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
Total-Body PET imaging is one of the most promising newly introduced modalities in the medical diagnostics. State-of-the-art PET scanners use inorganic scintillators such as L(Y)SO or BGO, however, those technologies are very expensive, prohibitng the broad total-body PET applications. We present the comparative studies of performance characteristics of the cost-effective Total-Body PET scanners using Jagiellonian PET (J-PET) technology that is based on plastic scintillators. Here, we investigated in silico five realistic Total-Body scanner geometries, varying the number of rings, scanner radius, and distance between the neighbouring rings. Monte Carlo simulations of two NEMA phantoms (2-meter sensitivity line source and image quality) and the anthropomorphic XCAT phantom, were used to assess the performance of the tested geometries. We compared the sensitivity profiles and we performed the quantitative analysis of the reconstructed images by using the quality metrics such as contrast recovery coefficient, background variability and root mean squared error. The optimal scanner design was selected for the first Total-Body J-PET scanner configuration.
Non-maximal entanglement of photons from positron-electron annihilation demonstrated using a novel plastic PET scanner
P. Moskal, D. Kumar, S. Sharma, E.Y. Beyene, N. Chug, A. Coussat, C. Curceanu, E. Czerwinski, M. Das, K. Dulski, M. Gorgol, B. Jasinska, K. Kacprzak, T. Kaplanoglu, L. Kaplon, K. Klimaszewski, T. Kozik, E. Lisowski, F. Lisowski, W. Mryka, S. Niedzwiecki, S. Parzych, E.P. del Rio, L. Raczynski, M. Radler, R.Y. Shopa, M. Skurzok, E. L. Stepien, P. Tanty, K. Tayefi Ardebili, K. Valsan Eliyan, W. Wislicki
abstract
In the state-of-the-art Positron Emission Tomography (PET), information about the polarization of annihilation photons is not available. Current PET systems track molecules labeled with positron-emitting radioisotopes by detecting the propagation direction of two photons from positron-electron annihilation. However, annihilation photons carry more information than just the site where they originated. Here we present a novel J-PET scanner built from plastic scintillators, in which annihilation photons interact predominantly via the Compton effect, providing information about photon polarization in addition to information on photon direction of propagation. Theoretically, photons from the decay of positronium in a vacuum are maximally entangled in polarization. However, in matter, when the positron from positronium annihilates with the electron bound to the atom, the question arises whether the photons from such annihilation are maximally entangled. In this work, we determine the distribution of the relative angle between polarization orientations of two photons from positron-electron annihilation in a porous polymer. Contrary to prior results for positron annihilation in aluminum and copper, where the strength of observed correlations is as expected for maximally entangled photons, our results show a significant deviation. We demonstrate that in porous polymer, photon polarization correlation is weaker than for maximally entangled photons but stronger than for separable photons. The data indicate that more than 40% of annihilations in Amberlite resin lead to a non-maximally entangled state. Our result indicates the degree of correlation depends on the annihilation mechanism and the molecular arrangement. We anticipate that the introduced Compton interaction-based PET system opens a promising perspective for exploring polarization correlations in PET as a novel diagnostic indicator.
Positronium image of the human brain in vivo
P. Moskal, J. Baran, S. Bass, J. Choiński, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, M. Das, K. Dulski, K.V. Eliyan, K. Fronczewska, A. Gajos, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, M. Kobylecka, G. Korcyl, T. Kozik, W. Krzemień, K. Kubat, D. Kumar, J. Kunikowska, J. Mączewska, W. Migdał, G. Moskal, W. Mryka, S. Niedźwiecki, S. Parzych, E. Perez del Rio, L. Raczyński, S. Sharma, Shivani, R.Y. Shopa, M. Silarski, M. Skurzok, F. Tayefi, K. Tayefi, P. Tanty, W. Wiślicki, L. Królicki, E. Ł. Stępień
abstract
Positronium is abundantly produced within the molecular voids of a patient?s body during positron emission tomography (PET). Its properties dynamically respond to the submolecular architecture of the tissue and the partial pressure of oxygen. Current PET systems record only two annihilation photons and cannot provide information about the positronium lifetime. This study presents the in vivo images of positronium lifetime in a human, for a patient with a glioblastoma brain tumor, by using the dedicated Jagiellonian PET system enabling simultaneous detection of annihilation photons and prompt gamma emitted by a radionuclide. The prompt gamma provides information on the time of positronium formation. The photons from positronium annihilation are used to reconstruct the place and time of its decay. In the presented case study, the determined positron and positronium lifetimes in glioblastoma cells are shorter than those in salivary glands and those in healthy brain tissues, indicating that positronium imaging could be used to diagnose disease in vivo.
