Assessment of the Effectiveness of a Visual Coaching Device Combined with Auditory Instructions on Reproducibility and Stability in Deep Inspiration Breath-Hold Radiotherapy

<b>Background/Objectives</b>: In left-sided breast cancer radiotherapy, deep inspiration breath-hold (DIBH) reduces radiation dose to the heart; however, its success depends on the patient's ability to maintain reproducible and stable breath-holds. Although visual and auditory guidance systems have been introduced to improve performance, quantitative data on their combined effects remain limited. <b>Methods</b>: We retrospectively analyzed 400 breath-hold sessions in 20 patients undergoing DIBH treatment using synchronized visual and auditory coaching. Real-time respiratory displacement data were used to calculate reproducibility and stability. Temporal trends and correlations between reproducibility and stability were also assessed. <b>Results</b>: The mean reproducibility was 0.51 ± 0.22 mm (range, 0.20-1.10 mm), and the mean stability was 0.77 ± 0.21 mm (range, 0.50-1.16 mm). Both measures showed significant improvement over the course of treatment, indicating a learning effect. Linear regression analysis revealed a significant positive correlation between poorer reproducibility and greater intrafractional instability (R² = 0.26, <i>p</i> = 0.021). Daily cone beam computed tomography-based image-guided radiotherapy demonstrated minimal isocenter shifts, confirming consistent patient setup with DIBH. <b>Conclusions</b>: Combined visual and auditory coaching during DIBH yielded low variability in reproducibility and stability, with progressive improvements over time. These findings highlight the ability of multimodal feedback systems to enhance respiratory consistency and support their integration into clinical practice, optimizing treatment precision.