@article{KleinesZiemonsZwoll1998,
  author    = {Kleines, H. and Ziemons, Karl and Zwoll, K.},
  title     = {Experiences with ATM in a multivendor pilot system at Forschungszentrum J{\"u}lich},
  series = {IEEE Transactions on Nuclear Science},
  volume    = {45},
  journal   = {IEEE Transactions on Nuclear Science},
  number    = {4},
  issn      = {0018-9499},
  pages     = {1867 -- 1871},
  year      = {1998},
  abstract  = {The ATM technology for high speed serial transmission provides a new quality of communication by introducing novel features in a LAN environment, especially support of real time communication, of both LAN and WAN communication and of multimedia streams. In order to evaluate ATM for future DAQ systems and remote control systems as well as for a high speed picture archiving and communications system for medical images, Forschungszentrum Julich has build up a pilot system for the evaluation of ATM and standard low cost multimedia systems. It is a heterogeneous multivendor system containing a variety of switches and desktop solutions, employing different protocol options of ATM. The tests conducted in the pilot system revealed major difficulties regarding stability, interoperability and performance. The paper presents motivations, layout and results of the pilot system. Discussion of results concentrates on performance issues relevant for realistic applications, e.g., connection to a RAID system via NFS over ATM},
  language  = {en}
}
@article{KhodaverdiWeberStreunetal.2006,
  author    = {Khodaverdi, M. and Weber, S. and Streun, M. and Parl, C. and Ziemons, Karl},
  title     = {High resolution imaging with ClearPET™ Neuro - first animal images},
  series = {2005 IEEE Nuclear Science Symposium Conference Record, Vol. 3},
  journal   = {2005 IEEE Nuclear Science Symposium Conference Record, Vol. 3},
  isbn      = {1082-3654},
  pages     = {1641 -- 1644},
  year      = {2006},
  abstract  = {The ClearPET™ Neuro is the first full ring scanner within the Crystal Clear Collaboration (CCC). It consists of 80 detector modules allocated to 20 cassettes. LSO and LuYAP:Ce crystals in phoswich configuration in combination with position sensitive photomultiplier tubes are used to achieve high sensitivity and realize the acquisition of the depth of interaction (DOI) information. The complete system has been tested concerning the mechanical and electronical stability and interplay. Moreover, suitable corrections have been implemented into the reconstruction procedure to ensure high image quality. We present first results which show the successful operation of the ClearPET™ Neuro for artefact free and high resolution small animal imaging. Based on these results during the past few months the ClearPET™ Neuro System has been modified in order to optimize the performance.},
  language  = {en}
}
@article{ChristHollendungLarueetal.2004,
  author    = {Christ, D. and Hollendung, A. and Larue, H. and Parl, C. and Streun, M. and Weber, S. and Ziemons, Karl and Halling, H.},
  title     = {Homogenization of the MultiChannel PM gain by inserting light attenuating masks},
  series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4},
  journal   = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4},
  issn      = {1082-3654},
  pages     = {2382 -- 2385},
  year      = {2004},
  abstract  = {MultiChannel Photomultipliers (PM), like the R7600-00-M64 or R5900-00-M64 from Hamamatsu, are often chosen as photodetectors in high-resolution positron emission tomography (PET). A major problem of this PM is the nonuniform channel gain. In order to solve this problem, light attenuating masks were created. The aim of the masks is a homogenization of the output of all 64 channels using different hole sizes at the channel positions. The hole area, which is individually defined for the different channels, is inversely proportional to the channel gain. The measurements by inserting light attenuating masks improved a homogenization to a ratio of 1:1.2.},
  language  = {en}
}
@article{PhilippEfthimiouPaganoetal.2022,
  author    = {Philipp, Mohr and Efthimiou, Nikos and Pagano, Fiammetta and Kratochwil, Nicolaus and Pizzichemi, Marco and Tsoumpas, Charalampos and Auffray, Etiennette and Ziemons, Karl},
  title     = {Image reconstruction analysis for positron emission tomography with heterostructured scintillators},
  series = {IEEE Transactions on Radiation and Plasma Medical Sciences},
  volume    = {7},
