Realistic Total-Body J-PET Geometry Optimization--Monte Carlo Study
J. Baran, W. Krzemień, L. Raczyński, M. Bała, A. Coussat, S. Parzych, N. Chug, E. Czerwiński, C. Oana Curceanu, M. Dadgar, K. Dulski, K. Eliyan, J. Gajewski, A. Gajos, B. Hiesmayr, K. Kacprzak, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, D. Kumar, S. Niedźwiecki, D. Panek, E. Perez del Rio, A. Ruciński, S. Sharma, Shivani, R.Y. Shopa, M. Skurzok, E. Stępień, F. Tayefiardebili, K. Tayefiardebili, W. Wiślicki, P. Moskal
abstract
Comparative studies of the sensitivities of sparse and full geometries of Total-Body PET scanners built from crystals and plastic scintillators
M. Dadgar*, S. Parzych, J. Baran, N. Chug, C. Curceanu, E. Czerwiński, K. Dulski, K. Elyan, A. Gajos, B.C. Hiesmayr, Ł. Kapłon, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, S. Niedźwiecki, D. Panek, E. Perez del Rio, L. Raczyński, S. Sharma, Shivani, R.Y. Shopa, M. Skurzok, E. L. Stępień, F. Tayefi Ardebili, K. Tayefi Ardebili, S. Vandenberghe, W. Wiślicki and P. Moskal
abstract
Background: Alongside the benefits of Total-Body imaging modalities, such as higher sensitivity, single-bed position, low dose imaging, etc., their final construction cost prevents worldwide utilization. The main aim of this study is to present a simulation-based comparison of the sensitivities of existing and currently developed tomographs to introduce a cost-efficient solution for
constructing a Total-Body PET scanner based on plastic scintillators.
Methods: For the case of this study, eight tomographs based on the uEXPLORER configuration with different scintillator materials (BGO, LYSO), axial field-of-view (97.4 cm and 194.8 cm), and detector configuration (full and sparse) were simulated. In addition, 8 J-PET scanners with different configurations, such as various axial field-of-view (200 cm and 250 cm), the different cross-sections of plastic scintillator, and the multiple numbers of the
plastic scintillator layers (2, 3, and 4), based on J-PET technology have been simulated by GATE software. Furthermore, Biograph Vision has been simulated to compare the results with standard PET scans. Two types of simulations have been performed. The first one with a centrally located source with a diameter of 1mm and a length of 250 cm, and the second one with the same source inside a water-filled cylindrical phantom with a diameter of 20 cm and a length of 183 cm.
Results: With regards to sensitivity, among all the proposed scanners, the ones constructed with BGO crystals give the best performance (? 350 cps/kBq at the center). The utilization of sparse geometry or LYSO crystals significantly lowers the achievable sensitivity of such systems. The J-PET design gives a similar sensitivity to the sparse LYSO crystal-based detectors while having full detector coverage over the body. Moreover, it provides uniform sensitivity over the body
with additional gain on its sides and provides the possibility for high-quality brain
imaging.
Conclusion: Taking into account not only the sensitivity but also the price of the Total-Body PET tomographs, which till now was one of the main obstacles in their widespread clinical availability, the J-PET tomography system based on plastic scintillators could be a cost-efficient alternative for Total-Body PET scanners.
