(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To show that a planner array and a 1D scanner (1DS) can be used rather than a 3D scanning system (3DS) for acceptance testing and commissioning of the Varian Halcyon/Eclipse TPS system.
Methods: The Halcyon linear accelerator has a single 6 MV FFF beam and has a non-adjustable beam model for the TPS. The beam was measured with 1DS, IC PROFILER (ICP), ionization chambers and electrometer. Profiles and PDDs were also measured using a 3DS. Acceptance testing and commissioning were done simultaneously by comparing the measured data with TPS calculated percent-depth-dose (PDD) and profiles. The ICP was used for measurements of profiles for various field sizes (10-, 20-, 28-cm^2) at depths of dmax(1.3cm) and 10cm(d10). The 1DS was used for output factors and PDDs. Profiles from the 3DS and TPS were down-sampled to 0.5cm spacing-resolution to match the ICP, and point-by-point comparisons were done for all points above the inflection points. Off-axis-ratios (OARs) were compared to PDD as an energy metric. Output factors were measured in 1DS for 81 conditions for various field sizes (2–28cm^2), and SSDs (95 and 90 cm), and compared to TPS calculations.
Results: The point-by-point differences between ICP and TPS (ICP and 3DS) were 0.13%±0.30% (–0.05%±0.30%) at dmax, and 0.04%±0.35% (–0.07%±0.36%) at d10 across the fields. For energy metrics, the OAR differences between ICP and TPS/3DS were 0.23%/–0.25% at dmax and 0.04%/–0.22% at d10 for 28×28cm^2 field, and the PDD(d10) differences between 1DS and TPS/3DS were 0.04%/0.01% for 10×10cm2 field. Both OAR and PDD show the energy of the beam is well matched to the TPS model. The average ratios of measured output factors to the TPS were 1.001±0.0020 for SSD 95cm, d5cm and 1.000±0.0027 for SSD 90cm, d10cm.
Conclusion: The Halcyon/Eclipse system can be accepted and commissioned without the need for a 3DS.
Funding Support, Disclosures, and Conflict of Interest: Song Gao supported by Sun Nuclear Corporation.
Keywords
Acceptance Testing, Commissioning, Validation
Taxonomy
TH- External beam- photons: Quality Assurance - Linear accelerator
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