accurate evaluation. After the contrast agent is injected into the origin of the aorta in an isolated perfused rat heart, the contrast agent is delivered directly into the coronary arteries with minimum dilution. The vascular internal diameter response of coronary arterial circulation is analyzed to evaluate the vessel function. Small blood vessels of more than about 50 μm diameters were visualized clearly at heart rates of around 300 beats/min. Vasodilation compared to the control was observed quantitatively using drug manipulation. Furthermore, the apparent increase in the number of small vessels with diameters of less than about 50 μm was observed after the vasoactive agents increased the diameters of invisible small blood vessels to visible sizes. This technique is expected to offer the potential for direct investigation of mechanisms of vascular dysfunctions.
一种X射线活体显微镜技术被开发出来，可在不暴露器官的情况下对大鼠的冠状动脉、脑动脉和肺动脉进行体内可视化，其空间分辨率在微米范围内，时间分辨率在毫秒范围内。我们在空间分辨率和曝光时间方面不断完善该系统。透过物体的X射线由一个X射线直接转换型探测器检测，该探测器包含一个X射线硒砷碲摄像管。空间分辨率已提高到6μm，能产生小动脉的清晰图像。使用新型旋转盘式X射线快门，曝光时间已缩短至约2ms，从而能够对跳动的大鼠心脏进行成像。X射线活体显微镜技术的定量评估是从最小可检测血管尺寸的测量和血管功能的检测中得出的。测量时观察到的最小直径血管主要由碘化造影剂的浓度决定。碘浓度取决于注射技术。我们使用兰根多夫灌注下的离体大鼠心脏进行准确评估。在将造影剂注入离体灌注大鼠心脏的主动脉起始处后，造影剂以最小程度的稀释直接输送到冠状动脉中。分析冠状动脉循环的血管内径反应以评估血管功能。在心率约为300次/分钟时，直径大于约50μm的小血管清晰可见。通过药物操作定量观察到与对照组相比的血管舒张情况。此外，在血管活性剂将不可见的小血管直径增加到可见尺寸后，观察到直径小于约50μm的小血管数量明显增加。预计该技术可为直接研究血管功能障碍机制提供潜力。
