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Measurement of electron energy fluence spectra from electron beam therapy machines

Thesis/Dissertation ·
OSTI ID:5087332
A technique capable of measuring the electron energy fluence spectra in a scattering medium was designed. These measurements were performed by setting a bremsstrahlung conversion target on the surface of a phantom, at an intermediate depth, and at a depth equal to electron mean range. The bremsstrahlung produced by the deceleration of electrons in the target was passed through an air channel in the phantom and passed forward by a pinhole collimator into a Na(Tl) detector. The measured pulse height data were unfolded to correct for the distortion of the spectrometer system by using the FORIST unfolding code. The unfolded bremsstrahlung spectra represent the electron energy fluence spectra convolution with the bremsstrahlung produced in the target. To generate the electron energy fluence spectra, the unfolded bremsstrahlung spectra were deconvoluted by using the MAZE2 unfolding code. CYLTRAN, a coupled electron-photon Monte Carlo transport code, was used to produce the deposition spectra of the detector. The unfolded bremsstrahlung obtained from the FORIST code show the maximum photon energies were 6, 12, and 20 MeV, respectively. The electron fluence spectra show that the high energy component decreases strongly with increasing depth; whereas the low-energy component increases rapidly. The unfolded electron fluence spectra are compared with the spectra calculated by Berger and Seltzer using the Monte Carlo method for 20 MeV.
Research Organization:
Cincinnati Univ., OH (USA)
OSTI ID:
5087332
Country of Publication:
United States
Language:
English