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6 MV dosimetric characterization of the 160 MLC™, the new Siemens multileaf collimator
Author(s) -
Tacke Martin B.,
Nill Simeon,
Häring Peter,
Oelfke Uwe
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2889782
Subject(s) - multileaf collimator , isocenter , collimator , nuclear medicine , materials science , dosimetry , penumbra , optics , linear particle accelerator , beam (structure) , physics , medicine , imaging phantom , ischemia , cardiology
New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer‐controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC TM , Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue‐and‐groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37 % due to a new design principle of slightly tilted leaves instead of the common tongue‐and‐groove design. But due to the tilt, the triangular tongue‐and‐groove effect occurs. Its magnitude of approximately 19 % is similar to the dose defect measured for MLCs with the common tongue‐and‐groove design. The average longitudinal penumbra measured at depthd max = 15 mm with standard 100 × 100mm 2fields is 4.1 ± 0.5 mm for the central range and increases to 4.9 ± 1.3 mm for the entire field range of 400 × 400mm 2 . The increase is partly due to the single‐focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage‐imaging panel. The maximum leaf velocities measured were 42.9 ± 0.6 mm / s . In addition, several typical intensity‐modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS™ MLC. An average decrease of 11 % in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC™ are capable of improving the quality of dose delivery with respect to precision and dose conformity.