ESTRO 2024 - Abstract Book

S1855

Clinical - Mixed sites, palliation

ESTRO 2024

107% of prescribed dose, >98% volume receives 95% of prescribed dose, <50% volume receives 102% of prescribed dose and > 50% volume receives 99% of prescribed dose. Treatment plans no longer sufficed when these criteria were not met. Differences between the true delivery times of clinically used and optimal treatment planning technique were tested for significance (p < 0.05) using a Wilcoxon signed-rank test. Dosimetric plan quality was evaluated using hospital patient specific quality assurance (PSQA) protocol; gamma pass-rate >95% on ArcCHECK (Sun Nuclear).

Results:

Reduction of MDT reduces irradiation time the most, while maintaining treatment plan quality. As seen in figure 1 the addition of a smaller arc or higher energy doesn’t significantly reduce the total delivery time (TDT).

Figure 1: The average TDT [s] per step MDT, for MDT, MDT + arc and MDT + 10 MV FFF, where the MDT 200 is the clinical dose planning. Note: the y-axis starts at 100 s and the x-axis starts at 200 s and decreases.

Planning techniques with different arc- length, energy or VGS didn’t maintain treatment plan quality and were excluded for the rest of this study. Furthermore, when the MDT is lowered below 100 seconds, plan quality no longer fulfills the requirements (Figure 2).