Purpose: To use logfiles generated by the linear accelerator to verify the dose delivered to the patient. Also, to incorporate the linac delivery errors deviations from the plan into the treatment plan.
Methods: We used the Standard Imaging LinacView (SILV) system to record the treatment deliveries of an Elekta VersaHD linear accelerator. Ten head and Neck patients were selected for this study all treated with VMAT. Then the recorded logfiles were converted into DICOM RT plans and imported back to the treatment planning system (RayStation, v9.2). Dose distributions were calculated using the MLC RTPLAN and the initial patient geometry. The isodose distributions and DVHs were then used to compare the approved plans against the logfile generated ones.
Results: Our MLC logfile based recalculated plans had a higher mean dose to the PTV (0.5-2.5%)and higher maximum dose. The PTV D98 did not always followed the same trend as some had lower D98 compared to the approved plans. The doses to the organs at risk were also higher on average about 0.4-2.2%. All MLC plans show that the dose is higher in general and the larger differences, as expected, are near tissue interfaces.
Conclusion: logfiles can be used to assess the impact of the linac delivery on the treatment plan and verify delivery. Differences of less than 3% have been observed when comparing the originally approved plans against the MLC generated ones. Such small difference makes the logfile based plan a viable method for patient specific QA as well as a treatment delivery verification tool.
Not Applicable / None Entered.