@article{StreunBrandenburgLarueetal.2003, author = {Streun, M. and Brandenburg, G. and Larue, H. and Saleh, H. and Zimmermann, E. and Ziemons, Karl and Halling, H.}, title = {Pulse shape discrimination of LSO and LuYAP scintillators for depth of interaction detection in PET}, series = {2002 IEEE Nuclear Science Symposium Conference Record, Vol. 3}, journal = {2002 IEEE Nuclear Science Symposium Conference Record, Vol. 3}, issn = {1082-3654}, pages = {1636 -- 1639}, year = {2003}, abstract = {A feasible way to gain the depth of interaction information in a PET scanner is the use of phoswich detectors. In general the layer of interaction is identified front the pulse shape of the corresponding scintillator material. In this work pulses from LSO and LuYAP crystals were investigated in order to find a practical method of distinguishing. It turned out that such a pulse processing could he kept simple due to an additional slow component in the light decay of the LuYAP pulse. At the same time the short decay time guarantees that the major amount of the light output is still collected within a short pulse recording time.}, language = {en} } @article{StreunBrandenburgLarueetal.2003, author = {Streun, M. and Brandenburg, G. and Larue, H. and Saleh, H. and Zimmermann, E. and Ziemons, Karl and Halling, H.}, title = {Pulse shape discrimination of LSO and LuYAP scintillators for depth of interaction detection in PET}, series = {IEEE Transactions on Nuclear Science}, volume = {50}, journal = {IEEE Transactions on Nuclear Science}, number = {3}, isbn = {0018-9499}, pages = {344 -- 347}, year = {2003}, abstract = {A feasible way to gain the depth of interaction information in a positron emission tomography scanner is the use of phoswich detectors. In general, the layer of interaction is identified from the pulse shape of the corresponding scintillator material. In this work, pulses from LSO and LuYAP crystals were investigated in order to find a practical method of distinguishing. It turned out that such a pulse processing could be kept simple because of an additional slow component in the light decay of the LuYAP pulse. At the same time, the short decay time guarantees that the major amount of the light output is still collected within a short pulse recording time.}, 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{ZiemonsAuffrayBarbieretal.2004, author = {Ziemons, Karl and Auffray, E. and Barbier, R. and Brandenburg, G.}, title = {The ClearPET TM LSO/LuYAP phoswich scanner: a high performance small animal PET system}, series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 3}, journal = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 3}, issn = {1082-3654}, pages = {1728 -- 1732}, year = {2004}, abstract = {A 2nd generation high performance small animal PET scanner, called ClearPET™, has been designed and a first prototype is built by working groups of the Crystal Clear Collaboration (CCC). In order to achieve high sensitivity and maintain good uniform spatial resolution over the field of view in high resolution PET systems, it is necessary to extract the depth of interaction (DOI) information and correct for spatial degradation. The design of the first ClearPET™ Demonstrator based on the use of the multi-anode photomultiplier tube (Hamamatsu R7600-M64) and a LSO/LuYAP phoswich matrix. The two crystal layers of 8*8 crystals (2*2*10 mm3) are stacked on each other and mounted without light guide as one to one on the PMT. A unit of four PMTs arranged in-line represents one of 20 sectors of the ring design. The opening diameter of the crystal ring is 137 mm, the axial detector length is 110 mm. The PMT pulses are digitized by free-running ADCs and digital data processing determines the gamma energy, the phoswich layer and even the pulse arrival time. Single gamma interactions are recorded and coincidences are found by software. The gantry allows rotation of the detector modules around the field of view. The measurements have been done using the first LSO/LuYAP detector cassettes.}, language = {en} } @article{StreunBrandenburgBroekeletal.2004, author = {Streun, M. and Brandenburg, G. and Br{\"o}kel, M. and Fuss, L. and Larue, H. and Parl, C. and Zimmermann, E. and Ziemons, Karl and Halling, H.