ESTRO 2024 - Abstract Book

S3403

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Figure 1: Perturbation correction factors (left axis) and the beam quality correction factor k Q (right axis) of the Semiflex3D ionization chamber as a function of measurement depth for the ZAP-X beam quality with the reference 25 mm cone diameter

Conclusion:

The beam quality correction factor k Q for reference dosimetry at the ZAP-X using the 25 mm diameter reference cone has been studied for measurement depths between 0.4 and 50 mm. At the depth of dose maximum (7 mm) , k Q is larger than unity, mainly attributed to the strong depth dependence of the gradient perturbation correction factor. Based on these results, it is therefore recommended to perform the reference dosimetry at the ZAP-X system at depths larger than 15 mm (up to the investigated 50 mm) to minimize the associated uncertainty due to chamber’s positioning, where the k Q can be considered as depth-independent. For these depths, a k Q value of 0.994(2) can be used.

Keywords: small field dosimetry, radiosurgery, Semiflex3D

References:

[1] Tekin, T., Blum, I., Delfs, B., Schönfeld, A. B., Poppe, B., & Looe, H. K. (2022). The magnetic field dependent displacement effect and its correction in reference and relative dosimetry. Physics in Medicine & Biology, 67(4), 045004.