ESTRO 2024 - Abstract Book

S4849

Physics - Quality assurance and auditing

ESTRO 2024

The mean DTA in the film measurements was 0.82mm [0.34 – 1.7 mm] with 43/60 plans having a DTA <1mm. When stratified for Dm,m, Dw,m and Dw,w these were 1.0mm, 0.7mm and 0.8mm, respectively. The difference in DTA grouped by dose reporting mode was also statistically significant (chi-squared = 6.77, p- = 0.034). Seventy-two percent of centres achieved a treatment accuracy of <1mm and all centres were within 2mm. All audited centres used a PTV/PRV margin ≥2mm. Gamma analysis had a mean pass rate of 89.5% [68.7 – 100%] and 87.3% [54.6 – 100%] for 3%/2mm and 5%/1mm, respectively. When stratified for Dm,m, Dw,m and Dw,w, this was 76.9%, 92% and 89.4% (5%/1mm) and 80.4%, 91.7% and 91.8% (3%/2mm) respectively. A scatter plot of these results per plan can be seen in Figure 2.