Monte Carlo-based down-scatter correction of SPECT attenuation maps

Tomislav Bokulić, Brendan Vastenhouw, Hugo W A M de Jong, Alice J van Dongen, Peter P van Rijk, Freek J Beekman

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Combined acquisition of transmission and emission data in single-photon emission computed tomography (SPECT) can be used for correction of non-uniform photon attenuation. However, down-scatter from a higher energy isotope (e.g. 99mTc) contaminates lower energy transmission data (e.g. 153Gd, 100 keV), resulting in underestimation of reconstructed attenuation coefficients. Window-based corrections are often not very accurate and increase noise in attenuation maps. We have developed a new correction scheme. It uses accurate scatter modelling to avoid noise amplification and does not require additional energy windows. The correction works as follows: Initially, an approximate attenuation map is reconstructed using down-scatter contaminated transmission data (step 1). An emission map is reconstructed based on the contaminated attenuation map (step 2). Based on this approximate 99mTc reconstruction and attenuation map, down-scatter in the 153Gd window is simulated using accelerated Monte Carlo simulation (step 3). This down-scatter estimate is used during reconstruction of a corrected attenuation map (step 4). Based on the corrected attenuation map, an improved 99mTc image is reconstructed (step 5). Steps 3-5 are repeated to incrementally improve the down-scatter estimate. The Monte Carlo simulator provides accurate down-scatter estimation with significantly less noise than down-scatter estimates acquired in an additional window. Errors in the reconstructed attenuation coefficients are reduced from ca. 40% to less than 5%. Furthermore, artefacts in 99mTc emission reconstructions are almost completely removed. These results are better than for window-based correction, both in simulation experiments and in physical phantom experiments. Monte Carlo down-scatter simulation in concert with statistical reconstruction provides accurate down-scatter correction of attenuation maps.

Original languageEnglish
Pages (from-to)1173-81
Number of pages9
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Volume31
Issue number8
DOIs
Publication statusPublished - Aug 2004

Keywords

  • Algorithms
  • Heart
  • Image Enhancement
  • Image Interpretation, Computer-Assisted
  • Monte Carlo Method
  • Phantoms, Imaging
  • Reproducibility of Results
  • Scattering, Radiation
  • Sensitivity and Specificity
  • Thorax
  • Tomography, Emission-Computed, Single-Photon
  • Evaluation Studies
  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Validation Studies

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