Impact of MRI fringe magnetic field on radiation beam characteristics of electron guns in real time MRI-guided radiotherapy
10.13929/j.1003-3289.201807094
- VernacularTitle: 实时MRI引导放射治疗中边缘磁场对电子枪束流特性的影响
- Author:
Lingli MAO
1
Author Information
1. Center of Radiological Medical Physics, School of Physical Science, University of Science and Technology of China
- Publication Type:Journal Article
- Keywords:
Electron gun;
Fringe magnetic field;
In-line configuration;
Magnetic resonance imaging;
Radiotherapy
- From:
Chinese Journal of Medical Imaging Technology
2019;35(3):433-438
- CountryChina
- Language:Chinese
-
Abstract:
Objective: To investigate the impact of MR fringe magnetic field on the electron beam characteristics of the electron gun in the MRI-guided radiotherapy (MRIgRT). Methods Electromagnetic field analysis software was used to simulate the beam characteristics of both Litton L2087 electron gun and Varian 600C electron gun under different magnetic field strengths for the in-line MRIgRT configuration. Results Two electron guns exhibited qualitatively similar behavior in the fringe magnetic field. As field strength increased, the current emitted by the cathode increased slowly, which could increase up to 2.72% and 1.93% from the original value without external magnetic field for Litton L2087 and Varian 600C electron gun, respectively. The current at the anode exit started to decrease after the initial plateau, and after reaching a minimum value, the current started to increase slowly, and the current loss could reach up to 80.25% and 73.48% of the initial value, respectively. At high values of the field strength, the beam radius changed periodically. Beam root mean square emittance fluctuated under different magnetic field strengths. Conclusion For in-line MRIgRT configuration, the fringe magnetic field can affect the trajectory of the beam and cause a large amount of current loss in the electron gun, and the beam RMS emittance varies greatly.
