SU-F-T-278: Evaluation of Commercially Available System for Patient Specific QA Using Dose Volume Histograms

Authors


Abstract

Purpose:

To evaluate a commercial system for patient specific quality assurance using measurements and re-calculated dose volume histograms.

Methods:

The PTW OCTAVIUS4D was used to physically measure the dose distribution from previously accepted IMRT patient plans for a variety of sites. PTW VeriSoft was used to for the IMRT QA evaluation. Patient plans, CT images, dose distribution and structures were imported in the VeriSoft. For each patient IMRT QA, the software can use the CT and structure information to calculate the dose to the patient from the measurement. The DVHs were then compared to the imported ones. The difference of the mean dose per organ was calculated for each plan and used in the comparison.

Results:

For treatment sites with no tissue inhomogeneities, such as pelvis, the DVHs produced by the TPS and VeriSoft showed good agreement; however, small structures such as eyes, optic nerves or brainstem did not adequately match up when comparing the DVH from the TPS to VeriSoft. For treatment sites with inhomogeneity, such as the lung, showed larger dose differences between the two methods, this is most likely due to dose calculation limitations of the PTW VeriSoft DVH algorithm.

Conclusion:

Overall, the DVHs produced by VeriSoft can give a physicist quick insight to the validity of the IMRT plan; however, there are limitations when plans of heterogeneous treatment sites are evaluated since the dose calculation algorithm in Verisoft cannot accurately account for it.

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