ESTRO 2025 - Abstract Book

S4078

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

ESTRO 2025

Material/Methods: Seven radiation oncologists (ROs) and five radiation therapists (RTTs) evaluated the quality of 50 CBCTs from liver SABR patients using a qualitative scale: 1–Excellent, 2–Correct, 3–Poor, and 4–Very poor. Half of these CBCTs were acquired with FB, half with MANIV-BH, all presented randomly and blindly (Figure 1). Operators scored their ease of performing a tumor-based rigid registration between planning CTs and CBCTs using only translations : 1–Very easy, 2–Easy, 3–Hard, and 4–Very hard. For each CBCT, the standard deviation of the registration vector was calculated across operators in right-left, antero-posterior and supero-inferior directions. The Wilcoxon test compared FB and BH values.

Results: The quality of CBCTs acquired with MANIV-BH significantly received better scores compared to FB (Excellent or Correct : 86% vs 27.0% respectively, p<0.001 Chi-square test, Figure 2A). IGRT was significantly easier using MANIV BH (Very easy or Easy: 67.3% vs 38.7% respectively, p<0.001 Chi-square test, Figure 2B). Standard deviations of registrations were similar between FB and MANIV-BH in the left-right (median: 2.6mm for FB vs. 2.3mm for MANIV BH, p=0.13) and antero-posterior axes (average of 2.7mm for FB vs. 3.1mm for MANIV-BH, p=0.13). In the supero inferior direction, these were greater for FB (median 3.2mm) compared to MANIV-BH (median 2.8mm, p=0.037).