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@ARTICLE{Slie:154627,
      author       = {J. R. R. Sølie and L. Volz$^*$ and H. E. S. E. S.
                      Pettersen and P. Piersimoni and O. H. Odland and D. Roehrich
                      and H. Helstrup and T. Peitzmann and K. Ullaland and M.
                      Varga-Kofarago and S. Mehendale and O. S. Grøttvik and V.
                      N. Eikeland and I. Meric and J. Seco$^*$},
      title        = {{I}mage quality of list-mode proton imaging without front
                      trackers.},
      journal      = {Physics in medicine and biology},
      volume       = {65},
      number       = {13},
      issn         = {1361-6560},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {DKFZ-2020-00895},
      pages        = {135012},
      year         = {2020},
      note         = {2020 Jul 9;65(13):135012#LA:E041#},
      abstract     = {List mode proton imaging relies on accurate reconstruction
                      of the proton most likely path (MLP) through the patient.
                      This typically requires two sets of position sensitive
                      detector systems, one upstream (front) and one downstream
                      (rear) of the patient. However, for a clinical
                      implementation it can be preferable to omit the front
                      trackers (single-sided proton imaging). For such a system,
                      the MLP can be computed from information available through
                      the beam delivery system and the remaining rear tracker set.
                      In this work, we use Monte Carlo simulations to compare a
                      conventional double-sided (using both front and rear
                      detector systems) with a single-sided system (only rear
                      detector system) by evaluating the spatial resolution of
                      proton radiographs (pRad) and proton CT images (pCT)
                      acquired with these set-ups. Both the pencil beam spot size,
                      as well as the spacing between spots was also adjusted to
                      identify the impact of these beam parameters on the image
                      quality. Relying only on the pencil beam central position
                      for computing the MLP resulted in severe image artifacts
                      both in pRad and pCT. Using the recently extended-MLP
                      formalism that incorporate pencil beam uncertainty removed
                      these image artifacts. However, using a more focused pencil
                      beam with this algorithm induced image artifacts when the
                      spot spacing was the same as the beam spot size. The spatial
                      resolution tested with a sharp edge gradient technique was
                      reduced by 40 $\%$ for single-sided $(MTF10\%=3.0$ lp/cm)
                      compared to double-sided (MTF10 $\%=4.9$ lp/cm) pRad with
                      ideal tracking detectors. Using realistic trackers the
                      difference decreased to $30\%,$ with $MTF10\%$ of4.0 lp/cm
                      for the realistic double-sided and 2.7 lp/cm for the
                      realistic single-sided setup. When studying an
                      anthropomorphic paediatric head phantom both single- and
                      double-sided set-ups performed similarly where the
                      difference between the two set-ups were less than 0.01 mm in
                      homogeneous areas of the head. Larger discrepancies between
                      the two set-ups were visible in high density gradients like
                      the facial structures. A complete CT reconstruction of a
                      Catphan® module was performed. Assuming ideal detectors,
                      the obtained spatial resolution was 5.1 lp/cm for
                      double-sided and 3.8 lp/cm for the single-sided setup.
                      Double- and single-sided pRad with realistic tracker
                      properties returned a spatial resolution of 3.8 lp/cm and
                      3.2 lp/cm, respectively. Future studies should investigate
                      the development of dedicated reconstruction algorithms
                      targeted for single-sided particle imaging.},
      cin          = {E041},
      ddc          = {530},
      cid          = {I:(DE-He78)E041-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:32344385},
      doi          = {10.1088/1361-6560/ab8ddb},
      url          = {https://inrepo02.dkfz.de/record/154627},
}