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  - 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  - Jahnke, Siegfried
A1  - Menzel, Marion I.
A1  - Dusschoten, Dagmar van
A1  - Roeb, Gerhard W.
A1  - Bühler, Jonas
A1  - Minwuyelet, Senay
A1  - Blümler, Peter
A1  - Temperton, Vicky M.
A1  - Hombach, Thomas
A1  - Streun, Matthias
A1  - Beer, Simone
A1  - Khodaverdi, Maryam
A1  - Ziemons, Karl
A1  - Coenen, Heinz H.
A1  - Schurr, Ulrich
T1  - Combined MRI–PET dissects dynamic changes in plant structures and functions
JF  - The Plant Journal
N2  - Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance imaging (MRI) and positron emission tomography (PET), we investigated three contrasting root/shoot systems growing in sand or soil, with respect to their structures, transport routes and the translocation dynamics of recently fixed photoassimilates labelled with the short-lived radioactive carbon isotope 11C. Storage organs of sugar beet (Beta vulgaris) and radish plants (Raphanus sativus) were assessed using MRI, providing images of the internal structures of the organs with high spatial resolution, and while species-specific transport sectoralities, properties of assimilate allocation and unloading characteristics were measured using PET. Growth and carbon allocation within complex root systems were monitored in maize plants (Zea mays), and the results may be used to identify factors affecting root growth in natural substrates or in competition with roots of other plants. MRI–PET co-registration opens the door for non-invasive analysis of plant structures and transport processes that may change in response to genomic, developmental or environmental challenges. It is our aim to make the methods applicable for quantitative analyses of plant traits in phenotyping as well as in understanding the dynamics of key processes that are essential to plant performance.
Y1  - 2009
SN  - 1365-313X
VL  - 59
IS  - 4
SP  - 634
EP  - 644
PB  - Wiley
CY  - Weinheim
ER  -