TY  - JOUR
A1  - Khodaverdi, M.
A1  - Pauly, F.
A1  - Schroder, G.
A1  - Ziemons, Karl
A1  - Sievering, R.
A1  - Halling, H.
T1  - Preliminary studies of a micro-CT for a combined small animal PET/CT scanner
JF  - 2001 IEEE Nuclear Science Symposium Conference Record, Vol. 3
N2  - We are developing an X-ray computed tomography (CT) system which will be combined with a high resolution animal PET system. This permits acquisition of both molecular and anatomical images in a single machine. In particular the CT will also be utilized for the quantification of the animal PET data by providing accurate data for attenuation correction. A first prototype has been built using a commercially available plane silicon diode detector. A cone-beam reconstruction provides the images using the Feldkamp algorithm. First measurements with this system have been performed on a mouse. It could be shown that the CT setup fulfils all demands for a high quality image of the skeleton of the mouse. It is also suited for soft tissue measurements. To improve contrast and resolution and to acquire the X-ray energy further development of the system, especially the use of semiconductor detectors and iterative reconstruction algorithms are planned.
Y1  - 2002
SN  - 1082-3654
SP  - 1605
EP  - 1606
ER  - 
TY  - JOUR
A1  - Streun, M.
A1  - Beer, S.
A1  - Hombach, T.
A1  - Jahnke, S.
A1  - Khodaverdi, M.
A1  - Larue, H.
A1  - Minwuyelet, S.
A1  - Parl, C.
A1  - Roeb, G.
A1  - Schurr, U.
A1  - Ziemons, Karl
T1  - PlanTIS: A positron emission tomograph for imaging 11C transport in plants
JF  - 2007 IEEE Nuclear Science Symposium Conference Record, Vol. 6
N2  - Plant growth and transport processes are highly dynamic. They are characterized by plant-internal control processes and by strong interactions with the spatially and temporally varying environment. Analysis of structure- function relations of growth and transport in plants will strongly benefit from the development of non-invasive techniques. PlanTIS (Plant Tomographic Imaging System) is designed for non-destructive 3D-imaging of positron emitting radiotracers. It will permit functional analysis of the dynamics of carbon distribution in plants including bulky organs. It will be applicable for screening transport properties of plants to evaluate e.g. temperature adaptation of genetically modified plants. PlanTIS is a PET scanner dedicated to monitor the dynamics of the 11C distribution within a plant while or after assimilation of 11CO2. Front end electronics and data acquisition architecture of the scanner are based on the ClearPETTM system [1]. Four detector modules form one of two opposing detector blocks. Optionally, a hardware coincidence detection between the blocks can be applied. In general the scan duration is rather long (~ 1 hour) compared to the decay time of 11C (20 min). As a result the count rates can vary over a wide range and accurate dead time correction is necessary.
Y1  - 2008
SN  - 1082-3654
SP  - 4110
EP  - 4112
ER  - 
TY  - JOUR
A1  - Ziemons, Karl
T1  - Muoproduction of J/ψ and the gluon distribution of the nucleon
JF  - Zeitschrift für Physik C Particles and Fields
N2  - 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<x<0.36 using a technique based on the colour singlet model. An arbitrary normalisation factor is required to obtain a reasonable integral of the gluon distribution. Some comments are made on the use of J/Ψ productionby virtual photons to extract the gluon distribution at HERA.
Y1  - 1992
SN  - 1431-5858
N1  - European Muon Collaboration
VL  - 56
IS  - 1
SP  - 21
EP  - 28
ER  - 
TY  - JOUR
A1  - Fink, G. R.
A1  - Marshall, J. C.
A1  - Shah, N. J.
A1  - Weiss, P.H.
A1  - Halligan, P. W.
A1  - Grosse-Ruyken, M.
A1  - Ziemons, Karl
A1  - Zilles, K.
A1  - Freund, H. J.
T1  - Line bisection judgments implicate right parietal cortex and cerebellum as assessed by fMRI
JF  - Neurology
Y1  - 2000
SN  - 1526-632X
VL  - 54
IS  - 6
SP  - 1324
EP  - 1331
ER  - 
TY  - JOUR
A1  - Berghoff, G.
A1  - Lanske, D.
A1  - Schultze, K.
