ESTRO 2025 - Abstract Book

S4092

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

ESTRO 2025

There are no clear biases in either single-isocenter and multi-isocenter scenarios, with all p -values > 0.05. Furthermore, there were no statistically significant differences in terms of variability of matching along lateral, longitudinal, vertical, and yaw between single-isocenter and multi-isocenter approaches. However, significantly greater variability was found in pitch and roll in the single-isocenter scenario ( p -value=0.03 and p -value<0.01). The vast majority (>90%) of the absolute differences in matching was within +/- 1 mm or +/- 1 degree in both scenarios for lateral, longitudinal, and yaw axes (Table 1). For vertical, roll, and pitch, the fraction of the differences within these ranges was 64%-91%. Agreement between observers was excellent for lateral, longitudinal, vertical, and yaw in both scenarios. However, in the multi-isocenter scenario, agreement for roll and pitch was slightly higher than in single-isocenter (ICC=0.90 and 0.97), although the agreement for pitch and roll in single-isocenter remained strong (ICC = 0.79 and 0.85). Conclusion: Our findings indicate that both single- and multi-isocenter techniques achieve similarly accurate patient positioning, with no significant systematic biases observed in translational or rotational shifts. However, single-isocenter positioning showed greater variability in pitch and roll, which may require additional attention to rotational alignment when this technique is used. Nevertheless, the inter-observer agreement was high in both techniques, showing the reliability of either method in clinical practice. Our results support the single-isocenter technique as an efficient approach for treating multiple targets, enhancing both patient throughput and comfort.

Keywords: IGRT, Single Iso, multiple volumes

2647

Digital Poster Evaluation of automatic versus manual Cone-Beam Computed Tomography registration in linac-based prostate Stereotactic Body Radiation Therapy Valerio Pisoni 1,2 , Nicolò Galluccio 2 , Denis Panizza 3,2 , Stefano Arcangeli 1,2 1 Department of Radiation Oncology, Foundation IRCCS San Gerardo dei Tintori, Monza, Italy. 2 School of Medicine and Surgery, University of Milano Bicocca, Milano, Italy. 3 Medical Physics Department, Foundation IRCCS San Gerardo dei Tintori, Monza, Italy