Physical and Dosimetric Aspect of Euromechanics Add-on Multileaf Collimator on Varian Clinac ۲۱۰۰ C/D

Background: Before treatment planning and dose delivery, quality assurance of multi-leaf collimator (MLC) has an important role in intensity-modulated radiation therapy (IMRT) due to the creation of multiple segments from optimization process. Objective: The purpose of this study is to assess the quality control of MLC leaves using EBT۳ Gafchromic films. Material and Methods: Leaf Position accuracy and leaf gap reproducibility were checked with Garden fence test. The garden fence test consists of ۵ thin bands A) ۰.۲ Cm width spaced at ۲ Cm intervals and B) ۱ Cm width spaced at ۱ Cm intervals. Each leaf accuracy was analyzed with measuring the full-width half-maximum (FWHM). Maximum and average leaf transmission were measured with gafchromic EBT۳ films from Ashland for both ۶ MV and ۱۸ MV beams.Results: Leaf positions were found to be in a range between ۱.۷۸ – ۲.۵۳ mm, instead of nominal ۲ mm for the test A and between ۹.۰۹ – ۱۰.۳۶ mm, instead of nominal ۱۰ mm for the test B. The Average radiation transmission of the MLC was noted ۱.۷۹% and ۱.۹۸% of the open ۱۰x۱۰ Cm۲ field at isocenter for ۶ MV and ۱۸ MV beams, respectively. Maximum radiation transmission was noted ۴.۱% and ۴.۴% for ۶ MV and ۱۸ MV beams, respectively. Conclusion: In this study, application of gafchromic EBT۳ films for the quality assurance of Euromechanics multileaf collimator was studied. Our results showed that the average leaf leakage and positional accuracy of this type of MLC were in the acceptance level based on the Protocols.

کلیدواژه ها:

Multileaf Collimator ، Mechanical Test ، Garden Fence Test ، Leaf Transmission ، Leaf End Transmission