A1  - Ziemons, Karl
T1  - Jets and QCD-effects in muon-nuclean scattering
JF  - Verhandlungen der Deutschen Physikalischen Gesellschaft
Y1  - 1988
SN  - 0420-0195
VL  - 23
IS  - 5
ER  - 
TY  - JOUR
A1  - Ziemons, Karl
T1  - Jet production and fragmentation properties in deep inelastic muon scattering
JF  - Zeitschrift für Physik C :  Particles and Fields
Y1  - 1987
SN  - 0170-9739
N1  - European Muon Collaboration
VL  - 36
IS  - 4
SP  - 527
EP  - 543
ER  - 
TY  - JOUR
A1  - Ziemons, Karl
A1  - Herzog, H.
A1  - Bosetti, P.
A1  - Feinendegen, L. E.
T1  - Iterative image reconstruction with weighted pixel contribution to projection elements
JF  - European Journal of Nuclear Medicine
Y1  - 1992
SN  - 1619-7089
N1  - Abstracts of the European Association of Nuclear Medicine Congress 23–26 August 1992 Lisboa, Portugal ; V143-2
VL  - 19
IS  - 8
SP  - 588
EP  - 588
ER  - 
TY  - JOUR
A1  - Ziemons, Karl
A1  - Herzog, H.
A1  - Feinendegen, L. E.
T1  - Iterative image reconstruction with weighted pixel contribution to projection element
JF  - European Journal of Nuclear Medicine
Y1  - 1990
SN  - 1619-7089
N1  - Abstracts of the European Association of Nuclear Medicine Congress ; V52
VL  - 16
IS  - 7
SP  - 403
EP  - 403
ER  - 
TY  - JOUR
A1  - Weckesser, Martin
A1  - Grießmeier, Martin
A1  - Schmidt, Daniela
A1  - Sonnenberg, Frank
A1  - Ziemons, Karl
A1  - Kemna, Lars
A1  - Holschbach, Marcus
A1  - Langen, Karl-J.
A1  - Müller-Gärtner, Hans-W.
T1  - Iodine-123 α-methyl tyrosine single-photon emission tomography of cerebral gliomas: standardised evaluation of tumour uptake and extent
JF  - European Journal of Nuclear Medicine
N2  - 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.
Y1  - 1998
SN  - 1619-7089
VL  - 25
IS  - 2
SP  - 150
EP  - 156
ER  - 
TY  - JOUR
A1  - Khodaverdi, M.
A1  - Chatziioannou, A. F.
A1  - Weber, S.
A1  - Ziemons, Karl
A1  - Halling, H.
A1  - Pietrzyk, U.
T1  - Investigation of different MicroCT scanner configurations by GEANT4 simulations
JF  - IEEE Transactions on Nuclear Science
N2  - 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.
Y1  - 2005
SN  - 0018-9499
VL  - 52
IS  - 1
SP  - 188
EP  - 192
ER  - 
TY  - JOUR
A1  - Khodaverdi, M.
A1  - Chaziioannou, A. F.
A1  - Weber, S.
A1  - Ziemons, Karl
A1  - Halling, H.
A1  - Pietrzyk, U.
T1  - Investigation of different microCT scanner configurations by GEANT4 simulations
JF  - 2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4
N2  - 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.
Y1  - 2004
SN  - 1082-3654
SP  - 2989
EP  - 2993
ER  - 
TY  - JOUR
A1  - Grießmeier, M.
A1  - Sonnenberg, F.
A1  - Weckesser, M.
A1  - Ziemons, Karl
A1  - Langen, K.-J.
A1  - Müller-Gärtner, H. W.
T1  - Improvement of SPECT quantification in small brain structures by using experiment based recovery-coefficient corrections
JF  - European Journal of Nuclear Medicine
Y1  - 1996
SN  - 1619-7089
N1  - Abstracts ; PSu827
VL  - 23
IS  - 9
SP  - 1238
EP  - 1238
ER  - 
TY  - JOUR
A1  - Philipp, Mohr
A1  - Efthimiou, Nikos
A1  - Pagano, Fiammetta
A1  - Kratochwil, Nicolaus
A1  - Pizzichemi, Marco
A1  - Tsoumpas, Charalampos
A1  - Auffray, Etiennette
A1  - Ziemons, Karl
T1  - Image reconstruction analysis for positron emission tomography with heterostructured scintillators
JF  - IEEE Transactions on Radiation and Plasma Medical Sciences
N2  - 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.
