Three-dimensional thermal analysis of thermal characteristics in a water-equivalent phantom thermal analysis of water-equivalent phantom

This study aimed to determine the temperature equilibrium time of three water-equivalent phantoms (Gammex SW557 Solid Water HE, Gammex RMI457 Solid Water, and Tough water phantom WD) with room temperature using thermocouples and three-dimensional thermal analysis. The water-equivalent phantom and thermocouples were arranged in a 30 cm x 30 cm x 15 cm phantom, and temperatures were measured at five points with insertion lengths of 3-15 cm from the outside of the water-equivalent phantom. The temperature equilibrium was defined as the point at which the temperature difference between the water-equivalent phantom and room temperature reached 0.5 degrees C. The temperature variation of the water-equivalent phantom over time during the measurements was obtained by a compact thermo-logger. The temperature distribution in the phantom was calculated by three-dimensional thermal analysis. The time required for the three water-equivalent phantoms to reach thermal equilibrium from 32 degrees C to 22 degrees C is about 21.5 h, so it is clear that there is a waiting period before the measurement. The temperature distribution inside the water-equivalent phantom was also shown, and the temperature variation at each measurement location was clarified, providing useful data for dosimetry in quality control and other applications. The data collected from this study will provide useful information for dosimetry of the water-equivalent phantom in standard measurement methods.