107 research outputs found
A novel method for calibration and monitoring of time synchronization of TOF-PET scanners by means of cosmic rays
All of the present methods for calibration and monitoring of TOF-PET scanner
detectors utilize radioactive isotopes such as e.g. Na or Ge,
which are placed or rotate inside the scanner. In this article we describe a
novel method based on the cosmic rays application to the PET calibration and
monitoring methods. The concept allows to overcome many of the drawbacks of the
present methods and it is well suited for newly developed TOF-PET scanners with
a large longitudinal field of view. The method enables also monitoring of the
quality of the scintillator materials and in general allows for the continuous
quality assurance of the PET detector performance.Comment: 10 pages, 7 figure
Compressive Sensing of Signals Generated in Plastic Scintillators in a Novel J-PET Instrument
The J-PET scanner, which allows for single bed imaging of the whole human
body, is currently under development at the Jagiellonian University. The dis-
cussed detector offers improvement of the Time of Flight (TOF) resolution due
to the use of fast plastic scintillators and dedicated electronics allowing for
sam- pling in the voltage domain of signals with durations of few nanoseconds.
In this paper we show that recovery of the whole signal, based on only a few
samples, is possible. In order to do that, we incorporate the training signals
into the Tikhonov regularization framework and we perform the Principal
Component Analysis decomposition, which is well known for its compaction
properties. The method yields a simple closed form analytical solution that
does not require iter- ative processing. Moreover, from the Bayes theory the
properties of regularized solution, especially its covariance matrix, may be
easily derived. This is the key to introduce and prove the formula for
calculations of the signal recovery error. In this paper we show that an
average recovery error is approximately inversely proportional to the number of
acquired samples
Application of the Compress Sensing Theory for Improvement of the TOF Resolution in a Novel J-PET Instrument
Nowadays, in Positron Emission Tomography (PET) systems, a Time of Flight
information is used to improve the image reconstruction process. In Time of
Flight PET (TOF-PET), fast detectors are able to measure the difference in the
arrival time of the two gamma rays, with the precision enabling to shorten
significantly a range along the line-of-response (LOR) where the annihilation
occurred. In the new concept, called J-PET scanner, gamma rays are detected in
plastic scintillators. In a single strip of J-PET system, time values are
obtained by probing signals in the amplitude domain. Owing to Compress Sensing
theory, information about the shape and amplitude of the signals is recovered.
In this paper we demonstrate that based on the acquired signals parameters, a
better signal normalization may be provided in order to improve the TOF
resolution. The procedure was tested using large sample of data registered by a
dedicated detection setup enabling sampling of signals with 50 ps intervals.
Experimental setup provided irradiation of a chosen position in the plastic
scintillator strip with annihilation gamma quanta
Test of a single module of the J-PET scanner based on plastic scintillators
Time of Flight Positron Emission Tomography scanner based on plastic
scintillators is being developed at the Jagiellonian University by the J-PET
collaboration. The main challenge of the conducted research lies in the
elaboration of a method allowing application of plastic scintillators for the
detection of low energy gamma quanta. In this article we report on tests of a
single detection module built out from BC-420 plastic scintillator strip (with
dimensions of 5x19x300mm^3) read out at two ends by Hamamatsu R5320
photomultipliers. The measurements were performed using collimated beam of
annihilation quanta from the 68Ge isotope and applying the Serial Data Analyzer
(Lecroy SDA6000A) which enabled sampling of signals with 50ps intervals. The
time resolution of the prototype module was established to be better than 80ps
(sigma) for a single level discrimination. The spatial resolution of the
determination of the hit position along the strip was determined to be about
0.93cm (sigma) for the annihilation quanta. The fractional energy resolution
for the energy E deposited by the annihilation quanta via the Compton
scattering amounts to sigma(E)/E = 0.044/sqrt(E[MeV]) and corresponds to the
sigma(E)/E of 7.5% at the Compton edge.Comment: 12 pages, 6 figures; Updated with editorial corrections related to
publication in NIM
System Response Kernel Calculation for List-mode Reconstruction in Strip PET Detector
Reconstruction of the image in Positron Emission Tomographs (PET) requires
the knowledge of the system response kernel which describes the contribution of
each pixel (voxel) to each tube of response (TOR). This is especially important
in list-mode reconstruction systems, where an efficient analytical
approximation of such function is required. In this contribution, we present a
derivation of the system response kernel for a novel 2D strip PET.Comment: 10 pages, 2 figures; Presented at Symposium on applied nuclear
physics and innovative technologies, Cracow, 03-06 June 201
Determination of the map of efficiency of the J-PET detector with the GATE package
A novel PET detector consisting of strips of polymer scintillators is being
developed by the J-PET Collaboration. The map of efficiency and the map of
geometrical acceptance of the 2-strip J-PET scanner are presented. Map of
efficiency was determined using the Monte Carlo simulation software GATE based
on GEANT4. Both maps were compared using method based on the chi2 test.Comment: 14 pages, 9 figures, proceeding from conference Symposium on Positron
Emission Tomography: http://koza.if.uj.edu.pl/pet-symposium-2013
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