ESTRO 2024 - Abstract Book

S3263

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

With the high equivalence of the solid water in calculations and measurements of the slabbed phantom at 10 cm depth, we proceeded to calculate and measure the dose in the cylindrical Advanced Electron Density phantom as a true E2E test. The measured doses deviated by no more than 1% compared to the calculated dose in RayStation based on CT HU for photon beam energies up to 10 MV, and for 18 MV, we found agreement between the calculated and the measured dose to be within 3%. To achieve this level of accuracy, it was required to apply the phantom dose conversion factor to the measurement, as determined using the slab phantom.

Conclusion:

With the determination of a phantom dose conversion factor, the CT HE Solid Water has been found useful for constancy checks of accelerator output when manufactured as slabs. In the cylindrical shape of the Advanced Electron Density phantom, the material is useful for true E2E testing where the HU values from a CT scan of the phantom are used to calculate the dose in the TPS. Such E2E test with a static beam should be complemented by a more challenging test of IMRT or VMAT delivery on a high-resolution diode array or using film dosimetry to verify the geometric accuracy of high-precision treatments.

Keywords: End-to-end, Solid Water, TRS-483