TITLE:
Automated Linac QA Using Scripting and Varian Developer Mode
AUTHORS:
Keith Pearman, Nicholas Koch, David Wiant, Han Liu, Benjamin Sintay
KEYWORDS:
Varian Developer Mode, Scripting, Automation
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.10 No.4,
November
23,
2021
ABSTRACT: Purpose: Linac quality assurance (QA)
can be time consuming involving set up, execution, analysis and subject to user
variability. The purpose of this study is to develop qualitative
automation tools for mechanical and imaging QA to improve efficiency,
consistency, and accuracy. Methods and Materials: Traditionally QA has been performed with graph
paper, film, and multiple phantoms. Analysis consists of ruler and vendor
provided software. We have developed a single four-phantom method for QA
procedures including light-radiation coincidence, imaging quality, table motion
and Isocentricity and separately cone beam computed tomography. XML
scripts were developed to execute a series of tasks using Varian’s Truebeam
Developer Mode. Non-phantom QA procedures have also been developed including
field size, dose rate, MLC position, MLC and gantry speed, star shot,
Winston-Lutz and Half Beam Block. All analysis is performed using inhouse
MATLAB codes. Results: Overall time savings were 2.2 hours per Linac per
month. Consistency improvements (standard deviation, STD) were observed for
some tests. For example: field size improved from 0.11 mm to 0.04 mm and table motion improved
from 0.17 mm to 0.12 mm. CBCT STD improved from 0.99 mm to 0.61 mm for slice thickness. No STD
change was observed for Isocentricity test. We noticed an increase in STD from
0.33 mm to 0.41 mm for light-radiation
coincidence test. There was a small drop in field size accuracy. Isocentricity
showed an increase in measurement accuracy from 0.47 mm to 0.15 mm. Table motion increased in
accuracy from 0.20 mm to 0.16 mm. Conclusion: Automation
is a viable, accurate and efficient option for monthly and annual QA.