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Proceedings Paper

Development of a new multielement detector system for megavoltage photons
Author(s): Ralf Hinderer; Jeff Kapatoes; Harald Keller; Richard Schmidt; Robert Jeraj; Kenneth J. Ruchala; David W. Pearson; Guang Fang; Gustavo Olivera; Thomas Mackie
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Paper Abstract

Currently employed megavoltage photon detector systems in radiotherapy suffer from their low detection efficiency. This paper presents a new, more efficient approach. A dense converter material is placed along the direction of the photon beam together with the interspersed active medium. The high-energy electrons, generated in the converter material, create a detectable signal in the active medium. The characteristics of single detector element prototypes consisting of different brass tubes filled with either air or xenon were investigated. The significance of the wall thickness and material of a two-dimensional array of such elements was analyzed by Monte Carlo studies. Saturation curves and the signal as a function of the gas pressure illustrate the equivalence of the prototypes to conventional ionization chambers. A high-density gas like xenon at a high pressure is required to get a sufficiently large signal-to-noise ratio. Acquired MVCT slice images revealed contrasts of - 2.4 percent at a dose of 40 cGy. Monte Carlo calculations suggest an optimal wall thickness of a few hundred micrometers for an element width of 1.5 mm. The superiority of high density and high atomic number materials like tungsten in terms of the amount of primary signal recorded and the extent of crosstalk is demonstrated.

Paper Details

Date Published: 3 May 2002
PDF: 10 pages
Proc. SPIE 4682, Medical Imaging 2002: Physics of Medical Imaging, (3 May 2002); doi: 10.1117/12.465632
Show Author Affiliations
Ralf Hinderer, Univ. of Wisconsin/Madison (United States)
Jeff Kapatoes, TomoTherapy Inc. (United States)
Harald Keller, Univ. of Wisconsin/Madison (United States)
Richard Schmidt, TomoTherapy Inc. (United States)
Robert Jeraj, Univ. of Wisconsin/Madison (United States)
Kenneth J. Ruchala, TomoTherapy Inc. (United States)
David W. Pearson, TomoTherapy Inc. (United States)
Guang Fang, TomoTherapy Inc. (United States)
Gustavo Olivera, TomoTherapy Inc. (United States)
Thomas Mackie, Univ. of Wisconsin/Madison (United States)

Published in SPIE Proceedings Vol. 4682:
Medical Imaging 2002: Physics of Medical Imaging
Larry E. Antonuk; Martin Joel Yaffe, Editor(s)

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