Ex-Vivo Positronium Lifetime Imaging with 44Sc using J-PET Scanner
Karol Kubat, Manish Das, Sushil Sharma, Bartosz Leszczyński, Ewa Ł. Stępień, and Pawel Moskal
abstract
Positronium Lifetime Imaging (PLI), an advanced extension of Positronium Emission
Tomography (PET), is an emerging diagnostic modality [1,2,3]. It has potential to probe
nano-scale environmental properties such as hypoxia, tumour microenvironment
pathology by mapping the spatial distribution of Ps lifetime in biological tissues [4, 5].
Despite the common consensus on its advantages and ongoing progress in adaptation of
reconstruction algorithms and detector technology, PLI faces slow translation in clinical
applications mainly due to two reasons: (1) measurement of nano-second positronium
lifetimes requires fast gamma-ray detectors, and (2) new radioisotopes that provide both
medically suitable half-life and high positron yield accompanying a prompt gamma signal
for Ps lifetime estimation. The first in-vivo results on PLI of human brain was reported
by J-PET collaboration using 68Ga radioisotope [6] However, the low prompt gamma
yield of 68Ga, only a ~1.34% prompt?? branching ratio, poses challenges for accurate
lifetime estimation due to limited statistics [7].
To address this, 44Sc has emerged as a highly promising isotope for PLI, boasting an
optimal decay profile: a clinically suitable half-life of 4.04 hours, an ultrashort deexcitation delay of 2.61 ps, and a 100% decay probability producing a single, high-energy
(1157 keV) prompt gamma following positron emission [7].
In this work, we report the successful application of PLI using 44Sc, performed with the
state-of-the-art Modular J-PET tomograph, featuring triggerless data acquisition enabling
simultaneous multiphoton detection [8].
For this study 44Sc was produced at the Heavy Ion Laboratory in Warsaw and transported
to Jagiellonian University in Kraków. Four phantoms containing cardiac myxoma tissue,
blood thrombi, adipose tissue, and Fused Silica were used, where the Fused Silica serving
as the certified material with a known o-Ps lifetime for quality control. Event selection
was based on the simultaneous detection of two 511 keV photons and one de-excitation
photon, enabling the reconstruction of positronium lifetime images. The reconstructed
annihilation positions, obtained using the two 511 keV photons along with the positron
lifetime, was used to identify regions of interest (ROIs) in image samples. Whereas the oPs lifetime was estimated utilizing the registration time of an additional prompt gamma
as the o-Ps formation time. The obtained o-Ps lifetime shows good agreement with
previously reported values for biological tissues [3, 9]
In this presentation, we will show the first-ever demonstration PLI with 44Sc, marking a
significant advancement and opening new possibilities for developing PLI for clinical
applications.
Acknowledgments
This work was supported by the National Science Centre of Poland (Grants:
2021/42/A/ST2/00423, 2021/43/B/ST2/02150, 2022/47/I/NZ7/03112), SciMat and
qLife under the Excellence Initiative at Jagiellonian University, and PLGrid (ACK
Cyfronet AGH, PLG/2024/017688).
Reference
[1] P. Moskal, Proc. 2019 IEEE Nucl. Sci. Symp. Med. Imaging Conf. (NSS MIC), Manchester (2019)
1-3, DOI: 10.1109/NSS/MIC42101.2019.9059856
[2] P. Moskal et al., IEEE Transactions on Radiation and Plasma Medical Sciences Early access
(2025), DOI: 10.1109/TRPMS.2025.3583554
[3] P. Moskal et al., Science Advances 7 (2021) eabh439
[4] P. Moskal et al., EJNMMI Physics 10 (2023) 22
[5] P. Moskal et. al., Bio-Algorithms and Med-Systems 17(4) (2021) 311-319
[6] P. Moskal et al., Science Advances 10 (2024) adp2840
[7] M. Das et al., Bio-Algorithms and Med-Systems 19 (2023) 87-95
[8] P. Moskal et al., Nature Communication 12 (2021) 5658
[9] Avachat, A.V., Mahmoud, K.H., Leja, A.G. et al. Ortho-positronium lifetime for soft-tissue
classification. Sci Rep 14, 21155 (2024
Ex-Vivo Positronium Lifetime Imaging with 44Sc using J-PET Scanner
Karol Kubat, Manish Das, Sushil Sharma, Bartosz Leszczyński, Ewa Ł. Stępień, and Pawel Moskal
abstract
Positronium Lifetime Imaging (PLI), an advanced extension of Positronium Emission
Tomography (PET), is an emerging diagnostic modality [1,2,3]. It has potential to probe
nano-scale environmental properties such as hypoxia, tumour microenvironment
pathology by mapping the spatial distribution of Ps lifetime in biological tissues [4, 5].
