Commissioning and clinical positioning assessment of a novel surface-guided radiation therapy (SGRT) system at a C-Arm linear accelerator.

backgroundSurface-guided radiation therapy (SGRT) has been increasingly adopted in modern radiotherapy, enabling radiation-dose-free, marker-free patient positioning with high accuracy. A novel SGRT system, LUNA 3D (LAP, Lüneburg, Germany), featuring a browser-based interface, GPU-accelerated surface reconstruction, high frame rates, 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.

methodsCommissioning tests were performed, including thermal 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 in the periods before and after the clinical implementation of LUNA 3D, employing Welch's two-sample t-test and Cohen's d effect size.

resultsThe thermal drift within the operating temperature range is ≤0.4 mm for all three axes. Across the reproducibility and translational/rotational shift tests, maximum deviations were ≤0.3 mm translational and ≤0.2° rotational with the SGRT-reference, and ≤0.8 mm translational and ≤0.2° rotational with the SIM-reference, the latter attributable to the difference 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 evaluated performance metrics are compared to the ESTRO-ACROP and AAPM TG-302 guidelines' tolerances. 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 (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).

conclusionsLUNA 3D was successfully commissioned, 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.