Balancing efficiency and quality: A dosimetric comparison of 6FFF and 10FFF for gated liver SMLC SBRT

This study aimed to evaluate the dosimetric and clinical differences of 6FFF versus 10FFF in gated liver stereotactic body radiation therapy (SBRT), focusing on plan quality and beam-on time (BOT). Given that 10FFF has a higher dose rate, it could improve treatment efficiency by reducing the treatment delivery time. However, it is important to investigate whether the plan quality with 10FFF is equivalent to 6FFF. Twelve liver SBRT plans for patients with hepatic cellular carcinoma (HCC), treated with 6FFF intensity-modulated radiation therapy (IMRT) and respiratory gating radiation therapy (RGRT), were reoptimized using 10FFF. The 10FFF plans were designed to meet the same clinical plan quality standards as the 6FFF plans, maintaining the same planning target volume (PTV) coverage. Plan quality was evaluated through target coverage, organ at risk (OAR) dose, dose fall-off, beam-on time (BOT), and radiation therapy oncology group (RTOG) conformity, gradient, homogeneity, and Paddick conformity index. The statistical significance of the metric comparisons was assessed with a paired student's T-test. The 10FFF plans had similar plan quality metrics, lower skin dose, and lower projected BOT. GTV and CTV coverage differences (based on clinical goals) were not statistically significant (p > 0.05). Mean dose to the GTV (52.31 ± 0.96 vs. 51.64 ± 0.79 Gy, p = 0.01) and CTV (52.36 ± 0.90 vs. 51.80 ± 0.53 Gy, p = 0.01) was significantly higher in 10FFF than 6FFF, respectively. Projected BOT was 26.5 ± 6.4 seconds faster on average for 10FFF than 6FFF (51.77 ± 12.45 vs. 78.30 ± 12.27 sec, p < 0.001); skin dose was also lower for 10FFF (24.40 ± 4 vs. 29.16 ± 5.47, p < 0.001) using the same IMRT beam arrangement. 10FFF is a viable treatment technique for liver SBRT IMRT, offering improved treatment efficiency and reduced skin dose. Although time savings are modest, 10FFF balances treatment efficiency with plan quality, making it a reasonable alternative.