Commissioning and clinical outcome assessment of a novel surface-guided radiation therapy (SGRT) system at a C-Arm linear accelerator
“Clinical implementation produced statistically significant and clinically meaningful improvements in patient positioning accuracy with anatomical site-specific benefits.”
Authors
Hui Khee Looe, Niklas Felix Hendrik Bartner, Björn Poppe, Kay C. Willborn
Source
https://doi.org/10.48550/arXiv.2604.00589
Background
Surface-guided radiation therapy (SGRT) has become standard-of-care in modern radiotherapy, enabling radiation-dose-free, marker-free patient positioning with sub millimeter accuracy. A novel SGRT system, LUNA 3D (LAP, Lüneburg, Germany) featuring browser-based interface, GPU-accelerated surface reconstruction, high frame rates exceeding 12 Hz, large field-of-view, and virtual laser projection capabilities, has been commissioned and implemented clinically.
Purpose
This study reports comprehensive commissioning procedures and the associated results for the LUNA 3D system and evaluates its clinical impact on patient positioning accuracy for breast and pelvic cancer treatments.
Methods
Commissioning tests were performed, including temperature drift, reproducibility, translational and rotational shift accuracy, camera occlusion assessment during gantry rotation, radiographic verification against cone-beam computed tomography (CBCT), and End-to-End dosimetric testing. Test results were compared using two reference surfaces: one captured by LUNA 3D (SGRT-reference) and the other derived from the CT external structure (SIM reference). A clinical evaluation was conducted to compare CBCT-derived positioning corrections from 192 breast and 259 pelvic treatment datasets acquired before and after the clinical implementation of LUNA 3D, employing Welch’s two-sample t-test and Cohen’s d effect size.
Results
The temperature drift within the operating temperature is found to be smaller than 0.4 mm for all three axes. Commissioning demonstrated submillimeter accuracy using SGRT reference (maximum deviations ≤ 0.3 mm translational, ≤ 0.2◦ rotational). The maximum deviations recorded using SIM-reference are higher (maximum deviations ≤ 0.8 mm translational, ≤ 0.2◦ rotational), attributable to a systematic bias introduced by the CT-derived reference surface. Radiographic verification showed agreement within 1.0 mm between LUNA 3D and CBCT corrections for both reference surfaces. End-to-End testing yielded CBCT residuals of 0.9–1.3 mm with 1.2% dosimetric deviation. All performance metrics satisfied ESTRO-ACROP guidelines. Clinical implementation resulted in significant positioning improvements: for breast treatments, 3D translational vector decreased 28.7% from 7.00 ± 4.35 mm to 4.99 ± 2.75 mm 1 (p < 0.001, Cohen’s d = 0.54); for pelvic treatments, 3D rotational vector decreased 24.0% from 2.31 ±0.96◦ to 1.76 ±0.67◦ (p < 0.001, Cohen’s d = 0.66)
Conclusion
LUNA 3D demonstrated high technical accuracy and reproducibility in commissioning tests, meeting international SGRT guidelines. Clinical implementation produced statistically significant and clinically meaningful improvements in patient positioning accuracy with anatomical site-specific benefits. These findings establish LUNA 3D as a reliable SGRT technology that enhances positioning accuracy in routine clinical practice.