S2355
Physics - Quality assurance and auditing
ESTRO 2026
1 shows a much wider spread of parameter values than those in figure 2, showing that plan quality decreases as the number of BMs increases. Also note that CI and GI deteriorate as the PTV volume decreases.
processes. PASC can be used to perform rapid and comprehensive validation of online adapted plans, providing treatment confidence where QA time is limited. The structured recording of data for QA can provide clinical trials and the department with valuable information that can translate into better treatments for patients. Keywords: Online, adaption, MR-Linac Digital Poster 2089 Monitoring treatment plan quality for LINAC-based stereotactic radiotherapy of multiple brain metastases with individual dose prescriptions Xander R. Staal 1 , Jaap D. Zindler 2,3 , Masomah Hashimzadah 2 , Lia C. Versluis 2 , Anna L. Petoukhova 1 1 Medical Physics, Haaglanden MC, Leidschendam, Netherlands. 2 Radiation oncology, Haaglanden MC, Leidschendam, Netherlands. 3 Radiation oncology, HollandPTC, Delft, Netherlands
Purpose/Objective: LINAC-based single isocenter non-coplanar
stereotactic radiotherapy is an efficient treatment for brain metastases (BMs). We recently changed the dose prescription from an equal dose to all brain metastases [1] to individual dose prescription for each BM based on planning target volume (PTV) according national Dutch guidelines.Here we present our method for monitoring plan quality during and after this transition. Material/Methods: For each clinical treatment plan, plan quality parameters were collected including the volume of the healthy brain (brain-GTV) receiving 5 Gy (V5Gy) and 12 Gy (V12Gy), conformity index (CI) and gradient index (GI). These data are compared with historical data to benchmark plan quality.Plan quality parameters are viewed in a graph, plotting the parameters for the current plan as well as all historical data against the total PTV volume of all PTVs in the plan. Optionally, the historical data can be filtered to only show historical plans with similar numbers of BMs. Results: Figures 1 and 2 show plan quality parameter comparisons for a patient with 4 BMs, either against all historical data or only against historical data of patients with 2-6 BMs. Comparing the plans with individual dose prescriptions (blue dots) against plans with single dose prescriptions (grey dots), the plan quality has not changed appreciably after the introduction of individual dose prescriptions for each BM. Comparing the current patient (red diamond) against the historical data (blue and grey dots), the plan falls within a normal range for its PTV volume and number of BMs. Note that the historical data in figure
Conclusion: The presented method for plan quality has helped assessing the impact of a change in dose prescription and provides an extra tool for evaluating treatment plans. With individual dose prescription for each BM we maintained high treatment plan quality compared to equal dose to all BM during stereotactic radiotherapy for BM. References: 1. Zindler JD, Bruynzeel AME, Eekers DBP, Hurkmans CW, Swinnen A, Lambin P. Whole brain radiotherapy versus stereotactic radiosurgery for 4-10 brain metastases: a phase III randomised multicentre trial. BMC Cancer. 2017 Jul;17(1):500. https://doi.org/10.1186/s12885-017-3494-z Keywords: Plan quality metrics, stereotactic, monitoring
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