Room: Exhibit Hall | Forum 4
Purpose: Accounting for the effectiveness of radiation in radiotherapy in addition to absorbed dose can allow for improved treatments; in order to do this, a novel device and technique was developed to measure the electron energy spectra at the point of measurement using lead doped plastic scintillators.
Methods: By measuring the signal produced by an energy dependent detector (S) while knowing each detectorâ€™s respective response function (R), the energy spectrum of electrons (Î¦) at the point of measurement can be obtained in matrix form Î¦=Râ?»Â¹S. The light signal from four differently doped scintillators (0%, 1%, 1.5%, 5.0% Pb; 5x5mm cylinders) was measured at a depth of 1.5 cm in water using an optical fiber connected to a PMT. Measurements were done for four Orthovoltage beam energies (100, 180, 250, and 300 kVp). The doped scintillator response matrix (R) was calculated using Birksâ€™ Law and GEANT4.10.3 Monte Carlo. The Î¦ measured using the doped scintillator technique was compared to the electron energy spectrum obtained using Monte Carlo simulation at the depth of measurement (all beams were modeled in GEANT4.10.3). For comparison purposes, the mean energy was calculated from the measured and simulated spectra. The resolution of the measured spectra was limited to four bins due to the limited number of differently doped scintillators.
Results: The relative electron energy spectra at a depth of 1.5 cm in water was measured for each beam. The mean energy of the measured spectra was approximately 30% lower than that obtained through Monte Carlo for each of the four beams.
Conclusion: Using differently doped plastic scintillators with the proposed method measures the electron energy spectra. The resolution of the spectra is based on the number of distinctly available scintillators. Further studies to reduce detector size and improve light collection are under way.