ESTRO 2025 - Abstract Book

S4090

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

A Python algorithm was developed to (i) automatically detect ArUCo markers in each camera image and (ii) infer the distance between markers across multiple camera images, as seen in Figure 1c. Contrary to most measurement systems, the proposed method does not require camera calibration, and any camera with sufficiently high image resolution can be used. Rigorous validation experiments, using simulated data, were performed to test the algorithm’s measurement accuracy for different marker separations and camera-to-marker distances.

Results:

Accuracy validation test results show that the proposed system has a measurement percentage error of 1%. The mean measurement error was below 1mm for all marker separations below 2cm. These errors are comparable to those of commercial SGRT systems, where similar measurement errors are reported (Saito et al. 2022, Rudat et al. 2023). Further experiments also justified the absence of a calibration process. Results showed that camera perspective effects and lens distortion were both negligible and had no significant effect on the measurement error. Conclusion: To conclude, this work developed and verified a low-cost, flexible, and accurate technique to study new immobilisation systems for radiotherapy and their associated positional reproducibility/stability. The algorithm developed has been packaged and documented for easy installation/use by other researchers. References: Hegarty, S. et al. (2022) ‘Please place your seat in the full upright position: A technical framework for landing upright radiation therapy in the 21st Century’, Frontiers in Oncology , 12. doi:10.3389/fonc.2022.821887. Saito, M. et al. (2022) ‘Evaluation of the detection accuracy of set-up for various treatment sites using surface-guided radiotherapy system, voxelan: A phantom study’, Journal of Radiation Research , 63(3), pp. 435–442. doi:10.1093/jrr/rrac015. Rudat, V. et al. (2023) ‘Setup accuracy and margins for surface-guided radiotherapy (SGRT) of head, thorax, abdomen, and pelvic target volumes’, Scientific Reports , 13(1). doi:10.1038/s41598-023-44320-2. Keywords: Immobilisation, Reproducibility, Computer Vision