Determination of Output Factor of Electron Beams for Varian2100 CD Accelerator Installed in Radiotherapy Department of Ahvaz-Golestan Hospital to Cancer Patients’ Treatment

Document Type : Original Article


1 Professor of Medical Physic.Department of Medical Physic, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

2 Assistant Professor of Medical Physic.Department of Medical Physic, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

3 M.Sc. Student of Medical Physics.Department of Medical Physic, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

4 M.Sc. of Medical Physics.Department of Radiology, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran.

5 Assistant Professor of Radiotherapy and Oncology.Department of Radiotherapy and Oncology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

6 M.Sc. Student of Medical Physics.Behbahan Faculty of Medical Sciences, Behbahan, Iran.


Background and Objectives: Electron beams, due to its fast reduction in dose, are widely used for the treatment of superficial tumors. The small fields are needed in order to achieve the optimal plan of treatment during electron therapy of small tumors. But lack of full lateral scattering equilibrium is a crucial obstacle during measuring of the output factor.The aim of this study is to find an analytical equation for the output factors of Varian2100 CD accelerator for different fields and energies.
Subjects and Methods: Varian2100 CD accelerator and 0.6 cc Farmer dosimeter located in reference depth inside the water phantom were used, to dose measurement. Using present applicators and shielding blocks inserted at the end scraper of 10 ´ 10 cm2 applicator, electron fields size range from 2 ´ 2 cm2 to 20 ´ 20 cm2 were established. Output factors for energies of 4, 6, 9, 12 and 15 MeV were measured and related equations were extracted.
Results: The best fit polynomial functions on the measured output factors were extracted. Low (4 MeV) and high (15 MeV) electron beams followed - 3.143 L-2.51+1.031 (R=0.97) and
-2.165L-2.02+1008(R=0.98) equations respectively. Output factors increase initially with increased field size up to 6´ 6 cm2 and then reach to the plateau around 15´ 5 cm2.
Conclusion: The obtained analytical equations can be used to calculate the needed output factors for all the field sizes and electron beams energies.


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