ESTRO 2024 - Abstract Book

S3461

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

values (Dx% equals the lowest dose value in the x% subvolume with highest dose) and a homogeneity index (HI), defined as (D1% - D99%)/200cGy.

Results:

Calculation of the autoplan and import in the TPS could be performed within 30 seconds. Dose parameters for different plans and normalizations are shown in Figure 2. When plans were normalized on a prescription point, the whole body mean dose did not vary substantially between plans (Mean+/-1SD: Auto: 207+/-2 cGy; APPA: 208+/- 4 cGy; LRRL: 203+/-11 cGy), however inhomogeneity was significantly higher for the LRRL plan (HI Auto 27%+/-3%; APPA 26%+/-2%; LRRL 50%+/-4%). Brain mean dose was significantly higher for the LRRL plan (Auto: 200+/-2 cGy; APPA: 200+/-6 cGy; LRRL: 241+/-13 cGy). Both the APPA and LRRL plans showed larger variation between patients than the auto plans in the whole-body and brain mean dose as well as D99% and D1%. After normalization of plans to the whole-body volume mean dose, variation between patients for the APPA and LRRL plans was comparable to the auto plans. The maximum absolute change in whole-body D1% and D99% for the auto plans due to shifting the patients by 1 cm with respect to the beams was 2 cGy and 3 cGy respectively, averaged over all patients. The maximum change observed in a patient was 7 cGy and 6 cGy, respectively.