Simplified sigmoidal curve fitting for a 6 MV FFF photon beam of the Halcyon to determine the field size for beam commissioning and quality assurance.

Background: An O-ring gantry-type linear accelerator (LINAC) with a 6-MV flattening filter-free (FFF) photon beam, Halcyon, includes a reference beam that contains representative information such as the percent depth dose, profile and output factor for commissioning and quality assurance. However, because it does not provide information about the field size, we proposed a method to determine all field sizes according to all depths for radiation therapy using simplified sigmoidal curve fitting (SCF).

Methods: After mathematical definition of the SCF using four coefficients, the defined curves were fitted to both the reference data (RD) and the measured data (MD).

Estimation of radiation shielding ability in electron therapy and brachytherapy with real time variable shape tungsten rubber.

Purpose: To clarify the physical characteristics of a newly developed real time variable shape rubber containing tungsten (STR) with changes in heat and estimate its shielding abilities against electron beams and γ-rays from Ir.

Methods: Dynamic mechanical analysis for the STR (density = 7.3 g/cm) was conducted at a frequency of 1.