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@ARTICLE{Lustermans:301300,
      author       = {D. Lustermans and G. P. Fonseca and C. Jeukens and V. T.
                      Taasti and K. Parodi and G. Landry$^*$ and F. Verhaegen},
      title        = {{E}valuating photon-counting computed tomography for
                      quantitative material characteristics and material
                      differentiation in radiotherapy.},
      journal      = {Physics in medicine and biology},
      volume       = {70},
      number       = {10},
      issn         = {0031-9155},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {DKFZ-2025-00983},
      pages        = {105013},
      year         = {2025},
      abstract     = {Objective.Photon-counting computed tomography (PCCT) counts
                      the individual photons and measures their energy, which
                      allows for energy binning and thereby multi-energy CT
                      imaging. It is expected that quantitative data can be
                      accurately extracted from the images and enable accurate
                      material separation, yet its potential in radiotherapy is
                      mostly unexplored. In this study, PCCT was assessed by
                      evaluating estimation accuracies for relative electron
                      density (RED), effective atomic number (Zeff), and proton
                      stopping-power ratio (SPR), as well as the potential for
                      material differentiation.Approach.PCCT images of a Gammex
                      Advanced Electron Density phantom (Sun Nuclear) with
                      tissue-equivalent materials were acquired in a small and
                      large phantom setup on a NAEOTOM Alpha PCCT scanner (Siemens
                      Healthineers). The scans were performed at 120 and 140 kVp,
                      and virtual monoenergetic images (VMIs) were generated.
                      These VMIs were used to estimate RED,Zeff, and SPR based on
                      two calibration methods for each of the two phantom sizes.
                      These results were compared to findings obtained based on
                      dual-energy CT (DECT) scans acquired on a SOMATOM Confidence
                      scanner (Siemens Healthineers) at 80 and 140 kVp, by using
                      the low and high energy pair and VMIs. Calibration accuracy
                      was quantified by the root-mean-squared error. Additional,
                      material differentiation was assessed for both
                      tissue-equivalent and calcium/iodine inserts by creating
                      [RED/Zeff]-space plots.Main results.There was minimal
                      differences between the two PCCT x-ray spectra, with SPR
                      errors below $0.8\%$ for the large phantom and $0.7\%$ for
                      the small phantom, which was comparable to DECT using VMIs.
                      Material differentiation showed similar results for DECT and
                      PCCT using VMIs, and resulted in lessZeffspread, than the
                      regular DECT kVp pair, possibly due to
                      denoising.Significance.This study showed the ability of PCCT
                      to retrieve material characteristics and possibility for
                      material differentiation between tissue-equivalent material
                      and calcium/iodine, with results comparable to DECT.},
      keywords     = {Phantoms, Imaging / Photons / Tomography, X-Ray Computed:
                      methods / Tomography, X-Ray Computed: instrumentation /
                      Calibration / photon-counting CT (Other) / quantitative
                      imaging (Other) / radiotherapy (Other) / spectral CT (Other)
                      / virtual monoenergetic imaging (Other)},
      cin          = {MU01},
      ddc          = {530},
      cid          = {I:(DE-He78)MU01-20160331},
      pnm          = {899 - ohne Topic (POF4-899)},
      pid          = {G:(DE-HGF)POF4-899},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:40315900},
      doi          = {10.1088/1361-6560/add3ba},
      url          = {https://inrepo02.dkfz.de/record/301300},
}