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@PHDTHESIS{Issa:976443,
      author       = {Issa, Ahlam Said Mohamad},
      othercontributors = {Shah, Nadim Joni and Neuner, Irene},
      title        = {{A} detector block-pairwise dead time correction method for
                      improved quantitation accuracy for a dedicated {B}rain{PET}
                      scanner},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-00241},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2023},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University 2024; Dissertation, Rheinisch-Westfälische
                      Technische Hochschule Aachen, 2023},
      abstract     = {A Detector Block-Pairwise Dead Time Correction Method for
                      Improved Quantitation Accuracy for a Dedicated BrainPET
                      Scanner Dead time correction (DTC) is of high significance
                      for accurate quantification in PET, just like other
                      corrections for attenuation, decay, and scatter. Many PET
                      systems use the global DTC, i.e., an average DTC factor is
                      computed for all scintillation detector blocks of the
                      system. However, the count rates of the individual
                      scintillation detector blocks are potentially very different
                      due to the individually varying irradiation of each block
                      detector, especially for systems where the allocation of
                      radiation shields is not possible, as in the case of our
                      dedicated Siemens 3T MR BrainPET insert. For that reason, we
                      have developed a block-pairwise DTC. In our approach, we
                      extended a previously published method that uses the delayed
                      random coincidence count rate to estimate the dead time in
                      the individual blocks and planes. This DTC was evaluated
                      with decay experiments using phantom measurements with
                      homogenous and inhomogeneous activity concentrations and
                      with and without out-of-FOV activity. We compared the
                      accuracy and the noise behavior with measurements using a
                      3-compartment phantom. Moreover, we showed that the global
                      and the improved block-pairwise DTC require different
                      calibration. Therefore, we cross-calibrated both methods
                      against each other. The differences in the quantification of
                      the BrainPET images were evaluated by using several
                      radioactive tracers. For this, we validated the method by
                      quantifying the impact on [11C]ABP688 time-activity curves
                      (TACs) and derived quantities such as the non-displaceable
                      binding potential (BPND) and the total distribution volume
                      (VT). We further studied the new method’s impact on
                      O-(2-[18F]fluoroethyl)-L-tyrosine (FET) TACs and tumor to
                      background ratios (TBRmax and TBRmean) and we evaluated the
                      impact on [15O]H2O TACs and the rate constants K1 and k2,
                      the regional cerebral blood flow (rCBF), and the VT obtained
                      by kinetic modeling. The phantom measurements showed that
                      the global DTC led to significant quantification biases in
                      mainly those regions with high activity concentrations,
                      while the block-pairwise DTC led to substantially less bias.
                      The noise level was comparable for both methods. The
                      evaluation of typical applications in volunteer and patient
                      measurements revealed relevant differences between the two
                      DTC, particularly relevant for research applications in
                      neuroscientific studies. In case of PET imaging with
                      [11C]ABP688 we found a relevant bias of VT in all studied
                      brain regions when using the global DTC. For [18F]-FET-PET,
                      differences in TBRmax of up to $10\%$ were observed when
                      comparing both DTC methods. These differences depend on the
                      distance of the tumor from the PET iso-center. For [15O]H2O,
                      we found relevant biases for rCBF, K1, k2, and VT in the
                      both regions (GM and WM).},
      cin          = {535000-5 ; 934020 ; 934010 / 080031},
      ddc          = {610},
      cid          = {$I:(DE-82)535000-5_20140620$ / $I:(DE-82)080031_20200305$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-00241},
      url          = {https://publications.rwth-aachen.de/record/976443},
}