102 research outputs found
Isolated iliac bone tuberculosis : a case report
Background: Isolated iliac bone tuberculosis is not easy for diagnosis as it can mimic many other conditions. The presentation of our case of isolated iliac bone tuberculosis with special emphasis to imaging findings is justified, by its rarity and not uncommon delay in diagnosis and therapy of such cases. Case Report: A case of isolated iliac bone tuberculosis, initially presented with low back pain and swelling, was unsuccessfully treated for three months before final diagnosis was established. Plain radiography revealed only slight sclerosis of the iliac side of the right sacro-iliac joint. MRI provided more precise and detailed information regarding the site, size and nature of the bony and soft tissue components of the lesion. The bony lesion showed low T1, high T2 signal and marginal enhancement on fat suppressed T1 post-gadolinium images. The soft tissue components also showed post-gadolinium enhancement and abscesses formation. CT scan confirmed the bony lytic lesion and provided guidance for biopsy. Histology confirmed tuberculous nature of the lesion. Conclusions: Imaging presentation of tuberculous osteomyelitis is nonspecific and may mimic many inflammatory and neoplastic conditions. Correlation with the patient's history, immune status, ethnicity, social environment is necessary in narrowing differential diagnosis. This means that iliac tuberculosis, despite its rarity, should be considered as one of diagnostic possibilities, especially in the patients from endemic areas. However, definitive diagnosis is best established with bone needle biopsy
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
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
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
Positronium imaging with the novel multiphoton PET scanner
In vivo assessment of cancer and precise location of altered tissues at
initial stages of molecular disorders are important diagnostic challenges.
Positronium is copiously formed in the free molecular spaces in the patient's
body during positron emission tomography (PET). The positronium properties vary
according to the size of inter- and intramolecular voids and the concentration
of molecules in them such as, e.g., molecular oxygen, O2; therefore,
positronium imaging may provide information about disease progression during
the initial stages of molecular alterations. Current PET systems do not allow
acquisition of positronium images. This study presents a new method that
enables positronium imaging by simultaneous registration of annihilation
photons and deexcitation photons from pharmaceuticals labeled with
radionuclides. The first positronium imaging of a phantom built from cardiac
myxoma and adipose tissue is demonstrated. It is anticipated that positronium
imaging will substantially enhance the specificity of PET diagnostics.Comment: 10 pages, 5 figure
Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET
We perform a parametric study of the newly developed time-of-flight (TOF)
image reconstruction algorithm, proposed for the real-time imaging in
total-body Jagiellonian PET (J-PET) scanners. The asymmetric 3D filtering
kernel is applied at each most likely position of electron-positron
annihilation, estimated from the emissions of back-to-back -photons.
The optimisation of its parameters is studied using Monte Carlo simulations of
a 1-mm spherical source, NEMA IEC and XCAT phantoms inside the ideal J-PET
scanner. The combination of high-pass filters which included the TOF filtered
back-projection (FBP), resulted in spatial resolution, 1.5 higher in
the axial direction than for the conventional 3D FBP. For realistic -minute
scans of NEMA IEC and XCAT, which require a trade-off between the noise and
spatial resolution, the need for Gaussian TOF kernel components, coupled with
median post-filtering, is demonstrated. The best sets of 3D filter parameters
were obtained by the Nelder-Mead minimisation of the mean squared error between
the resulting and reference images. The approach allows training the
reconstruction algorithm for custom scans, using the IEC phantom, when the
temporal resolution is below 50 ps. The image quality parameters, estimated for
the best outcomes, were systematically better than for the non-TOF FBP
Developing Composite Insulating Cross-Arms for 400 kV Lattice Towers
\u3cp\u3ePolymorphism of organic semiconducting materials exerts critical effects on their physical properties such as optical absorption, emission and electrical conductivity, and provides an excellent platform for investigating structure–property relations. It is, however, challenging to efficiently tune the polymorphism of conjugated polymers in aggregated, semi-crystalline phases due to their conformational freedom and anisotropic nature. Here, two distinctly different semi-crystalline polymorphs (β\u3csub\u3e1\u3c/sub\u3e and β\u3csub\u3e2\u3c/sub\u3e) of a low-bandgap diketopyrrolopyrrole polymer are formed through controlling the solvent quality, as evidenced by spectroscopic, structural, thermal and charge transport studies. Compared to β\u3csub\u3e1\u3c/sub\u3e, the β\u3csub\u3e2\u3c/sub\u3e polymorph exhibits a lower optical band gap, an enhanced photoluminescence, a reduced π-stacking distance, a higher hole mobility in field-effect transistors and improved photocurrent generation in polymer solar cells. The β\u3csub\u3e1\u3c/sub\u3e and β\u3csub\u3e2\u3c/sub\u3e polymorphs provide insights into the control of polymer self-organization for plastic electronics and hold potential for developing programmable ink formulations for next-generation electronic devices.\u3c/p\u3
Feasibility study of the time reversal symmetry tests in decay of metastable positronium atoms with the J-PET detector
This article reports on the feasibility of testing of the symmetry under reversal in time in a purely leptonic system constituted by positronium atoms using the J-PET detector. The present state of T symmetry tests is discussed with an emphasis on the scarcely explored sector of leptonic systems. Two possible strategies of searching for manifestations of T violation in nonvanishing angular correlations of final state observables in the decay of metastable triplet states of positronium available with J-PET are proposed and discussed. Results of a pilot measurement with J-PET and assessment of its performance in reconstruction of three-photon decays are shown along with an analysis of its impact on the sensitivity of the detector for the determination of T-violation sensitive observables
A method to produce linearly polarized positrons and positronium atoms with the J-PET detector
A method for creating linearly polarized positrons and ortho-positronium (o-Ps) atoms with the J-PET detector is presented. The unique geometry and properties of the J-PET tomography enable one to design a positron source such that the quantization axis for the estimation of the linear polarization of produced o-Ps can be determined on the event by event basis in a direction of the positron motion. We intend to use ²²Na or other β⁺ decay isotopes as a source of polarized positrons. Due to the parity violation in the beta decay, the emitted positrons are longitudinally polarized. The choice of the quantization axis is based on the known position of the positron emitter and the reconstructed position of the positronium annihilation. We show that the J-PET tomography is equipped with all needed components
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