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A more accurate reconstruction system matrix for quantitative proton computed tomography

Journal Article


Abstract


  • An accurate system matrix is required for quantitative proton CT (pCT) image reconstruction with

    iterative projection algorithms. The system matrix is composed of chord lengths of individual

    proton path intersections with reconstruction pixels. In previous work, reconstructions were performed

    assuming constant intersection chord lengths, which led to systematic errors of the reconstructed

    proton stopping powers. The purpose of the present work was to introduce a computationally

    efficient variable intersection chord length in order to improve the accuracy of the system

    matrix. An analytical expression that takes into account the discrete stepping nature of the pCT

    most likely path (MLP) reconstruction procedure was created to describe an angle-dependent effective

    mean chord length function. A pCT dataset was simulated with GEANT4 using a parallel

    beam of 200 MeV protons intersecting a computerized head phantom consisting of tissueequivalent

    materials with known relative stopping power. The phantom stopping powers were

    reconstructed with the constant chord length, exact chord length, and effective mean chord length

    approaches, in combination with the algebraic reconstruction technique. Relative stopping power

    errors were calculated for each anatomical phantom region and compared for the various methods.

    It was found that the error of approximately 10% in the mean reconstructed stopping power value

    for a given anatomical region, resulting from a system matrix with a constant chord length, could be

    reduced to less than 0.5% with either the effective mean chord length or exact chord length

    approaches. Reconstructions with the effective mean chord length were found to be approximately

    20% faster than reconstructions with an exact chord length. The effective mean chord length

    method provides the possibility for more accurate, computationally efficient quantitative pCT

    reconstructions.

Authors


  •   Penfold, Scott (external author)
  •   Rosenfeld, Anatoly B.
  •   Schulte, Reinhard W. (external author)
  •   Schubert, Keith (external author)

Publication Date


  • 2009

Citation


  • Penfold, S. N., Rozenfeld, A., Schulte, R. W. & Schubert, K. E. (2009). A more accurate reconstruction system matrix for quantitative proton computed tomography. Medical Physics, 36 (10), 4511-4518.

Scopus Eid


  • 2-s2.0-70349705642

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5443

Number Of Pages


  • 7

Start Page


  • 4511

End Page


  • 4518

Volume


  • 36

Issue


  • 10

Abstract


  • An accurate system matrix is required for quantitative proton CT (pCT) image reconstruction with

    iterative projection algorithms. The system matrix is composed of chord lengths of individual

    proton path intersections with reconstruction pixels. In previous work, reconstructions were performed

    assuming constant intersection chord lengths, which led to systematic errors of the reconstructed

    proton stopping powers. The purpose of the present work was to introduce a computationally

    efficient variable intersection chord length in order to improve the accuracy of the system

    matrix. An analytical expression that takes into account the discrete stepping nature of the pCT

    most likely path (MLP) reconstruction procedure was created to describe an angle-dependent effective

    mean chord length function. A pCT dataset was simulated with GEANT4 using a parallel

    beam of 200 MeV protons intersecting a computerized head phantom consisting of tissueequivalent

    materials with known relative stopping power. The phantom stopping powers were

    reconstructed with the constant chord length, exact chord length, and effective mean chord length

    approaches, in combination with the algebraic reconstruction technique. Relative stopping power

    errors were calculated for each anatomical phantom region and compared for the various methods.

    It was found that the error of approximately 10% in the mean reconstructed stopping power value

    for a given anatomical region, resulting from a system matrix with a constant chord length, could be

    reduced to less than 0.5% with either the effective mean chord length or exact chord length

    approaches. Reconstructions with the effective mean chord length were found to be approximately

    20% faster than reconstructions with an exact chord length. The effective mean chord length

    method provides the possibility for more accurate, computationally efficient quantitative pCT

    reconstructions.

Authors


  •   Penfold, Scott (external author)
  •   Rosenfeld, Anatoly B.
  •   Schulte, Reinhard W. (external author)
  •   Schubert, Keith (external author)

Publication Date


  • 2009

Citation


  • Penfold, S. N., Rozenfeld, A., Schulte, R. W. & Schubert, K. E. (2009). A more accurate reconstruction system matrix for quantitative proton computed tomography. Medical Physics, 36 (10), 4511-4518.

Scopus Eid


  • 2-s2.0-70349705642

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5443

Number Of Pages


  • 7

Start Page


  • 4511

End Page


  • 4518

Volume


  • 36

Issue


  • 10