Calculation of the ratio of absorbed dose to different tissues to water for medical accelerators of Electa 25MV and Siemens 6MV

In this paper, the ratio of adsorbed dose to the tissues of muscle, blood and bone to water for medical accelerators of Electa 25MV and Siemens 6MV is calculated using an analytical method based on cavity theory and Monte Carlo simulation. To confirm the validation of these methods, the ratio of absorbed dose to air to water was determined experimentally for radiation field of 60Co in Secondary Standard Dosimetry Laboratory (SSDL). The relative difference between the measured value and calculated values was less than 10% which confirms the validation of analytical and simulation methods.
The ratio of absorbed dose to muscle and blood to water is close to unity due to their atomic composition and density similar to water. The ratio of absorbed dose to bone to absorbed dose to water is calculated 0.96 and 0.91 for radiation fields of Electa 25MV and Siemens 6MV, respectively due to the discrepancy between atomic composition and density of bone and water. Further, the obtained results reveals that the ratio of absorbed dose to different tissues to absorbed dose to water is depended on radiation field energy. The results of this paper can be useful to determine the absorbed dose delivered to an organ in a treatment planning systems.