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@ARTICLE{GhesquiereDierickx:178611,
      author       = {L. Ghesquiere-Dierickx$^*$ and R. Félix-Bautista$^*$ and
                      A. Schlechter$^*$ and L. Kelleter$^*$ and M. Reimold$^*$ and
                      G. Echner$^*$ and P. Soukup and O. Jäkel$^*$ and T.
                      Gehrke$^*$ and M. Martisikova$^*$},
      title        = {{D}etecting perturbations of a radiation field inside a
                      head-sized phantom exposed to therapeutic carbon-ion beams
                      through charged-fragment tracking.},
      journal      = {Medical physics},
      volume       = {49},
      number       = {3},
      issn         = {0094-2405},
      address      = {College Park, Md.},
      publisher    = {AAPM},
      reportid     = {DKFZ-2022-00160},
      pages        = {1776-1792},
      year         = {2022},
      note         = {#EA:E040#LA:E040# / 2022 Mar;49(3):1776-1792},
      abstract     = {Non-invasive methods to monitor carbon-ion beams in
                      patients are desired to fully exploit the advantages of
                      carbon-ion radiotherapy. Prompt secondary ions produced in
                      nuclear fragmentations of carbon ions are of particular
                      interest for monitoring purposes as they can escape the
                      patient, and thus be detected and tracked to measure the
                      radiation field in the irradiated object. This study aims to
                      evaluate the performance of secondary-ion tracking to
                      detect, visualize and localize an internal air cavity used
                      to mimic inter-fractional changes in the patient anatomy at
                      different depths along the beam axis.In this work, a
                      homogeneous head phantom was irradiated with a realistic
                      carbon-ion treatment plan with a typical prescribed fraction
                      dose of 3 Gy (RBE). Secondary ions were detected by a
                      mini-tracker with an active area of 2 cm2 , based on the
                      Timepix3 semiconductor pixel detector technology. The
                      mini-tracker was placed 120 mm behind the center of the
                      target at an angle of 30 degrees with respect to the beam
                      axis. To assess the performance of the developed method, a
                      2-mm-thick air cavity was inserted in the head phantom at
                      several depths: in front of as well as at the entrance, in
                      the middle and at the distal end of the target volume.
                      Different reconstruction methods of secondary-ion emission
                      profile were studied using the FLUKA Monte Carlo simulation
                      package. The perturbations in the emission profiles caused
                      by the air cavity were analyzed to detect the presence of
                      the air cavity and localize its position.The perturbations
                      in the radiation field mimicked by the 2-mm-thick cavity
                      were found to be significant. A detection significance of at
                      least three standard deviations in terms of spatial
                      distribution of the measured tracks was found for all
                      investigated cavity depths, while the highest significance
                      (6 standard deviations) was obtained when the cavity was
                      located upstream of the tumor. For a tracker with an
                      eight-fold sensitive area, the detection significance rose
                      to at least 9 standard deviations, and up to 17 standard
                      deviations respectively. The cavity could be detected at all
                      depths and its position measured within 6.5 mm ± 1.4 mm,
                      which is sufficient for the targeted clinical performance of
                      10 mm.The presented systematic study concerning the
                      detection and localization of small inter-fractional
                      structure changes in a realistic clinical setting
                      demonstrates that secondary ions carry a large amount of
                      information on the internal structure of the irradiated
                      object, and are thus attractive to be further studied for
                      non-invasive monitoring of carbon-ion treatments. This
                      article is protected by copyright. All rights reserved.},
      keywords     = {carbon-ion radiotherapy (Other) / inter-fractional changes
                      (Other) / non-invasive ion-beam monitoring (Other) / nuclear
                      fragmentation (Other) / secondary ions (Other) /
                      secondary-ion tracking (Other) / semiconductor pixel
                      detector Timepix3 (Other)},
      cin          = {E040},
      ddc          = {610},
      cid          = {I:(DE-He78)E040-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:35073413},
      doi          = {10.1002/mp.15480},
      url          = {https://inrepo02.dkfz.de/record/178611},
}