}, title = {The ClearPET data acquisition}, series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5}, journal = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5}, issn = {1082-3654}, pages = {3097 -- 3100}, year = {2004}, abstract = {Within the Crystal Clear Collaboration a modular system for a small animal PET scanner (ClearPET™) has been developed. The modularity allows the assembly of scanners of different sizes and characteristics in order to fit the specific needs of the individual member institutions. Now a first demonstrator is being completed in Julich. The system performs depth of interaction detection by using a phoswich arrangement combining LSO and LuYAP scintillators which are coupled to multi-channel photomultipliers (PMTs). A free-running ADC digitizes the signal from the PMT and the complete scintillation pulses are sampled by an FPGA and sent with 20 MB/S to a PC for preprocessing. The pulse provides information about the gamma energy and the scintillator material which identifies the interaction layer. Furthermore, the exact pulse starting time is obtained from the sampled data. This is important as no hardware coincidence detection is implemented. All single events are recorded and coincidences are identified by software. An advantage of that is that the coincidence window and the dimensions of the field of view can be adjusted easily. The ClearPET™ demonstrator is equipped with 10240 crystals on 80 PMTs. This paper presents an overview of the data acquisition system.}, 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{ZiemonsHeinrichsStreunetal.2004, author = {Ziemons, Karl and Heinrichs, U. and Streun, M. and Pietrzyk, U.}, title = {Validation of GEANT3 simulation studies with a dual-head PMT ClearPET™ prototype}, series = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5}, journal = {2003 IEEE Nuclear Science Symposium Conference Record, Vol. 5}, issn = {1082-3654}, pages = {3053 -- 3056}, year = {2004}, abstract = {The ClearPET™ project is proposed by working groups of the Crystal Clear Collaboration (CCC) to develop a 2nd generation high performance small animal positron emission tomograph (PET). High sensitivity and high spatial resolution is foreseen for the ClearPET™ camera by using a phoswich arrangement combining mixed lutetium yttrium aluminum perovskite (LuYAP:Ce) and lutetium oxyorthosilicate (LSO) scintillating crystals. Design optimizations for the first photomultiplier tube (PMT) based ClearPET camera are done with a Monte-Carlo simulation package implemented on GEANT3 (CERN, Geneva, Switzerland). A dual-head prototype has been built to test the frontend electronics and was used to validate the implementation of the GEANT3 simulation tool. Multiple simulations were performed following the experimental protocols to measure the intrinsic resolution and the sensitivity profile in axial and radial direction. Including a mean energy resolution of about 27.0\% the simulated intrinsic resolution is about (1.41±0.11)mm compared to the measured of (1.48±0.06)mm. The simulated sensitivity profiles show a mean square deviation of 12.6\% in axial direction and 3.6\% in radial direction. Satisfactorily these results are representative for all designs and confirm the scanner geometry.}, language = {en} } @article{StreunChristHellendungetal.2005, author = {Streun, M. and Christ, D. and Hellendung, A. and Larue, H. and Ziemons, Karl and Halling, H.}, title = {Effects of crosstalk and gain nonuniformity using multichannel PMTs in the Clearpet® scanner}, series = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, volume = {537}, journal = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, number = {1-2}, isbn = {0168-9002}, pages = {402 -- 405}, year = {2005}, abstract = {The ClearPET® scanners developed by the Crystal Clear Collaboration use multichannel PMTs as photodetectors with scintillator pixels coupled individually to each channel. In order to localize an event each channel anode is connected to a comparator that triggers when the anode signal exceeds a common predefined threshold. Two major difficulties here are crosstalk of light and the gain nonuniformity of the PMT channels. Crosstalk can generate false triggering in channels adjacent to the actual event. On the one hand this can be suppressed by sufficiently increasing the threshold, but on the other hand a threshold too high can already prevent valid events on the lower gain channels from being detected. Finally, both effects restrict the dynamic range of pulse heights that can be processed. The requirements to the dynamic range are not low as the ClearPET® scanners detect the depth of interaction by phoswich pixels consisting of LSO and Lu0.7Y0.3AP, two scintillators with different light yields. We will present a model to estimate the achievable dynamic range and show solutions to increase it.}, language = {en} } @article{ZiemonsAuffrayBarbieretal.2005, author = {Ziemons, Karl and Auffray, E. and Barbier, R. and Brandenburg, G. and Bruyndonckx, P.