München 2004 – scientific programme

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ST: Strahlenphysik und Strahlenwirkung

ST 4: Strahlenbiophysik

ST 4.4: Fachvortrag

Tuesday, March 23, 2004, 11:45–12:00, HS 129

Dosmetrical characterization of a mid-sized multileaf collimator (MLC) — •Eugen Wehrwein, Gernot Echner, Guenther Hartmann, Otto Pastyr, and Wolfgang Schlegel — DKFZ-Heidelberg, Abteilung: medizinische Physik E040

We have started to develop a new type of a mid-sized MLC which is designed as a supplemental device with the following key features: leaf width 4.5 mm leaf numbers 39 field size 17.5 cm x 17.7 cm overtravel 7.5 cm max. leakage less than 4 collimation double focussing There are three specific mechanical construction details that represent a substantial improvement of the MLC concept and may contribute to a still wider application of MLCs. a) double focussing is achieved perpendicular to the leaf motion by a conical leaf shape and parallel to the leaf motion by a pivoted piece at each leaf. This piece consists of two parts: a front part which has the shape of a half moon where the orientation of the flat side is always directed to the focus by virtue of the second part which is connected to the front part and which is forced by the gear drive to move adequately. This new true doubly focussing leaf design is much easier to construct. b) the leaf guiding system which only requires loose support at one leaf side and again offers a simple construction feature c) extremely flat potentiometer which are used as pairs embedded in each leaf to control and addtionally check the leaf position with high accuracy.