ESTRO 2024 - Abstract Book

S3446

Physics - Dose calculation algorithms

ESTRO 2024

Variant H1 resulted in the irradiation of almost all the circulating blood (V >0Gy = 99.8 ± 0.7%) at the end of VMAT treatment, at a mean dose of 309.9 ± 74.7 mGy (Table 1 and Fig. 1). Taking into account lymphocytes recirculation in H2 variant, the fraction of lymphocytes receiving a non-zero dose dropped to 40.4 ± 10.2%, with a lower mean dose estimated at 52.6 ± 21.1 mGy, especially because irradiated lymphocytes passed through the irradiation field only 1.58 ± 0.91 times on average due to slow recirculation between lymphoid organs in the M 1 model. The most realistic scenario, including the OOF dose component (variant H3), showed that almost all the lymphocytes (97.6 ± 2.5%) were irradiated at the end of the VMAT treatment, mostly due to the OOF dose (mean dose equal to 265.6 ± 48.5).

Average dose

D2%

D50%

V >0.125Gy (%)

Model V >0Gy (%)

(mGy)

(mGy)

(mGy)

to all lymphocytes

to all lymphocytes

to all lymphocytes

to V>0Gy

to V>0Gy

to V>0Gy

87.6 ± 10.4

699.1

±

H1

99.8 + 0.7

309.9 ± 74.7 309.9 ± 74.7

285.4 ± 71.3 285.9 ± 71.1

699.4 ± 215.3

215.0

3.5 ± 2.1

H2

40.4 + 10.2

19.8 ± 4.8

52.6 ± 21.1

0.4 ± 0.9

34.3 ± 15.6

161.8 ± 55.6 223.7 ± 116.5