Using PHITS to simulate the effects of the technique factors in the quality of posteroanterior chest X-ray images

Abstract

Chest X-ray (CXR) is a widely used diagnostic imaging technique that requires careful selection of technique factors to balance image quality and absorbed dose. Monte Carlo simulations are used to study these effects as they provide accurate dose calculations without patient radiation exposure and are more cost-effective than physical measurements. In this study, we investigate the effects of varying tube voltage (100-120 kV) on image quality and radiation dose using PHITS Monte Carlo simulations. X-ray spectra generated with SpekCalc were implemented in PHITS using stylized anthropomorphic phantoms. Image quality was evaluated through contrast-to-noise ratio (CNR), while radiation risk was assessed via both absorbed dose (D) and effective dose (E). The results demonstrate that lower kV settings improve image contrast but increase radiation exposure. The 100 kV setting yielded the highest CNR (10.7) but also the highest doses (lung D = 0.1021 mGy, E = 0.01225 mSv; heart D = 0.1124 mGy, E = 0.013488 mSv). Increasing to 120 kV reduced doses (lung D = 0.0475 mGy, E = 0.0057 mSv; heart D = 0.0508 mGy, E = 0.006096 mSv) while decreasing CNR to 3.33. These effective dose values align with clinical reference levels, validating our simulation. The study highlights the importance of optimizing technique factors to achieve the ideal balance between diagnostic image quality and patient radiation protection in CXR imaging.