Feasibility of the J-PET to monitor range oftherapeutic proton beams
J. Baran, D. Borys, K. Brzeziński, J. Gajewski, M. Silarski, N. Chug, A. Coussat, E. Czerwiński, M. Dadgar, K. Dulski, K.V. Eliyan, A. Gajos, K. Kacprzak, Ł. Kapłon, K. Klimaszewski, P. Konieczka, R. Kopeć, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, A.J. Lomax, K. McNamara, S. Niedźwiecki, P. Olko, D. Panek, S. Parzych, E. Perez del Rio, L. Raczyński, M. Simbarashe, S. Sharma, Shivani, R.Y. Shopa, T. Skóra, M. Skurzok, P. Stasica, E.Ł. Stępień, K. Tayefi, F. Tayefi, D.C. Weber, C. Winterhalter, W. Wiślicki, P. Moskal, A. Ruciński
abstract
Objective: The aim of this work is to investigate the feasibility of the JagiellonianPositron Emission Tomography (J-PET) scanner for intra-treatment proton beamrange monitoring. Approach: The Monte Carlo simulation studies with GATE and PET imagereconstruction with CASToR were performed in order to compare six J-PET scannergeometries (three dual-heads and three cylindrical). We simulated proton irradiationof a PMMA phantom with a Single Pencil Beam (SPB) and Spread-Out BraggPeak (SOBP) of various ranges. The sensitivity and precision of each scanner werecalculated, and considering the setup?s cost-effectiveness, we indicated potentiallyoptimal geometries for the J-PET scanner prototype dedicated to the proton beamrange assessment. Main results: The investigations indicate that the double-layer cylindrical andtriple-layer double-head configurations are the most promising for clinical application.We found that the scanner sensitivity is of the order of 10?5coincidences per primaryproton, while the precision of the range assessment for both SPB and SOBP irradiationplans was found below 1 mm. Among the scanners with the same number of detectormodules, the best results are found for the triple-layer dual-head geometry. Significance: We performed simulation studies demonstrating that the feasibilityof the J-PET detector for PET-based proton beam therapy range monitoring ispossible with reasonable sensitivity and precision enabling its pre-clinical tests in theclinical proton therapy environment. Considering the sensitivity, precision and cost-effectiveness, the double-layer cylindrical and triple-layer dual-head J-PET geometryconfigurations seem promising for the future clinical application. Experimental testsare needed to confirm these findings.
