An institutional experience of quality assurance of a treatment planning system on photon beam

Aim

The purpose of the present study is to show the application of the IAEA TRS-430 QA procedures of Eclipse™v7.5 TPS for photon energies. In addition, the trends of the deviations found in the conducted tests were determined.

Background

In the past, the lack of complete TPS QA procedures led to some serious accidents. So, QA in the radiotherapy treatment planning process is essential for determination of accuracy in the radiotherapy process and avoidance of treatment errors.

Materials and methods

The calculations of TPS and measurements of irradiations of the treatment device were compared in the study. As a result, the local dose deviation values (δ₁: central beam axis, δ₂: penumbra and build up region, δ₃: inside field, δ₄: outside beam edges, δ_50–90: beam fringe, RW₅₀: radiological width) and their confidence limit values (including systematic and random errors) were obtained.

Results

The confidence limit values of δ₄ were detected to increase with expanding field size. The values of δ₁ and δ₃ of hard wedge were larger than open fields. The values of δ₂ and δ_50–90 of the inhomogeneity effect test were larger, especially than other tests of this study. The average deviation was showed to increase with the rise of the wedge angle. The values of δ₃ and δ₄ of lung irradiation were outside tolerance.

Conclusions

The QA of TPS was done and it was found that there were no reservations in its use in patient treatment. The trend of the deviations is shown.