Work

Cardio-respiratory-gated proton pencil beam scanning for cardiac ablation: workflow and end-to-end validation

Year: 2026

Type: article

Abstract: Background Stereotactic Arrhythmia Radiotherapy (STAR) offers a non-invasive alternative for ventricular tachycardia ablation, yet motion management remains a critical challenge. While respiratory gating is established, cardiac gating requires a dedicated workflow and gating device. Methods This study establishes and validates an end-to-end workflow for cardiorespiratory gated proton STAR in six healthy swine. Key innovations include a novel pencil-beam scanning (PBS) controller enabling mid-spot beam pausing and resumption, and the integration of CardioKit, an ultrasound-based image-guidance system for real-time soft-tissue tracking. The workflow was evaluated by comparing single-gated (respiratory only) and dual-gated (cardiorespiratory) delivery strategies, assessing system latency, dosimetric accuracy on dynamic phantoms, and motion tracking fidelity against 4D-CT benchmarks. Results The upgraded PBS system demonstrated a gate response latency of <550 µs, effectively mitigating interplay effects in dynamic phantom measurements through gated beam deliveries. CardioKit provided respiratory motion traces highly correlated with 4D-CT data (Pearson r > 0.97) and responded to arrhythmic events within 5 ms. In vivo , dual-gating restricted delivery to the diastolic window (70–100% R–R), which resulted in a reduction in the Internal Target Volume (ITV) expansion by a mean of 45% compared to single-gating (19% vs. 64%), thereby substantially sparing healthy myocardium. Although dual-gating increased total beam-on time, the mid-spot interrupt capability ensured robust dose accumulation without treatment aborts. Conclusion The workflow for imaging, treatment planning, and cardiorespiratory-gated beam delivery was viable for treating all six subjects. The PBS system responded to gating commands < 550 µs and CardioKit responded to irregularities in heartbeat in <5 ms. Cardiorespiratory gating enabled an average 45% reduction in target expansion due to cardiac motion. Comparison of CardioKit respiratory motion traces with respiratory 4D-CT yielded differences of 1.1-1.4 mm in total motion amplitude and 0.97-0.99 Pearson correlation factor. These findings are valuable for establishing a workflow for cardiorespiratory-gated STAR treatment with CardioKit.

Source: Frontiers in Oncology

DOI: 10.3389/fonc.2026.1923998