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@ARTICLE{Hamad:304436,
      author       = {Y. Hamad$^*$ and F. K. Sari$^*$ and R. Félix-Bautista$^*$
                      and M. Martišíková$^*$ and A. Mairani and T. Gehrke$^*$},
      title        = {{LET} measurements in proton and helium-ion beams of
                      therapeutic energies using a silicon pixel detector towards
                      a tool for quality assurance.},
      journal      = {Medical physics},
      volume       = {52},
      number       = {9},
      issn         = {0094-2405},
      address      = {Hoboken, NJ},
      publisher    = {Wiley},
      reportid     = {DKFZ-2025-01849},
      pages        = {e18085},
      year         = {2025},
      note         = {#EA:E040#LA:E040#},
      abstract     = {As advanced treatment plans increasingly include optimizing
                      both dose and linear energy transfer (LET), there is a
                      growing demand for tools to measure LET in clinical
                      settings. Although various detection systems have been
                      investigated in this pursuit, the scarcity of detectors
                      capable of providing per-ion data for a fast and streamlined
                      verification of LET distributions remains an issue. Silicon
                      pixel detector technology bridges this gap by enabling rapid
                      tracking of single-ion energy deposition.This study proposes
                      a methodology for assessing LET and relative biological
                      effectiveness (RBE) in mixed radiation fields produced by
                      clinical proton and helium ion beams, using a hybrid silicon
                      pixel detector equipped with a Timepix3 chip.The Timepix3
                      detector was placed behind PMMA slabs of different
                      thicknesses and exposed to initially monoenergetic proton
                      and helium-ion beams. The detector featured a 300 µm-thick
                      silicon sensor operated in partial depletion. Silicon-based
                      LET spectra were derived from single-ion deposited energy
                      across the sensor and subsequently converted to
                      water-equivalent spectra. Track- and dose-averaged LET (LETt
                      and LETd) were calculated from these spectra. LET
                      measurements were used as input to estimate the RBE via the
                      modified microdosimetric kinetic model (mMKM) assuming an
                      (α/β)γ value of 2 Gy. Measurements were compared with
                      simulations performed using the FLUKA Monte Carlo code.
                      Energy deposition spectra, LETt and LETd values were
                      simulated at various depths in PMMA for the radiation fields
                      used, by considering the contribution from the secondary
                      particles generated in the ion interaction processes as
                      well.Energy deposition spectra were validated against Monte
                      Carlo simulations, showing good agreement in both spectral
                      shapes and positions. However, a depth uncertainty of less
                      than 1 mm and other potential differences between
                      measurements and simulations led to deviations, particularly
                      in the distal region of the Bragg curve. Relative
                      differences of LETd between measurements and simulations
                      were within $3\%$ for protons and $10\%$ for helium ions
                      upstream of the Bragg curves. Notably, larger discrepancies
                      were observed in the distal part of the Bragg curve, with
                      maximum relative differences of $7\%$ for protons and $17\%$
                      for helium ions. Average differences between RBE predictions
                      from measured and simulated LET spectra were within $1\%$
                      and $6\%$ for protons and helium, respectively.
                      Nevertheless, for both particle types, most measurements
                      agreed with simulations within 1σ experimental uncertainty
                      across the measured depths, with deviations beyond 1σ
                      generally remaining within 3σ.This study demonstrates the
                      performance of silicon pixel detectors with respect to LET
                      measurements and RBE estimation in clinical proton and
                      helium-ion beams. The streamlined and accessible outline of
                      the proposed methodology supports easy implementation into
                      clinical routines, promising a viable and sound quality
                      assurance tool for particle therapy.},
      keywords     = {Silicon / Helium: therapeutic use / Linear Energy Transfer
                      / Proton Therapy: instrumentation / Quality Assurance,
                      Health Care / Quality Control / Radiometry: instrumentation
                      / Monte Carlo Method / Relative Biological Effectiveness /
                      Monte Carlo simulations (Other) / helium‐beam radiotherapy
                      (Other) / linear energy transfer (Other) / proton therapy
                      (Other) / relative biological effectiveness (Other) /
                      silicon pixel Timepix3 detector (Other) / Silicon (NLM
                      Chemicals) / Helium (NLM Chemicals)},
      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:40905421},
      doi          = {10.1002/mp.18085},
      url          = {https://inrepo02.dkfz.de/record/304436},
}