Wen Zhifei, Fahrig Rebecca, Pelc Norbert J
Department of Radiology and Department of Physics, Stanford University, Stanford, California 94305.
Department of Radiology, Stanford University, Stanford, California 94305.
Med Phys. 2005 Jul;32(7Part1):2327-2336. doi: 10.1118/1.1944267.
A hybrid system that combines an x-ray fluoroscopic system and a magnetic resonance (MR) system can provide physicians with the synergy of exquisite soft tissue contrast (from MR) and high temporal and spatial resolutions (from x ray), which may significantly benefit a number of image-guided interventional procedures. However, the system configuration may require the x-ray tube to be placed in a magnetic field, which can hinder the proper functioning of the x-ray tube by deflecting its electron beam. From knowledge of how the magnetic field affects the electron trajectories, we propose creating another magnetic field along the cathode-anode axis using either solenoids or permanent magnets to reduce the deflection of the electron beam for two cases: a strong and slightly misaligned field or a weak field that is arbitrary in direction. Theoretical analysis is presented and the electron beam is simulated in various external magnetic fields with a finite element modeling program. Results show that both correction schemes enhance the robustness of the x-ray tube operation in an externally applied magnetic field.
一种将X射线荧光透视系统与磁共振（MR）系统相结合的混合系统，可为医生提供（来自MR的）精细软组织对比度与（来自X射线的）高时间和空间分辨率的协同作用，这可能会使许多图像引导介入手术受益匪浅。然而，系统配置可能要求将X射线管放置在磁场中，这会通过使电子束偏转而阻碍X射线管的正常运行。根据磁场如何影响电子轨迹的知识，我们建议在两种情况下，使用螺线管或永久磁铁沿阴极-阳极轴创建另一个磁场，以减少电子束的偏转：一种是强且略微未对准的磁场，另一种是方向任意的弱磁场。进行了理论分析，并使用有限元建模程序在各种外部磁场中对电子束进行了模拟。结果表明，两种校正方案都提高了X射线管在外部施加磁场中的运行稳健性。
