Surface-guided radiotherapy setup using an open-face mask for head and neck cancer; the OPEN trial approach

Head and neck (H&N) radiotherapy requires reproducible immobilisation to maintain geometric accuracy; however, conventional thermoplastic masks are associated with patient discomfort and anxiety. Surface-guided radiotherapy (SGRT) provides non-ionising, real-time guidance for patient positioning and intrafraction monitoring from setup through to treatment completion. However, its application in H&N radiotherapy requires careful consideration of the complex and independently mobile anatomy of the face, neck and shoulders. This MethodsX protocol accompanies the OPEN Phase III randomised control trial and describes the technical and clinical workflow for the SGRT-supported open-face immobilisation arms. It provides a reproducible framework for centres seeking to implement the OPEN approach.•Initial alignment is performed using SGRT postural video guidance based on the patient's external contour.•A facial setup ROI is used for head positioning.•A larger monitoring ROI encompassing the face, neck and upper thorax is then used to refine lower neck and shoulder position while maintaining facial alignment, and for continuous intrafraction monitoring during treatment.The OPEN trial demonstrated that this workflow maintained setup accuracy, intrafraction stability and clinical efficiency while supporting open-face immobilisation. This companion protocol provides the practical detail required to reproduce the workflow in clinical practice.