Using trajectory log files as additional tool for dosimetry verification plan. A case in practice

In this survey, we investigate the usage of Trajectory log data in a single case of a patient undergoing Stereotactic Radiosurgery (SRS) treatment. A dedicated linear accelerator machine Varian TrueBeam STX was used. The software was developed for analyzing the log files which were created by the machine when a certain plan was performed in treatment mode or QA mode. Four plans were created with 7 no-coplanar fields. Additional structures must be added by the physicist in the contouring section in order to optimize the plans. Dosimetry equipment ArcCHECK was used to verify the dose distribution for the created plan. The evaluation of γ passing rate (%GP) from the Trajectory log was done for each field separately using Pylinac v.2.2.6 API (application programing interface) for Machine quality control. It was shown that for one of the plans the values of %GP in some of the fields were very low with about less than 15% passing and at the same time the ArcCHECK shows a good %GP of about 90%. When verifying the plans using the analyzed Trajectory log files it can be detected if there are problems with the rotation of the collimator, the positioning of the collimator jaws or with over-modulating of the plan.