Comparative studies of plastic scintillator strips with high technical attenuation length for the total-body J-PET scanner
Ł. Kapłon, J. Baran, N. Chug, A. Coussat, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, J. Gajewski, A. Gajos, B. Hiesmayr, E. Kavya Valsan, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Moskal, S. Niedźwiecki, D. Panek, S. Parzych, E. Pérez del Rio, L. Raczyński, A. Ruciński, S. Sharma, S. Shivani, R. Shopa, M. Silarski, M. Skurzok, E. Stępień, F. Tayefi Ardebili, K. Tayefi Ardebili, W. Wiślicki, P. Moskal
abstract
Plastic scintillator strips are considered as one of the promising solutions for the cost-effective construction of total-body positron emission tomography, (PET) system. The purpose of the performed measurements is to compare the transparency of long plastic scintillators with dimensions 6 mm
24 mm
1000 mm and with all surfaces polished. Six different types of commercial, general purpose, blue-emitting plastic scintillators with low attenuation of visible light were tested, namely: polyvinyl toluene-based BC-408, EJ-200, RP-408, and polystyrene-based Epic, SP32 and UPS-923A. For determination of the best type of plastic scintillator for total-body Jagiellonian positron emission tomograph (TB-J-PET) construction, emission and transmission spectra, and technical attenuation length (TAL) of blue light-emitting by the scintillators were measured and compared. The TAL values were determined with the use of UV lamp as excitation source, and photodiode as light detector. Emission spectra of investigated scintillators have maxima in the range from 420 nm to 429 nm. The BC-408 and EJ-200 have the highest transmittance values of about 90% at the maximum emission wavelength measured through a 6 mm thick scintillator strip and the highest technical attenuation length reaching about 2000 mm, allowing assembly of long detection modules for time-of-flight (TOF) J-PET scanners. Influence of the 6 mm × 6 mm, 12 mm × 6 mm, 24 mm × 6 mm cross-sections of the 1000 mm long EJ-200 plastic scintillator on the TAL and signal intensity was measured. The highest TAL value was determined for samples with 24 mm × 6 mm cross-section.
J-PET detection modules based on plastic scintillators for performing studies with positron and positronium beams
S. Sharma, J. Baran, R.S. Brusa, R. Caravita, N. Chug, A. Coussat, C. Curceanu, E. Czerwinski, M. Dadgar, K. Dulski, K. Eliyan, A. Gajos, B.C. Hiesmayr, K. Kacprzak, L. Kaplon, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, W. Krzemien D. Kumar, S. Mariazzi, S. Niedźwiecki, L. Panasa, S. Parzych, L. Povolo, E. Perez del Rio, L. Raczynski Shivani, R.Y. Shopa, M. Skurzok, E.L. Stepien, F. Tayefi, K. Tayefi, W. Wislicki and P. Moskal
abstract
The J-PET detector, which consists of inexpensive plastic scintillators, has demonstrated its potential in the study of fundamental physics. In recent years, a prototype with 192 plastic scintillators arranged in 3 layers has been optimized for the study of positronium decays. This allows performing precision tests of discrete symmetries (C, P, T) in the decays of positronium atoms. Moreover, thanks to the possibility of measuring the polarization direction of the photon based on Compton scattering, the predicted entanglement between the linear polarization of annihilation photons in positronium decays can also be studied. Recently, a new J-PET prototype was commissioned, based on a modular design of detection units. Each module consists of 13 plastic scintillators and can be used as a stand-alone, compact and portable detection unit. In this paper, the main features of the J-PET detector, the modular prototype and their applications for possible studies with positron and positronium beams are discussed. Preliminary results of the first test experiment performed on two detection units in the continuous positron beam recently developed at the Antimatter Laboratory (AML) of Trento are also reported.
TOF MLEM Adaptation for the Total-Body J-PET with a Realistic Analytical System Response Matrix
R.Y. Shopa, J. Baran, K. Klimaszewski, W. Krzemień, L. Raczyński, W. Wiślicki, K. Brzeziński, N. Chug, A. Coussat, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, J. Gajewski, A. Gajos, B.C. Hiesmayr, E. Kavya Valsan, G. Korcyl, T. Kozik, D. Kumar, Ł. Kapłon, G. Moskal, S. Niedźwiecki, D. Panek, S. Parzych, E. Pérez del Rio, A. Ruciński, S. Sharma, Shivani, M. Silarski, M. Skurzok, E. Stepień, F. Tayefi Ardebili, K. Tayefi Ardebili, P. Moskal
abstract
We report a study of the original image reconstruction algorithm based on the time-of-flight maximum likelihood expectation maximisation (TOF MLEM), developed for the total-body (TB) Jagiellonian PET (J-PET) scanners. The method is applicable to generic cylindrical or modular multi-layer layouts and is extendable to multi-photon imaging. The system response matrix (SRM) is represented as a set of analytical functions, uniquely defined for each pair of plastic scintillator strips used for the detection. A realistic resolution model (RM) in detector space is derived from fitting the Monte Carlo simulated emissions and detections of annihilation photons on oblique transverse planes. Additional kernels embedded in SRM account for TOF, parallax effect and axial smearing. The algorithm was tested on datasets, simulated in GATE for the NEMA IEC and static XCAT phantoms inside a 24-module 2-layer TB J-PET. Compared to the reference TOF MLEM with none or a shift-invariant RM, an improvement was observed, as evaluated by the analysis of image quality, difference images and ground truth metrics. We also reconstructed the data with additive contributions, pre-filtered geometrically and with non-TOF scatter correction applied. Despite some deterioration, the obtained results still capitalise on the realistic RM with better edge preservation and superior ground truth metrics. The envisioned prospects of the TOF MLEM with analytical SRM include its application in multi-photon imaging and further upgrade to account for the non-collinearity, positron range and other factors.
