Varian linear accelerators store information of their deliveries in log files which can be extracted from the machine and analysed. These files contain a wealth of information, including the actual and expected position of each leaf throughout the treatment.
The analysis of Varian log files has been a growing field of interest ever since the turn of the millennia. The high resolution log files allow deep analysis into treatment plans delivered by Varian treatment machines.
This thesis undertook an international multicenter study that sought to find trends in the positional error of the MLC when compared to factors such as; the velocity of the leaves, the gantry angle, the age of the machine, the treatment site, the treatment modality, and the treatment machine. A program was devised in MATLAB to perform statistical analysis on the Varian log files. Additionally another MATLAB program was written to clinically assess these Varian log files.
By analysing the Varian log files, this thesis found a positive trend between the error of the MLC to the age of the machine. VMAT treatments had greater error than their dIMRT and Step and Shoot counterparts. The prostate treatment site had less error than the H&N and PPN treatment sites. And Varian Truebeam machines possessed less error, by a full order of magnitude, than Varian Clinac iX or Varian Trilogy machines. There was a trend towards greater error for leaves with increased velocity. In general there was greater error for leaves at positions more vulnerable to the force of gravity. This trend was not present for Sliding Gap tests delivered at discrete gantry angles.
Varian log files were used to assess thousands of deliveries performed by Varian linear accelerators. The information available in each file allowed trends to be drawn between the positional error of the MLC and the age, model, modality, treatment site, and leaf velocity.
|State||Unpublished - 2015|