Patrick Musmann

Forschungszentrum Jülich, Düren, North Rhine-Westphalia, Germany

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Publications (8)1.41 Total impact

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    ABSTRACT: Scatter reduces the image quality in Positron Emission Tomography (PET). In this paper we discuss a) methods to estimate the scatter fraction in the raw data set as well as b) analysis of the different scatter components (e.g. phantom scatter, gantry scatter) arising from activity outside the field of view (OFOV). The PET detection system does not allow a discrimination of scattered events, thus Monte Carlo Simulations were used. The accuracy of the different scatter estimation methods was analyzed. Simulations with OFOV activity showed that small animal PET systems are indeed sensitive to random and scattered events from OFOV.
    12/2006: pages 109-114;
  • Brigitte Gundlich, Patrick Musmann, Simone Weber
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    ABSTRACT: Dynamic reconstruction methods are studied for the small animal PET (positron emission tomography) scanner ClearPET™ Neuro. In dynamic reconstruction the data are usually sorted into timeframes and reconstructed independently of each other. Using this timeframe approach, an appropriate trade-off between time resolution and noise has to be found. A more advanced method is dynamic reconstruction with temporal basis functions, where voxel values are time dependent modeled as weighted sum of basis functions. In a simulated example list-mode data are generated for the ClearPET™ Neuro and reconstructed with timeframe reconstruction and with dynamic reconstruction using B-Splines as temporal basis functions. Time activity curves are computed for various reconstructions with different timeframes and B-Splines. The example demonstrates the potential of dynamic reconstruction with temporal B-Splines.
    12/2006: pages 25-30;
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    ABSTRACT: The small-animal PET scanner ClearPET Neuro developed at the Research Centre in Jülich is based on an unconventional scanner geometry. It represents axial and transaxial gaps that lead to sinograms with missing data. Images reconstructed from uncorrected data include artefacts and a high variation of spatial resolution between different slices. Methods to compensate these artefacts are applied by taking the geometrical sensitivity into account. In this work the effects of compensation strategies with regard to the slice by slice variation of spatial resolution are examined.
    12/2006: pages 19-24;
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    ABSTRACT: The list-mode format is particularly suitable for high-resolution tomographic systems, where the precision of the data have not to be compromised, but also claims new demands on data processing and image reconstruction. We apply a ray-tracing algorithm to calculate the three-dimensional coincidence response function. The algorithm is embedded in a list-mode reconstruction framework and has been previously assessed with data from the small-animal ClearPETtrade Neuro scanner. In order to compare and verify our algorithm, exemplary response functions are simulated using GATE. Long reconstruction time has been overcome by implementing a reconstruction framework for distributed computing. The implementation uses the message passing interface for communication and a simple master/slave model with dynamical load balancing of the slaves.
    Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
  • B. Gundlich, P. Musmann, S. Weber
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    ABSTRACT: In dynamic reconstruction of positron emission tomography (PET) data a sequence of measured data sets is usually reconstructed independently from each other. Using this timeframe reconstruction, an appropriate trade-off between time resolution and noise has to be found. To overcome these drawbacks smoothing techniques and advanced dynamic reconstruction algorithms are more and more applied. Especially for the last, list-mode reconstruction is the predestinated approach, as the data are acquired in the highest possible spatial and temporal resolution. In this contribution we study dynamic reconstruction algorithms that base on the ML-EM algorithm for the small animal PET scanner ClearPETtradeNeuro. In a simulated example we generate list-mode data and compute time activity curves from the reconstructed images. We compare dynamic reconstruction methods, like time-frame reconstruction - with and without temporal smoothing - and reconstruction with B-splines as temporal basis functions.
    Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
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    ABSTRACT: Positron emission tomography (PET), intrinsically a 3D imaging technique, was for a long time exclusively operated in 2D mode, using septa to shield the detectors from photons emitted obliquely to the detector planes. However, the use of septa results in a considerable loss of sensitivity. From the late 1980s, significant efforts have been made to develop a methodology for the acquisition and reconstruction of 3D PET data. This paper focuses on the differences between data acquisition in 2D and 3D mode, especially in terms of data set sizes and representation. Although the real time data acquisition aspect in 3D has been mostly solved in modern PET scanner systems, there still remain questions on how to represent and how to make best use of the information contained in the acquired data sets. Data representation methods, such as list-mode and matrix-based methods, possibly with additional compression, will be discussed. Moving from 2D to 3D PET has major implications on the way these data are reconstructed to images. Two fundamentally different approaches exist, the analytical one and the iterative one. Both, at different expenses, can be extended to directly handle 3D data sets. Either way the computational burden increases heavily compared to 2D reconstruction. One possibility to benefit from the increased sensitivity in 3D PET while sticking to high-performance 2D reconstruction algorithms is to rebin 3D into 2D data sets. The value of data rebinning will be explored. An ever increasing computing power and the concept of distributed or parallel computing have made direct 3D reconstruction feasible. Following a short review of reconstruction methods and their extensions to 3D, we focus on numerical aspects that improve reconstruction performance, which is especially important in solving large equation systems in 3D iterative reconstruction. Finally exemplary results are shown to review the properties of the discussed algorithms. This paper concludes with an overview on future trends in data representation and reconstruction.
    Zeitschrift für Medizinische Physik 02/2006; 16(1):31-46. · 1.41 Impact Factor
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    ABSTRACT: Conventionally, positron emission tomography data are sorted into sinograms prior to image reconstruction. This leads to a loss of spatial and temporal resolution due to histogramming of events. An alternative data representation is the so-called list-mode format which allows to store more attributes of each individual event, like involved detectors, energy, time, gantry state or even the depth of interaction. The format has the advantage, that it keeps the data in their highest possible temporal and spatial resolution. The additional number of attributes, if considered in the system model, can lead to a significant improvement in image quality. We develop a subsetized list-mode expectation-maximization image reconstruction with a ray-tracing technique to compute an enhanced system model. The algorithm approximates the three-dimensional coincidence response function for two arbitrarily oriented cubic detector elements, incorporated into crystal matrices. The geometry of the involved detector modules is evaluated at event time, tracing the ray paths of gamma quanta from one detector to the other through the field of view. The algorithm has been assessed using list-mode data for the ClearPET™ Neuro, and is compared to a standard ordered-subset expectation-maximization reconstruction method for projections.
    Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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    ABSTRACT: At present a high-resolution PET scanner (ClearPET Neuro) is constructed at the Research Centre Jülich. While human PET systems have a spatial resolution of 5–7 mm, high resolution PET needs a resolution of
    International Congress Series 01/2005; 1281:131-136.