ABSTRACT
Objective To explore the application of CT value in calculating the proton incident energy in proton treatment planning system. Methods Bethe-Block formula and the formula for calculating the proton range were analyzed to study the correlation of the range of proton beam ( 70-250 MeV ) between a variety of radiation equivalent material and water. Procedure of Monte Carlo SRIM2008 was used to verify the possibility of a constant proportional coefficient of range ( Ci ). The proportional coefficient ( Ci ) of range in radiation-equivalent material and the CT value were fitted by using Origin 8.0 software to study the functional relation of CT value and Ci. The actual range of proton was equivalent to a range of water and incident proton energy could be calculated. Results There was a constant range of Ci of proton beam (70-250 MeV) between a variety of radiation equivalent material and water. There was a functional relation between CT value and Ci ( r = 0.999). The actual range of proton in radiation equivalent material can be equivalent to a range of the water. Conclusions CT values and a range of proportional coefficient ( Ci ),and the actual required range of the tumor could be used to accurately calculate the water equivalent range,and the incident proton energy to the position of Bragg peak. A new exploration for using CT technology in proton treatment planning system could be obtained.