Enhancing patient positioning precision: a comparative analysis of surface-guided radiation therapy systems

This study evaluated the positioning precision of various surface-guided radiation therapy (SGRT) systems to enhance patient setup accuracy in radiotherapy. A female torso phantom (Electronics Research & Development Corporation) was employed to assess and compare the accuracy of four SGRT devices: AlignRT (Vision RT, United Kingdom), Catalyst (C-rad AB, Sweden), VOXELAN (Electronics Research&Development Corporation, Okayama, Japan) and ExacTrac Dynamic (Brainlab, Germany). The external body contour was used as a reference surface image. For positioning precision measurement, the treatment couch was moved in predetermined directions, distances, and angles and the amount of movement evaluated by the SGRT system was compared to the known amount. The results demonstrated that while all SGRT systems-maintained positioning errors within nominal precision thresholds (1 mm for translational movements and 1° for rotational movements), significant inter-device variability was observed. AlignRT and ExacTrac Dynamic exhibited superior accuracy across all movement categories. In contrast, Catalyst demonstrated a higher fraction of positioning errors (16.0%) in the abdominal region, primarily due to lower camera resolution and the use of a deformable registration algorithm. VOXELAN displayed increased errors in the anterior-posterior direction, likely due to interpolation-based surface estimation. These findings highlight the need for standardized evaluation protocols to ensure fair comparisons and improve clinical adoption of SGRT systems.