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Title: SU-E-T-671: Range-Modulation Effects of Carbon Ion Beams in Lung Tissue

Abstract

Purpose: When particles traversing inhomogeneous materials like lung they show a characteristic range modulation which cannot be observed in homogeneous materials. It is possible to describe the range modulation by a convolution of an unperturbed Bragg-Curve and a normal distribution. The sigma of the normal distribution is a parameter for the strength of the modulation effect. A new material parameter (modulation power, P-mod) is introduced which is independent of the material thickness. It is defined as the square of sigma divided by the mean water equivalent thickness of the target (µ). Methods: The modulation power of lung tissue was determined by actual Bragg-peak measurements after traversing an ex-vivo porcine lung and by Monte-Carlo simulations with micro-CT data of human lung tissue. The determined modulation powers were used to show the effect of range modulation effects in a simplified treatment situation. A four centimeter spread-out Bragg-peak after traversing eight centimeter of lung tissue was simulated in FLUKA. The SOBP with and without consideration of range modulation effects were compared. Results: As well in the measurements as in the MC simulations range modulation effects of lung tissue were observed. The determined modulation powers showed a great range from 0.05 mm, in themore » micro-CT data, to 0.7 mm in the lung measurements. The SOBP comparison showed that range modulation effects Result in over- and underdosages at the distal and proximal edge of the SOBP. In the investigated case, the last 0.5 cm of the SOBP showed an underdosage of up to 50% at the distal edge, while 0.5 cm distal to the SOBP an overdosage of up to 50% was observed. Conclusion: Range modulation effects occur in inhomogeneous materials like lung. These modulation effects may Result in clinically relevant over- and underdosages but are currently not considered in commercially available treatment planning systems.« less

Authors:
 [1]; ; ;  [2]
  1. Marburg Ion Beam Therapy Center (MIT), Marburg, Hessen (Germany)
  2. Institute of Medical Physics and Radiation Protection, Giessen, Hessen (Germany)
Publication Date:
OSTI Identifier:
22538179
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ANIMAL TISSUES; BRAGG CURVE; CARBON IONS; COMPUTERIZED SIMULATION; COMPUTERIZED TOMOGRAPHY; ION BEAMS; LUNGS; MATERIALS; MODULATION; MONTE CARLO METHOD

Citation Formats

Witt, M, Weber, U, Simeonov, Y, and Zink, K. SU-E-T-671: Range-Modulation Effects of Carbon Ion Beams in Lung Tissue. United States: N. p., 2015. Web. doi:10.1118/1.4925034.
Witt, M, Weber, U, Simeonov, Y, & Zink, K. SU-E-T-671: Range-Modulation Effects of Carbon Ion Beams in Lung Tissue. United States. doi:10.1118/1.4925034.
Witt, M, Weber, U, Simeonov, Y, and Zink, K. Mon . "SU-E-T-671: Range-Modulation Effects of Carbon Ion Beams in Lung Tissue". United States. doi:10.1118/1.4925034.
@article{osti_22538179,
title = {SU-E-T-671: Range-Modulation Effects of Carbon Ion Beams in Lung Tissue},
author = {Witt, M and Weber, U and Simeonov, Y and Zink, K},
abstractNote = {Purpose: When particles traversing inhomogeneous materials like lung they show a characteristic range modulation which cannot be observed in homogeneous materials. It is possible to describe the range modulation by a convolution of an unperturbed Bragg-Curve and a normal distribution. The sigma of the normal distribution is a parameter for the strength of the modulation effect. A new material parameter (modulation power, P-mod) is introduced which is independent of the material thickness. It is defined as the square of sigma divided by the mean water equivalent thickness of the target (µ). Methods: The modulation power of lung tissue was determined by actual Bragg-peak measurements after traversing an ex-vivo porcine lung and by Monte-Carlo simulations with micro-CT data of human lung tissue. The determined modulation powers were used to show the effect of range modulation effects in a simplified treatment situation. A four centimeter spread-out Bragg-peak after traversing eight centimeter of lung tissue was simulated in FLUKA. The SOBP with and without consideration of range modulation effects were compared. Results: As well in the measurements as in the MC simulations range modulation effects of lung tissue were observed. The determined modulation powers showed a great range from 0.05 mm, in the micro-CT data, to 0.7 mm in the lung measurements. The SOBP comparison showed that range modulation effects Result in over- and underdosages at the distal and proximal edge of the SOBP. In the investigated case, the last 0.5 cm of the SOBP showed an underdosage of up to 50% at the distal edge, while 0.5 cm distal to the SOBP an overdosage of up to 50% was observed. Conclusion: Range modulation effects occur in inhomogeneous materials like lung. These modulation effects may Result in clinically relevant over- and underdosages but are currently not considered in commercially available treatment planning systems.},
doi = {10.1118/1.4925034},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}