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@ARTICLE{Volz:348126,
      author       = {Volz, Lennart and Graeff, Christian and Durante, Marco and
                      Collins-Fekete, Charles-Antoine},
      title        = {{F}ocus stacking single-event particle radiography for high
                      spatial resolution images and 3{D} feature localization.},
      journal      = {Physics in medicine and biology},
      volume       = {69},
      number       = {2},
      issn         = {0031-9155},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {GSI-2024-00172},
      pages        = {024001},
      year         = {2024},
      note         = {PMID: 38056016. Original content from this work may be used
                      under the terms of the Creative Commons Attribution 4.0
                      licence},
      abstract     = {Objective.We demonstrate a novel focus stacking technique
                      to improve spatial resolution of single-event particle
                      radiography (pRad), and exploit its potential for 3D feature
                      detection.Approach.Focus stacking, used typically in optical
                      photography and microscopy, is a technique to combine
                      multiple images with different focal depths into a single
                      super-resolution image. Each pixel in the final image is
                      chosen from the image with the largest gradient at that
                      pixel's position. pRad data can be reconstructed at
                      different depths in the patient based on an estimate of each
                      particle's trajectory (called distance-driven binning; DDB).
                      For a given feature, there is a depth of reconstruction for
                      which the spatial resolution of DDB is maximal. Focus
                      stacking can hence be applied to a series of DDB images
                      reconstructed from a single pRad acquisition for different
                      depths, yielding both a high-resolution projection and
                      information on the features' radiological depth at the same
                      time. We demonstrate this technique with Geant4 simulated
                      pRads of a water phantom (20 cm thick) with five bone cube
                      inserts at different depths (1 × 1 × 1 cm3) and a lung
                      cancer patient.Main results.For proton radiography of the
                      cube phantom, focus stacking achieved a median resolution
                      improvement of $136\%$ compared to a state-of-the-art
                      maximum likelihood pRad reconstruction algorithm and a
                      median of $28\%$ compared to DDB where the reconstruction
                      depth was the center of each cube. For the lung patient,
                      resolution was visually improved, without loss in accuracy.
                      The focus stacking method also enabled to estimate the depth
                      of the cubes within few millimeters accuracy, except for one
                      shallow cube, where the depth was underestimated by 2.5
                      cm.Significance.Focus stacking utilizes the inherent 3D
                      information encoded in pRad by the particle's scattering,
                      overcoming current spatial resolution limits. It further
                      opens possibilities for 3D feature localization. Therefore,
                      focus stacking holds great potential for future pRad
                      applications.},
      keywords     = {depth detection (Other) / focus stacking (Other) / ion
                      imaging (Other) / particle imaging (Other) / particle
                      radiography (Other) / proton imaging (Other) / spatial
                      resolution (Other) / DDB (NLM Chemicals) / Protons (NLM
                      Chemicals)},
      cin          = {BIO / BIO@FAIR},
      ddc          = {530},
      cid          = {I:(DE-Ds200)BIO-20160831OR354 / I:(DE-Ds200)Coll-FAIR-BIO},
      pnm          = {633 - Life Sciences – Building Blocks of Life: Structure
                      and Function (POF4-633) / SUC-GSI-Darmstadt - Strategic
                      university cooperation GSI-TU Darmstadt (SUC-GSI-DA) /
                      HITRIplus - Heavy Ion Therapy Research Integration plus
                      (101008548) / DFG project G:(GEPRIS)491382106 -
                      Open-Access-Publikationskosten / 2025-2027 / GSI
                      Helmholtzzentrum für Schwerionenforschung (491382106)},
      pid          = {G:(DE-HGF)POF4-633 / G:(DE-Ds200)SUC-GSI-DA /
                      G:(EU-Grant)101008548 / G:(GEPRIS)491382106},
      experiment   = {$EXP:(DE-Ds200)External_experiment-20200803$},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:38056016},
      UT           = {WOS:001139761800001},
      doi          = {10.1088/1361-6560/ad131a},
      url          = {https://repository.gsi.de/record/348126},
}