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 - Brandenburg, G. A1 - Khodaverdi, M. A1 - Larue, H. A1 - Parl, C. A1 - Ziemons, Karl T1 - Timemark correction for the ClearPET™ scanners JF - 2005 IEEE Nuclear Science Symposium Conference Record, Vol. 4 N2 - 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 Y1 - 2006 SN - 1082-3654 SP - 2057 EP - 2060 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 - Beer, S. A1 - Streun, M. A1 - Hombach, T. A1 - Buehler, J. 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 - Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants JF - Physics in Medicine and Biology N2 - 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. Y1 - 2010 U6 - http://dx.doi.org/10.1088/0031-9155/55/3/006 SN - 1361-6560 VL - 55 IS - 3 SP - 635 EP - 646 PB - IOP CY - Bristol 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 - 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 - 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 - 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 -