A new tool for measuring therapeutic electron beam energies with scintillation light

In order to facilitate quality control (QC) of the electron linear accelerator (LINAC), we propose a new method of measuring the mean energy of the therapeutic electron beam by using the visible scintillation light generated when the electron beam is irradiated on a plastic scintillator. We used the light capture system consisting of a tissue equivalent plastic scintillator and a charge coupled device (CCD) camera, and measured the brightness from the pixel of the image recorded by the CCD camera. Measurements of dose rate dependence and dose linearity were performed as the characterization of this system. In this research we determined the mean energy of the electron beams of 4 MeV and 6 MeV by measuring the depth brightness distribution of scintillation light, and then we compared it to the energy obtained from the percentage depth dose (PDD) in the water phantom. From the experimental results, the brightness was found to be linear in the dose rate. Moreover, the brightness increased in proportion to the absorbed dose. Although, there was a shift in the energy by 3.2% or less between the measured energies, we consider it possible to check the energy daily by correcting this shift measured in advance. Therefore, this new energy measuring tool can be useful for daily quality control of LINAC.