ESTRO 2024 - Abstract Book

S3307

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Table 1. Penumbra widths of 5 cm x 5 cm profiles, calculated on both sides (left (L) and right (R)), before- and after replacing the x-ray target.

Penumbra X-direction

Penumbra Y-direction

Left [mm]

Right [mm]

Left [mm]

Right [mm]

Before

After

Before

After

Before

After

Before

After

3.34

3.23

3.39

3.30

3.95

4.03

4.03

4.11

Ratio After/Before

Ratio After/Before

Ratio After/Before

Ratio After/Before

0.968

0.972

1.019

1.020

Conclusion:

This work has shown that 6 MV small-field lateral dose profiles are impacted in the flattened region when the x-ray target is replaced. The penumbra of larger fields indicates a decrease in spot size in the X-direction and an increase in spot size in the Y-direction. OF were unchanged before and after x-ray target replacement and this was attributed to the effect of the increase/decrease of the spot size, cancelling each other out. The DLG was shown to increase after the replacement and this was attributed to the decrease of spot size in the X-direction. It is recommended to perform a rigorous verification after replacing the x-ray target, especially for linacs dedicated for small-field treatments.