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@ARTICLE{Sawall:296163,
      author       = {S. Sawall$^*$ and E. Baader$^*$ and P. Trapp$^*$ and M.
                      Kachelriess$^*$},
      title        = {{CT} material decomposition with contrast agents: {S}ingle
                      or multiple spectral photon-counting {CT} scans? {A}
                      simulation study.},
      journal      = {Medical physics},
      volume       = {52},
      number       = {4},
      issn         = {0094-2405},
      address      = {College Park, Md.},
      publisher    = {AAPM},
      reportid     = {DKFZ-2025-00090},
      pages        = {2167-2190},
      year         = {2025},
      note         = {#EA:E025#LA:E025# / 2025 Apr;52(4):2167-2190},
      abstract     = {With the widespread introduction of dual energy computed
                      tomography (DECT), applications utilizing the spectral
                      information to perform material decomposition became
                      available. Among these, a popular application is to
                      decompose contrast-enhanced CT images into virtual
                      non-contrast (VNC) or virtual non-iodine images and into
                      iodine maps. In 2021, photon-counting CT (PCCT) was
                      introduced, which is another spectral CT modality. It allows
                      for scans with more than two different detected spectra.
                      With these systems, it becomes possible to distinguish more
                      than two materials. It is frequently proposed to administer
                      more than one contrast agent, perform a single PCCT scan,
                      and then calculate the VNC images and the contrast agent
                      maps. This may not be optimal because the patient is
                      injected with a material, only to have it computationally
                      extracted again immediately afterwards by spectral CT. It
                      may be better to do an unenhanced scan followed by one or
                      more contrast-enhanced scans. The main argument for the
                      spectral material decomposition is patient motion, which
                      poses a significant challenge for approaches involving two
                      or more temporally separated scans. In this work, we assume
                      that we can correct for patient motion and thus are free to
                      scan the patient more than once. Our goal is then to
                      quantify the penalty for performing a single
                      contrast-enhanced scan rather than a clever series of
                      unenhanced and enhanced scans. In particular, we consider
                      the impact on patient dose and image quality.We simulate CT
                      scans of three differently sized phantoms containing various
                      contrast agents. We do this for a variety of tube voltage
                      settings, a variety of patient-specific prefilter (PSP)
                      thicknesses and a variety of threshold settings of the
                      photon-counting detector with up to four energy bins. The
                      reconstructed bin images give the expectation values of soft
                      tissue and of the contrast agents. Error propagation of
                      projection noise into the images yields the image noise.
                      Dose is quantified using the total CT dose index (CTDI)
                      value of the scans. When combining multiple scans, we
                      further consider all possible tube current (or dose) ratios
                      between the scans. Material decomposition is done
                      image-based in a statistical optimal way. Error propagation
                      into the material-specific images yields the signal-to-noise
                      ratio at unit dose (SNRD). The winning scan strategy is the
                      one with the highest total SNRD, which is related to the
                      SNRD of the material that has the lowest signal-to-noise
                      ratio (SNR) among the materials to decompose into. We
                      consider scan strategies with up to three scans and up to
                      three materials (water W, contrast agent X and contrast
                      agent Y).In all cases, those scan strategies yield the best
                      performance that combine differently enhanced scans, for
                      example, W+WX, W+WXY, WX+WXY, W+WX+WY, with W denoting an
                      unenhanced scan and WX, WY and WXY denoting X-, Y-, and
                      X-Y-enhanced scans, respectively. The dose efficiency of
                      scans with a single enhancement scheme, such as WX or WXY,
                      is far lower. The dose penalty to pay for these single
                      enhancement strategies is about two or greater. Our findings
                      also apply to scans with a single energy bin and thus also
                      to CT systems with conventional, energy-integrating
                      detectors, that is, conventional DECT. Dual source CT (DSCT)
                      scans are preferable over single source CT scans, also
                      because one can use a PSP on the high Kilovolt spectrum to
                      better separate the detected spectra. For the strategies and
                      tasks considered here, it does not make sense to
                      simultaneously scan with two different types of contrast
                      agents. Iodine outperforms other high Z elements in nearly
                      all cases.Given the significant dose penalty when performing
                      only one contrast-enhanced scan rather than a series of
                      unenhanced and enhanced scans, one should consider avoiding
                      the single-scan strategies. This requires to invest in the
                      development of accurate registration algorithms that can
                      compensate for patient and contrast agent motion between
                      separate scans.},
      keywords     = {material decomposition (Other) / multiple contrast agents
                      (Other) / virtual noniodine (Other) / virtual non‐contrast
                      (Other)},
      cin          = {E025},
      ddc          = {610},
      cid          = {I:(DE-He78)E025-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:39791354},
      doi          = {DOI:10.1002/mp.17604},
      url          = {https://inrepo02.dkfz.de/record/296163},
}