Abstract
Micro‐multileaf collimator systems coupled to linear accelerators for radioneurosurgery treatments require a rigorous dosimetric characterization in order to be used in 3D conformal and intensity modulated stereotactic radiosurgery and radiotherapy applications. This characterization involves high precision measurements of leaf transmission, leakage and beam penumbra through the collimation system and requires the use of detectors with high spatial resolution, high sensitivity and practically no energy dependence. In this work the use of GafChromic EBT radiochromic film to measure the basic dosimetric properties of the m3‐mMLC (BrainLAB, Germany) micro‐multileaf collimator system integrated to a 6 MV linear accelerator, is reported. Results show that average values of transmission and leakage radiation are 0.93±0.05% and 1.08±0.08%, respectively. The 80–20% beam penumbra were found to be 2.26±0.11 mm along the leaf side (perpendicular to leaf motion) and 2.31±0.11 mm along the leaf end (parallel to leaf motion) using square field sizes ranging from 9.1 to 1.8 cm. These measurements are in agreement with values reported in the literature for the same type of mMLC using different radiation detectors.PACS number: 87.56.N‐
Highlights
Multileaf collimators (MLCs) are beam modifiers coupled to medical linear accelerators to shape the photon beam in order to match the geometry of the lesion to be irradiated
Current mMLCs are designed for the treatment of lesions smaller than 8.0 cm
In this work we report experimental measurements of radiation transmission, leakage and 80-20% beam penumbra of the m3-mMLC (BrainLAB, Germany) micro-multileaf collimator system coupled to a 6 MV linear accelerator using GafChromic EBT radiochromic film, and compare our results with those reported previously using other type of detectors
Summary
Multileaf collimators (MLCs) are beam modifiers coupled to medical linear accelerators to shape the photon beam in order to match the geometry of the lesion to be irradiated. The general structure of these devices consists of a set of leaves generally made of a tungsten alloy. The position of the leaves is individually controlled by a computer, allowing their movement along a direction perpendicular to the beam axis. A variation of this device is the so-called micro-MLC (mMLC). The main difference between standard MLCs and mMLCs is the leaf width. A standard MLC has leaf widths ranging from 0.5 to 1.0 cm, while an mMLC has leaf widths ranging from 0.1 to 0.4 cm. Current mMLCs are designed for the treatment of lesions smaller than 8.0 cm
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