I Patel et al 2005 Phys. Med. Biol. 50 5479 doi:10.1088/0031-9155/50/23/004
I Patel, A G Glendinning and M C Kirby
Show affiliationsThe dosimetric characteristics of a production pilot multi-leaf collimator (Elekta Beam Modulator™, Elekta Oncology Systems, Crawley, UK) having a 4 mm leaf width (at isocentre) have been investigated. Characteristics explored included leaf bank set-up, penumbra width (80–20%) as a function of leaf position, leaf positioning reproducibility, interleaf leakage and leaf transmission. The penumbra values for leaf ends were measured to be between 4.2 and 4.8 mm for various large rectangular fields studied using Kodak X-omat V film at isocentre (1.5 cm deep). Similar films were taken with a standard 1 cm width multi-leaf collimator (MLC) and the penumbra for leaf ends was found to range from 4.3 to 5.2 mm. Other results showed that the rounded leaf tip provided tight control of the penumbra across the leaves' full range of travel. The positioning of the leaves was within a 0.5 mm range when approaching from the same direction. The maximum interleaf leakage was found to be 1.7% and the average leaf transmission less than 1.0%. No major differences were observed in leakage and transmission with changing gantry angle.
Issue 23 (7 December 2005)
Received 30 June 2005, in final form 19 August 2005
Published 9 November 2005
I Patel et al 2005 Phys. Med. Biol. 50 5479
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