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@ARTICLE{Pettersen:165909,
      author       = {H. E. S. Pettersen and L. Volz$^*$ and J. R. Sølie and J.
                      Alme and G. G. Barnaföldi and R. Barthel and A. van den
                      Brink and V. Borshchov and M. Chaar and V. N. Eikeland and
                      G. Genov and O. S. Grøttvik and H. Helstrup and R. Keidel
                      and C. Kobdaj and N. van der Kolk and S. Mehendale and I.
                      Meric and O. H. Odland and G. Papp and T. Peitzmann and P.
                      Piersimoni and M. Protsenko and A. U. Rehman and M. Richter
                      and A. T. Samnøy and J. Seco$^*$ and H. Shafiee and A.
                      Songmoolnak and G. Tambave and I. Tymchuk and K. Ullaland
                      and M. Varga-Kofarago and B. Wagner and R. Xiao and S. Yang
                      and H. Yokoyama and D. Roehrich},
      title        = {{H}elium radiography with a digital tracking calorimeter-a
                      {M}onte {C}arlo study for secondary track rejection.},
      journal      = {Physics in medicine and biology},
      volume       = {66},
      number       = {3},
      issn         = {1361-6560},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {DKFZ-2020-02466},
      pages        = {035004},
      year         = {2021},
      note         = {2021 Jan 26;66(3):035004},
      abstract     = {Radiation therapy using protons and heavier ions is a
                      fast-growing therapeutic option for cancer patients. A
                      clinical system for particle imaging in particle therapy
                      would enable online patient position verification,
                      estimation of the dose deposition through range monitoring
                      and a reduction of uncertainties in the calculation of the
                      relative stopping power of the patient. Several prototype
                      imaging modalities offer radiography and computed tomography
                      using protons and heavy ions. A Digital Tracking Calorimeter
                      (DTC), currently under development, has been proposed as one
                      such detector. In the DTC 43 longitudinal layers of
                      laterally stacked ALPIDE CMOS monolithic active pixel sensor
                      chips are able to reconstruct a large number of
                      simultaneously recorded proton tracks. In this study, we
                      explored the capability of the DTC for helium imaging which
                      offers favorable spatial resolution over proton imaging.
                      Helium ions exhibit a larger cross section for inelastic
                      nuclear interactions, increasing the number of produced
                      secondaries in the imaged object and in the detector itself.
                      To that end, a filtering process able to remove a large
                      fraction of the secondaries was identified, and the track
                      reconstruction process was adapted for helium ions. By
                      filtering on the energy loss along the tracks, on the
                      incoming angle and on the particle ranges, $97.5\%$ of the
                      secondaries were removed. After passing through 16 cm water,
                      $50.0\%$ of the primary helium ions survived; after the
                      proposed filtering $42.4\%$ of the primaries remained;
                      finally after subsequent image reconstruction $31\%$ of the
                      primaries remained. Helium track reconstruction leads to
                      more track matching errors compared to protons, due to the
                      increased available focus strength of the helium beam. In a
                      head phantom radiograph, the Water Equivalent Path Length
                      error envelope was 1.0 mm for helium and 1.1 mm for protons.
                      This accuracy is expected to be sufficient for helium
                      imaging for pre-treatment verification purposes.},
      cin          = {E041},
      ddc          = {530},
      cid          = {I:(DE-He78)E041-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:33181502},
      doi          = {10.1088/1361-6560/abca03},
      url          = {https://inrepo02.dkfz.de/record/165909},
}