Room: AAPM ePoster Library
Purpose: To characterize the performance of IMRT, SBRT and SRS Patient Plan QA modes in a novel BgRT machine.
Methods: The newly introduced RefleXion™ X1 machine has IMRT, SBRT and SRS modes when BgRT is not used. Patient plan QA performance was evaluated for multiple treatment plans including three clinical cases (IMRT- Prostate bed, SBRT-Lung and SRS- Brain) and five mock IMRT TG-119 cases (C1: multitarget, C2: mock prostate, C3: mock head/neck, C4: C- shape easy and C4: C- shape hard). Patient QA versions of these plans were created, where the expected dose is calculated assuming the plan is delivered into an ArcCHECK (AC) dosimetry device instead of the patient.
Primary measurements were made with the ArcCHECK device. Point doses were measured using A14SL ion chambers inserted in the AC multi-plug insert. The dose difference (DD) criteria for point doses was set to = 2%. Gamma Analysis pass (GP) criteria were set to be 3%/3mm with a pass rate of >90% for the clinical plans and >95% for the TG-119 plans, consistent with the original TG-119 study.
Results: All point dose difference measurements met the dose difference pass criteria of = 2%. All five TG-119 Plan QA deliveries met the GP criteria of at least 95% of measurement points meeting a 3%/3mm criteria. The average percentage of points passing the criteria was quite high with a mean of 98.4% and standard deviation of 1.02%. All three clinical Patient Plan QA deliveries met the GP criteria with an average of 96.9% of the measurement points meeting the 3%/3mm criteria.
Conclusion: The experimental results demonstrated that Patient Plan QA in the IMRT, SBRT and SRS modes of the X1 machine is robust and passed patient-specific QA dosimetric goals outlined in the AAPM TG-119 report.
Funding Support, Disclosures, and Conflict of Interest: Research supported by RefleXion Medical
Quality Assurance, Treatment Planning, Treatment Techniques