ESTRO 2024 - Abstract Book

S5598

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

ESTRO 2024

Well-setup and bad-setup groups were composed of 278 patients (1677 fractions) and 88 patients (723 fractions), respectively. Mean (maximum) intra-fraction errors found were (mean± 1SD) 2.1 ± 1.3 mm (1.9 ± 2.0 mm) and 2.2± 2.4 mm (2.5±6.1 mm) for well-setup and bed-setup respectively. Considering the differences in standard deviation between the two groups, we quantified the percentage of fraction with a mean (maximum) error higher than 5 mm, resulting in 1.37% vs 3.18% (2.92% vs 5.12%) for well- and bad-setup, respectively. This difference resulted statistically significant with the chi-square test (p=0.003 and p=0.008 for mean and maximum error, respectively). Figure 1 shows intra-fraction errors over the three directions as a function of treatment time for each group: for all (Figure1A (mean errors) and Figure1B (maximum error)), well-setup (Figure1C (mean errors) and Figure1D (maximum error)) and bad-setup (Figure1E (mean errors) and Figure1F (maximum error)). Anova test showed a significative correlation with the treatment duration for all groups analysed (p<0.001 in all cases), confirming an increase of intra fraction error with session time in all groups of patients. Figure 2 shows the intra-faction errors as a function of fraction number (between 1st and 13th, common fractions in both fractionation schemes) for all datasets, showing a slightly increasing trend with the fraction number. Anova test confirmed a significative correlation between intra-fraction error and treatment fraction number for all groups analysed and for both mean and maximum errors (p<0.001 in all cases).