71 research outputs found
3D PET image reconstruction based on Maximum Likelihood Estimation Method (MLEM) algorithm
Positron emission tomographs (PET) do not measure an image directly. Instead,
they measure at the boundary of the field-of-view (FOV) of PET tomograph a
sinogram that consists of measurements of the sums of all the counts along the
lines connecting two detectors. As there is a multitude of detectors build-in
typical PET tomograph structure, there are many possible detector pairs that
pertain to the measurement. The problem is how to turn this measurement into an
image (this is called imaging). Decisive improvement in PET image quality was
reached with the introduction of iterative reconstruction techniques. This
stage was reached already twenty years ago (with the advent of new powerful
computing processors). However, three dimensional (3D) imaging remains still a
challenge. The purpose of the image reconstruction algorithm is to process this
imperfect count data for a large number (many millions) of lines-of-responce
(LOR) and millions of detected photons to produce an image showing the
distribution of the labeled molecules in space.Comment: 10 pages, 7 figure
Studies of discrete symmetries in decays of positronium atoms
A positronium - a bound state of electron and positron - is an eigenstate of parity and charge conjugation operators which decays into photons. It is a unique laboratory to study discrete symmetries whose precision is limited, in principle, by the effects due to the weak interactions expected at the level of 10−14 and photon-photon interactions expected at the level of 10−9.
The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging as well as for physics studies involving detection of electronpositron annihilation into photons. The physics case covers the areas of discrete symmetries studies and genuine multipartite entanglement. The J-PET detector has high angular and time resolution and allows for determination of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for studies of discrete symmetries in decays of positronium atoms
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 fl ight (TOF) information is used to improve the image reconstruction process. In 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 signifi cantly 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 compressive sensing (CS) 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
Plastic scintillators for positron emission tomography obtained by the bulk polymerization method
This paper describes three methods regarding the production of plastic
scintillators. One method appears to be suitable for the manufacturing of
plastic scintillator, revealing properties which fulfill the requirements of
novel positron emission tomography scanners based on plastic scintillators. The
key parameters of the manufacturing process are determined and discussed.Comment: 7 pages, 4 figure
Analysis procedure of the positronium lifetime spectra for the J-PET detector
Positron Annihilation Lifetime Spectroscopy (PALS) has shown to be a powerful
tool to study the nanostructures of porous materials. Positron Emissions
Tomography (PET) are devices allowing imaging of metabolic processes e.g. in
human bodies. A newly developed device, the J-PET (Jagiellonian PET), will
allow PALS in addition to imaging, thus combining both analyses providing new
methods for physics and medicine. In this contribution we present a computer
program that is compatible with the J-PET software. We compare its performance
with the standard program LT 9.0 by using PALS data from hexane measurements at
different temperatures. Our program is based on an iterative procedure, and our
fits prove that it performs as good as LT 9.0.Comment: 4 figures, 8 page
Simulating NEMA characteristics of the modular total-body J-PET scanner -- an economic total-body PET from plastic scintillators
The purpose of the presented research is estimation of the performance
characteristics of the economic Total-Body Jagiellonian-PET system (TB-J-PET)
constructed from plastic scintillators. The characteristics are estimated
according to the NEMA NU-2-2018 standards utilizing the GATE package. The
simulated detector consists of 24 modules, each built out of 32 plastic
scintillator strips (each with cross section of 6 mm times 30 mm and length of
140 cm or 200 cm) arranged in two layers in regular 24-sided polygon
circumscribing a circle with the diameter of 78.6 cm. For the TB-J-PET with an
axial field-of-view (AFOV) of 200 cm, a spatial resolutions of 3.7 mm
(transversal) and 4.9 mm (axial) are achieved. The NECR peak of 630 kcps is
expected at 30 kBq/cc activity concentration and the sensitivity at the center
amounts to 38 cps/kBq. The SF is estimated to 36.2 %. The values of SF and
spatial resolution are comparable to those obtained for the state-of-the-art
clinical PET scanners and the first total-body tomographs: uExplorer and
PennPET. With respect to the standard PET systems with AFOV in the range from
