ESTRO 2025 - Abstract Book

S4124

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

ESTRO 2025

The histogram shows 94.04% of SGRT rotations and 91.1% of TTB rotations were within the setup threshold of +/- 2° (Figure 1).

The root cause analysis revealed that large rotational CBCT registration results during setup with SGRT were linked to factors such as Region of Interest placement, alterations in external contour, shape changes due to bladder volume variations, and positional inconsistencies such as the patient being more/less tense than the reference scan. These factors were observed in cases identified within the cohort. Conclusion: Results demonstrate that Varian’s IDENTIFY system provides at least comparable rotational setup for prostate cancer radiotherapy patients in comparison to TTB alignment, suggesting that SGRT setup is sufficiently accurate to replace traditional tattoo skin markings for this treatment site.

Keywords: SGRT, patient setup, positioning