Despite the common consensus on its advantages and ongoing progress in adaptation of
reconstruction algorithms and detector technology, PLI faces slow translation in clinical
applications mainly due to two reasons: (1) measurement of nano-second positronium
lifetimes requires fast gamma-ray detectors, and (2) new radioisotopes that provide both
medically suitable half-life and high positron yield accompanying a prompt gamma signal
for Ps lifetime estimation. The first in-vivo results on PLI of human brain was reported
by J-PET collaboration using 68Ga radioisotope [6] However, the low prompt gamma
yield of 68Ga, only a ~1.34% prompt?? branching ratio, poses challenges for accurate
lifetime estimation due to limited statistics [7].
To address this, 44Sc has emerged as a highly promising isotope for PLI, boasting an
optimal decay profile: a clinically suitable half-life of 4.04 hours, an ultrashort deexcitation delay of 2.61 ps, and a 100% decay probability producing a single, high-energy
(1157 keV) prompt gamma following positron emission [7].
In this work, we report the successful application of PLI using 44Sc, performed with the
state-of-the-art Modular J-PET tomograph, featuring triggerless data acquisition enabling
simultaneous multiphoton detection [8].
For this study 44Sc was produced at the Heavy Ion Laboratory in Warsaw and transported
to Jagiellonian University in Kraków. Four phantoms containing cardiac myxoma tissue,
blood thrombi, adipose tissue, and Fused Silica were used, where the Fused Silica serving
as the certified material with a known o-Ps lifetime for quality control. Event selection
was based on the simultaneous detection of two 511 keV photons and one de-excitation
photon, enabling the reconstruction of positronium lifetime images. The reconstructed
annihilation positions, obtained using the two 511 keV photons along with the positron
lifetime, was used to identify regions of interest (ROIs) in image samples. Whereas the oPs lifetime was estimated utilizing the registration time of an additional prompt gamma
as the o-Ps formation time. The obtained o-Ps lifetime shows good agreement with
previously reported values for biological tissues [3, 9]
In this presentation, we will show the first-ever demonstration PLI with 44Sc, marking a
significant advancement and opening new possibilities for developing PLI for clinical
applications.
Acknowledgments
This work was supported by the National Science Centre of Poland (Grants:
2021/42/A/ST2/00423, 2021/43/B/ST2/02150, 2022/47/I/NZ7/03112), SciMat and
qLife under the Excellence Initiative at Jagiellonian University, and PLGrid (ACK
Cyfronet AGH, PLG/2024/017688).