Feasibility studies for imaging e+e- annihilation with modular multi-strip detectors
S. Sharma, L. Povolo, S. Mariazzi, G. Korcyl, K. Kacprzak, D. Kumar, S. Niedzwiecki, J. Baran, E. Beyene, R. S. Brusa, R. Caravita, N. Chug, A. Coussat, C. Curceanu, E. Czerwinski, M. Dadgar, M. Das, K. Dulski, K. Eliyan, A. Gajos, N. Gupta, B. C. Hiesmayr, L. Kaplon, T. Kaplanoglu, K. Klimaszewski, P. Konieczka, T. Kozik, M. K. Kozani, W. Krzemien, S. Moyo, W. Mryka, L. Penasa, S. Parzych, E. Perez Del Rio, L. Raczynski, R. Y. Shopa, M. Skurzok, E. L. Stepien, P. Tanty, F. Tayefi, K. Tayefi, W. Wislicki, P. Moskal
abstract
Studies based on imaging the annihilation of the electron (e-) and its antiparticle positron (e+) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the direct conversion of ee into photons and the formation of their atomically bound state, the positronium atom (Ps), which can be used as a probe for fundamental studies. With the ability to produce large quantities of Ps, manipulate them in long-lived Ps states, and image their annihilations after a free fall or after passing through atomic interferometers, this purely leptonic antimatter system can be used to perform inertial sensing studies in view of a direct test of Einstein equivalence principle. It is envisioned that modular multistrip detectors can be exploited as potential detection units for this kind of studies. In this work, we report the results of the first feasibility study performed on a e beamline using two detection modules to evaluate their reconstruction performance and spatial resolution for imaging ee annihilations and thus their applicability for gravitational studies of Ps.
Discrete symmetries tested at 10^-4 precision using linear polarization of photons from positronium annihilations
P. Moskal, E. Czerwiński, J. Raj, S. D. Bass, E. Beyene, N. Chug, A. Coussat, C. Curceanu, M. Dadgar, M. Das, K. Dulski, A. Gajos, M. Gorgol, B. C. Hiesmayr, B. Jasińska, K. Kacprzak, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, S. Moyo, W. Mryka, S. Niedźwiecki, S. Parzych, E. Pérez del Río, L. Raczyński, S. Sharma, S. Choudhary, R. Y. Shopa, M. Silarski, M. Skurzok, E. Ł. Stępień, P. Tanty, F. T. Ardebili, K. T. Ardebili, K. V. Eliyan, W. Wiślicki
abstract
Discrete symmetries play an important role in particle physics with violation of CP connected to the matter-antimatter imbalance in the Universe. We report the most precise test of P, T and CP invariance in decays of ortho-positronium, performed with methodology involving polarization of photons from these decays. Positronium, the simplest bound state of an electron and positron, is of recent interest with discrepancies reported between measured hyperfine energy structure and theory at the level of 10^-4 signaling a need for better understanding of the positronium system at this level. We test discrete symmetries using photon polarizations determined via Compton scattering in the dedicated J-PET tomograph on an event-by-event basis and without the need to control the spin of the positronium with an external magnetic field, in contrast to previous experiments. Our result is consistent with QED expectations at the level of 0.0007 and one standard deviation.
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.
Transformation of PET raw data into images for event classification using convolutional neural networks
P. Konieczka, L. Raczyński, W. Wiślicki, O. Fedoruk, K. Klimaszewski, P. Kopka, W. Krzemień, R.Y. Shopa, J. Baran, A. Coussat, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, A. Gajos, B.C. Hiesmayr, K. Kacprzak, Ł. Kapłon, G. Korcyl, T. Kozik, D. Kumar, S. Niedźwiecki, S. Parzych, E. Pérez del Río, S. Sharma, S. Shivani, M. Skurzok, E.Ł. Stępień, F. Tayefi, P. Moskal
abstract
In positron emission tomography (PET) studies, convolutional neural networks (CNNs) may be applied directly to the reconstructed distribution of radioactive tracers injected into the patient's body, as a pattern recognition tool. Nonetheless, unprocessed PET coincidence data exist in tabular format. This paper develops the transformation of tabular data into -dimensional matrices, as a preparation stage for classification based on CNNs. This method explicitly introduces a nonlinear transformation at the feature engineering stage and then uses principal component analysis to create the images. We apply the proposed methodology to the classification of simulated PET coincidence events originating from NEMA IEC and anthropomorphic XCAT phantom. Comparative studies of neural network architectures, including multilayer perceptron and convolutional networks, were conducted. The developed method increased the initial number of features from 6 to 209 and gave the best precision results (79.8) for all tested neural network architectures; it also showed the smallest decrease when changing the test data to another phantom.
