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

## TL;DR

This study shows that automated deep-inspiration breath-hold breast radiotherapy is feasible, efficient, and safe for patients, with minimal side effects and good treatment outcomes.

## Contribution

The first experience of automated DIBH gated delivery on a ring-based accelerator for breast irradiation is presented.

## Key findings

- Automated DIBH breast radiotherapy was completed by all 20 patients with consistent PTV coverage and OOI objectives met.
- Workflow efficiency was demonstrated with a median fraction duration of 10 minutes and high patient compliance confirmed by 3511 reproducible breath-holds.
- Acute side effects were mild to moderate, with no severe reactions observed at 2 months.

## Abstract

•Study performed on twenty patients receiving locoregional breast irradiation.•Median fraction duration was 10 min, including setup, imaging and delivery.•Over 3500 reproducible breath-holds confirmed patient compliance and feasibility.•Only mild to moderate early side effects observed and no severe reactions.

Study performed on twenty patients receiving locoregional breast irradiation.

Median fraction duration was 10 min, including setup, imaging and delivery.

Over 3500 reproducible breath-holds confirmed patient compliance and feasibility.

Only mild to moderate early side effects observed and no severe reactions.

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.

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.

All patients completed DIBH treatment. PTV coverage was consistently achieved (mean V95%: 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.

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.