Multi-photon time-of-flight MLEM application for the positronium imaging in J-PET
R. Shopa, K. Dulski
abstract
We develop a positronium imaging method for the Jagiellonian PET (J-PET) scanners based on the time-of-flight maximum likelihood expectation maximisation (TOF MLEM). The system matrix elements are calculated on-the-fly for the coincidences comprising two annihilation and one de-excitation photons that originate from the ortho-positronium (o-Ps) decay. Using the Geant4 library, a Monte Carlo simulation was conducted for four cylindrical 22Na sources of ?+ decay with diverse o-Ps mean lifetimes, placed symmetrically inside the two JPET prototypes. The estimated time differences between the annihilation and the positron emission were aggregated into histograms (one per voxel), updated by the weights of the activities reconstructed by TOF MLEM. The simulations were restricted to include only the o-Ps decays into back-to-back photons, allowing a linear fitting model to be employed for the estimation of the mean lifetime from each histogram built in the log scale. To suppress the noise, the exclusion of voxels with activity below 2% ? 10% of the peak was studied. The estimated o-Ps mean lifetimes were consistent with the simulation and distributed quasi-uniformly at high MLEM iterations. The proposed positronium imaging technique can be further upgraded to include various correction factors, as well as be modified according to realistic o-Ps decay models.
Investigation of novel preclinical Total Body PET designed with J-PET technology: A simulation study
M. Dadgar, S. Parzych, F. Tayefi Ardebili, J. Baran, N. Chug, C. Curceanu, E. Czerwiński, K. Dulski, K. Eliyan, A. Gajos, B.C. Hiesmayr, K. Kacprzak, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, S. Niedźwiecki, D. Panek, E. Perez del Rio, L. Raczyński, S. Sharma, R.Y. Shopa, M. Skurzok, K. Tayefi Ardebili, S. Vandenberghe, W. Wiślicki, E.Ł. Stępień, P. Moskal
abstract
The growing interest in human-grade Total Body PET systems has also application in small animal research. Due to the existing limitations in human-based studies involving drug development and novel treatment monitoring, animalbased research became a necessary step for testing and protocol preparation. In this simulation-based study two unconventional, cost effective small animal Total Body PET scanners (for mouse and rat studies) have been investigated in order to inspect their feasibility for preclinical research. They were designed with the novel technology explored by the Jagiellonian PET Collaboration (J-PET). Two main PET characteristics: sensitivity and spatial resolution were mainly inspected to evaluate their performance. Moreover, the impact of the scintillator dimension and time-offlight on the latter parameter were examined in order to design the most efficient tomographs. The presented results show that for mouse TB J-PET the achievable system sensitivity is equal to 2.35% and volumetric spatial resolution to 9.46 +- 0.54 mm3, while for rat TB J-PET they are equal to 2.6% and 14.11 ? 0.80 mm3, respectively. Furthermore, it was shown that the designed tomographs are almost parallax-free systems, hence they resolve the problem of the acceptance criterion trade-off between enhancing spatial resolution and reducing sensitivity.
ProTheRaMon - a GATE simulation framework for proton therapy range monitoring using PET imaging
D. Borys, J. Baran, K.W. Brzezinski, J. Gajewski, N. Chug, A. Coussat, E. Czerwiński, M. Dadgar, K. Dulski, K. Valsan Eliyan, A. Gajos, K. Kacprzak, Ł. Kapłon, K. Klimaszewski, P. Konieczka, R. Kopec, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, A. John Lomax, K. McNamara, S. Niedźwiecki, P. Olko, D. Panek, S. Parzych, E. Pérez del Río, L. Raczyński, S. Sharma, S. Shivani, R.Y. Shopa, T. Skóra, M. Skurzok, P. Stasica, E. Stępień, K. Tayefi Ardebili, F. Tayefi, D. Charles Weber, C. Winterhalter, W. Wiślicki, P. Moskal, A. Rucinski
abstract
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.
