Impact of kV-CBCT protocol selection on organ dose in head-and-neck IGRT: an OSLD phantom study

While essential for precision in image-guided radiation therapy (IGRT), kilovoltage (kV) cone beam computed tomography (CBCT) contributes a cumulative radiation dose to organs at risk. This study quantifies absorbed organ doses in head-and-neck IGRT, emphasizing the benefit of optimized anatomy-specific protocols. Using OSLDs in an anthropomorphic phantom, we measured doses for two dedicated head-and-neck protocols (Standard S10/CBCT2 and Low-dose S20/CBCT3). Additionally, a non-optimized chest protocol (CBCT1) was evaluated to quantify the dosimetric penalty of potential protocol misapplication. The misapplied chest protocol resulted in severe overexposure (spinal cord dose ≈ 81 mGy per scan). In contrast, the optimized head-and-neck protocols maintained organ doses below 20 mGy per scan. Comparing the optimized protocols, the Standard S10 provided a balanced dose profile, while the Low-dose S20 reduced exposure but showed higher variability near bone interfaces. Results show that strict adherence to anatomy-specific protocols is a critical radiation protection imperative to avoid unnecessary exposure.