}, title = {The ClearPET™ project: Development of a 2nd generation high-performance small animal PET scanner}, series = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, volume = {537}, journal = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, number = {1-2}, issn = {0168-9002}, pages = {307 -- 311}, year = {2005}, abstract = {Second generation high-performance PET scanners, called ClearPET™1, have been developed by working groups of the Crystal Clear Collaboration (CCC). High sensitivity and high spatial resolution for the ClearPET camera is achieved by using a phoswich arrangement combining two different types of lutetium-based scintillator materials: LSO from CTI and LuYAP:Ce from the CCC (ISTC project). In a first ClearPET prototype, phoswich arrangements of 8×8 crystals of 2×2×10 mm3 are coupled to multi-channel photomultiplier tubes (Hamamatsu R7600). A unit of four PMTs arranged in-line represents one of 20 sectors of the ring design. The opening diameter of the ring is 120 mm, the axial detector length is 110 mm.The PMT pulses are digitized by free-running ADCs and digital data processing determines the gamma energy, the phoswich layer and even the exact pulse starting time, which is subsequently used for coincidence detection. The gantry allows rotation of the detector modules around the field of view. Preliminary data shows a correct identification of the crystal layer about (98±1)\%. Typically the energy resolution is (23.3±0.5)\% for the luyap layer and (15.4±0.4)\% for the lso layer. early studies showed the timing resolution of 2 ns FWHM and 4.8 ns FWTM. the intrinsic spatial resolution ranges from 1.37 mm to 1.61 mm full-width of half-maximum (FWHM) with a mean of 1.48 mm FWHM. further improvements in image and energy resolution are expected when the system geometry is fully modeled.}, language = {en} } @article{BeerStreunHombachetal.2010, author = {Beer, S. and Streun, M. and Hombach, T. and Buehler, J. and Jahnke, S. and Khodaverdi, M. and Larue, H. and Minwuyelet, S. and Parl, C. and Roeb, G. and Schurr, U. and Ziemons, Karl}, title = {Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants}, series = {Physics in Medicine and Biology}, volume = {55}, journal = {Physics in Medicine and Biology}, number = {3}, publisher = {IOP}, address = {Bristol}, issn = {1361-6560}, doi = {10.1088/0031-9155/55/3/006}, pages = {635 -- 646}, year = {2010}, abstract = {Positron emitters such as 11C, 13N and 18F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is 11CO2 since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET™ system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.}, language = {en} } @article{HerzogPietrzykShahetal.2010, author = {Herzog, Hans and Pietrzyk, Uwe and Shah, N. Jon and Ziemons, Karl}, title = {The current state, challenges and perspectives of MR-PET}, series = {Neuroimage}, volume = {49}, journal = {Neuroimage}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1053-8119}, doi = {10.1016/j.neuroimage.2009.10.036}, pages = {2072 -- 2082}, year = {2010}, abstract = {Following the success of PET/CT during the last decade and the recent increasing proliferation of SPECT/CT, another hybrid imaging instrument has been gaining more and more interest: MR-PET. First combined, simultaneous PET and MR studies carried out in small animals demonstrated the feasibility of the new approach. Concurrently, some prototypes of an MR-PET scanner for simultaneous human brain studies have been built, their performance is being tested and preliminary applications have already been shown. Through this pioneering work, it has become clear that advances in the detector design are necessary for further optimization. Recently, the different issues related to the present state and future prospects of MR-PET were presented and discussed during an international 2-day workshop at the Forschungszentrum J{\"u}lich, Germany, held after, and in conjunction with, the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference in Dresden, Germany on October 27-28, 2008. The topics ranged from small animal MR-PET imaging to human MR-BrainPET imaging, new detector developments, challenges/opportunities for ultra-high field MR-PET imaging and considerations of possible future research and clinical applications. This report presents a critical summary of the contributions made to the workshop.}, language = {en} } @article{ParlLarueStreunetal.2011, author = {Parl, C. and Larue, H. and Streun, M. and Ziemons, Karl}, title = {Double-side-readout technique for SiPM-matrices}, series = {2010 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, journal = {2010 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)}, publisher = {IEEE}, address = {New York}, issn = {1095-7863}, pages = {1486 -- 1487}, year = {2011}, abstract = {In our case the double-side-method is used to minimize the complexity of a matrix-readout. Here the number of channels is reduced to 2√N̅. It is also possible to benefit from the method in a single pixel readout system. One signal can be used to measure position and energy of the event, the other one can be applied to a fast trigger-circuit at the same time. In a next step we will investigate timing behavior and electrical crosstalk of the circuit.