S1797
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Medical Systems, Palo Alto, CA) was used. The Eclipse script called DoseConverter for EQD2 calculation was evaluated (https://medicalaffairs.varian.com/esapi- projects). For an EBRT plan with a total dose (D) and n fractions, the script calculates the EQD2 using the well- known formula EQD2 = D (a/b + D/n) / (a/b + 2), where a/b is the alpha-beta parameter. Ten prostate EBRT plans (prescribed dose: 5 × 7.25 Gy) were randomly selected. The values for the metrics “Dx%” and “D1cc” (see Figure 1) were retrieved from each plan and converted into EQD2 values using the EQD2 formula (“true values”). Values of a/b = 1.5 Gy and 3.0 Gy were used for the planning target volume (PTV) and organs- at-risk (OARs), respectively. The script was executed using 2 approaches: Simultaneously entering the a/b values for the PTV and OARs and activating the “forced” option of the script. The options called “a/b ascending order” and “a/b descending order” of the script were selected to obtain the EQD2 values for PTV and OARs, respectively.Entering only an a/b value to the whole external patient contour (“body” structure), while the a/b values for the remaining structures were left blank. The option called “a/b ascending order” was used, and the “forced” option was not activated. To obtain the EQD2 values for the PTV and OARs, a/b values of 1.5 Gy and 3.0 Gy were entered, respectively.Validation of the EQD2 script was performed by comparing the EQD2 values computed by the script with the respective true values. Results: Figure 1 shows the mean differences (over 10 cases) found between the script-based EQD2 values and the corresponding true values.Unacceptably high differences were found when the script was executed using approach 1. Figure 2 shows a case with a difference of -57% in D98%.Low differences (mostly <0.5%) were found by executing the script with approach 2.
Conclusion: The script produced large errors in the EQD2 doses when it was executed by entering multiple a/b values to consider the PTV and OARs in a simultaneous way. We recommend using the script by entering just a single a/b value for EQD2 calculation. Keywords: EQD2, script, Eclipse
Digital Poster Highlight 117
Automated workflow for accumulated dose monitoring in hypofractionated prostate radiotherapy Maximilian Grohmann 1 , David Krug 1 , Andrea Baehr 1 , Cordula Petersen 1 , Manuel Todorovic 1 , Sebastian Schäfer 2 , Lukas Clemens Böckelmann 1 , Elisabetta Gargioni 1 1 Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. 2 Department of Radiation Oncology, University of Leipzig Medical Center, Leipzig, Germany Purpose/Objective: Anatomical variations during prostate radiotherapy can lead to substantial discrepancies between planned and delivered dose, particularly in hypofractionated regimens [1-4]. While online adaptive radiotherapy (oART) addresses these variations, it is resource- intensive and not yet widely accessible. We aimed to develop and validate a fully automated workflow for efficient accumulated dose estimation without deformable image registration (DIR) or daily dose
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