Energy response characteristics of radiochromic film at CT radiation quality

Abstract

Introduction Radiochromic films (RF) have been developed for measurement of the absorbed dose of low-energy photons and to measure CT dose profiles. RF are self-developing and radiation sensitive, and the amount of darkening is proportional to the absorbed dose. RF are easy to handle due to their insensitivity to interior room light. Purpose In this study, energy response of GAFCHROMIC XR-QA2 film (XR-QA2) was evaluated to obtain an accurate measurement of CT dose. Materials and methods The measured dose and energy range of the XR-QA2 was designed to be 2–500 mGy and 20–200 kVp. XR-QA2 is a reflective-type film, and a flatbed scanner was used for the measurement of image density. To obtain the calibration curves, XR-QA2 were irradiated at 0–120 mGy (air-kerma) using 10–150 kVp (10 kVp intervals) photon beam with industrial X-ray System(Titan;GE). For image density acquisition, XR-QA2 were scanned before and after irradiate using a flatbed scanner (Epson GS-11000) in RGB (48 bit) mode, 150 dpi. Results The calibration curves varied according to the tube voltage. The energy response was best at 50 kVp and decreased according to increase tube voltage within the range of 50–150 kVp. Additionally, energy response was decreased rapidly below 40 kVp. Conclusion The dose differences were around 10% at 80–140 kVp. This indicated that single calibration curve is not adequate for CT dosimetry performed at different energies. To obtain an accurate measurement of CT dose, calibration curve has to make based on used energy. Disclosure We have no disclosure and financial support.