ESTRO 2022 - Abstract Book

S1543

Abstract book

ESTRO 2022

rate. Lastly, the dose in OAR and PTV were compared between the two different dose calculation algorithms. The main differences occur in PTV D95 and D98 where using 6FFF beams gave less than 1 Gy difference while 10FFF beams gave less than 3 Gy difference. The difference in doses in the OARs are less than 0.5%.

Figure 2 shows the percentage difference in point dose between treatment plans (AXB and AAA; 1mm and 2mm) and measurement (Pinpoint and Farmer). Conclusion This study shows that 10FFF beam is recommended for hypo-fractionated treatment and similar dosimetric accuracy are obtained for 3, 4 and 6 arcs plan. The point dose measurement results also support the use of the AXB dose calculation dose algorithm with a 1mm calculation grid size.

PO-1742 Feasibility of using a process control framework to simplify treatment planning decisions

T. Orovwighose 1,2 , V. Batista 1,2 , B. Rhein 1,2,3 , O. Jäkel 1,2,3,4

1 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany; 2 Heidelberg Institute of Radiation Oncology , (HIRO), Heidelberg, Germany; 3 Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg, Germany; 4 German Cancer Research Center (DKFZ), Dep. Medical Physics in Radiation Oncology, Heidelberg, Germany Purpose or Objective This work explores the feasibility to use statistical process control (SPC) on various plan evaluation metrics to standardize the treatment planning decisions. Furthermore, these metrics were cross-correlated to assess which parameters are more suitable to quantify plan quality. Materials and Methods The baseline for the SPC was established with a pilot data set of 105 VMAT bronchial treatment plans. The centre line (CL), upper (UCL) , and lower control limit (LCL) were calculated for various parameters, such as dose coverage (DC), homogeneity index (HI), gradient index, PMU (plan normalized monitor unit used to predict the degree of plan modulation (Park 2019, doi: 10.1002/acm2.12589)), plan quality index (PQI, use to compare the achievement of planning goals) (Jornet 2014, doi.org/10.1016/j.radonc.2014.06.016), dose differences and Gamma-index of an independent dose calculation- based (cD.Pat-QA) and a measurement-based patient-specific plan verification (mPat.QA). The cross-calibration of 11 plan quality metrics was achieved with the multivariable correlation (Pearson) and the parameters with the strongest correlation were chosen to assess the plan quality. Results Fig.1 shows the result of the SPC of four of the plan quality metrics that were examined. In general, a quick overview of the plan quality and the weakness of a plan compared to the others can be achieved. The analysis of the SPC showed some treatment plans have only a single weakness (plan 2, poor DC), while others have multiple problems (plan 61, high PMU, poor DC, and gamma-index). The result of the multivariable correlation analysis shows PMU, DC, and mPat-QA gamma index have multiple weak or strong correlations with most of the plan quality metrics that were evaluated. Plan quality index (PQI) didn´t correlate with any other plan quality metrics evaluated. This is similar to the findings of Jornet 2014, who found no correlation between plan complexity and PQI.