Speaker
Description
Objective.
Extending upright particle therapy to moving targets requires more than reproducible positioning: respiratory guidance, external motion monitoring and reliable external-to-internal mapping must operate as an integrated motion-management workflow. This doctoral project investigates these components sequentially, from human-in-the-loop respiratory guidance to stress-testing of surrogate-based internal-motion prediction, with the long-term aim of developing a VR-enabled respiratory guidance and motion-management system for upright treatment.
Methods.
In a volunteer study, 11 healthy participants performed guided and unguided breathing tasks in supine and upright postures while respiratory motion was monitored optically. The study characterised guidance-related changes in respiratory behaviour and posture-related changes in thoracoabdominal organisation. These measurements subsequently parameterised a volunteer-informed synthetic benchmark comprising 83 quality-controlled trials, five controlled external-to-internal correspondence families, seven respiratory and postural stress scenarios and eleven prediction models. Mapping robustness was evaluated using absolute prediction error, realised internal-motion scale, scale-adjusted error and a coherence-based coupling-fidelity descriptor.
Results.
Visual guidance improved respiratory task execution and regularity, while upright posture altered thoracoabdominal organisation rather than producing a uniform deterioration in breathing performance. In the mapping benchmark, realised motion scale and external-to-internal coupling fidelity emerged as distinct determinants of robustness: absolute error increased strongly with target-motion scale, whereas coupling fidelity was largely scale-independent and was associated with scale-adjusted predictability. During clean breathing, upright posture did not show poorer relative mapping performance than supine posture after motion-scale normalisation. By contrast, postural sway produced a disproportionate upright degradation that persisted after normalisation, identifying non-target postural contamination as a specific failure mode. Guided breathing was associated with increased realised motion scale and, consequently, higher absolute mapping error, while relative mapping fidelity remained largely preserved.
Outlook $\&$ Discussion.
These studies show that respiratory regularity alone is insufficient to define a robust upright motion-management strategy. Future system design should jointly consider respiratory behaviour, motion scale, postural contamination and mapping confidence, supported by posture/sway sensing and an explicit verification or fallback pathway. Future work will translate these findings into a VR-enabled visual-guidance and motion-management platform for upright treatment of moving targets, while validating external-to-internal relationships against measured patient internal motion and investigating the mechanisms through which interactive guidance influences respiratory behaviour, engagement and patient empowerment.
The UPLIFT project is funded by the European Union under Grant Agreement No. 101168955.