Detection of range shifts in proton beam therapy using the J-PET scanner: a patient simulation study
K. Brzeziński, J. Baran, D. Borys, J. Gajewski, N. Chug, A. Coussat, E. Czerwiński, M. Dadgar, K. Dulski, K.V. Eliyan, A. Gajos, K. Kacprzak, Ł. Kapłon, K. Klimaszewski, P. Konieczka, R. Kopeć, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, A.J. Lomax, K. McNamara, S. Niedźwiecki, P. Olko, D. Panek, S. Parzych, E. Perez del Rio, L. Raczyński, S. Sharma, Shivani, R.Y. Shopa, T. Skóra, M. Skurzok, P. Stasica, E.Ł. Stępień, K. Tayefi, F. Tayefi, D.C. Weber, C. Winterhalter, W. Wiślicki, P. Moskal, A. Ruciński
abstract
Objective. The Jagiellonian positron emission tomography (J-PET) technology, based on plastic scintillators, has been proposed as a cost effective tool for detecting range deviations during proton therapy. This study investigates the feasibility of using J-PET for range monitoring by means of a detailed Monte Carlo simulation study of 95 patients who underwent proton therapy at the Cyclotron Centre Bronowice (CCB) in Krakow, Poland. Approach. Discrepancies between prescribed and delivered treatments were artificially introduced in the simulations by means of shifts in patient positioning and in the Hounsfield unit to the relative proton stopping power calibration curve. A dual-layer, cylindrical J-PET geometry was simulated in an in-room monitoring scenario and a triple-layer, dual-head geometry in an in-beam protocol. The distribution of range shifts in reconstructed PET activity was visualized in the beam's eye view. Linear prediction models were constructed from all patients in the cohort, using the mean shift in reconstructed PET activity as a predictor of the mean proton range deviation. Main results. Maps of deviations in the range of reconstructed PET distributions showed agreement with those of deviations in dose range in most patients. The linear prediction model showed a good fit, with coefficient of determination r2 = 0.84 (in-room) and 0.75 (in-beam). Residual standard error was below 1 mm: 0.33 mm (in-room) and 0.23 mm (in-beam). Significance. The precision of the proposed prediction models shows the sensitivity of the proposed J-PET scanners to shifts in proton range for a wide range of clinical treatment plans. Furthermore, it motivates the use of such models as a tool for predicting proton range deviations and opens up new prospects for investigations into the use of intra-treatment PET images for predicting clinical metrics that aid in the assessment of the quality of delivered treatment.
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 x 24 mm x 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.
Efficiency determination of J-PET: first plastic scintillators-based PET scanner
S. Sharma, J. Baran, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Eliyan, A. Gajos, N. Gupta-Sharma, B. C. Hiesmayr, K. Kacprzak, Ł. Kapłon, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, Sz. Niedźwiecki, D. Panek, S. Parzych, E. Perez del Rio, L. Raczyński, Shivani, R. Y. Shopa, M. Skurzok, E. Ł. Stępień, F. Tayefi, K. Tayefi , W. Wiślicki and P. Moskal
abstract
Background:
The Jagiellonian Positron Emission Tomograph is the 3-layer prototype
of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators
are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV
photons emitted in e+e- annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures
the precise labeling of the 511 keV photons.
Results:
By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70-270 keV, where it varies between 20 and 100%. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons.
Conclusion:
A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion-beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.
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.
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.
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.
