A Novel Electron-Beam Combined with Magnetic Field Application for Radiotherapy
D Alezra1*, E Nardi1, S Koren2, D Bragilovski2, I Orion2,(1) Sheba Medical Center, Tel Hashomer,(2) Nuclear Engineering Dept, Ben Gurion University, Beer Sheva,SU-E-T-279 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: The new beam and delivery system consists of an electron accelerator and a system of magnets (one or more). Introducing a transverse magnetic field in and near the tumor, causes the electrons to spiral in this region, thereby producing an effective peak in the depth dose distribution, within the tumor volume. Although the basic idea is not new, we suggest here for the first time, a viable as well as a workable, magnetic field configuration, which in addition to focusing the beam does not interfere with its propagation to the target.
Methods: The electron accelerator: can be a linear accelerator or any other type electron accelerator, capable of producing different electron energies for different depths and dose absorption accumulation. The Field size can be as small as a pencil beam and as big as any of the other standard field sizes that are used in radiotherapy. The scatter filter can be used or removed. The dose rate accumulation can be as higher as possible.
The magnets are able to produce magnetic fields. The order, direction, width, place, shape and number of the magnetic fields define the shape and the Percentage Depth Dose (PDD) curve of the electron beam.
Prototypes were successfully tested by means of computer simulation, using:
COMSOL-Multiphsics for magnetic fields calculations.
FLUKA package, for electron beam MC simulation.
Results: Our results suggest that by using an electron beam at different energies, combined with magnetic fields, we could modify the delivered dose. This is caused by manipulating the electron motion via the Lorentz force. The applied magnetic field, will focus the electron beam at a given depth and deposit the energy in a given volume and depth, where otherwise the electron energy will have spread deeper.
The direction and magnitude of the magnetic fields will prevent the scattering of the electron beam and its absorption in remote volumes. In practice, we get a pseudo Bragg peak depth dose distribution, applying a relatively low cost system. The therapeutic efficiency induced by the system is of similar efficiency as the ion beam therapy techniques.
Conclusions: Our novel concept demonstrates treatment that is almost similar to proton therapy and in some parameters even better performance.
Unlike the current high-energy electron therapy, our system's beam deposit almost all of its energy on its target, with a low amount of radiation deposited in tissues from the surface of the skin to the front of tumor, and almost no "exit dose" beyond the tumor. This property will enables to hit tumors with higher, potentially more effective radiation doses, while being considerably less expensive.