Commissioning and Acceptance Testing of the existing linear accelerator upgraded to volumetric modulated arc therapy

Abstract

Aim

The RapidArc commissioning and Acceptance Testing program will test and ensure accuracy in DMLC position, precise dose-rate control during gantry rotation and accurate control of gantry speed.

Background

Recently, we have upgraded our linear accelerator capable of performing IMRT which was functional from 2007 with image guided RapidArc facility. The installation of VMAT in the existing linear accelerator is a tedious process which requires many quality assurance procedures before the proper commissioning of the facility and these procedures are discussed in this study.

Materials and methods

Output of the machine at different dose rates was measured to verify its consistency at different dose rates. Monitor and chamber linearity at different dose rates were checked. DMLC QA comprising of MLC transmission factor measurement and dosimetric leaf gap measurements were performed using 0.13[[ce:hsp sp="0.25"/]]cm³ and 0.65[[ce:hsp sp="0.25"/]]cm³ Farmer type ionization chamber, dose 1 dosimeter, and IAEA 30[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]30[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]30[[ce:hsp sp="0.25"/]]cm water phantom. Picket fence test, garden fence test, tests to check leaf positioning accuracy due to carriage movement, calibration of the leaves, leaf speed stability effects due to the acceleration and deceleration of leaves, accuracy and calibration of leaves in producing complex fields, effects of interleaf friction, etc. were verified using EDR2 therapy films, Vidar scanner, Omnipro accept software, amorphous silicon based electronic portal imaging device and EPIQA software.[[ce:cross-refs id="crfs0005" refid="bib0005 bib0010 bib0015 bib0020 bib0025 bib0030 bib0035 bib0040"]]^1–8

Results

All the DMLC related quality assurance tests were performed and evaluated by film dosimetry, portal dosimetry and EPIQA.[[ce:cross-ref id="crf0025" refid="bib0035"]]⁷

Conclusion

Results confirmed that the linear accelerator is capable of performing accurate VMAT.