PMID: 15377088Sep 21, 2004Paper

On empirical methods to determine scatter factors for irregular MLC shaped beams

Medical Physics
Dietmar GeorgMikael Karlsson

Abstract

Multileaf collimators (MLCs) are in clinical use for more than a decade and are a well accepted tool in radiotherapy. For almost each MLC design different empirical or semianalytical methods have been presented for calculating output ratios in air for irregularly shaped beams. However, until now no clear recommendations have been given on how to handle irregular fields shaped by multileaf collimators for independent monitor unit (MU) verification. The present article compares different empirical methods, which have been proposed for independent MU verification, to determine (1) output ratios in air (Sc) and (2) phantom scatter factors (Sp) for irregular MLC shaped fields. Ten dedicated field shapes were applied to five different types of MLCs (Elekta, Siemens, Varian, Scanditronix, General Electric). All calculations based on empirical relations were compared with measurements and with calculations performed by a treatment planning system with a fluence based algorithm. For most irregular MLC shaped beams output ratios in air could be adequately modeled with an accuracy of about 1%-1.5% applying a method based on the open field aperture defined by the leaf and jaw setting combined with the equivalent square formula suggested by...Continue Reading

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Citations

May 15, 2008·International Journal of Gynecological Cancer : Official Journal of the International Gynecological Cancer Society·J PahisaJ A Lejárcegui
Apr 28, 2011·Medical Physics·Dietmar GeorgBrendan McClean
Jul 17, 2010·Medical Physics·Parham Alaei, Patrick Higgins
Oct 2, 2007·Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology·Dietmar GeorgMikael Karlsson
Jul 25, 2019·Australasian Physical & Engineering Sciences in Medicine·So-Yeon ParkSang-Tae Kim
Dec 24, 2019·Nihon Hoshasen Gijutsu Gakkai zasshi·Takahide HayakawaRyuta Sasamoto

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