Maskless head and neck radiotherapy using surface-guided radiation therapy: initial clinical feasibility of real-time setup, intrafraction monitoring, and automatic beam-hold

Abstract

Background

Thermoplastic immobilization remains standard for head and neck radiation therapy, but rigid face masks may produce clinically meaningful anxiety, claustrophobia, and treatment intolerance in some patients. Surface-guided radiation therapy (SGRT) provides non-ionizing surface setup guidance and continuous intrafraction motion monitoring, potentially enabling reduced-immobilization treatment approaches.

Purpose

To describe and initially evaluate the clinical feasibility of a thermoplastic-maskless head and neck radiation therapy workflow using a posterior dorsal shell, SGRT-guided setup, cone-beam computed tomography (CBCT) verification, and real-time intrafraction monitoring with automatic beam-hold.

Methods

Ten patients with head and neck cancer were treated without a thermoplastic face mask. Patients were positioned in a posterior dorsal shell. Daily setup began with SGRT followed by CBCT verification and couch correction. During delivery, SGRT (AlignRT v6.3, Vision RT, London, UK) monitored head position in six degrees of freedom (6DoF); automatic beam-hold was triggered when translational displacement exceeded 2 mm or rotational displacement exceeded 2°. Post-treatment CBCT and SGRT log files were reviewed for every fraction to characterize residual displacement, threshold events, and repositioning. Intrafraction motion and residual displacement were summarized as medians with interquartile range (IQR).

Results

Across 330 delivered fractions, sgrt-recorded intrafraction motion was small:: per-axis signed real-time deltas had a median [IQR] of 0.10 mm [−0.15, 0.30] translationally and 0.10° [−0.05, 0.20] rotationally. No fraction had a mean real-time delta exceeding the ± 2 mm/ ± 2° tolerance, and automatic beam-hold interruptions occurred in approximately 2% of fractions (7 of 330); no fraction was abandoned. Per-axis post-treatment CBCT residuals were −0.01 mm [−0.04, 0.05] translationally and 0.15° [−0.40, 0.55] rotationally. All patients completed the maskless course; 3 of 10 had previously declined or been unable to tolerate mask-based treatment, and all reported the maskless workflow to be well tolerated on an end-of-course questionnaire.

Conclusions

A thermoplastic-maskless head and neck workflow using SGRT, CBCT verification, predefined beam-hold thresholds, and dorsal shell support was feasible in this initial 10-patient experience, maintaining small observed intrafraction motion while directly addressing mask intolerance. Larger prospective evaluation with validated patient-reported outcomes, dosimetric analysis, and multi-institutional QA is warranted.