Positronium imaging with the novel multiphoton PET scanner
P. Moskal, K. Dulski, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, J. Gajewski, A. Gajos, G. Grudzień, B.C. Hiesmayr, K. Kacprzak, Ł. Kapłon, H. Karimi, K. Klimaszewski, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, P. Małczak, S. Niedźwiecki, M. Pawlik-Niedźwiecka, M. Pędziwiatr, L. Raczyński, J. Raj, A. Ruciński, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, E.Ł. Stępień, M. Szczepanek, F. Tayefi, W. Wiślicki
abstract
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.
Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography
P. Moskal, A. Gajos, M. Mohammed, J. Chhokar, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, M. Gorgol, J. Goworek, B. Hiesmayr, B. Jasińska, K. Kacprzak, Ł. Kapłon, H. Karimi, D. Kisielewska, K. Klimaszewski, G. Korcyl, P. Kowalski, N. Krawczyk, W. Krzemień, T. Kozik, E. Kubicz, S. Niedźwiecki, S. Parzych, M. Pawlik-Niedźwiecka, L. Raczyński, J. Raj, S. Sharma, S. Choudhary, R. Shopa, A. Sienkiewicz, M. Silarski, M. Skurzok, E. Stepien, F. Tayefi, W. Wiślicki
abstract
Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remain scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron-positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by the knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without a magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with a single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10^{-4}, with an over threefold improvement on the previous measurement.
Simulating NEMA characteristics of the modular total-body J-PET scanner - an economic total-body PET from plastic scintillators
P. Moskal, P. Kowalski, R.Y. Shopa, L. Raczyński, J. Baran, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, A. Gajos, B.C. Hiesmayr, K. Kacprzak, Ł. Kapłon, D. Kisielewska, K. Klimaszewski, P. Kopka, G. Korcyl, N. Krawczyk, W. Krzemień, E. Kubicz, Sz. Niedźwiecki, Sz. Parzych, J. Raj, S. Sharma, S. Shivani, E. Stępień, F. Tayefi, W. Wiślicki
abstract
The purpose of the presented research is the 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 NEMANU-2-2018 standards utilizing the GATE package. The simulated detector consists of 24 modules, each built out of 32 plastic scintillator strips
(each with a cross-section of 6 mm times 30 mm and length of 140 or 200 cm) arranged in two layers in regular 24-sided polygon circumscribing a circle with a diameter of 78.6 cm. For the TB-J-PET with an axial field-of-view (AFOV) of 200 cm, a spatial resolution (SRs) of 3.7mm (transversal) and 4.9mm (axial) are achieved. The noise equivalent count rate (NECR) peak of 630 kcps is expected at 30 kBq cc^-1. Activity concentration and the sensitivity at the center amount to 38 cps kBq^-1. The scatter fraction (SF) is estimated to 36.2 %. The values of SF and SR 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 systemswithAFOVin the range from16 to 26 cm, the TBJ-PET is characterized by an increase inNECRapproximately by a factor of 4 and by the increase of the whole-body sensitivity by a factor of 12.6 to 38. The time-of-flight resolution for the TB-J-PETis expected to be at the level ofCRT=240 ps fullwidth at half-maximum. For the TB-J-PETwith an AFOVof 140 cm, an image quality of the reconstructed images of a NEMAIEC phantom was presented with a contrast recovery coefficient and a background variability parameters. The increase of the whole-body sensitivity andNECRestimated for the TB-J-PET with respect to current commercial PETsystems makes the TB-J-PET a promising cost-effective solution for the broad clinical applications of total-body PET scanners. TB-J-PETmay constitutes an economic alternative for the crystal TB-PET scanners, since plastic scintillators are much cheaper than BGO or LYSO crystals and the axial arrangement of the strips significantly reduces the costs of readout electronics and SiPMs.
