Accurate model of photon beams as a tool for commissioning and quality assurance of treatment planning calculations
Main Article Content
Abstract
Simulation of a linear accelerator (linac) head requires determining the parameters that characterize the primary electron beam striking on the target which is a step that plays a vital role in the accuracy of Monte Carlo calculations. In this work, the commissioning of photon beams (6 MV and 15 MV) of an Elekta Precise accelerator, using the Monte Carlo code EGSnrc, was performed. The influence of the primary electron beam characteristics on the absorbed dose distribution for two photon qualities was studied. Using different combinations of mean energy and radial FWHM of the primary electron beam, deposited doses were calculated in a water phantom, for different field sizes. Based on the deposited dose in the phantom, depth dose curves and lateral dose profiles were constructed and compared with experimental values measured in an arrangement similar to the simulation. Taking into account the main differences between calculations and measurements, an acceptability criteria based on confidence limits was implemented. As expected, the lateral dose profiles for small field sizes were strongly infl uenced by the radial distribution (FWHM). The combinations of energy/FWHM that best reproduced the experimental results were used to generate the phase spaces, in order to obtain a model with the motorized wedge included and to calculate output factors. A good agreement was obtained between simulations and measurements for a wide range of fi eld sizes , being all the results found within the range of tolerance.
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How to Cite
Linares Rosales, H. M., Lara Mas, E., & Alfonso Laguardia, R. (1). Accurate model of photon beams as a tool for commissioning and quality assurance of treatment planning calculations. Nucleus, (57). Retrieved from http://nucleus.cubaenergia.cu/index.php/nucleus/article/view/604
Section
Ciencias Nucleares
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References
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2. VENSELAAR J, WELLEWEERDB H & MIJNHEER B. Tolerances for the accuracy of photon beam dose calculations of treatment planning systems. Radiother. Oncol. 2001; 60(2): 191-201.
3. LIBBY B, SIEBERS J & MOHAN R. Validation of Monte Carlo generated phase-space descriptions of medical linear accelerators. Med. Phys. 1999; 26(8): 1476-1483.
4. TZEDAKIS A, DAMILAKISJ E, MAZONAKIS M. et. al. Influence of initial electron beam parameters on Monte Carlo calculated absorbed dose distributions for radiotherapy photon beams. Med. Phys. 2004; 31(4): 907-913.
5. INDRIN J, CURRAN B, CYGLER J, et. al. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning.. Med. Phys. 2007; 34(12): 4818-4853.
6. KAWRAKOW I & WALTERS BRB. Efficient photon beam dose calculations using DOSXYZnrc with BEAMnrc. Med. Phys. 2006; 33(8): 3046-3056.
7. SHEIKH-BAGHERI D & ROGERS DWO. Sensitivity of megavoltage photon beam Monte Carlo simulations to electron beam and other parameters. Med. Phys. 2002; 29(3): 379-390.
8. ROGERS DWO, WALTERS B & KAWRAKOW I. BEAMnrcUsers Manual. NRCC Report PIRS-0509(A). 2011.
9. KAWRAKOW I, ROGERS DWO & WALTERS BRB. Large efficiency improvements in BEAMnrc using directional bremsstrahlung splitting. Med. Phys 2004; 31(10): 2883-2898.
10. International Atomic Energy Agency. Commissioning and Quality Assurance of Computerized Planning Systems for Radiation Treatment of Cancer. IAEA Technical Report Series 430. Vienna: IAEA, 2003.