ESTRO 2024 - Abstract Book

S5601

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

Phase 2 will encompass:

1. Optimizing MB: in cooperation with physicians and RTTs, physicists will define and contour new match structures, which could for example include:

a. "Absolute minimum": complies with constraints, max. 1 fraction at this size. b. "Acceptable": well within constraints, acceptable for all fractions.

2. Updating worksheet and instructing RTTs on scoring bladder volume using new structures, and establishing guidelines for necessary actions.

Results:

RTT consensus when scoring bladder volume was 95%.

Bladder volume was scored by comparing daily filling to PB and MB volumes. In Phase 1A, average MB was 55% of PB, mean number of fractions larger than MB was 28,5. In Phase 1B, average MB was 52% of PB, mean number of fractions larger than MB was 32. In Phase 1C, average MB was 66% of PB, mean number of fractions larger than MB was 29,5.

Assessing the effects of the new regime is complicated by the fact that our current definition of MB does not necessarily indicate acceptable dose.

As seen in Fig. 2, in one case, although the volume of MB was 90% of PB, it was barely within constraints. In another example, an MB of only 33% of PB volume was more than acceptable.