(Sunday, 7/29/2018) 4:00 PM - 4:30 PM
Room: Exhibit Hall | Forum 4
Purpose: We present our experience with commissioning and validation of Brainlab Elements Multiple Metastases (BEMM) for clinical use on an Elekta VersaHD equipped with ExacTrac.
Methods: 6MV beam data, including percent-depth-dose, output factors, diagonal and transverse profiles, was collected for iPlan Pencil Beam algorithm using IBA’s Blue Phantom with Sun Nuclear’s Edge Detector for small field measurement. Open fields for data collection were created using Elekta iComCAT due to guard leaves not permitted for iPlan data collection. Beam model was transferred to Physics Administration (v.5.0) for use with BEMM. A mono-isocenter plan with two brain metastases of 1.8cm diameter, 1.163cc’s and 1.4cm diameter, 0.997cc’s was created with BEMM. Both PTV’s were treated to a dose of 24Gy in a single fraction per RTOG 0320 using a 6 non-coplanar dynamic conformal arc beam arrangement. The plan was transferred to a solid water phantom with a single drilled Standard Imaging A16 micro-chamber and to MobiusFX for 3D dose verification. Regions of high dose were centered on the active volume of the chamber and shifts from isocenter were determined geometrically. ExacTrac imaging with 6DOF couch was employed for phantom measurement. BEMM beam model verification was used to further validate the overall model by comparison of point dose measurements for various field sizes, depths and setup.
Results: Small field output factors collected are 0.671, 0.798, 0.837, and 0.861 for 10x10, 20x20, 30x30, and 40x40mm respectively using the “daisy-chain� method at 1000mm SSD and 100mm depth. Total percent difference of micro-chamber phantom measurements was reported as -0.98% and -2.91% for metastases 1 and 2 respectively. Gamma-Index passing rate was 99.5% at 3%/3mm criteria. Maximum dose difference for open small field measurements was <2%.
Conclusion: Commissioning data collected was validated using multiple independent measurement tools and QA tests. Good agreement between BEMM and measurement was observed.
Keywords
Commissioning, Validation, Stereotactic Radiosurgery
Taxonomy
TH- External beam- photons: General (most aspects)
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