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Validation of a 3D Treatment Verification System Based On AAPM TG-119 Recommendations

S Gajdos

S Gajdos*, J Donaghue, Akron General Medical Center, Akron, OH

SU-E-T-721 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To use AAPM TG-119 protocol to determine validity of a commercially available 3D treatment verification software system. The software determines dose in the patient CT dataset via a collapsed cone algorithm which is modeled on energy fluence of the linear accelerator. The software provides the user the ability to evaluate the dose difference and gamma factor relative to the treatment planning system (TPS).

Methods: TG-119 protocol structures were downloaded into a CT dataset of a plastic phantom which included an ion chamber planar array. The four central chambers were also contoured for dose statistics. IMRT plans were created in the TPS based on the protocol specifications. The plan parameters were transferred to the verification system for analysis via DICOM RT. Average dose and average gamma were determined for PTVs and OARs as well as the central chambers. V(100) was also determined for the PTVs. The ratio between the verification system and the TPS was tracked. Gamma analysis was based on 2%/2 mm deviation.

Results: The normalized average dose (+/- 2σ) for PTVs, OARs, and centrally located chambers is 1.00 +/- 0.02, 0.95 +/- 0.10, and 0.98 +/- 0.08, respectively. The normalized V(100) for PTV is 0.98 +/- 0.08. The average gamma for PTVs, OARs and centrally located chambers is 0.27 +/- 0.26, 0.29 +/- 0.23, and 0.30 +/- 0.44, respectively.

Conclusion: The TG-119 protocol provides for an effective way to evaluate a 3D verification software system. It allows the user to ensure the system is functioning to institution specifications and also gives the user another method to assess quality of treatment plans.

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