Determination of the sensitivity of trajectory log files gamma analysis - A method based on python scripts

The aim of the study is to investigate and compare gamma index (γ) results obtained from the Trajectory log (TL) file of linear accelerator (Linac) to γ results obtained by Portal Dosimetry (PD) measurements. The Treatment planning system Eclipse was used to change the Dosimetric Leaf Gap (DLG) in order to study its influence on γ. In this paper, we used the python script API Pylinac (v.2.2.6) to analyze the TL file which stores the performance parameter data of the Linac for radiotherapy, in our case Varian True Beam STX. The results for the gamma passing rate (%GP) obtained from TL tend to be higher from those obtained by PD. We found that the values of %GP obtained by the two methods become comparable when the dose difference criterion used for TL data is 8 to 10 times smaller than the same criterion used with PD data. The methodology described here would allow a verification of the gamma analysis results by using the python script API Pylinac. This could make the verication of the plan before the treatment process more precise and reliable.The aim of the study is to investigate and compare gamma index (γ) results obtained from the Trajectory log (TL) file of linear accelerator (Linac) to γ results obtained by Portal Dosimetry (PD) measurements. The Treatment planning system Eclipse was used to change the Dosimetric Leaf Gap (DLG) in order to study its influence on γ. In this paper, we used the python script API Pylinac (v.2.2.6) to analyze the TL file which stores the performance parameter data of the Linac for radiotherapy, in our case Varian True Beam STX. The results for the gamma passing rate (%GP) obtained from TL tend to be higher from those obtained by PD. We found that the values of %GP obtained by the two methods become comparable when the dose difference criterion used for TL data is 8 to 10 times smaller than the same criterion used with PD data. The methodology described here would allow a verification of the gamma analysis results by using the python script API Pylinac. This could make the verication of the plan before the trea...