16 cm to 26 cm, the TB-J-PET is characterized by an increase in NECR
approximately by factor of 4 and by the increase of the whole-body sensitivity
by factor of 12.6 to 38. The TOF resolution for the TB-J-PET is expected to be
at the level of CRT=240 ps (FWHM). For the TB-J-PET with an axial field-of-view
(AFOV) of 140 cm, an image quality of the reconstructed images of a NEMA IEC
phantom was presented with a contrast recovery coefficient (CRC) and a
background variability parameters. The increase of the whole-body sensitivity
and NECR estimated for the TB-J-PET with respect to current commercial PET
systems makes the TB-J-PET a promising cost-effective solution for the broad
clinical applications of total-body PET scanners.Comment: 31 pages, 11 figures, 6 tables, submitted to Physics in Medicine and
Biology 202
Overview of the software architecture and data flow for the J-PET tomography device
Modern TOF-PET scanner systems require high-speed computing resources for efficient data processing, monitoring and image reconstruction. In this article, we present the data flow and software architecture for the novel TOF-PET scanner developed by the J-PET Collaboration. We discuss the data acquisition system, reconstruction framework and image reconstruction software. Also, the concept of computing outside hospitals in the remote centers such as Świerk Computing Centre in Poland is presented
Estimating the NEMA characteristics of the J-PET tomograph using the GATE package
The novel whole-body PET system based on plastic scintillators is developed
by the {J-PET} Collaboration. It consists of plastic scintillator strips
arranged axially in the form of a cylinder, allowing the cost-effective
construction of the total-body PET. In order to determine properties of the
scanner prototype and optimize its geometry, advanced computer simulations
using the GATE software were performed.
The spatial resolution, the sensitivity, the scatter fraction and the noise
equivalent count rate were estimated according to the NEMA norm as a function
of the length of the tomograph, number of the detection layers, diameter of the
tomographic chamber and for various types of the applied readout. For the
single-layer geometry with the diameter of 85 cm, strip length of 100 cm,
cross-section of 4 mm x 20 mm and silicon photomultipliers with the additional
layer of wavelength shifter as the readout, the spatial resolution (FWHM) in
the centre of the scanner is equal to 3 mm (radial, tangential) and 6 mm
(axial). For the analogous double-layer geometry with the same readout,
diameter and scintillator length, with the strip cross-section of 7 mm x 20 mm,
the NECR peak of 300 kcps was reached at 40 kBq/cc activity concentration, the
scatter fraction is estimated to about 35% and the sensitivity at the centre
amounts to 14.9 cps/kBq. Sensitivity profiles were also determined
ProTheRaMon : a GATE simulation framework for proton therapy range monitoring using PET imaging
Objective. This paper reports on the implementation and shows examples of the use of the ProTheRaMon framework for simulating the delivery of proton therapy treatment plans and range monitoring using positron emission tomography (PET). ProTheRaMon offers complete processing of proton therapy treatment plans, patient CT geometries, and intra-treatment PET imaging, taking into account therapy and imaging coordinate systems and activity decay during the PET imaging protocol specific to a given proton therapy facility. We present the ProTheRaMon framework and illustrate its potential use case and data processing steps for a patient treated at the Cyclotron Centre Bronowice (CCB) proton therapy center in Krakow, Poland. Approach. The ProTheRaMon framework is based on GATE Monte Carlo software, the CASToR reconstruction package and in-house developed Python and bash scripts. The framework consists of five separated simulation and data processing steps, that can be further optimized according to the user’s needs and specific settings of a given proton therapy facility and PET scanner design. Main results. ProTheRaMon is presented using example data from a patient treated at CCB and the J-PET scanner to demonstrate the application of the framework for proton therapy range monitoring. The output of each simulation and data processing stage is described and visualized. Significance. We demonstrate that the ProTheRaMon simulation platform is a high-performance tool, capable of running on a computational cluster and suitable for multi-parameter studies, with databases consisting of large number of patients, as well as different PET scanner geometries and settings for range monitoring in a clinical environment. Due to its modular structure, the ProTheRaMon framework can be adjusted for different proton therapy centers and/or different PET detector geometries. It is available to the community via github (Borys et al 2022)
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