  journal   = {IEEE Transactions on Radiation and Plasma Medical Sciences},
  number    = {1},
  publisher = {IEEE},
  address   = {New York, NY},
  issn      = {2469-7311},
  doi       = {10.1109/TRPMS.2022.3208615},
  pages     = {41 -- 51},
  year      = {2022},
  abstract  = {The concept of structure engineering has been proposed for exploring the next generation of radiation detectors with improved performance. A TOF-PET geometry with heterostructured scintillators with a pixel size of 3.0×3.1×15 mm3 was simulated using Monte Carlo. The heterostructures consisted of alternating layers of BGO as a dense material with high stopping power and plastic (EJ232) as a fast light emitter. The detector time resolution was calculated as a function of the deposited and shared energy in both materials on an event-by-event basis. While sensitivity was reduced to 32\% for 100 μm thick plastic layers and 52\% for 50 μm, the CTR distribution improved to 204±49 ps and 220±41 ps respectively, compared to 276 ps that we considered for bulk BGO. The complex distribution of timing resolutions was accounted for in the reconstruction. We divided the events into three groups based on their CTR and modeled them with different Gaussian TOF kernels. On a NEMA IQ phantom, the heterostructures had better contrast recovery in early iterations. On the other hand, BGO achieved a better contrast to noise ratio (CNR) after the 15th iteration due to the higher sensitivity. The developed simulation and reconstruction methods constitute new tools for evaluating different detector designs with complex time responses.},
  language  = {en}
}
@article{GriessmeierSonnenbergWeckesseretal.1996,
  author    = {Grießmeier, M. and Sonnenberg, F. and Weckesser, M. and Ziemons, Karl and Langen, K.-J. and M{\"u}ller-G{\"a}rtner, H. W.},
  title     = {Improvement of SPECT quantification in small brain structures by using experiment based recovery-coefficient corrections},
  series = {European Journal of Nuclear Medicine},
  volume    = {23},
  journal   = {European Journal of Nuclear Medicine},
  number    = {9},
  issn      = {1619-7089},
  pages     = {1238 -- 1238},
  year      = {1996},
  language  = {en}
}
@article{KhodaverdiChatziioannouWeberetal.2005,
  author    = {Khodaverdi, M. and Chatziioannou, A. F. and Weber, S. and Ziemons, Karl and Halling, H. and Pietrzyk, U.},
  title     = {Investigation of different MicroCT scanner configurations by GEANT4 simulations},
  series = {IEEE Transactions on Nuclear Science},
  volume    = {52},
  journal   = {IEEE Transactions on Nuclear Science},
  number    = {1},
  isbn      = {0018-9499},
  pages     = {188 -- 192},
  year      = {2005},
  abstract  = {This study has been performed to design the combination of the new ClearPET (ClearPET is a trademark of the Crystal Clear Collaboration), a small animal positron emission tomography (PET) system, with a micro-computed tomography (microCT) scanner. The properties of different microCT systems have been determined by simulations based on GEANT4. We will demonstrate the influence of the detector material and the X-ray spectrum on the obtained contrast. Four different detector materials (selenium, cadmium zinc telluride, cesium iodide and gadolinium oxysulfide) and two X-ray spectra (a molybdenum and a tungsten source) have been considered. The spectra have also been modified by aluminum filters of varying thickness. The contrast between different tissue types (water, air, brain, bone and fat) has been simulated by using a suitable phantom. The results indicate the possibility to improve the image contrast in microCT by an optimized combination of the X-ray source and detector material.},
  language  = {en}
}
@article{KhodaverdiChaziioannouWeberetal.2004,
  author    = {Khodaverdi, M. and Chaziioannou, A. F. and Weber, S. and Ziemons, Karl and Halling, H. and Pietrzyk, U.},
  title     = {Investigation of different microCT scanner configurations by GEANT4 simulations},
  series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4},
  journal   = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4},
  issn      = {1082-3654},
  pages     = {2989 -- 2993},
  year      = {2004},