KW  - TOF PET
KW  - Heterostructure
KW  - Metascintillator
KW  - Multiple TOF kernels
KW  - Image Reconstruction
Y1  - 2022
U6  - http://dx.doi.org/10.1109/TRPMS.2022.3208615
SN  - 2469-7311
SN  - 2469-7303
VL  - 7
IS  - 1
SP  - 41
EP  - 51
PB  - IEEE
CY  - New York, NY
ER  - 
TY  - JOUR
A1  - Christ, D.
A1  - Hollendung, A.
A1  - Larue, H.
A1  - Parl, C.
A1  - Streun, M.
A1  - Weber, S.
A1  - Ziemons, Karl
A1  - Halling, H.
T1  - Homogenization of the MultiChannel PM gain by inserting light attenuating masks
JF  - 2003 IEEE Nuclear Science Symposium Conference Record, Vol. 4
N2  - 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.
Y1  - 2004
SN  - 1082-3654
SP  - 2382
EP  - 2385
ER  - 
TY  - JOUR
A1  - Khodaverdi, M.
A1  - Weber, S.
A1  - Streun, M.
A1  - Parl, C.
A1  - Ziemons, Karl
T1  - High resolution imaging with ClearPET™ Neuro - first animal images
JF  - 2005 IEEE Nuclear Science Symposium Conference Record, Vol. 3
N2  - 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.
Y1  - 2006
SN  - 1082-3654
SP  - 1641
EP  - 1644
ER  - 
TY  - JOUR
A1  - Streun, M.
A1  - Christ, D.
A1  - Hellendung, A.
A1  - Larue, H.
A1  - Ziemons, Karl
A1  - Halling, H.
T1  - Effects of crosstalk and gain nonuniformity using multichannel PMTs in the Clearpet® scanner
JF  - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
N2  - 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.
Y1  - 2005
SN  - 0168-9002
N1  - Proceedings of the 7th International Conference on Inorganic Scintillators and their Use in Scientific and Industrial Applications
VL  - 537
IS  - 1-2
SP  - 402
EP  - 405
ER  - 
TY  - JOUR
A1  - Weckesser, Matthias
A1  - Hufnagel, Andreas
A1  - Ziemons, Karl
A1  - Grießmeier, Martin
A1  - Sonnenberg, Frank
A1  - Hackländer, Thomas
A1  - Langen, Karl-J.
A1  - Holschbach, Markus
A1  - Elger, Christian E.
A1  - Müller-Gärtner, Hans-W.
T1  - Effect of partial volume correction on muscarinic cholinergic receptor imaging with single-photon emission tomography in patients with temporal lobe epilepsy
JF  - European Journal of Nuclear Medicine
N2  - Animal experiments and preliminary results in humans have indicated alterations of hippocampal muscarinic acetylcholine receptors (mAChR) in temporal lobe epilepsy. Patients with temporal lobe epilepsy often present with a reduction in hippocampal volume. The aim of this study was to investigate the influence of hippocampal atrophy on the quantification of mAChR with single photon emission tomography (SPET) in patients with temporal lobe epilepsy. Cerebral uptake of the muscarinic cholinergic antagonist [123I]4-iododexetimide (IDex) was investigated by SPET in patients suffering from temporal lobe epilepsy of unilateral (n=6) or predominantly unilateral (n=1) onset. Regions of interest were drawn on co-registered magnetic resonance images. Hippocampal volume was determined in these regions and was used to correct the SPET results for partial volume effects. A ratio of hippocampal IDex binding on the affected side to that on the unaffected side was used to detect changes in muscarinic cholinergic receptor density. Before partial volume correction a decrease in hippocampal IDex binding on the focus side was found in each patient. After partial volume no convincing differences remained. Our results indicate that the reduction in hippocampal IDex binding in patients with epilepsy is due to a decrease in hippocampal volume rather than to a decrease in receptor concentration.
Y1  - 1997
SN  - 1619-7089
VL  - 24
IS  - 9
SP  - 1156
EP  - 1161
ER  - 
TY  - JOUR
A1  - Parl, C.
