Biomedical and X-Ray Physics, Department of Applied Physics, KTH Royal Institute of Technology/Albanova, Stockholm, Sweden.
Phys Med Biol. 2012 May 7;57(9):2603-17. doi: 10.1088/0031-9155/57/9/2603. Epub 2012 Apr 13.
We demonstrate a laboratory method for imaging small blood vessels using x-ray propagation-based phase-contrast imaging and carbon dioxide (CO(2)) gas as a contrast agent. The limited radiation dose in combination with CO(2) being clinically acceptable makes the method promising for small-diameter vascular visualization. We investigate the possibilities and limitations of the method for small-animal angiography and compare it with conventional absorption-based x-ray angiography. Photon noise in absorption-contrast imaging prevents visualization of blood vessels narrower than 50 µm at the highest radiation doses compatible with living animals, whereas our simulations and experiments indicate the possibility of visualizing 20 µm vessels at radiation doses as low as 100 mGy. Experimental computed tomography of excised rat kidney shows blood vessels of diameters down to 60 µm with improved image quality compared to absorption-based methods. With our present prototype x-ray source, the acquisition time for a tomographic dataset is approximately 1 h, which is long compared to the 1-20 min common for absorption-contrast micro-CT systems. Further development of the liquid-metal-jet microfocus x-ray sources used here and high-resolution x-ray detectors shows promise to reduce exposure times and make this high-resolution method practical for imaging of living animals.
我们展示了一种使用基于 X 射线传播的相位对比成像和二氧化碳 (CO2) 气体作为对比剂来对小血管成像的实验室方法。由于辐射剂量有限且 CO2 在临床上是可接受的，因此该方法有望用于可视化小直径血管。我们研究了该方法在小动物血管造影中的可能性和局限性，并将其与传统的基于吸收的 X 射线血管造影进行了比较。在吸收对比成像中的光子噪声阻止了在与活体动物兼容的最高辐射剂量下可视化小于 50 µm 的血管，而我们的模拟和实验表明，在低至 100 mGy 的辐射剂量下可视化 20 µm 血管是可能的。对切除的大鼠肾脏进行的实验性计算机断层扫描显示，与基于吸收的方法相比，血管直径可达 60 µm，图像质量得到改善。使用我们目前的原型 X 射线源，对层析数据集的采集时间约为 1 小时，与常见的 1-20 分钟的吸收对比微 CT 系统相比，采集时间较长。进一步开发这里使用的液态金属喷射微焦点 X 射线源和高分辨率 X 射线探测器有望减少曝光时间，并使这种高分辨率方法适用于活体动物成像。
