Lillaney P, Shin M, Hinshaw W, Fahrig R
Stanford University, Stanford, CA.
Med Phys. 2012 Jun;39(6Part27):3949. doi: 10.1118/1.4736118.
To design a rotating anode X-ray tube capable of operating in strong magnetic field environments. This tube design can be used in 'close proximity" hybrid X-ray/MR system geometries where the imaging fields of view are separated by only ∼1.2 meters.
Existing rotating anode X-ray tube designs fail in strong magnetic field environments because the fields alter the electron trajectories in the tube and act as a brake on the induction motor, reducing the rotation speed of the anode. We propose an X- ray tube design that utilizes optimized resistive coils to shield a fraction of the MR fringe field. The remainder of the correction is performed using bias voltages on electrodes adjacent to the x-ray tube filament. Furthermore, we replace the induction motor with a novel motor design that is analogous to a three-phase brushed DC motor with the MR fringe field serving as the stator field.
Space charge simulations of the electron optics show that the combined magnetostatic/electrostatic method can correct for a magnetic field strength of 152 mT with approximately 590 A/cm applied to the shielding coils and a 35 kV potential difference applied to the bias electrodes. A prototype of the motor design was machined and assembled. The performance of this prototype motor was evaluated at various magnetic field strengths, and was found to accelerate to the minimum operating speed of 3000 rpm in 10 seconds for an external field of 60 mT.
The space charge simulations validate that the electron trajectories can be controlled using our combined approach. Testing of the motor prototype demonstrates that our design outperforms existing induction motors in strong magnetic field environments. Integrating this design with our modified flat panel detector will allow, for the first time, a "close proximity" hybrid system in which imaging performance is not compromised. NIH R01 EB007626 Richard M. Lucas Foundation Stanford Bio-X Fellowship.
设计一种能够在强磁场环境中运行的旋转阳极X射线管。这种管设计可用于“近距离”混合X射线/磁共振成像（MR）系统几何结构中，其中成像视野仅相隔约1.2米。
现有的旋转阳极X射线管设计在强磁场环境中失效，因为磁场会改变管内电子轨迹，并对感应电动机起到制动作用，降低阳极转速。我们提出一种X射线管设计，利用优化的电阻线圈屏蔽一部分MR边缘磁场。其余的校正通过在与X射线管灯丝相邻的电极上施加偏置电压来完成。此外，我们用一种新颖的电动机设计取代感应电动机，这种设计类似于三相有刷直流电动机，其中MR边缘磁场作为定子磁场。
电子光学的空间电荷模拟表明，通过在屏蔽线圈上施加约590 A/cm的电流以及在偏置电极上施加35 kV的电位差，静磁/静电组合方法可以校正152 mT的磁场强度。加工并组装了电动机设计的原型。在各种磁场强度下对该原型电动机的性能进行了评估，发现在60 mT的外部磁场中，它能在10秒内加速到3000 rpm的最低运行速度。
空间电荷模拟验证了使用我们的组合方法可以控制电子轨迹。电动机原型的测试表明，我们的设计在强磁场环境中优于现有的感应电动机。将这种设计与我们改进的平板探测器集成，将首次实现一种“近距离”混合系统，且成像性能不受影响。美国国立卫生研究院R01 EB007626资助 理查德·M·卢卡斯基金会 斯坦福生物-X奖学金
