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@ARTICLE{Metzner:287462,
      author       = {M. Metzner$^*$ and D. Zhevachevska$^*$ and A.
                      Schlechter$^*$ and F. Kehrein$^*$ and J. Schlecker$^*$ and
                      C. Murillo$^*$ and S. Brons and O. Jaekel$^*$ and M.
                      Martisikova$^*$ and T. Gehrke$^*$},
      title        = {{E}nergy painting: helium-beam radiography with thin
                      detectors and multiple beam energies.},
      journal      = {Physics in medicine and biology},
      volume       = {69},
      issn         = {0031-9155},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {DKFZ-2024-00254},
      pages        = {055002},
      year         = {2024},
      note         = {#EA:E040#LA:E040# / Phys. Med. Biol. 69 (2024) 055002},
      abstract     = {$\
Objective.Compact$ ion imaging systems based on thin
                      detectors are a promising prospect for the clinical
                      environment since they are easily integrated into the
                      clinical workflow. Their measurement principle is based on
                      energy deposition instead of the conventionally measured
                      residual energy or range. Therefore, thin detectors are
                      limited in the water-equivalent thickness range they can
                      image with high precision. This article presents our energy
                      painting method, which has been developed to render high
                      precision imaging with thin detectors feasible even for
                      objects with larger, clinically relevant WET
                      $ranges.\
Approach.$ A detection system exclusively
                      based on pixelated silicon Timepix detectors was used at the
                      Heidelberg ion-beam therapy center to track single helium
                      ions and measure their energy deposition behind the imaged
                      object. Calibration curves were established for five initial
                      beam energies to relate the measured energy deposition to
                      water-equivalent thickness (WET). They were evaluated
                      regarding their accuracy, precision and temporal stability.
                      Furthermore, a 60 mm × 12 mm region of a wedge phantom was
                      imaged quantitatively exploiting the calibrated energies and
                      five different mono-energetic images. These mono-energetic
                      images were combined in a pixel-by-pixel manner by averaging
                      the WET-data weighted according to their single-ion WET
                      precision (SIWP) and the number of contributing
                      $ions.\
Main$ result.A quantitative helium-beam
                      radiograph of the wedge phantom with an average SIWP of
                      (1.82 ± 0.05) $\%$ over the entire WET interval from 150 mm
                      to 220 mm was obtained. Compared to the previously used
                      methodology, the SIWP improved by a factor of 2.49 ± 0.16.
                      The relative stopping power value of the wedge derived from
                      the energy-painted image matches the result from range
                      pullback measurements with a relative deviation of only 0.4
                      $\%.\
Significance.The$ proposed method overcomes the
                      insufficient precision for wide WET ranges when employing
                      detection systems with thin detectors. Applying this method
                      is an important prerequisite for imaging of patients. Hence,
                      it advances detection systems based on energy deposition
                      measurements towards clinical $implementation.\&#xD.$},
      keywords     = {Timepix (Other) / ion imaging (Other) / ion-beam
                      radiography (Other) / ion-beam radiotherapy (Other) / proton
                      therapy (Other) / relative stopping power (Other) / silicon
                      pixel detectors (Other)},
      cin          = {E040 / E220 / E020},
      ddc          = {530},
      cid          = {I:(DE-He78)E040-20160331 / I:(DE-He78)E220-20160331 /
                      I:(DE-He78)E020-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:38295403},
      doi          = {10.1088/1361-6560/ad247e},
      url          = {https://inrepo02.dkfz.de/record/287462},
}