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2014 | 59 | 1 | 15-23

Article title

Monte Carlo calculated CT numbers for improved heavy ion treatment planning


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Better knowledge of CT number values and their uncertainties can be applied to improve heavy ion treatment planning. We developed a novel method to calculate CT numbers for a computed tomography (CT) scanner using the Monte Carlo (MC) code, BEAMnrc/EGSnrc. To generate the initial beam shape and spectra we conducted full simulations of an X-ray tube, filters and beam shapers for a Siemens Emotion CT. The simulation output files were analyzed to calculate projections of a phantom with inserts. A simple reconstruction algorithm (FBP using a Ram-Lak filter) was applied to calculate the pixel values, which represent an attenuation coefficient, normalized in such a way to give zero for water (Hounsfield unit (HU)). Measured and Monte Carlo calculated CT numbers were compared. The average deviation between measured and simulated CT numbers was 4 ± 4 HU and the standard deviation σ was 49 ± 4 HU. The simulation also correctly predicted the behaviour of H-materials compared to a Gammex tissue substitutes. We believe the developed approach represents a useful new tool for evaluating the effect of CT scanner and phantom parameters on CT number values.










Physical description


1 - 03 - 2014
25 - 03 - 2014


  • West German Proton Therapy Centre Essen (WPE), Hufelandstraße 55, 45147 Essen, Germany
  • Division of Accelerator Physics, National Centre for Nuclear Research (NCBJ), 7 Andrzeja Soltana Str., 05-400 Otwock/Świerk, Poland, Tel.: +48 22 718 0423, Fax: +48 22 779 3481
  • Heidelberg Ion-Beam Therapy Centre HIT, Im Neuenheimer Feld 450, 69120 Heidelberg, Germany


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