Abstract
Background:Measurement of Collimator helmet factors (CHF) is an important quality assurance procedure to be performed on Leksell Gamma Knife unit at regular interval to make sure that the interchangeable collimator helmet fit into the source channels without any positional inaccuracy which leads to major treatment error. The primary aim of this study is to measure the CHFs for Elekta Leksell Gamma knife 4C helmets using GafChromic EBT3 film and Image J software. Methods:GafChromic EBT3 film, EPSON expression 10000 XL scanner and Image J analysis software was used for this study. The calibration curve of GafChromic EBT3 film was generated with known dose values for 14 mm collimator helmet using ImageJ software. The collimator helmet factor (CHF) for 4mm, 8mm and 14 mm collimator helmets were measured by normalizing dose rates of 4mm, 8mm and 14 mm to the dose rate of 18 mm collimator helmet using the previously generated calibration curve. The measured CHF was compared to Elekta reference value and previously published mean values. Results:The measured CHFs were 0.896, 0.958, and 0.986 for 4mm, 8mm and 14mm collimators respectively. The percentage difference obtained was 1.7 %, 0.21 %, 0.1 % between measured values and reference values. Conclusion:The measurement of CHFs in LGK 4C unit using GafChromic EBT3 film and ImageJ software is a reliable method to verify the manufacturer quoted CHFs in routine quality assurance procedures.
Highlights
Stereotactic radiosurgery (SRS) is a useful treatment option for benign lesions of the brain such as arteriovenous malformations (AVMs), meningiomas, and acoustic neuromas and to treat many malignant tumors such as brain metastases
Measurement of Collimator helmet factors (CHF) is an important quality assurance procedure to be performed on Leksell Gamma Knife unit at regular interval to make sure that the interchangeable collimator helmet fit into the source channels without any positional inaccuracy which leads to major treatment error
The collimator helmet factor for 4mm, 8mm, 14 mm and 18 mm were performed on Leksell Gamma-Knife (LGK) 4C using GafChromic EBT 3 film and ImageJ film analysis software
Summary
Stereotactic radiosurgery (SRS) is a useful treatment option for benign lesions of the brain such as arteriovenous malformations (AVMs), meningiomas, and acoustic neuromas and to treat many malignant tumors such as brain metastases. The Leksell Gamma Knife (Elekta Instruments) model 4C contains 201 60Co sources with a common focus point aiming dose to be delivered only to the treatment area. It has fixed primary collimation for each of Co60 sources and interchangeable four secondary collimators called as collimator helmets each comprises of 201 apertures which align with primary collimation source channels. The primary aim of this study is to measure the CHFs for Elekta Leksell Gamma knife 4C helmets using GafChromic EBT3 film and Image J software. Conclusion: The measurement of CHFs in LGK 4C unit using GafChromic EBT3 film and ImageJ software is a reliable method to verify the manufacturer quoted CHFs in routine quality assurance procedures
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