Investigating the Quality of Data Required to Commission a Treatment Planning System
Presentations
WE-C1000-IePD-F4-5 (Wednesday, 7/13/2022) 10:00 AM - 10:30 AM [Eastern Time (GMT-4)]
Exhibit Hall | Forum 4
Purpose: Investigating measurement quantity and quality necessary to accurately commission a treatment planning system.
Methods: Datasets required for commissioning the Eclipse® planning system, Varian Medical System (Palo Alto, CA), includes: depth doses, 2D dose profiles, output factors, and absolute point doses. For each of these datasets, we intentionally degraded the quality of the commissioning measurements by either reducing the number of data points or adding noise. To reduce the number of points in the dose profiles, several strategies were employed that includes uniform reduction of data points, which essentially reduces the resolution of the dose profiles, and a Monte Carlo sampling algorithm using profile gradient as probability densities. To introduce noise, a statistical Gaussian was added with 1% to 5% deviations, depending on what was allowed by Eclipse. A virtual machine was created in Eclipse that was identical to a clinically commissioned machine. Then data was interchanged, one at a time. Each time, the virtual machine was fully commissioned, dose was calculated for standard fields and results were compared against the dose calculated on clinically commissioned machine. The dose calculation comparison was analyzed with a gamma criterion of 1%/1mm.
Results: We found that the error checking routine in Eclipse prohibited some datasets such as the sets with significant noise. However, once data was accepted by Eclipse, the calculation had significant agreement. The most significant influence was adding noise to dose profiles. Another conclusion was that there were multiple strategies employed to reduce the size of the data sets, by as much as 85%, but this had limited effects on resulting dose calculation.
Conclusion: We conclude that Physicists may be acquiring commissioning data that is unnecessarily large. However, a Physicist should pay close attention to the degree of measurement noise which could have significant impact on dosimetric accuracy.
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Taxonomy
TH- External Beam- Photons: Calibration protocol and primary standards
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