Room: AAPM ePoster Library
Purpose: To investigate the feasibility for clinical end-to-end (E2E) quality assurance for fractionated stereotactic radiation therapy (FSRT) for brain metastases using an in house developed phantom. The motivation is to determine if in-house E2E QA that tests the multiple decision based modifications staff implement during a patient’s treatment course is possible.
Methods: A purpose-built anthropomorphic head phantom was manufactured with a PRUSA i3-MK3 3D printed skull (using iron-filled PLA at 100% infill) and regions filled with water and polydoh plastic. The phantom could accommodate a variety of dosimeters: a Capintec PR-05P 0.07cc ion chamber, EBT3 Gafchromic film, and leucocrystal violet micelle or Fricke-xylenol gel dosimeters.
Once prepared, the phantom with a specific dosimeter was given to radiation therapy staff for CT imaging, treatment planning, and VMAT FSRT delivery using our clinical protocols. Dose measurements were performed by medical physics staff. The film and gel measurements were analysed using the film or gel dosimetry slicelets in the open source 3D Slicer.
Results: The phantom closely resembles a human head under imaging and set-up. It was easy for staff to use and enabled E2E QA tests. Manufacture was economical with a materials cost of ~$300. The therapists managed the head phantom exactly as a patient: easily performing CT simulation, treatment planning, phantom set-up, CBCT imaging and alignment, and radiation delivery. The multi-dosimeter approach enabled treatment dose delivery validation in multiple dimensions. Measurements indicated excellent agreement with the planned dose delivery.
Conclusion: E2E tests that mimic the real patient IGRT process with relevant staff performing each step in the clinical workflow are feasible using in-house manufactured phantoms. The E2E testing provided a complete evaluation of our VMAT FSRT radiation therapy process. Our results give us confidence that our clinical workflow is safe, accurate, and effective at treating small targets.
Funding Support, Disclosures, and Conflict of Interest: This work was funded by the grants: Canadian Institutes for Health Research (CIHR) project MOP-115101 and Collaborative Health Research Project (CHRP) project CIHR 151964 and NSERC CHRPJ 508528-2017.