The J-PET detector - a tool for precision studies of ortho-positronium decays
K. Dulski, S.D. Bass, J. Chhokar, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, J. Gajewski, A. Gajos, M. Gorgol, R. Del Grande, B.C. Hiesmayr, B. Jasińska, K. Kacprzak, Ł. Kapłon, H. Karimi, D. Kisielewska, K. Klimaszewski, P. Kopka, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, P. Małczak, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, M. Pędziwiatr, L. Raczyński7, J. Raj, A. Ruciński, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, E. Ł. Stępień, F. Tayefi, W. Wiślicki, B. Zgardzińska, P. Moskal
abstract
The J-PET tomograph is constructed from plastic scintillator strips arranged axially in concentric cylindrical layers. It enables investigations of positronium decays by measurement of the time, position, polarization and energy deposited by photons in the scintillators, in contrast to studies conducted so far with crystal and semiconductor based detection systems where the key selection of events is based on the measurement of the photons energies. In this article we show that the J-PET tomography system constructed solely from plastic scintillator detectors is capable of exclusive measurements of the decays of ortho-positronium atoms. We present the first positronium production results and its lifetime distribution measurements. The obtained results prove the capability of the J-PET tomograph for (i) fundamental studies of positronium decays (in particular test of discrete symmetries in purely leptonic systems), (ii) positron annihilation lifetime spectroscopy, as well as (iii) molecular imaging diagnostics and (iv) observation of entanglement
Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET
R.Y. Shopa, K. Klimaszewski, P. Kopka, P. Kowalski, W. Krzemień, L. Raczyński, W. Wiślicki, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, A. Gajos, B.C. Hiesmayr, K. Kacprzak, Ł. Kapłon, D. Kisielewska, G. Korcyl, N. Krawczyk, E. Kubicz, Sz. Niedźwiecki, J. Raj, S. Sharma, Shivani, E.Ł. Stępień, F. Tayefi, P. Moskal
abstract
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 gamma-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 scan- ner. The combination of high-pass filters which included the TOF filtered back-projection (FBP), resulted in spatial resolution, 1.5 times higher in the axial direction than for the conventional 3D FBP. For real- istic 10-minute scans of NEMA IEC and XCAT, which require a trade-offbetween the noise and spatial resolution, the need for Gaussian TOF kernel components, coupled with median post-filtering, is demon- strated. 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 recon- struction 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.
Feasibility study of the positronium imaging with the J-PET tomograph
P. Moskal, D. Kisielewska, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, M. Gorgol, B. Hiesmayr, B. Jasińska, K. Kacprzak, Ł. Kapłon, G. Korcyl, P. Kowalski, W. Krzemień, T. Kozik, E. Kubicz, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, L. Raczyński, J. Raj, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, E. Stępień, W. Wiślicki, B. Zgardzińska
abstract
A detection system of the conventional PET tomograph is set-up to record data from e+ e- annihilation into two photons with energy of 511 keV, and it gives information on the density distribution of a radiopharmaceutical in the body of the object. In this paper we explore the possibility of performing the three gamma photons imaging based on ortho- positronium annihilation, as well as the possibility of positronium average lifetime imaging with the J-PET tomograph constructed from plastic scintillators. For this purposes simulations of the ortho-positronium formation and its annihilation into three photons were performed taking into account distributions of photons' momenta as predicted by the theory of quantum electrodynamics and the response of the J-PET tomograph. In order to test the proposed ortho-positronium lifetime image reconstruction method, we concentrate on the decay of the ortho-positronium into three photons and applications of radiopharmaceuticals labeled with isotopes emitting a prompt gamma quantum. The proposed method of imaging is based on the determination of hit-times and hit-positions of registered photons which enables the reconstruction of the time and position of the annihilation point as well as the lifetime of the ortho-positronium on an event-by-event basis. We have simulated the production of the positronium in a cylindrical phantom composed of a set of different materials in which the ortho-positronium lifetime varied from 2 ns to ~2.9 ns, as expected for ortho-positronium created in the human body. The presented reconstruction method for total-body J-PET like detector allows to achieve a mean lifetime resolution of about 40 ps. Recent Positron Annihilation Lifetime Spectroscopy measurements of cancerous and healthy uterine tissues show that this sensitivity may allow to study the morphological changes in cell structures.
