X-ray tube in parallel magnetic fields
X-ray tube in parallel magnetic fields
复制标题
平行磁场中的 X 射线管
DOI：
10.1117/12.480256
复制
发表时间：
2003
影响因子：
24
通讯作者：
N. Pelc
中科院分区：
文献类型：
--
作者：
Z. Wen;R. Fahrig;N. Pelc
我们的混合X射线/MR系统（介入MR系统中的固定阳极X射线透视系统）提供X射线透视的高空间和时间分辨率以及MRI的软组织对比度、3D可视化和生理信息。X射线是在X射线管中通过高能电子轰击靶而产生的，高能电子从阴极电离，然后被阴极和阳极之间的电场加速。在混合系统中，X射线管被放置在高磁场中，对准成平行于管的阴极-阳极轴。一个有限元程序被用来模拟电子轨迹的几何形状类似于我们的固定阳极管。模拟了平行于阴极-阳极轴的外部磁场，范围从0到0.5T。实验上，在0 ~ 0.5T的磁场范围内，用30μm针孔在8.9倍放大率下采集焦斑图像。无论是在模拟还是实验中，如果磁场和阴极-阳极轴对齐，无论场强如何，都没有观察到焦斑的横向偏转。但是，电场强度影响焦斑的大小和电流密度分布。我们的结论是，固定阳极X射线管可以在磁场中使用，虽然其所需的电子光学必须是相当“直”的，阴极-阳极轴必须很好地与磁场对齐。应仔细考虑焦斑尺寸变化引起的其他问题，如目标过热，以及较小程度上的系统空间分辨率。
Our hybrid x-ray/MR system (a fixed-anode x-ray fluoroscopic system in an interventional MR system) provides the high spatial and temporal resolution of x-ray fluoroscopy with the soft-tissue contrast, 3D visualization and physiological information of MRI. X-rays are produced in an x-ray tube by bombarding a target with high-energy electrons, ionized from the cathode, then accelerated by the electric field between the cathode and anode. In the hybrid system, the x-ray tube is placed in a high magnetic field, aligned to be parallel to the cathode-anode axis of the tube. A finite-element program was used to simulate the electron trajectories in a geometry similar to our fixed anode tube. External magnetic fields parallel to the cathode-anode axis, ranging from 0 to 0.5T, were simulated. Experimentally, focal spot images were acquired using a 30μm pinhole at a magnification of 8.9 in magnetic fields ranging from 0 to 0.5T. No lateral deflection of the focal spot was observed in either the simulation or the experiment, if the magnetic field and the cathode-anode axis were aligned, regardless of the field strength. However, the field strength affected the size and the current density distribution of the focal spot. We conclude that fixed anode x-ray tubes can be used in a magnetic field although its desired electron optics must be fairly “straight” and the cathode-anode axis must be well aligned with the field. Further issues arising from the focal spot size change, such as overheating of the target, and to a lesser extent the system spatial resolution, should be carefully considered.