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An EPID-based method for comprehensive verification of gantry, EPID and the MLC carriage positional accuracy in Varian linacs during arc treatments.

Rowshanfarzad P, McGarry CK, Barnes MP, Sabet M, Ebert MA - Radiat Oncol (2014)

Bottom Line: The EPID sag showed a considerable improvement in TrueBeam linacs.The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation.It is reproducible and accurate and can be easily performed as a routine test in clinics.

View Article: PubMed Central - PubMed

Affiliation: School of Physics, University of Western Australia, Crawley, WA, 6009, Australia. pejman.rowshanfarzad@uwa.edu.au.

ABSTRACT

Background: In modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance.

Methods: The Varian EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in MLC carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated.

Results: The average EPID sag was within 1 mm for all tested linacs. All machines showed less than 1 mm gantry sag. Changes in SDD values were within 1.7 mm except for three linacs of one centre which were within 9 mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum sag in MLC leaf bank assemblies was around 1 mm. The EPID sag showed a considerable improvement in TrueBeam linacs.

Conclusion: The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation. It is reproducible and accurate and can be easily performed as a routine test in clinics.

Show MeSH
Comparison of the measured sag values in leaf bank assemblies of the tested linacs for: (a) gun side, (b) target side, (c) left side, and (d) right side. Each data point represents the average over three sets of measurements made at zero collimator angle.
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Fig7: Comparison of the measured sag values in leaf bank assemblies of the tested linacs for: (a) gun side, (b) target side, (c) left side, and (d) right side. Each data point represents the average over three sets of measurements made at zero collimator angle.

Mentions: FigureĀ 7 shows the measured sag patterns in the MLC carriages of the tested linacs in four directions.Figure 7


An EPID-based method for comprehensive verification of gantry, EPID and the MLC carriage positional accuracy in Varian linacs during arc treatments.

Rowshanfarzad P, McGarry CK, Barnes MP, Sabet M, Ebert MA - Radiat Oncol (2014)

Comparison of the measured sag values in leaf bank assemblies of the tested linacs for: (a) gun side, (b) target side, (c) left side, and (d) right side. Each data point represents the average over three sets of measurements made at zero collimator angle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4252011&req=5

Fig7: Comparison of the measured sag values in leaf bank assemblies of the tested linacs for: (a) gun side, (b) target side, (c) left side, and (d) right side. Each data point represents the average over three sets of measurements made at zero collimator angle.
Mentions: FigureĀ 7 shows the measured sag patterns in the MLC carriages of the tested linacs in four directions.Figure 7

Bottom Line: The EPID sag showed a considerable improvement in TrueBeam linacs.The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation.It is reproducible and accurate and can be easily performed as a routine test in clinics.

View Article: PubMed Central - PubMed

Affiliation: School of Physics, University of Western Australia, Crawley, WA, 6009, Australia. pejman.rowshanfarzad@uwa.edu.au.

ABSTRACT

Background: In modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance.

Methods: The Varian EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in MLC carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated.

Results: The average EPID sag was within 1 mm for all tested linacs. All machines showed less than 1 mm gantry sag. Changes in SDD values were within 1.7 mm except for three linacs of one centre which were within 9 mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum sag in MLC leaf bank assemblies was around 1 mm. The EPID sag showed a considerable improvement in TrueBeam linacs.

Conclusion: The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation. It is reproducible and accurate and can be easily performed as a routine test in clinics.

Show MeSH