Simulation studies of annihilation-photon's polarisation via Compton scattering with the J-PET tomograph
N. Krawczyk, B.C. Hiesmayr, J. Chhokar, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, M. Gorgol, N. Gupta-Sharma, B. Jasińska, D. Kisielewska, G. Korcyl, P. Kowalski, W. Krzemień, T. Kozik, E. Kubicz, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, L. Raczyński, J. Raj, K. Rakoczy, Z. Rudy, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, W. Wiślicki, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
J-PET is the first positron-emission tomograph (PET) constructed from plastic scintillators. It was optimized for the detection of photons from electron-positron annihilation. Such photons, having an energy of 511 keV, interact with electrons in plastic scintillators predominantly via the Compton effect. Compton scattering is at most probable at an angle orthogonal to the electric field vector of the interacting photon. Thus registration of multiple photon scatterings with J-PET enables to determine the polarization of the annihilation photons. In this contribution we present estimates on the physical limitation in the accuracy of the polarization determination of 511 keV photons with the J-PET detector.
A feasibility study of the time reversal violation test based on polarization of annihilation photons from the decay of ortho-Positronium with the J-PET detector
J. Raj, A. Gajos, C. Curceanu, E. Czerwiński, K. Dulski, M. Gorgol, N. Gupta-Sharma, B. C. Hiesmayr, B. Jasińska, K. Kacprzak, Ł. Kapłon, D. Kisielewska, K. Klimaszewski, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, L. Raczyński, K. Rakoczy, Z. Rudy, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, W. Wiślicki, B. Zgardzińska, P. Moskal
abstract
The Jagiellonian Positron Emission Tomograph (J-PET) is a novel device being developed at Jagiellonian University in Krakow, Poland based on organic scintillators. J-PET is an axially symmetric and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pursue tests of discrete symmetries in decays of positronium in addition to medical
imaging. J-PET enables the measurement of both momenta and the polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows the study of time reversal symmetry violation operator which can be constructed solely from the annihilation photons momenta before and after the scattering in the detector.
Feasibility study of the time reversal symmetry tests in decay of metastable positronium atoms with the J-PET detector
A. Gajos, C. Curceanu, E. Czerwinski, K. Dulski, M. Gorgol, N. Gupta-Sharma, B.C. Hiesmayr, B. Jasinska, K. Kacprzak, L. Kaplon, D. Kisielewska, G. Korcyl, P. Kowalski, T. Kozik, W. Krzemien, E. Kubicz, M. Mohammed, Sz Niedzwiecki, M. Paalka, M. Pawlik-Niedzwiecka, L. Raczynski, J. Raj, Z. Rudy, S. Sharma, Shivani, R. Shopa, M. Silarski, M. Skurzok, W. Wislicki, B. Zgardzinska, M. Zielinski, P. Moskal
abstract
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 non-vanishing angular correlations of final state observables in the decays 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.
Estimating the NEMA characteristics of the J-PET tomograph using the GATE package
P. Kowalski, W. Wiślicki, R.Y. Shopa, L. Raczyński, K. Klimaszewski, C. Curcenau, E. Czerwiński, K. Dulski, A. Gajos, M. Gorgol, N. Gupta-Sharma, B. Hiesmayr, B. Jasińska, Ł. Kapłon, D. Kisielewska-Kamińska, G. Korcyl, T. Kozik, W. Krzemień, E. Kubicz, M. Mohammed, S. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, J. Raj, K. Rakoczy, Z. Rudy, S. Sharma, S. Shivani, M. Silarski, M. Skurzok, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
A novel whole-body positron emission tomography (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 system. In order to
determine the properties of the scanner prototype and optimize its geometry, advanced computer
simulations were performed using the GATE (Geant4 application for tomographic emission)
software.
The spatial resolution, sensitivity, scatter fraction and noise equivalent count rate were estimated
according to the National Electrical Manufacturers Association norm, as a function of the length
of the tomograph, the number of detection layers, the diameter of the tomographic chamber and
for various types of applied readout. For the single-layer geometry with a diameter of 85 cm, a strip
length of 100 cm, a cross-section of 4 mm × 20 mm and silicon photomultipliers with an additional
layer of wavelength shifter as the readout, the spatial resolution (full width at half maximum) 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 a strip crosssection
of 7 mm × 20 mm, a noise equivalent count rate peak of 300 kcps was reached at 40 kBq cc?1
activity concentration, the scatter fraction is estimated to be about 35% and the sensitivity at the
centre amounts to 14.9 cps kBq?1. Sensitivity profiles were also determined.
