ESTRO 2024 - Abstract Book

S3364

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Material/Methods:

Study the basic dosimetric characteristics of the double-layer arc-shaped ionization chamber matrix: dose linearity, dose rate dependence, and direction dependence. In the dose verification of two three-dimensional detectors, square-field and four-field box irradiation plans were designed; and 10 patient plans for IMRT, 10 VMAT, 10 SBRT, and 10 TOMO were randomly selected. Before verification, the Monte Carlo algorithm is used to compare the verification errors of the two verification devices. Set the dose threshold to 10%, and evaluate the verification results based on the standard gamma pass rates of 3-2%/2mm and 2%/1mm.

Results:

The dosimetric properties of the ionization chamber matrix all performed well. For the standard 2%/1mm gamma pass rate, the measurement results of the square field and four field box plans are both greater than 98.3%; the box plot comparing the dose verification and calculation results of ArcMap and ArcCheck is shown in the figure. The measured dose distribution and the calculated geometric distribution on the corresponding plane showed good consistency. However, compared to ArcCheck, ArcMap has more evaluation points and a smaller distance between detectors, which may be the reason why the verification results are slightly better. However, we found that while ArcMap is more sensitive to dose difference tolerance, ArcCheck is more sensitive to distance difference tolerance.