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
Classification of Signal Events for CPT Symmetry Studies with J-PET Using Machine Learning Techniques
N. Chug, P. Moskal
published in: Acta Phys. Pol. B Proc. Suppl. 17 (2024) 7-A2
The deviations from combined Charge, Parity, and Time (CPT) symmetry could indicate the presence of new physics beyond the current theoretical framework. The positronium (Ps), the lightest bound state of an electron?positron pair, offers a unique probe for such investigations because it is an eigenstate of charge conjugation (C) and parity (P). This work explores the potential of the Jagiellonian Positron Emission Tomography (J-PET) detector for sensitive tests of CPT symmetry in the three-photon decay of ortho-Ps (o-Ps) atom. The CPT symmetry invariance in o-Ps decays has been previously tested using the J-PET detector, measuring the CPT-violating angular correlation between the o-Ps spin and its annihilation photon momenta, achieving a precision of
. However, a range of five orders of magnitude is still unexplored to test its exactness. A Monte Carlo simulation study is presented to distinguish between the o-Ps signal and background events using Multivariate Data Analysis (TMVA). We discuss the impact of improving the sample purity in enhancing the sensitivity of the CPT symmetry test.
Exploring the limits of CPT symmetry in ortho-positronium decays with J-PET
N. Chug, On behalf of the J-PET Collaboration
published in: PoS(EPS-HEP2023)366
The CPT symmetry is one of the most fundamental symmetries in physics. Any violation of this symmetry would have profound implications for our understanding of the universe. In this study, we report the CPT symmetry tests in 3? decays of polarised 3S1 positronium using the Jagiellonian Positron Emission Tomography device. The J-PET experiment allows sensitive and precise tests of CPT symmetry by measuring the angular correlation between the spin of ortho-positronium and the momenta direction of the annihilation photons emitted in ortho-positronium decay. The potential of J-PET in determining the full range of the expectation value of this correlation has improved the precision of the CPT symmetry test to 10?4 already. The accuracy of this previous measurement was limited by statistics only. The new test is based on the increased statistics due to the modified experimental setup aiming at the improvement of detection efficiency and due to the usage of different positronium production chambers. The high precision of this test would open the possibility of exploring the limits of CPT symmetry validity in the charged leptonic sector. In this work, we discuss the evaluation of background sources in the CPT symmetry test with J-PET which is a crucial factor in improving the precision of such studies.
Improved test of CPT invariance in ortho-positronium decays at J-PET
N. Chug and A. Gajos, On behalf of the J-PET collaboration
published in: PoS(DISCRETE2022)064
Symmetry violation under the combined transformation of charge (C), parity (P), and time reversal
(T) in the charged leptonic sector can be sought through the non-vanishing expectation value of
certain angular correlation operators that are odd under the CPT transformation. Here, we discuss
the experimental approach for a CPT symmetry test by measuring angular correlations between
the spin and momenta of photons originating from ortho-positronium (o-Ps?3????) decays. This
experiment is performed with the J-PET detector which measures a broad range of kinematical
configurations of ortho-positronium annihilation into three photons and is the first experiment
to determine the full range of the CPT-odd angular correlation. A novel technique to estimate
the spin of ortho-positronium and momenta of annihilation photons for a single recorded ortho-
positronium event allowed J-PET to measure the expectation value of CPT symmetry odd angular
correlation operator at the precision level of 10?4, a factor of three better than the previous best
result. There are new measures and perspectives for J-PET in improving the sensitivity to CPT
violating effects beyond the level of 10?4 by increasing the efficiency for detection of photons
from ortho-positronium decays by means of using a new modular J-PET detector and spherical
annihilation chamber.
