The dose kernels of pencil and differential pencil photon beams with the spectrum of treatment machines with a ⁶⁰Co source in water and their analytical approximation

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• 作者：V. A. Klimanov ; A. N. Moiseev ; M. A. Kolyvanova…
• 关键词：external radiation therapy ; photons ; ROKUS treatment machine ; pencil beam ; differential pencil beam ; 3D treatment planning ; collapsed cone convolution ; pencil beam algorithm
• 刊名：Moscow University Physics Bulletin
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：71
• 期：4
• 页码：431-439
• 全文大小：958 KB
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics
  Mathematical and Computational Physics
  Russian Library of Science
  
• 出版者：Allerton Press, Inc. distributed exclusively by Springer Science+Business Media LLC
• ISSN：1934-8460
• 卷排序：71

文摘

This article presents the results of calculations by the Monte-Carlo method in the EGSnrc toolkit of the spatial distributions of absorbed energy or dose kernels in water for a pencil beam or differential pencil beam (point spread function) with the spectrum of ROKUS-M treatment machines. The photon spectrum of the ROKUS-M machines was also calculated by the Monte-Carlo method. The calculated dose-kernel results were approximated separately for the radial distribution of the primary and the scattered component of dose kernels by sums of exponential functions divided by the squared radius for a differential pencil beam and by the radius for a pencil beam. This approximation makes direct implementation possible for wellknown model-based techniques for finding 3D dose distributions in external radiation therapy. A simple analytical procedure to verify approximation formulas is proposed. It is also applicable in independent checks of dose distributions along the treat beam axis, which is an important guideline of the Radiation Therapy Quality Assurance Program.