Clinical Implications of AAA Commissioning Errors and Ability of Common Commissioning & Credentialing Procedures to Detect Them
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Purpose: To test the ability of the TG-119 commissioning process and the IROC credentialing to detect errors in the commissioning process for a commercial treatment planning system.
Methods: We introduced commissioning errors into the commissioning process for the Anisotropic Analytical Algorithm (AAA) within the Eclipse Treatment Planning System (TPS). We included errors in MLC Dosimetric Leaf Gap (DLG), electron contamination modeling parameters, incorrect flattening filter material, and beam profile measurement with an inappropriately large farmer chamber (simulated using sliding window smoothing of the input dose profiles). We evaluated the clinical impact of these errors for a variety of clinical intensity modulated radiation therapy (IMRT) plans by looking at PTV D99 and mean and max dose to OARs. The different cases included a head and neck plan, low and intermediate risk prostate plans, a lung plan, and a scalp plan. Finally, for the errors with substantial clinical impact, we determined the sensitivity of the commissioning & credentialing processes with the TG119 C-shape and RPC IMRT head and neck phantoms. This was determined by comparing plans before and after commissioning errors were introduced in the commissioning process using the technique suggested by each respective organization. IROC IMRT credentialing includes film analysis at the midpoint between PTV and OAR using a 4mm distance to agreement metric along with a 7% TLD dose comparison. The TG119 C-shape IMRT phantom looks at 3 separate dose planes and using gamma criteria of 3% 3mm.
Results: The most clinically significant commissioning errors came from large changes in the MLC DLG with a change of 1mm resulting in up to a 5% change in the primary PTV D99. This resulted in a discrepancy in the IROC TLDs in the PTVs and OARs of 7.1% and 13.6% respectively, which would have resulted in detection. While use of incorrect flattening filter caused only subtle errors (<1%) in clicnical plans, the effect was also most pronounced for the IROC TLDs in the OARs (>6%).
Conclusion: The AAA commissioning process within the Eclipse TPS is surprisingly robust to user error. When errors do occur, the IROC and T119 commissioning credentialing criteria are effective at detecting them; however the OAR TLDs are the most sensitive to errors despite the IROC currently excluding them from their analysis.
McVicker, Andrew Thinnes (2014). Clinical Implications of AAA Commissioning Errors and Ability of Common Commissioning & Credentialing Procedures to Detect Them. Master's thesis, Duke University. Retrieved from https://hdl.handle.net/10161/8859.
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