Influence of Compensator Thickness and Field Size on Buildup factor of a Brass Compensator for Intensity- Modulated Radiation Therapy

Introduction: Radiotherapy is one of the effective methods in the treatment of cancer. In the recent methods of radiotherapy, intensity modulated radiotherapy (IMRT) technique by compensators is used. when photon beam passes the compensator, scattered photons can be generated within the compensator. The presence of scattered photons may complicate the design of compensators as well as the subsequent calculations of dose distributions. The buildup factor, ‘B’, is one of these important properties of a material to be used for compensator construction. It directly affects the dose quantity. Materials and Methods: Radiotherapy is one of the effective methods in the treatment of cancer. In the recent methods of radiotherapy, intensity modulated radiotherapy (IMRT) technique by compensators is used. when photon beam passes the compensator, scattered photons can be generated within the compensator. The presence of scattered photons may complicate the design of compensators as well as the subsequent calculations of dose distributions. The buildup factor, ‘B’, is one of these important properties of a material to be used for compensator construction. It directly affects the dose quantity. Results: Our results indicated that the compensator thickness and field size have the most significant effect on the calculation of buildup factor for the 6-MV photon beam. Conclusion: Influence of compensator thickness and field size on calculation buildup factor can reduce the error due to delivered dose to target volume and organs at risk