}, 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{StreunBrandenburgLarueetal.2006, author = {Streun, M. and Brandenburg, G. and Larue, H. and Parl, C. and Ziemons, Karl}, title = {The data acquisition system of ClearPET neuro - a small animal PET scanner}, series = {IEEE Transactions on Nuclear Science}, volume = {53}, journal = {IEEE Transactions on Nuclear Science}, number = {3}, isbn = {0018-9499}, pages = {700 -- 703}, year = {2006}, abstract = {The Crystal Clear Collaboration has developed a modular system for a small animal PET scanner (ClearPET). The modularity allows the assembly of scanners of different sizes and characteristics in order to satisfy the specific needs of the individual member institutions. The system performs depth of interaction detection by using a phoswich arrangement combining LSO and LuYAP scintillators which are coupled to Multichannel Photomultipliers (PMTs). For each PMT a free running 40 MHz ADC digitizes the signal and the complete scintillation pulse is sampled by an FPGA and sent with 20 MB/s to a PC for preprocessing. The pulse provides information about the gamma energy and the scintillator material which identifies the interaction layer. Furthermore, the exact pulse starting time is obtained from the sampled data. This is important as no hardware coincidence detection is implemented. All single events are recorded and coincidences are identified by software. The system in J{\"u}lich (ClearPET Neuro) is equipped with 10240 crystals on 80 PMTs. The paper will present an overview of the data acquisition system.}, 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{StreunBrandenburgKhodaverdietal.2006, author = {Streun, M. and Brandenburg, G. and Khodaverdi, M. and Larue, H. and Parl, C. and Ziemons, Karl}, title = {Timemark correction for the ClearPET™ scanners}, series = {2005 IEEE Nuclear Science Symposium Conference Record, Vol. 4}, journal = {2005 IEEE Nuclear Science Symposium Conference Record, Vol. 4}, isbn = {1082-3654}, pages = {2057 -- 2060}, year = {2006}, abstract = {The small animal PET scanners developed by the Crystal Clear Collaboration (ClearPETtrade) detect coincidences by analyzing timemarks which are attached to each event. The scanners are able to save complete single list mode data which allows analysis and modification of the timemarks after data acquisition. The timemarks are obtained from the digitally sampled detector pulses by calculating the baseline crossing of the rising edge of the pulse which is approximated as a straight line. But the limited sampling frequency causes a systematic error in the determination of the timemark. This error depends on the phase of the sampling clock at the time of the event. A statistical method that corrects these errors will be presented}, 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{Ziemons1991, author = {Ziemons, Karl}, title = {Comparison of forward hadrons produced in muon interactions on nuclear targets and deuterium}, series = {Zeitschrift f{\"u}r Physik C Particles and Fields}, volume = {52}, journal = {Zeitschrift f{\"u}r Physik C Particles and Fields}, number = {1}, isbn = {1431-5858}, pages = {1 -- 11}, year = {1991}, abstract = {Differential multiplicities of forward produced hadrons in deep inelastic muon scattering on nuclear targets have been compared with those from deuterium. The ratios are observed to increase towards unity as the virtual photon energy increases with no significant dependence on the other muon kinematic variables. The hadron transverse momentum distribution is observed to be broadened in nuclear targets. The dependence on the remaining hadron variables is investigated and the results are discussed in the framework of intranuclear interaction models and in the context of the EMC effect.}, language = {en} } @article{Ziemons1992, author = {Ziemons, Karl}, title = {Muoproduction of J/ψ and the gluon distribution of the nucleon}, series = {Zeitschrift f{\"u}r Physik C Particles and Fields}, volume = {56}, journal = {Zeitschrift f{\"u}r Physik C Particles and Fields}, number = {1}, isbn = {1431-5858}, pages = {21 -- 28}, year = {1992}, abstract = {Measurements are presented of the inclusive distributions of the J/Ψ meson produced by muons of energy 200 GeV from an ammonia target. The gluon distribution of the nucleon has been derived from the data in the range 0.04