TY  - JOUR
A1  - Ziemons, Karl
T1  - An investigation of the spin structure of the proton in deep inelastic scattering of polarised muons and polarised protons
JF  - Nuclear Physics B
N2  - The spin asymmetry in deep inelastic scattering of longitudinally polarised muons by longitudinally polarised protons has been measured in the range 0.01<×<0.7. The spin dependent structure function g1(x) for the proton has been determined and, combining the data with earlier SLAC measurements, its integral over x found to be 0.126±0.010(stat.)±0.015(syst.), in disagreement with the Ellis-Jaffe sum rule. Assuming the validity of the Biorken sum rule, this result implies a significant negative value for the integral of g1 for the neutron. These integrals lead to the conclusion, in the naïve quark parton model, that the total quark spin constitutes a rather small fraction of the spin of the nucleon. Results are also presented on the asymmetries in inclusive hadron production which are consistent with the above picture.
Y1  - 1989
SN  - 0550-3213
N1  - European Muon Collaboration
VL  - 328
IS  - 1
SP  - 1
EP  - 35
ER  - 
TY  - JOUR
A1  - Ziemons, Karl
T1  - Comparison of forward hadrons produced in muon interactions on nuclear targets and deuterium
JF  - Zeitschrift für Physik C Particles and Fields
N2  - 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.
Y1  - 1991
SN  - 1431-5858
N1  - European Muon Collaboration
VL  - 52
IS  - 1
SP  - 1
EP  - 11
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  - Ziemons, Karl
T1  - A measurement of the ratio of the nucleon structure function in copper and deuterium
JF  - Zeitschrift für Physik C Particles and Fields
N2  - Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function,F 2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.
Y1  - 1993
SN  - 1431-5858
N1  - European Muon Collaboration
VL  - 57
IS  - 2
SP  - 211
EP  - 218
ER  - 
TY  - JOUR
A1  - Wedrowski, M.
A1  - Bruyndonckx, P.
A1  - Tavernier, S.
A1  - Zhi, L.
A1  - Dang, J.
A1  - Mendes, P. R.
A1  - Perez, J. M.
A1  - Ziemons, Karl
T1  - Robustness of neural networks algorithm for gamma detection in monolithic block detector, positron emission tomography
JF  - 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)
N2  - The monolithic scintillator block approach for gamma detection in the Positron Emission Tomography (PET) avoids estimating Depth of Interaction (DOI), reduces dead zones in detector and diminishes costs of detector production. Neural Networks (NN) are very efficient to determine the entrance point of a gamma incident on a scintillator block. This paper presents results on the robustness of the spatial resolution as a function of the random fraction in the data, temperature and HV fluctuations. This is important when implementing the method in a real scanner. Measurements were done with two Hamamatsu S8550 APD arrays, glued on a 20 × 20 × 10 mm3 monolithic LSO crystal block.
Y1  - 2009
SN  - 1082-3654
SP  - 2625
EP  - 2628
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  - 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  - Taylor, J. G.
A1  - Schmitz, N.
A1  - Ziemons, Karl
A1  - Grosse-Ruyken, M.-L.
A1  - Gruber, O.
A1  - Müller-Gärtner, H.-W.
A1  - Shah, N. J.
T1  - The network of brain areas involved in the motion aftereffect
JF  - Neuroimage
N2  - A network of brain areas is expected to be involved in supporting the motion aftereffect. The most active components of this network were determined by means of an fMRI study of nine subjects exposed to a visual stimulus of moving bars producing the effect. Across the subjects, common areas were identified during various stages of the effect, as well as networks of areas specific to a single stage. In addition to the well-known motion-sensitive area MT the prefrontal brain areas BA44 and 47 and the cingulate gyrus, as well as posterior sites such as BA37 and BA40, were important components during the period of the motion aftereffect experience. They appear to be involved in control circuitry for selecting which of a number of processing styles is appropriate. The experimental fMRI results of the activation levels and their time courses for the various areas are explored. Correlation analysis shows that there are effectively two separate and weakly coupled networks involved in the total process. Implications of the results for awareness of the effect itself are briefly considered in the final discussion.
Y1  - 2000
SN  - 1053-8119
VL  - 11
IS  - 4
SP  - 257
EP  - 270
ER  - 
TY  - JOUR
A1  - Streun, M.
A1  - Larue, H.
A1  - Parl, C.
A1  - Ziemons, Karl
T1  - A compact PET detector readout using charge-to-time conversion
JF  - 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)
N2  - The readout of gamma detectors is considerably simplified when the event intensity is encoded as a pulse width (Pulse Width Modulation, PWM). Time-to-Digital-Converters (TDC) replace the conventional ADCs and multiple TDCs can be realized easily in one PLD chip (Programmable Logic Device). The output of a PWM stage is only one digital signal per channel which is well suited for transport so that further processing can be performed apart from the detector. This is particularly interesting for large systems with high channel density (e.g. high resolution scanners). In this work we present a circuit with a linear transfer function that requires a minimum of components by performing the PWM already in the preamp stage. This allows a very compact and also cost-efficient implementation of the front-end electronics.
Y1  - 2009
SN  - 1082-3654
SP  - 1868
EP  - 1870
PB  - IEEE
CY  - New York
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  -