Determination of Mercury Attenuation Coefficient for Mercury Shielding for Radiotherapy Patients

The aim of radiotherapy is deliver enough doses to the tumor and protecting organs at risk that are around the tumor. In order to get appropriate dose distribution one can use radiation modifiers and compensators. So knowing attenuation coefficient of absorbers is necessary for treatment calculations. In this study mercury was introduced as suitable material for radiotherapy shielding. A new method is presented by physics of interaction of photon with matter and complex integration calculation to calculate attenuation coefficient for any material with different thickness and energies. Radiation quality changes with thickness of absorber and this variation were significant. However، changes in field sizes did not produce any significant variations. Variation of attenuation coefficient with thickness of absorber can not be ignored and it is necessary for accurate radiotherapy treatment. On the other hand using one number as an attenuation coefficient for radiotherapy compensators or modifiers is not accurate enough and variation of attenuation coefficient with thickness of absorber must be considered in radiotherapy treatment planning systems.