Feasibility and workflow efficiency of automated deep inspiration breath-hold for locoregional breast irradiation on a ring-gantry accelerator

Purpose: To evaluate the feasibility, dosimetric quality, workflow efficiency, and early tolerance of automated deep-inspiration breath-hold (DIBH) breast radiotherapy delivered on a ring-gantry platform. Materials and methods: Twenty patients requiring locoregional irradiation were treated on a Radixact ring-gantry system between February and September 2025 using a static-beam intensity-modulated technique in automated DIBH. Dose/volume metrics for targets and organs of interest (OOIs), workflow parameters, and acute side effects were collected. Benchmark helical tomotherapy plans in DIBH conditions were reoptimized for comparison. Results: : 97.2% for low-risk and 99.2% for boost volumes) and OOI objectives were met. Daily image acquisition required 20-32 s. Median expected beam-on time was 230 s, while delivered beam-on time was 416 s. Median fraction duration was approximately 10 min, including setup, imaging and delivery. A total of 3511 gated beam segments were recorded (median duration 1.8 s), confirming reproducibility and patient compliance. Compared with helical delivery in a theoretical DIBH scenario, static-beam IMRT method reduced contralateral exposure, while helical delivery yielded slightly lower cardiac doses; planned beam-on times were significantly longer with helical mode (+54%). Acute side effects were limited to grade 1 (60%) or 2 (10%) dermatitis and grade 1 esophagitis (15%), with no grade ≥3 events at median 2 months. Conclusions: Fully automated DIBH breast radiotherapy on a ring-based accelerator is feasible, safe and compatible with routine workflow. This study provides the first experience supporting automated DIBH gated delivery on a ring-based accelerator.