A1  - Larue, H.
A1  - Streun, M.
A1  - Ziemons, Karl
T1  - Double-side-readout technique for SiPM-matrices
JF  - 2010 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)
N2  - 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.
Y1  - 2011
SN  - 1095-7863
SP  - 1486
EP  - 1487
PB  - IEEE
CY  - New York
ER  - 
TY  - JOUR
A1  - Mosset, J.-B.
A1  - Devroede, O.
A1  - Krieguer, M.
A1  - Rey, M.
A1  - Vieira, J.-M.
A1  - Jung, J. H.
A1  - Kuntner, C.
A1  - Streun, M.
A1  - Ziemons, Karl
A1  - Auffray, E.
A1  - Sempere-Roldan, P.
A1  - Lecoq, P.
A1  - Bruyndonckx, P.
A1  - Loude, J.-F.
A1  - Tavernier, S.
A1  - Morcel, C.
T1  - Development of an optimized LSO/LuYAP phoswich detector head for the Lausanne ClearPET demonstrator
JF  - IEEE Transactions on Nuclear Science
N2  - This paper describes the LSO/LuYAP phoswich detector head developed for the ClearPET small animal PET scanner demonstrator that is under construction in Lausanne within the Crystal Clear Collaboration. The detector head consists of a dual layer of 8×8 LSO and LuYAP crystal arrays coupled to a multi-anode photomultiplier tube (Hamamatsu R7600-M64). Equalistion of the LSO/LuYAP light collection is obtained through partial attenuation of the LSO scintillation light using a thin aluminum deposit of 20-35 nm on LSO and appropriate temperature regulation of the phoswich head between 30°C to 60°C. At 511keV, typical FWHM energy resolutions of the pixels of a phoswich head amounts to (28±2)% for LSO and (25±2)% for LuYAP. The LSO versus LuYAP crystal identification efficiency is better than 98%. Six detector modules have been mounted on a rotating gantry. Axial and tangential spatial resolutions were measured up to 4 cm from the scanner axis and compared to Monte Carlo simulations using GATE. FWHM spatial resolution ranges from 1.3 mm on axis to 2.6 mm at 4 cm from the axis.
Y1  - 2006
SN  - 0018-9499
VL  - 53
IS  - 1
SP  - 25
EP  - 29
ER  - 
TY  - JOUR
A1  - Choi, Chang-Hoon
A1  - Felder, Tim
A1  - Felder, Jörg
A1  - Tellmann, Lutz
A1  - Hong, Suk-Min
A1  - Wegener, Hans-Peter
A1  - Shah, N Jon
A1  - Ziemons, Karl
T1  - Design, evaluation and comparison of endorectal coils for hybrid MR-PET imaging of the prostate
JF  - Physics in Medicine & Biology
N2  - Prostate cancer is one of the most common cancers among men and its early detection is critical for its successful treatment. The use of multimodal imaging, such as MR-PET, is most advantageous as it is able to provide detailed information about the prostate. However, as the human prostate is flexible and can move into different positions under external conditions, it is important to localise the focused region-of-interest using both MRI and PET under identical circumstances. In this work, we designed five commonly used linear and quadrature radiofrequency surface coils suitable for hybrid MR-PET use in endorectal applications. Due to the endorectal design and the shielded PET insert, the outer face of the coils investigated was curved and the region to be imaged was outside the volume of the coil. The tilting angles of the coils were varied with respect to the main magnetic field direction. This was done to approximate the various positions from which the prostate could be imaged. The transmit efficiencies and safety excitation efficiencies from simulations, together with the signal-to-noise ratios from the MR images were calculated and analysed. Overall, it was found that the overlapped loops driven in quadrature were superior to the other types of coils we tested. In order to determine the effect of the different coil designs on PET, transmission scans were carried out, and it was observed that the differences between attenuation maps with and without the coils were negligible. The findings of this work can provide useful guidance for the integration of such coil designs into MR-PET hybrid systems in the future.
Y1  - 2020
U6  - http://dx.doi.org/10.1088/1361-6560/ab87f8
SN  - 0031-9155
VL  - 65
IS  - 11
PB  - IOP
CY  - Bristol
ER  -