Human Tissue Investigations Using PALS Technique - Free Radicals Influence
B. Jasińska, B. Zgardzińska, G. Chołubek, M. Pietrow, M. Gorgol, K. Wiktor, K. Wysogląd, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, B.C. Hiesmayr, B. Jodłowska-Jędrych, D. Kamińska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, S. Niedźwiecki, M. Pałka, L. Raczyński, Z. Rudy, N.G. Sharma, S. Sharma, R. Shopa, M. Silarski, M. Skurzok, A. Wieczorek, H. Wiktor, W. Wiślicki, M. Zieliński, P. Moskal
abstract
The positron annihilation lifetime spectroscopy was applied to the samples of the human uterine leiomyomas and the normal myometrium tissues taken from the selected place of the uterus during a surgery. The method indicated differences in values of the measured positron annihilation lifetime spectroscopy parameters (lifetimes and intensities) between healthy and diseased tissue samples. The additional measurements were performed either in darkness or in presence of visible light which influenced the free radicals present in both kind of tissues and, as a result, made changes in free annihilation and o-Ps decay lifetime and intensity values.
Preliminary Studies of J-PET Detector Spatial Resolution
M. Pawlik-Niedźwiecka, S. Niedźwiecki, D. Alfs, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, M. Gorgol, B. C. Hiesmayr, B. Jasińska, D. Kisielewska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, M. Pałka, L. Raczyński, J. Raj, Z. Rudy, Shivani, M. Silarski, M. Skurzok, N.G. Sharma, S. Sharma, R.Y. Shopa, A. Strzelecki, A. Wieczorek, W. Wiślicki, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
The J-PET detector, based on long plastic scintillator strips, was recently constructed at the Jagiellonian University. It consists of 192 modules axially arranged into three layers, read out from both sides by digital constant-threshold front-end electronics. This work presents preliminary results of measurements of the spatial resolution of the J-PET tomograph performed with 22Na source placed at selected position inside the detector chamber.
Introduction of total variation regularization into filtered backprojection algorithm
L. Raczyński, W. Wiślicki, K. Klimaszewski, W. Krzemień, P. Kowalski, R. Shopa, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski A. Gajos, B. Głowacz, M. Gorgol, B. Hiesmayr, B. Jasińska, D. Kisielewska-Kamińska, G. Korcyl, T. Kozik, N. Krawczyk, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, S. Niedźwiecki, M. Pałka, Z. Rudy, N.G. Sharma, S. Sharma, M. Silarski, M. Skurzok, A. Wieczorek, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
In this paper we extend the state-of-the-art filtered backprojection (FBP) method with application of the concept of Total Variation regularization. We compare the performance of the new algorithm with the most common form of regularizing in the FBP image reconstruction via apodizing functions. The methods are validated in terms of cross-correlation coefficient between reconstructed and real image of radioactive tracer distribution using standard Derenzo-type phantom. We demonstrate that the proposed approach results in higher cross-correlation values with respect
to the standard FBP method.
Commissioning of the J-PET Detector for Studies of Decays of Positronium Atoms
E. Czerwiński, K. Dulski, P. Białas, C. Curceanu, A. Gajos, B. Głowacz, M. Gorgol, B.C. Hiesmayr, B. Jasińska, D. Kisielewska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, Sz. Niedźwiecki, M. Pałka, M. Pawlik-Niedźwiecka, L. Raczyński, Z. Rudy, N.G. Sharma, S. Sharma, R.Y. Shopa, M. Silarski, M. Skurzok, A. Wieczorek, W. Wiślicki, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging of the whole human body as well as for physics studies involving detection of electron?positron annihilation into photons. J-PET has high angular and time resolution, and allows for measurement 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 the background rejection in the decays of positronium atoms.
J-PET: A New Technology for the Whole-body PET Imaging
S. Niedźwiecki, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, M. Gorgol, B.C. Hiesmayr, B. Jasińska, Ł. Kapłon, D. Kisielewska-Kamińska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, M. Pałka, L. Raczyński, Z. Rudy, N.G. Sharma, S. Sharma, R.Y. Shopa, M. Silarski, M. Skurzok, A. Wieczorek, W. Wiślicki, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET built from plastic scintillators. J-PET prototype consists of 192 detection modules arranged axially in three layers forming a cylindrical diagnostic chamber with the inner diameter of 85 cm and the axial field-of-view of 50 cm. An axial arrangement of long strips of plastic scintillators, their small light attenuation, superior timing properties, and relative ease of the increase of the axial field-of-view opens promising perspectives for the cost effective construction of the whole-body PET scanner, as well as construction of MR and CT compatible PET inserts. Present status of the development of the J-PET tomograph will be presented and discussed.
