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@ARTICLE{Hfel:285223,
      author       = {S. Höfel and P. Liebig and M. K. Fix and M. Drescher and
                      F. Zwicker$^*$},
      title        = {{A}dapting a practical {EPR} dosimetry protocol to measure
                      output factors in small fields with alanine.},
      journal      = {Journal of applied clinical medical physics},
      volume       = {24},
      number       = {12},
      issn         = {1526-9914},
      address      = {Reston, Va.},
      publisher    = {ACMP},
      reportid     = {DKFZ-2023-02258},
      pages        = {e14191},
      year         = {2023},
      note         = {#LA:E055# / 2023 Dec;24(12):e14191},
      abstract     = {Modern radiotherapy techniques often deliver small
                      radiation fields. In this work, a practical Electron
                      Paramagnetic Resonance (EPR) dosimetry protocol is adapted
                      and applied to measure output factors (OF) in small fields
                      of a 6 MV radiotherapy system. Correction factors and
                      uncertainties are presented and OFs are compared to the
                      values obtained by following TRS-483 using an ionization
                      chamber (IC).Irradiations were performed at 10 cm depth
                      inside a water phantom positioned at 90 cm source to surface
                      distance with a 6 MV flattening filter free photon beam of a
                      Halcyon radiotherapy system. OFs for different nominal field
                      sizes (1 × 1, 2 × 2, 3 × 3, 4 × 4, normalized to 10 ×
                      10 cm2 ) were determined with a PinPoint 3D (PTW 31022) IC
                      following TRS-483 as well as with alanine pellets with a
                      diameter of 4 mm and a height of 2.4 mm. EPR readout was
                      performed with a benchtop X-band spectrometer. Correction
                      factors due to volume averaging and due to positional
                      uncertainties were derived from 2D film measurements.OFs
                      obtained from both dosimeter types agreed within $0.7\%$
                      after applying corrections for the volume averaging effect.
                      For the used alanine pellets, volume averaging correction
                      factors of 1.030(2) for the 1 × 1 cm2 field and <1.002 for
                      the larger field sizes were determined. The correction
                      factor for positional uncertainties of 1 mm was in the order
                      of 1.018 for the 1 × 1 cm2 field. Combined relative
                      standard uncertainties uc for the OFs resulting from alanine
                      measurements were estimated to be below $1.5\%$ for all
                      field sizes. For IC measurements, uc was estimated to be
                      below $1.0\%.A$ practical EPR dosimetry protocol is
                      adaptable for precisely measuring OFs in small fields down
                      to 1 × 1 cm2 . It is recommended to consider the effect of
                      positional uncertainties for field sizes <2 × 2 cm2 .},
      keywords     = {EPR dosimetry (Other) / alanine (Other) / density effect
                      (Other) / output factor (Other) / small field (Other) /
                      volume effect (Other)},
      cin          = {E055},
      ddc          = {530},
      cid          = {I:(DE-He78)E055-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:37922380},
      doi          = {10.1002/acm2.14191},
      url          = {https://inrepo02.dkfz.de/record/285223},
}