Insights to Achieve More Accuracy for the Conventional Treatment Planning Systems

Many documents and protocols had been published in the field of treatment planning systems (TPS) quality assurance, verifying dose calculation to the relevant measurements. International Atomic Energy Agency (IAEA) had published Technical Documents (TEC-DOCs) concerned with the TPS quality assurance intended to the developing countries to suits the conventional facilities in their centers. This work aimed to evaluate the dosimetric performance of the TPS that available in our department, following the guidelines of IAEA. Twelve test cases were chosen to verify the TPS dosimetric performance in homogenous water that can be applied by our available dosimetric tools. Two of these test cases related to the absolute dose measurements on the central axis of the open square field sizes (relative output factor (Sc,p)) and wedge output factor (WOF) for wedged square field sizes. The other test cases involved relative measurements as percentage depth dose (PDD) curves, beam profiles, off-axis ratio (OAR) dose values, penumbra region, and radiological width (RW)50. The results analyzed by the confidence limit concept and the tolerance criteria of acceptability stated by IAEA TEC-DOCs. Results show that TPS calculations are in good agreement with the measurements and within limits except for the parameters (RW)50 and (WOF) of the tested field sizes that exceeding the tolerance limits. The deviation () in the TPS calculations of (RW)50 = 2.5 mm, the penumbra regions are 2.6 mm and 2.8 mm for photon beam energies 6 and 10 MV, respectively. The proposed analysis display, determining clearly the orientations of calculation errors. This method elaborates errors and their directions in a good way.