Radiation transmission, leakage and beam penumbra measurements of a micro‐multileaf collimator using GafChromic EBT film

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‐

Physical characterization and comparison of two commercially available micro-MLCs

“…The Novalis' mMLC has a consistently smaller penumbra for the circular fields and compared to the Synergy-S' MLC. It is to be noted that the measured penumbra for Novalis (BrainLAB) closely matched with that reported by Clark et al [4], Chern et al [5], and García-Garduño et al [8]. The effective penumbras for these circular fields range from about 4 AE 0.15 mm to 7 AE 0.27 mm for the Synergy-S mMLC (Fig.…”

“…Chern et al [5] reported that the 3 mm mMLC of BrainLAB provided better target conformity and greater normal tissue sparing than the 5 mm MLC in stereotactic radiosurgery using dynamic conformal arcs. García-Garduño et al [8] have recently reported penumbra (2.26 AE 0.11 mm along leaf side and 2.31 AE 0.11 mm along lead end), transmission (0.93 AE 0.05%), and leakage (1.08 AE 0.08%) of m 3 -mMLC of BrainLAB for 6 MV photon beam study using EBT film.…”

Characteristics and performance of the first commercial multileaf collimator for a robotic radiosurgery system

“…Asnaashari et al 16 assessed two MLCs for radiosurgery and reported penumbrae in the range of 3.5-4.8 mm. Fischer et al 17 and García-Garduño et al 18 determined penumbrae of around 2.5 mm, in a slightly different measurement setup. Sharma et al 19 found a range of 2-4 mm for 6 MV delivery modes and different field sizes, and Solberg et al 20 reported around 4.5 mm for a 10×10 cm 2 field on a gimbaled Linac.…”

Evaluation of a Gafchromic EBT2 film dosimetry system for radiotherapy quality assurance

“…Since its introduction in 2004, Gafchromic's EBT radiochromic film (International Specialty Products, Wayne, USA) has been widely adopted for use in quality assurance testing of clinical radiotherapy treatments including 3D conformal [1], intensity modulated and stereotactic treatments [2][3][4][5] as well as arc therapies [6] including tomotherapy [7]. EBT has been rigorously investigated and found to be capable of producing reliable and reproducible dose measurements, with a high degree of spatial accuracy and uniformity of response [1,[8][9][10][11][12][13].…”