Feasibility study of positronium imaging with Biograph Vision Quadra and Modular J-PET
S. Parzych, J. Baran, E. Yitayew Beyene, M. Conti, A. Coussat, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Valsan Eliyan, A. Gajos, B. Hiesmayr, A. Jędruszczak, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Łapkiewicz, L. Mercolli, W. Migdał, S. Moyo, W. Mryka, S. Niedźwiecki, E. Pérez Del Río, L. Raczyński, A. Rominger, H. Sari, S. Sharma, K. Shi, S. Shivani, R. Shopa, M. Skurzok, W.M. Steinberger, E. Stępień, P. Tanty, F. Tayefi, K. Tayefi Ardebili, W. Wiślicki, P. Moskal
published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
Positronium Imaging is gaining interest as a new promising method that may improve the diagnostic specificity of Positron Emission Tomography. Recently, the first ex-vivo and in-vivo positronium lifetime images were demonstrated by means of the dedicated multi-photon J-PET system. The latest upgrades of the Biograph Vision Quadra (Siemens Healthineers) to the singles mode acquisition open the possibility of multi-photon imaging. In this simulation-based work, sensitivity of both systems has been assessed as a function of the energy window applied for registration of the prompt photon. The research was conducted using four radioisotopes: 124 I, 68 Ga, 44 Sc, 22 Na, which were chosen due to their medical or laboratory utilization. Simulations were performed with the GATE software. The result indicates that Biograph Vision Quadra provides about 400 times higher sensitivity with respect to the modular J-PET prototype used to demonstrate the first positronium images, assuming full energy acquisition of the prompt photon.
Performance of NEMA characteristics of Modular J-PET
F. Tayefi Ardebili, S. Niedźwiecki, J. Baran, E. Beyene, D. Borys, K. Brzezinski, N. Chug, A. Coussat, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Eliyan, J. Gajewski, A. Gajos, B. Hiesmayr, A. Jędruszczak, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Łapkiewicz, W. Migdał, S. Moyo, W. Mryka, S. Parzych, E. Pérez del Río, L. Raczyński, S. Sharma, S. Shivani, R. Shopa, M. Skurzok, P. Tanty, K. Tayefi Ardebili, W. Wislicki, E. Stępień, P. Moskal
published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
The Modular J-PET scanner, developed by the J-PET collaboration, is a new prototype PET scanner developed based on axially arranged plastic scintillators as a large axial field of view (50cm) affordable tomograph. In this study, the performance characteristics of the scanner were evaluated according to NEMA NU2-2018 standards using Monte Carlo simulation. In order to ensure the selection of true coincidence events, certain criteria were established. Specifically, each photon emitting from a single annihilation must deposit at least 200 keV within 4 ns of a coincidence time window. The preliminary results showed that the sensitivity profile peak was 4 cps/kBq at the center of the detector, While the scatter fraction was estimated to be 39% using the single slice rebinning algorithm. Spatial resolution was estimated around 4.5 mm in the radial and tangential direction and 18 mm in the axial direction.
Normalization and scatter corrections for the J-PET scanner
A. Coussat, W. Krzemień, J. Baran, S. Parzych, L. Raczyński, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, J. Gajewski, B. Hiesmayr, K. Valsan Eliyan, A. Jędruszczak, K. Kacprzak, A. Gajos, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, T. Kozik, G. Łapkiewicz, G. Korcyl, S. Moyo, D. Kumar, W. Mryka, S. Niedźwiecki, S. Sharma, E. Pérez Del Río, S. Shivani, R. Shopa, P. Tanty, M. Skurzok, K. Tayefi, F. Tayefi, E. Stępień, W. Wiślicki, P. Moskal
published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
The Jagiellonian PET scanner is a cost-effective large axial FOV Positron Emission Tomography technology that enables multi-photon imaging and is currently under development at the Jagiellonian University. The current 50 cm prototype, named Modular J-PET, is being investigated for various applications. It is well known that PET data can be affected by several effects during acquisition, such as scattered gamma photons or variations in detection efficiency. Consequently, achieving the reconstruction of images of satisfactory quality requires a set of corrections to be applied to each line-of-response. This summary discusses the implementation and performance of scatter and normalization corrections for the Modular J-PET, and their extension prior to the assembly of a total-body Jagiellonian PET scanner. Normalization correction is achieved using component-based normalization, a method particularly suitable for large scanners with a high number of lines-of-response. Scatter correction is achieved using an extension of the single scatter simulation technique that incorporates time-of-flight information. Reconstruction of reference phantoms based on Monte Carlo simulations highlight improvements in image quality. The application of normalization reduces the non-uniformity in the reconstructed image by a factor of 10 in the axial direction and 2 in the radial direction.