  abstract  = {This study has been performed to design the combination of the new ClearPET TM (ClearPET is a trademark of the Crystal Clear Collaboration), a small animal Positron Emission Tomography (PET) system, with a microComputed Tomography (microCT) scanner. The properties of different microCT systems have been determined by simulations based on GEANT4. We demonstrate the influence of the detector material and the X-ray spectrum on the obtained contrast. Four different detector materials (selenium, cadmium zinc telluride, cesium iodide and gadolinium oxysulfide) and two X-ray spectra (a molybdenum and a tungsten source) have been considered. The spectra have also been modified by aluminum filters of varying thickness. The contrast between different tissue types (water, air, brain, bone and fat) has been simulated by using a suitable phantom. The results indicate the possibility to improve the image contrast in microCT by an optimized combination of the X-ray source and detector material.},
  language  = {en}
}
@article{WeckesserGriessmeierSchmidtetal.1998,
  author    = {Weckesser, Martin and Grießmeier, Martin and Schmidt, Daniela and Sonnenberg, Frank and Ziemons, Karl and Kemna, Lars and Holschbach, Marcus and Langen, Karl-J. and M{\"u}ller-G{\"a}rtner, Hans-W.},
  title     = {Iodine-123 α-methyl tyrosine single-photon emission tomography of cerebral gliomas: standardised evaluation of tumour uptake and extent},
  series = {European Journal of Nuclear Medicine},
  volume    = {25},
  journal   = {European Journal of Nuclear Medicine},
  number    = {2},
  isbn      = {1619-7089},
  pages     = {150 -- 156},
  year      = {1998},
  abstract  = {Single-photon emission tomography (SPET) with the amino acid analogue l-3-[123I]iodo-α-methyl tyrosine (IMT) is helpful in the diagnosis and monitoring of cerebral gliomas. Radiolabelled amino acids seem to reflect tumour infiltration more specifically than conventional methods like magnetic resonance imaging and computed tomography. Automatic tumour delineation based on maximal tumour uptake may cause an overestimation of mean tumour uptake and an underestimation of tumour extension in tumours with circumscribed peaks. The aim of this study was to develop a program for tumour delineation and calculation of mean tumour uptake which takes into account the mean background activity and is thus optimised to the problem of tumour definition in IMT SPET. Using the frequency distribution of pixel intensities of the tomograms a program was developed which automatically detects a reference brain region and draws an isocontour region around the tumour taking into account mean brain radioactivity. Tumour area and tumour/brain ratios were calculated. A three-compartment phantom was simulated to test the program. The program was applied to IMT SPET studies of 20 patients with cerebral gliomas and was compared to the results of manual analysis by three different investigators. Activity ratios and chamber extension of the phantom were correctly calculated by the automatic analysis. A method based on image maxima alone failed to determine chamber extension correctly. Manual region of interest analysis in patient studies resulted in a mean inter-observer standard deviation of 8.7\%±6.1\% (range 2.7\%-25.0\%). The mean value of the results of the manual analysis showed a significant correlation to the results of the automatic analysis (r = 0.91, P<0.0001 for the uptake ratio; r = 0.87, P<0.0001 for the tumour area). We conclude that the algorithm proposed simplifies the calculation of uptake ratios and may be used for observer-independent evaluation of IMT SPET studies. Three-dimensional tumour recognition and transfer to co-registered morphological images based on this program may be useful for the planning of surgical and radiation treatment.},
  language  = {en}
}
@article{ZiemonsHerzogFeinendegen1990,
  author    = {Ziemons, Karl and Herzog, H. and Feinendegen, L. E.},
  title     = {Iterative image reconstruction with weighted pixel contribution to projection element},
  series = {European Journal of Nuclear Medicine},
  volume    = {16},
  journal   = {European Journal of Nuclear Medicine},
  number    = {7},
  isbn      = {1619-7089},
  pages     = {403 -- 403},
  year      = {1990},
  language  = {en}
}
@article{ZiemonsHerzogBosettietal.1992,
  author    = {Ziemons, Karl and Herzog, H. and Bosetti, P. and Feinendegen, L. E.},
  title     = {Iterative image reconstruction with weighted pixel contribution to projection elements},
  series = {European Journal of Nuclear Medicine},
  volume    = {19},
  journal   = {European Journal of Nuclear Medicine},
  number    = {8},
  isbn      = {1619-7089},
  pages     = {588 -- 588},
  year      = {1992},
  language  = {en}
}