ESTRO 2023 - Abstract Book

S1759

Digital Posters

ESTRO 2023

Results 223 dose lines have been evaluated. Figure 2a and 2b show the average over all detectors of measured depth dose line versus average lines calculated in TPS for CT and VCT. In Figure 2c the difference between measurement and calculation of R80 parameter for every detector is shown. Figure 2d shows a heat map of error ranges in VCT calculation with errors larger than 2mm in dark blue (underestimation) and dark red (overestimation). They are located in air-tissues interfaces and in high density bone areas. For calculation on real CT, average of R90, R80 and R50 TPS-MatriXX differences is 0.11 mm and standard deviation (SD) of 0.89 mm. Assuming uncertainties of 0.2mm in R-values evaluation, 0.3mm in patient setup and k-factor of 2, would yield an estimated uncertainty in range calculation of about 1.6%, normalizing at 10 cm of physical phantom thickness

For VCT calculation, mean range error is -0.19 mm and SD of 1.51 mm with an estimated range uncertainty of 2.9%.