ESTRO 2024 - Abstract Book

S4192

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

For the anthropomorphic head phantom, the spot-wise PGI range shifts were larger with mean range shifts of -0.89, -0.53 and -0.24 mm and standard deviations (2σ) of 1.01, 0.54 and 0.20 mm for the CBCT, cCBCT and vCT, respectively. For the post-processed datasets with improved image quality (cCBCT, vCT), the PGI simulation was closer to the simulation on the fan-beam CT. The observed spot-wise deviations of PGI simulations on CBCT data compared to simulations on the fan-beam CT followed again closely the deviations of the corresponding IDD calculations (correlation ρ=0.74) (Figure 2). Hence, the changes in material composition (additionally influencing spectral PG emission) had a marginal effect on the PGI-retrieved ranges. For the corrected CBCT and the virtual CT, 98.5% of the PGI-retrieved ranges differed less than 1 mm from the IDD retrieved ranges.

Conclusion:

In this phantom study, we have shown that CBCT data are suitable for PGI reference simulation where CBCT-based range prediction was correct. PGI range shifts and IDD range shifts showed a good correlation, revealing negligible additional impact of uncertainties in material assignment on PGI simulations.