Three-dimensional Image Reconstruction in J-PET Using Filtered Back-projection Method
R.Y. Shopa, K. Klimaszewski, P. Kowalski, W. Krzemień, L. Raczyński, W. Wiślicki, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, M. Gorgol, B. Hiesmayr, B. Jasińska, D. Kisielewska-Kamińska, G. Korcyl, T. Kozik, N. Krawczyk, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, S. Niedźwiecki, M. Pałka, Z. Rudy, N.G. Sharma, S. Sharma, M. Silarski, M. Skurzok, A. Wieczorek, B. Zgardzińska, M. Zieliński, P. Moskal
abstract
We present a method and preliminary results of the image reconstruction in the Jagiellonian PET tomograph. Using GATE (Geant4 Application for Tomographic Emission), interactions of the 511 keV photons with a cylindrical detector were generated. Pairs of such photons, flying back-to-back, originate from e+e? annihilations inside a 1 mm spherical source. Spatial and temporal coordinates of hits were smeared using experimental resolutions of the detector. We incorporated the algorithm of the 3D Filtered Back Projection, implemented in the STIR and TomoPy software packages, which differ in approximation methods. Consistent results for the Point Spread Functions of ? 5 ÷ 7 mm and ? 9 ÷ 20 mm were obtained, using STIR, for transverse and longitudinal directions, respectively, with no time-of-flight information included.
Human Tissues Investigation Using PALS Technique
B. Jasińska, B. Zgardzińska, G. Chołubek, M. Gorgol, K. Wiktor, K. Wysogląd, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, B. Hiesmayr, B. Jodłowska-Jędrych, D. Kamińska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, S. Niedźwiecki, M. Pałka, L. Raczyński, Z. Rudy, N.G. Sharma, S. Sharma, R. Shopa, M. Silarski, M. Skurzok, A. Wieczorek, H. Wiktor, W. Wiślicki, M. Zieliński, P. Moskal
abstract
Samples of uterine leiomyomatis and normal tissues taken from patients after surgery were investigated using the Positron Annihilation Lifetime Spectroscopy (PALS). Significant differences in all PALS parameters between normal and diseased tissues were observed. For all studied patients, it was found that the values of the free annihilation and ortho-positronium lifetime are larger for the tumorous tissues than for the healthy ones. For most of the patients, the intensity of the free annihilation and ortho-positronium annihilation was smaller for the tumorous than for the healthy tissues. For the first time, in this kind of studies, the 3? fraction of positron annihilation was determined to describe changes in the tissue porosity during morphologic alteration.
Human Tissues Investigation Using PALS Technique
B. Jasińska, B. Zgardzińska, G. Chołubek, M. Gorgol, K. Wiktor, K. Wysogląd, P. Białas, C. Curceanu, E. Czerwiński, K. Dulski, A. Gajos, B. Głowacz, B.C. Hiesmayr, B. Jodłowska-Jędrych, D. Kamińska, G. Korcyl, P. Kowalski, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, M. Mohammed, M. Pawlik-Niedźwiecka, S. Niedźwiecki, M. Pałka, L. Raczyński, Z. Rudy, N.G. Sharma, S. Sharma, R. Shopa, M. Silarski, M. Skurzok, A. Wieczorek, H. Wiktor, W. Wiślicki, M. Zieliński, P. Moskal
abstract
Samples of uterine leiomyomatis and normal tissues taken from patients
after surgery were investigated using the Positron Annihilation Lifetime
Spectroscopy (PALS). Significant differences in all PALS parameters
between normal and diseased tissues were observed. For all studied patients,
it was found that the values of the free annihilation and orthopositronium
lifetime are larger for the tumorous tissues than for the healthy
ones. For most of the patients, the intensity of the free annihilation and
ortho-positronium annihilation was smaller for the tumorous than for the
healthy tissues. For the first time, in this kind of studies, the 3gamma fraction
of positron annihilation was determined to describe changes in the tissue
porosity during morphologic alteration.
