ESTRO 2025 - Abstract Book

S4071

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

ESTRO 2025

Data was not normally distributed, non-parametric tests were performed (PRISM, GraphPad, USA). Median (IQR) independent prostate interfraction motion, for 799-fractions, measured 0.1mm (-0.4 - 0.6) left-right (LR), 0.3mm (-1.5 - 2.0) superior-inferior (SI) and -0.3mm (-2.2 - 1.5) anterior-posterior (AP). Median (IQR) intrafraction total motion , over 197-fractions, measured -0.1mm (-0.7 - 0.5) LR, 0.0mm (-1.2 - 0.5) SI and -0.7mm (-2.1 - 0.9) AP. SI and AP intrafraction total motion was significantly lower, p<0.0001 in this group, compared to the enema cohort, with median (IQR) motion of 0.0mm (-0.7 - 0.5) LR, 0.7mm (-0.4 - 1.7) SI and -1.2mm (-2.6 - -0.3) AP. Intrafraction total motion range was greatest in the AP direction, range was higher in all directions for the enema cohort ( Figure 1 ).

Rectal volume per timepoint was not significantly different between cohorts. CBCT rectal volume and independent prostate intrafraction motion had a weak but significant correlation SI ((r s (197) = 0.276, p<0.0001 )) and AP ((r s (197) = 0.271, p<0.0001 )) ( Figure 2 ).

Conclusion: