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  • 1.
    Hegysei, G.
    et al.
    Institute of Nuclear Research of the Hungarian Academy of Sciences.
    Imrek, J.
    Institute of Nuclear Research of the Hungarian Academy of Sciences.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Ethernet based distributed data acquistion system for small animal PET2006In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, no 4Article in journal (Refereed)
    Abstract [en]

    We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer and digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system, coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and it generates a time stamp with a coincidence resolution of 2 to 3 ns. The data acquisition System is based on Ethernet network and is highly scalable in size and performance

  • 2.
    Ren, Wuwei
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Colarieti-Tosti, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Stationary SPECT with multi-layer multiple-pinhole-arrays2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), IEEE , 2012, p. 2594-2597Conference paper (Refereed)
    Abstract [en]

    The potential of Multiple Pinhole Arrays (MPA) collimators for developing a Single Photon Emission Computer Tomography (SPECT) system without rotating or moving elements is investigated. A four layer arrangement is proposed and the system performance is evaluated using the simulation toolkit GATE [1]. For a camera with a field of view (FOV) of the order of a human brain (a sphere of radius 100 mm), a sensitivity of 86, 0 cps/MBq and an overall resolution of 5 mm have been estimated, indicating that performances comparable to traditional parallel-hole-collimator cameras can be achieved.

  • 3.
    Turco, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Colarieti-Tosti, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Modular miniPET: A comparison between 10 and 12 detector modules2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), IEEE , 2012, p. 2598-2602Conference paper (Refereed)
    Abstract [en]

    By means of computer simulations, scatter fraction, spatial resolution and sensitivity of two 10-detector-module small-animal PET (r77-miniPET and r106-miniPET), are analyzed and compared to the performance of the 12-detector-module PET scanner miniPET II [1]. All simulations have been performed with the well validated Geant4 Application for Emission Tomography (GATE) [2]. Sensitivity and scatter fraction speak in favor of the 10-module scanner: a clear improvement in count rate and scatter fraction was found. Moreover, steeper slopes of noise equivalent count rate curves at low levels of activity was found. Spatial resolution instead was found to be better in the 12-module scanner.

  • 4.
    Valastyán, Iván
    KTH, School of Engineering Sciences (SCI), Physics.
    Applications of tomographic imaging in nuclear medicine2006Licentiate thesis, comprehensive summary (Other scientific)
  • 5.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Software Solutions for Nuclear Imaging Systems in Cardiology, Small Animal Research and Education2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The sensitivity for observing physiological processes makes nuclear imaging an important tool in medical diagnostics. Different types of nuclear imaging modalities, with emphasis on the software components and image reconstructions, are presented in this thesis:  the Cardiotom for myocardial heart studies at the Karolinska University Hospital, the small animal Positron Emission Tomograph (PET) scanners for research and the SPECT, PET, spiral CT and Cardiotom demonstrators for the Royal Institute of Technology medical imaging laboratory.

    A modular and unified software platform has been developed for data representation, acquisition, visualization, reconstruction and presentation of the programs of the imaging devices mentioned above. The high performance 3D ML-EM and OS-EM iterative image reconstruction methods are implemented both on Cardiotom and miniPET scanners.

    As a result, the in-slice resolution of the first two prototypes of the Cardiotom today is the same as the formerly used filtered back-projection, however the in-depth resolution is considerably increased. Another improvement due to the new software is the shorter time that is required for data acquisition and image reconstruction. The new electronics with the newly developed software ensure images for medical diagnosis within 10 minutes from the start ofthe examination. The first system from the standardized production of the Cardiotom cameras is in the test phase.

    The performance parameters (sensitivity, spatial and energy resolution, coincidence time resolution) of the full ring mini PET camera are comparable to other small animal PETsystems.

  • 6.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Bone, D.
    Brodin, L.-A.
    Elmqvist, H.
    Lagerlöf, J.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnar, J.
    Novak, D.
    Validation of an iterative reconstruction for a mobile tomographic gamma camera system - The Cardiotom2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 580, no 2, p. 1097-1100Article in journal (Refereed)
    Abstract [en]

    The Cardiotom is a mobile gamma camera that uses ectomography, an alternative method of acquisition to SPECT. It is designed for early diagnosis of myocardial and cerebral infarctions in the emergency room. Ectomography is a limited view angle method, using a rotating slant hole collimator and a stationary camera head, to acquire projection images. The aim of this work was to validate a fully 3D ML-EM iterative reconstruction algorithm for the Cardiotom. Validation measurements were performed with Tc-99m point sources. Resolution in the reconstructed volume was determined in X, Y. and Z directions from the point spread functions. The results were compared with the values for the formerly used filtered back projection (FBP). The new reconstruction algorithm provides greatly improved depth resolution with respect to the FBP method previously implemented on the Cardiotom. Furthermore, for clinical examinations, images can be available for interpretation within 15 min of the injection, therefore, valuable information can be obtained without delaying treatment of the patient. (c) 2007 Elsevier B.V. All rights reserved.

  • 7.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Bonec, D.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnár, J.
    Novák, D.
    Unified software platform for nuclear medical image representation visualization and reconstructionIn: Journal of InstrumentsArticle in journal (Other academic)
  • 8.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Elmqvist, Håkan
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnar, J.
    Novak, D.
    Ribbe, T.
    Gated tomographic imaging in ectomography using a dynamic heart phantom2007In: Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE, IEEE , 2007, p. 3414-3417Conference paper (Refereed)
    Abstract [en]

    A new computer controlled dynamic heart phantom and the connection of an ECG unit to a tomographic gamma camera system, developed for ectomographic imaging, is presented. The phantom is used for validation of the camera. Measurements were performed to test the phantom as well as to study the feasibility of gated imaging in ectomography. The camera is intended for early diagnosis of myocardial and cerebral infarctions.

  • 9.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Colarieti-Tostia, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Rena, W.
    Turcoa, A.
    Kereka, A.
    Monte Carlo simulation of a dental Positron Emission Tomograph and image reconstruction of scatter and true coincidence events2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), IEEE , 2012, p. 3484-3487Conference paper (Refereed)
    Abstract [en]

    Detection of inflammation with nuclear medical imaging techniques [1], especially using PET, has an important role because the location of the disease helps the doctor in the choice of the treatment. In dental applications, the proper treatment of the inflammation might save a tooth.

  • 10.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Gal, J.
    Hegyesi, G.
    Kalinka, G.
    Nagy, F.
    Kiraly, B.
    Imrek, J.
    Molnar, J.
    Colarieti-Tosti, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Szabo, Z.
    Balkay, L.
    Novel time over threshold based readout method for MRI compatible small animal PET detector2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), IEEE , 2012, p. 1295-1299Conference paper (Refereed)
    Abstract [en]

    Combined PET-MRI scanners start a new era in medical imaging. However the development of MRI compatible PET detector module is a challenging task. SiPM sensors are insensitive to magnetic field and constitute a promising solution. A drawback is the high dark current. A readout concept for SiPM based small animal PET detector module is presented in this paper. The results show that the readout of the SiPM is possible using only four ADC channels and the position map is comparable to the ideal solution. The detector modules based on the method are feasible solution for MRI compatible PET scanners.

  • 11.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Hegyesi, G.
    Molnar, J.
    Novak, D.
    Bone, D.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Data acquisition and image reconstruction systems from the MiniPET scanners to the CARDIOTOM camera2007In: Nuclear Physics Methods And Accelerators In Biology And Medicine / [ed] Granja, C; Leroy, C; Stekl, I, American Institute of Physics (AIP), 2007, Vol. 958, p. 282-283Chapter in book (Refereed)
    Abstract [en]

    Nuclear imaging devices play an important role in medical diagnosis as well as drug research. The first and second generation data acquisition systems and the image reconstruction library developed provide a unified hardware and software platform for the miniPET-I, miniPET-II small animal PET scanners and for the CARDIOTOM(TM).

  • 12.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Hegyesi, Gy.
    Kalinka, G.
    Molnar, J.
    Novak, D.
    Sipos, A.
    Bagamery, I.
    Balkay, L.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Experimental scanner setup from miniPET II detector module2009In: 2008 IEEE Nuclear Science SYmposium Conference Record, 2009, p. 3121-3124Chapter in book (Other academic)
    Abstract [en]

    The PET technique is widely used in human clinical studies and recent developments of image resolution has made it suitable for small animal research. The second generation of our PET scanner consists of 12 detector modules and has a field of view large enough to image mice and rats. Parameters of the incoming data are extracted by Digital Signal Processing in the detector modules and a System-on-Module is used to transmit the data through an Ethernet network for storage and reconstruction. The experimental scanner setup described in this paper was constructed in order to investigate the applicability of the developed detector modules in a full ring small animal PET camera. The preliminary results of the system are also presented.

  • 13.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Molnár, J.
    Novák, D.
    Balkay, L.
    Emri, M.
    Trón, L.
    Bükki, T.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Full 3-D cluster-based iterative image reconstruction tool for a small animal PET camera2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 571, no 1-2, p. 219-222Article in journal (Refereed)
    Abstract [en]

    Iterative reconstruction methods are commonly used to obtain images with high resolution and good signal-to-noise ratio in nuclear imaging. The aim of this work was to develop a scalable, fast, cluster based, fully 3-D iterative image reconstruction package for our small animal PET camera, the miniPET. The reconstruction package is developed to determine the 3-D radioactivity distribution from list mode type of data sets and it can also simulate noise-free projections of digital phantoms. We separated the system matrix generation and the fully 3-D iterative reconstruction process. As the detector geometry is fixed for a given camera, the system matrix describing this geometry is calculated only once and used for every image reconstruction, making the process much faster. The Poisson and the random noise sensitivity of the ML-EM iterative algorithm were studied for our small animal PET system with the help of the simulation and reconstruction tool. The reconstruction tool has also been tested with data collected by the miniPET from a line and a cylinder shaped phantom and also a rat.

  • 14.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Hegyesi, G.
    Kalinka, G.
    Molnar, J.
    Novak, D.
    LSO based dual slice helical CT and PET demonstrators2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, p. S300-S302Article in journal (Refereed)
    Abstract [en]

    Two demonstrators, a spiralCT and a miniPET, have been designed and constructed for educational purposes. Computed tomographs (CTs) and positron emission tomographs (PETs) are some of the most commonly used structural and functional imaging devices in medicine, respectively. There is a need for transparent demonstrators where the principles of the different modalities and their functions are presented. The aim of the developments of these systems was to present the major building blocks of CT and PET for undergraduate students. Photon detection in both systems is based on small pixelised scintillation crystals with position sensitive PMT readout. Similar analogue and digital data processing based on FPGA technique is applied for the demonstrators and common image reconstruction and presentation software components are used.

  • 15.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnar, J.
    Novak, D.
    Vegh, J.
    Emri, M.
    Tron, L.
    A SPECT demonstrator - revival of a gamma camera2006In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, no 1, p. 274-277Article in journal (Refereed)
    Abstract [en]

    A gamma camera has been updated and converted to serve as a demonstrator for educational purposes. The gantry and the camera head were the only part of the system that remained untouched. The main reason for this modernization was to increase the transparency of the gamma camera by partitioning the different logical building blocks of the system and thus providing access for inspection and improvements throughout the chain. New data acquisition and reconstruction software has been installed. By taking these measures, the camera is now used in education and also serves as a platform for tests of new hardware and software solutions. The camera is also used to demonstrate 3D (SPECT) imaging by collecting 2D projections from a rotatable cylindrical phantom. Since the camera head is not attached mechanically to the phantom, the effect of misalignment between the head and the rotation axis of the phantom can be studied. (c) 2006 Elsevier B.V. All rights reserved.

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