Dosimetry of very high energy electrons (VHEE) for radiotherapy applications: using radiochromic film measurements and Monte Carlo simulations

Abstract

Very high energy electrons (VHEE) in the range from 100-250 MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetry properties compared with MV photons from contemporary medical linear accelerators. Due to the need for accurate dosimetry of small field size VHEE beams we have performed dose measurements using EBT2 Gafchromic® film. Calibration of the film has been carried out for beams of two different energy ranges: 20 MeV and 165 MeV from conventional radio frequency linear accelerators. In addition, EBT2 film has been used for dose measurements with 135 MeV electron beams produced by a laser-plasma wakefield accelerator. The dose response measurements and percentage depth dose profiles have been compared with calculations carried out using the general-purpose FLUKA Monte Carlo (MC) radiation transport code. The impact of induced radioactivity on film response for VHEEs has been evaluated using the MC simulations. A neutron yield of the order of 10 −5 neutrons cm −2 per incident electron has been estimated and induced activity due to radionuclide production is found to have a negligible effect on total dose deposition and film response. Neutron and proton contribution to the equivalent doses are negligible for VHEE. The study demonstrates that EBT2 Gafchromic film is a reliable dosimeter that can be used for dosimetry of VHEE. The results indicate an energy-independent response of the dosimeter for 20 MeV and 165 MeV electron beams and has been found to be suitable for dosimetry of VHEE.

Very high‐energy electron ( VHEE ) beams in radiation therapy; Treatment plan comparison between VHEE , VMAT , and PPBS

“…Further, a limitation of the present study is that the neutron contribution to the VHEE and proton treatments was not considered. However, this contribution in dose has previously been shown to be negligible for proton PPBS and 165 MeV VHEE beams in water . Another limitation of the present study is the use of real clinical beam data for the simulation of the photon and proton fields used to generate the VMAT and PPBS plans while the VHEE data were taken from MC‐simulated beams.…”

Wide-angle electron beams from laser-wakefield accelerators

“…[7][8][9][10][11][12][13][14] There are, however, applications such as non-destructive-testing, ultra-fast studies in condensed matter, radiolysis, isotope production and radiotherapy that require high-charge, low-energy electron beams. [15][16][17][18][19] Ionization-assisted injection in high-Z or clustering gas targets has been explored to boost the charge to 100s pC at 10s-100s MeV energies. [20][21][22] At even lower energies, high-charge beams can be obtained by exploiting the little known property of laser-wakefield accelerators that intrinsically leads to MeV electrons at wide angles as part of the bubble formation process.…”

Laser-Driven Very High Energy Electron/Photon Beam Radiation Therapy in Conjunction with a Robotic System

“…However, the limited penetration depth and low quality of the transverse penumbra at the energy range of [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] MeV delivered from present medical RF linear accelerators currently prevent the aforementioned advanced modalities from being used in cancer treatment. These drawbacks can be overcome if the electron energy is increased above 50 MeV, whereby the penetration depth becomes longer and the transverse penumbra sharper, though the longitudinal penumbra is also increased.…”

“…Therefore, most of the investigations for verifying beam characteristics and dose distributions in specific cancer treatment have been studied by Monte Carlo simulations [8][9][10][11][12]. Referring to the results of Monte Carlo simulations carried out by DesRosiers et al [8], depth-dose distributions from 200 MeV electron beams are illustrated for single-field, parallel opposed two-field, and orthogonal two-field arrangements as well as a 160 MeV proton beam with a Bragg peak at a depth of 15 cm, as shown in Figure 1.…”