S2704
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
in conjunction with SGRT for patient setup and intrafractional monitoring. Material/Methods: A total of seventeen post-treatment CBCT images were analysed from five patients who underwent SRS using an open face thermoplastic mask. Each patient was set up using SGRT with tolerances set at 1mm and 1 degree in each direction. A pre-treatment, post- correction and post-treatment CBCT was acquired on each fraction. Translational and rotational variations were retrospectively measured between post- correction and post-treatment CBCTs to assess intrafractional stability. Results: The reported absolute mean translational and rotational variations on post-treatment imaging across patients demonstrated minimal motion between post- correction CBCT and post-treatment CBCT. The mean translational variations across all fractions were; 0.03 cm (X), 0.02 cm (Y), and 0.01 cm (Z). Rotational (ROT) variations were 0.21° (X), 0.06° (Y), and 0.18° (Z). The largest individual rotational variation was observed in patient 2, with 0.3° of roll. See Table 1 for results. PatientMean translations (cm)Mean ROT (°)XYZXYZ10.000.000.030.000.030.0020.000.030.000.30 0.100.2730.070.070.030.030.230.140.040.020.000.240.
References: 1. Kovács P, Szita E, Schvarcz K, Kamu S, Kalincsák J, Kovács Á, et al. [Setup margin for head-and-neck cancer patients receiving 2D-2D and 3D image-guided intensity-modulated radiation therapy]. Orv Hetil. 2018;159(29):1193-200.2. Kang H, Lovelock DM, Yorke ED, Kriminski S, Lee N, Amols HI. Accurate positioning for head and neck cancer patients using 2D and 3D image guidance. J Appl Clin Med Phys. 2010;12(1):3270.3. Li H, Zhu XR, Zhang L, Dong L, Tung S, Ahamad A, et al. Comparison of 2D Radiographic Images and 3D Cone Beam Computed Tomography for Positioning Head-and-Neck Radiotherapy Patients. International Journal of Radiation Oncology, Biology, Physics. 2008;71(3):916-25. Keywords: Proton Therapy, Setup variations, Image guidance Digital Poster 1042 Open-Face SGRT-Guided SRS: Combining Accuracy and Patient Comfort Orla McKivitt 1 , Michael Roche 1 , Martin Higgins 1,2 , Micheal O'Cathail 1 , Oisin O'Sullivan 1 , Carol McGibney 1 1 Radiation Oncology, Cork University Hospital, Cork, Ireland. 2 Cancer Research@UCC, University College Cork, Cork, Ireland Purpose/Objective: Stereotactic radiosurgery (SRS) requires precise treatment delivery, achieved through strict immobilisation and robust image-guideance (IGRT) protocols. Traditionally, immobilisation for SRS has relied on frame-based systems or reinforced thermoplastic masks to minimise intrafractional motion [1-2]. Surface-guided radiotherapy (SGRT) provides real-time patient monitoring, enabling intrafractional tracking of patient position in six- degree-of-freedom (6DoF). This has the potential to provide improved treatment accuracy while using a less invasive, open-face immobilisation system. This study aims to evaluate patient positioning accuracy on cone-beam CT (CBCT) when using an open-face mask
020.1050.030.000.000.030.000.07Mean (all fractions)0.030.020.010.210.060.18Standard
Deviation0.050.040.030.330.090.21Table 1: Absolute mean translational and rotational variations, Median and Standard Deviation Conclusion: This study demonstrates that integrating SGRT with open-face mask immobilisation achieves submillimetre translational and sub-degree rotational accuracy in SRS. These results demonstrate the feasibility and accuracy of this protocol with a potential reduction in patient discomfort compared to traditional frame-based or reinforced thermoplastic immobilisation systems. In summary, SGRT-guided open-face immobilisation provides an accurate and patient-friendly solution for SRS delivery. References: 1.Babic S, Lee Y, Ruschin M, Lochray F, Chan G, Tsao M, et al. To frame or not to frame? Cone-beam CT-based analysis of intrafraction motion during intracranial stereotactic radiosurgery. J Appl Clin Med Phys. 2018 Jan;19(1):111–120. doi:10.1002/acm2.122512.Carminucci A, Nie K, Weiner J, Hargreaves E, Danish SF. Assessment of motion error for frame-based and noninvasive mask-based fixation using the Leksell Gamma Knife Icon radiosurgery system. J Neurosurg. 2018;129(Suppl 1):133–139. doi:10.3171/2018.7.GKS181516 Keywords: SRS, Open-face, Surface Guided radiotherapy
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