Speaker
Description
Objective
Upright radiotherapy is emerging as an alternative to conventional supine delivery for head and neck (HN) cancer treatment, but immobilisation systems, principally custom-moulded thermoplastic masks, were designed and validated exclusively for supine positioning. The objective of this narrative review was to synthesise evidence on patient comfort during immobilisation and to apply human factors and usability engineering principles to characterise the resulting design gap, establishing a foundation for developing immobilisation systems specific to upright HN radiotherapy.
Methods
Literature was synthesised across five areas: the clinical context of HN cancer and upright radiotherapy delivery, existing evidence on immobilisation reproducibility and clinician ergonomics in upright versus supine positioning, human factors and usability engineering frameworks for medical device design, instruments and approaches for measuring patient comfort in radiotherapy and analogous head-worn device contexts, and principles relevant to designing for non-trained, clinically heterogeneous users. Sources were drawn from radiotherapy, medical physics, regulatory, and occupational ergonomics literature, including usability engineering standards, setup reproducibility studies using upright positioning chairs, and prior human factors evaluations of upright radiotherapy.
Results
While upright positioning itself has been associated with comfort benefits for HN patients, particularly regarding swallowing and breathing difficulties exacerbated by supine posture, these postural advantages have not been shown to extend to the immobilisation interface itself. Comfort in radiotherapy has been studied through nursing-grounded comfort theory, and human factors methods have been used to compare supine and upright modalities broadly, but no study has applied a structured usability engineering methodology, such as IEC 62366-1, to immobilisation device design, and the upright HN configuration remains entirely unaddressed. Reported mask-related anxiety affects 14 to 58 per cent of patients across studies. Contact pressure beneath thermoplastic masks is distributed non-uniformly, with the forehead consistently identified as the region of highest force. Reproducibility studies testing immobilisation devices in upright positioning chairs report interfractional and intrafractional setup errors within clinically comparable ranges to supine delivery, but comfort and tolerability across different chair configurations, including backrest tilt, remain unexplored. General comfort and radiotherapy experience instruments lack the spatially localised, device-specific data needed to guide redesign; the Body Part Discomfort Scale, established in occupational ergonomics, offers a methodological precedent not yet applied in radiotherapy.
Outlook & Discussion
These findings establish that immobilisation for upright HN radiotherapy requires evidence-based redesign, grounded in an established usability engineering methodology and informed jointly by patient comfort, setup reproducibility, and clinician ergonomics, rather than adaptation of supine systems alone. Next steps include an anthropometric characterisation of seated HN positioning across multiple tilt angles, beginning with a healthy volunteer pilot study, to generate the design evidence this review identifies as absent.