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@ARTICLE{Simard:362971,
      author       = {Simard, Mikaël and Fullarton, Ryan and Volz, Lennart and
                      Schuy, Christoph and Robertson, Daniel G. and Toltz, Allison
                      and Baker, Colin and Beddar, Sam and Graeff, Christian and
                      Fekete, Charles-Antoine Collins},
      title        = {{A} comparison of carbon ions versus protons for integrated
                      mode ion imaging},
      journal      = {Medical physics},
      volume       = {52},
      number       = {5},
      issn         = {0094-2405},
      address      = {Hoboken, NJ},
      publisher    = {Wiley},
      reportid     = {GSI-2025-01214},
      pages        = {3097 - 3106},
      year         = {2025},
      note         = {This is an open access article under the terms of the
                      Creative Commons Attribution License, which permits use,
                      distribution and reproduction in any medium, provided the
                      original work is properly cited.},
      abstract     = {Incorporating image guidance into ion beam therapy is
                      critical for minimizing beam range uncertainties and
                      realizing the modality's potential. One promising avenue for
                      image guidance is to capture transmission ion radiographs
                      (iRads) before and/or during treatment. iRad image quality
                      is typically maximized using a single-event imaging system,
                      which involves tracking individual ions, albeit the approach
                      is generally not suited to clinical beam settings. An
                      alternative faster and clinically compatible method is
                      integrated mode imaging, where individual pencil beam data
                      is acquired, rather than single ion data. To evaluate the
                      usefulness of transmission ion imaging for image guidance,
                      it is crucial to evaluate the image quality of integrated
                      mode iRad systems.We report extensive image quality metrics
                      of integrated mode carbon ion radiographs (cRads) and
                      compare them with proton radiographs (pRads).iRads were
                      obtained at the Marburg Ion Beam Therapy Center using a
                      plastic volumetric scintillator equipped with CCD cameras.
                      The detector captures orthogonal views of the 3D energy
                      deposition in the scintillator from individual pencil beams.
                      Four phantoms were scanned using a 15 × 15 cm 2 $15\times
                      15 \ {\rm cm}^2$ field of view and a beam spacing of 1 mm.
                      First, 9 tissue-substitute inserts were used to evaluate
                      water equivalent thickness (WET) accuracy. Radiographs of
                      those inserts were reconstructed for beam spacings ranging
                      from 1 to 7 mm to evaluate the impact of spacing on
                      quantitative accuracy. For spatial resolution, custom 3D
                      printed line pair (lp) modules ranging from 0.5 to 10 lp/cm
                      were scanned. To evaluate low contrast detectability, a
                      custom 3D printed low contrast module consisting of 20 holes
                      with depths ranging from 1 to 8 mm and diameters from 1 to
                      10 mm was scanned. iRads of an anthropomorphic head phantom
                      were also obtained.Spatial resolution and low contrast
                      detection are systematically improved for cRads compared to
                      pRads. Image resolution was 3.7 lp/cm for cRads and 1.7
                      lp/cm for pRads in the center of the field of view. Spatial
                      resolution was found to vary with the object's location in
                      the field of view. While pRads could mostly resolve low
                      contrast holes of 10 mm in diameter, cRads could resolve
                      holes of up in 4 mm diameter. WET accuracy is similar for
                      both ion species, with a root mean squared error of
                      approximately 1 mm. WET accuracy was stable (maximum of 0.1
                      mm increase) across beam spacings, although important
                      under-sampling artifacts were observed for iRads
                      reconstructed using large beam spacings, especially for
                      cRads. iRads of the anthropomorphic head phantom showed
                      improved apparent contrast using cRads, especially to
                      identify bony structures.This work is the first
                      investigation of image quality metrics such as spatial
                      resolution and low contrast detectability for integrated
                      mode cRads, with a full comparison with pRads. Enhanced
                      image quality is obtained with cRads compared to pRads,
                      although pRads still maintain high WET accuracy and deliver
                      image quality within acceptable bounds.},
      keywords     = {Phantoms, Imaging / Carbon / Protons / Heavy Ion
                      Radiotherapy / Radiotherapy, Image-Guided: methods /
                      image‐guided radiotherapy (Other) / integrated mode
                      (Other) / ion beam therapy (Other) / ion imaging (Other) /
                      ion radiography (Other) / Carbon (NLM Chemicals) / Protons
                      (NLM Chemicals)},
      cin          = {BIO},
      ddc          = {610},
      cid          = {I:(DE-Ds200)BIO-20160831OR354},
      pnm          = {633 - Life Sciences – Building Blocks of Life: Structure
                      and Function (POF4-633) / HITRIplus - Heavy Ion Therapy
                      Research Integration plus (101008548)},
      pid          = {G:(DE-HGF)POF4-633 / G:(EU-Grant)101008548},
      experiment   = {$EXP:(DE-Ds200)External_experiment-20200803$},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.1002/mp.17645},
      url          = {https://repository.gsi.de/record/362971},
}