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| Reconstruction of 6MV Xray Spectra of Medical Linear Accelerator Based on Simulated Annealing Algorithm |
| Department of Nuclear Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China |
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Abstract A method based on simulated annealing (SA) algorithm to reconstruct 6MV X-ray energy spectra from medical linear accelerators was investigated in this work, utilizing both measured percentage depth doses (PDD) and MonteCarlo simulated central axis PDD of monoenergy photons. As for the SA optimization, 60 energy bins were employed with different relative weights and the objective function was chosen as the correlation coefficient between reconstructed PDD (the products of relative weights and Monte-Carlo simulated PDD) and measured PDD. The optimal solution calculated by SA algorithm was exactly the spectrum of the accelerator. To verify the proposed method, a Monte-Carlo simulation of the accelerator treatment head was performed to calculate the 6MV photon energy spectrum for comparison. Results showed that the reconstructed spectrum was in good agreement with the MonteCarlo simulated spectrum in both shape and peak position; the derived PDD from reconstructed spectrum were highly consistent with the measured PDD with a rootmeansquare error of 1.56×10-4. Above experimental results indicated that reconstructing photon spectra based on SA algorithm with measured PDD was effective and reliable.
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