Modular J-PET with Improved o-Ps Detection Efficiency for CPT Tests
N. Chug and A. Gajos, On behalf of the J-PET Collaboration
published in: Ninth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, May 17-26, 2022
J-PET is a photon detector built of plastic scintillators, which already has been commissioned for CPT studies in the decays of positronium. In the first experiment, J-PET has achieved a sensitivity to CPT violation at a level of 10^{-4}, and now it aims to reach a level of 10^{-5}. This will be done by enhancing the three-photon registration efficiency for ortho-positronium decays using a new layer of densely packed plastic scintillators termed Modular J-PET. We present the simulation studies performed for different experimental detection setups to be used for the next CPT test with the Modular J-PET detector.
Towards Improving the Sensitivity of the CPT Symmetry in Positronium Decays with the Modular J-PET Detector
N. Chug, A. Gajos
published in: Acta Phys. Polon. B Proc. Suppl. 15 (2022) 4-A6
The Jagiellonian Positron Emission Tomograph (J-PET) is the first plastic scintillator-based tomographic device used to test discrete symmetries in the charged leptonic sector. One of such tests is for the CPT symmetry, under the combined transformation of charge, parity, and time reversal in the decays of positronium atoms. J-PET performed its first measurement for the CPT symmetry test by searching for non-vanishing CPT-violating angular correlations between the spin and orientation of the decay plane of ortho-positronium (o-Ps) atoms, which is the triplet state of positronium. The sensitivity of testing CPT symmetry with the J-PET detector reaches the precision level of 10?4. Here, we will discuss the prospects of improving the sensitivity of this test beyond the level of 10?4 by enhancing the photon registration efficiency using a new layer of densely packed plastic scintillators and a spherical annihilation chamber as a positronium production medium.
CPT symmetry test in positronium annihilations with the J-PET detector
N. Chug and A. Gajos, On behalf of the J-PET collaboration
published in: PoS PANIC2021 (2022) 440
Discrete symmetry under combined transformation of charge, parity and time reversal (CPT) can be tested in the decays of positronium atom, the lightest bound system built of charged leptons. Jagiellonian Positron Emission Tomograph (J-PET) device constructed from plastic scintillators, detects the photons originating from electron positron annihilation. This feature enables J-PET to
study CPT symmetry in the three photon annihilations of the triplet state of positronium. Signs of violation of the CPT symmetry can be sought as a non-vanishing expectation value of an angular correlation operator that is odd under CPT transformation. A technique to estimate the spin of ortho-positronium and momenta of annihilation photons for single recorded ortho-positronium
annihilation events allows J-PET to measure the expectation value of a CPT symmetry odd angular correlation operator. J-PET measures a broad range of kinematical configurations of ortho-positronium annihilation to three photons and is the first experiment to determine the full range of the CPT-odd angular correlation.
From tests of discrete symmetries to medical imaging with J-PET detector
P. Moskal, J. Baran, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, J. Gajewski, A. Gajos, M. Gorgol, B.C. Hiesmayr, B. Jasińska, K. Kacprzak, Ł. Kapłon, H. Karimi, K. Klimaszewski, P. Konieczka, G. Korcyl, T. Kozik, N. Krawczyk, W. Krzemień, E. Kubicz, D. Kumar, S. Niedźwiecki, D. Panek, S. Parzych, E. Perez del Rio, 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
published in: PoS PANIC2021 (2022) 033
We present results on CPT symmetry tests in decays of positronium performed with the precision at the level of 10?4, and positronium images determined with the prototype of the J-PET tomograph. The first full-scale prototype apparatus consists of 192 plastic scintillator strips readout from both ends with vacuum tube photomultipliers. Signals produced by photomultipliers are probed in the amplitude domain and are digitized by FPGA-based readout boards in triggerless mode. In this contribution we report on the first two- and three-photon positronium images and tests of CPT symmetry in positronium decays.
