Accuracy and workflow efficiency of surface-guided open-face vs. closed-face masks in SRT/SRS for brain metastases

Open-face masks (OFMs) provide comparable immobilization or superior accuracy with greater patient comfort than closed-face masks (CFMs), but their impact on workflow efficiency in stereotactic radiotherapy (SRT) and radiosurgery (SRS) for brain metastases remains unclear. This study compared immobilization accuracy, setup-related interruptions, and workflow efficiency of OFM with surface-guided radiotherapy (SGRT) versus CFM.

We retrospectively analyzed 180 consecutive SRT/SRS courses for brain metastases (March 2020-February 2024) using OFM/SGRT or CFM. Setup accuracy, repeat imaging, repositioning, and session duration were extracted from treatment and CBCT records. Translational and rotational errors were compared using Mann-Whitney U-tests; session times with t-tests.

OFM/SGRT achieved smaller mean x- (1.1 ± 1.0 vs. 1.3 ± 1.1 mm) and z-axis displacements (0.7 ± 0.7 vs. 1.3 ± 1.1 mm) but slightly larger y-axis displacement (2.0 ± 1.7 vs. 1.4 ± 1.4 mm; all p < 0.01). Rotational stability was superior (pitch 0.10° vs. 0.74°, yaw 0.64° vs. 1.10°, roll 0.57° vs. 0.74°; all p < 0.01). Setup-related issues were fewer with OFM/SGRT (2 vs. 7), while patient (5 vs. 3) and technical (2 vs. 1) issues were slightly higher. Mean session times were similar for initial (21.88 vs. 21.87 min; p = 0.98) and subsequent fractions (16.92 vs. 16.74 min; p = 0.47).

OFM combined with SGRT provides improved rotational stability and comparable translational setup accuracy overall compared with CFMs in SRT/SRS, despite inferior longitudinal (y-axis) accuracy. OFM/SGRT was associated with fewer setup-related deviations during initial positioning. While overall session durations were comparable between workflows, reduced setup-related interruptions were observed with OFM/SGRT. These findings support OFM/SGRT as a clinically viable and patient-friendly alternative to conventional CFMs in SRT/SRS.