Reference
[1] P. Moskal, Proc. 2019 IEEE Nucl. Sci. Symp. Med. Imaging Conf. (NSS MIC), Manchester (2019)
1-3, DOI: 10.1109/NSS/MIC42101.2019.9059856
[2] P. Moskal et al., IEEE Transactions on Radiation and Plasma Medical Sciences Early access
(2025), DOI: 10.1109/TRPMS.2025.3583554
[3] P. Moskal et al., Science Advances 7 (2021) eabh439
[4] P. Moskal et al., EJNMMI Physics 10 (2023) 22
[5] P. Moskal et. al., Bio-Algorithms and Med-Systems 17(4) (2021) 311-319
[6] P. Moskal et al., Science Advances 10 (2024) adp2840
[7] M. Das et al., Bio-Algorithms and Med-Systems 19 (2023) 87-95
[8] P. Moskal et al., Nature Communication 12 (2021) 5658
[9] Avachat, A.V., Mahmoud, K.H., Leja, A.G. et al. Ortho-positronium lifetime for soft-tissue
classification. Sci Rep 14, 21155 (2024
Quality control of plastic scintillators for the total-body J-PET scanner
Ł. Kapłon, E. Beyene, N. Chug, C. Curceanu, E. Czerwiński, M. Das, K. Eliyan, K. Kacprzak, T. Kaplanoglu, G. Korcyl, K. Kubat, D. Kumar, E. Lisowski, F. Lisowski, J. Mędrala-Sowa, G. Moskal, W. Mryka, S. Niedźwiecki, P. Pandey, S. Parzych, E. Pérez del Rio, S. Sharma, M. Skurzok, P. Tanty, K. Tayefi, A. Venadan, E. Stępień and P. Moskal
abstract
The construction of the total-body Jagiellonian positron emission tomography scanner requires component verification before detector assembly. The purpose of this research is to verify the quality of BC-408 plastic scintillators with dimensions 6 mm × 30 mm × 330 mm. The scintillators were inspected for optical and mechanical defects and all dimensions were measured. Scratches, mechanically damaged corners and edges, as well as encapsulated dust and fibers within the scintillators, were identified under ceiling lamp illumination. Line defects on the as-cast surfaces were easily visible in a plane polariscope setup consisting of crossed horizontal and vertical polarizer foils. The transmittance at the wavelength of maximum emission through 6 mm thick scintillator samples and the technical attenuation length along 330 mm long scintillator samples were measured on a linear CCD array spectrometer for randomly selected scintillators from each delivered batch. Selected properties of the emission spectra, such as their FWHM and the values of the emission maxima as a function of the distance between the excitation point and the spectrometer fiber, were measured. Additionally, the scintillators optical homogeneity was measured on a light transfer setup consisting of an LED and photodiode matrix. The majority of the obtained plastic scintillators meets the transparency criteria and falls within the dimensional tolerances.
muPPET: Investigating the Muon Puzzle with J-PET Detectors
A. Porcelli, K. Valsan Eliyan, G. Moskal, N. Nasrin Protiti, D. L. Sirghi, E. Yitayew Beyene, N. Chug, C. Curceanu, E. Czerwiński, M. Das, M. Gorgol, J. Hajduga, S. Jalali, B. Jasińska, K. Kacprzak, T. Kaplanoglu, Ł. Kapłon, K. Kasperska, A. Khreptak, G. Korcyl, T. Kozik, D. Kumar, K. Kubat, E. Lisowski, F. Lisowski, J. Mędrala-Sowa, W. Mryka, S. Moyo, S. Niedźwiecki, S. Parzych, P. Pandey, E. Perez del Rio, B. Rachwał, M. Rädler, S. Sharma, M. Skurzok, E. Ł. Stępień, T. Szumlak, P. Tanty, K. Tayefi Ardebili, S. Tiwari, and P. Moskal
abstract
The muPPET [muon Probe with J-PET] project aims to investigate the Muon
Puzzle seen in cosmic ray air showers. This puzzle arises from the observation of a significantly
larger number of muons on Earth's surface than that predicted by the current
theoretical models. The investigated hypothesis is based on recently observed asymmetries
in the parameters for the strong interaction cross-section and trajectory of an outgoing particle
due to projectile-target polarization. The measurements require detailed information
about muons at the ground level, including their track and charge distributions. To achieve
this, the two PET scanners developed at the Jagiellonian University in Krakow (Poland),
the J-PET detectors, will be employed, taking advantage of their well-known resolution
and convenient location for detecting muons that reach long depths in the atmosphere.
One station will be used as a muon tracker, while the second will reconstruct the core of
the air shower. In parallel, the existing hadronic interaction models will be modified and
fine-tuned based on the experimental results. In this work, we present the conceptualization
and preliminary designs of muPPET.
Positronium Imaging: History, Current Status, and Future Perspectives
Paweł Moskal, Aleksander Bilewicz, Manish Das, Bangyan Huang, Aleksander Khreptak, Szymon Parzych, Jinyi Qi, Axel Rominger, Robert Seifert, Sushil Sharma, Kuangyu Shi, William Steinberger, Rafał Walczak, Ewa Stępień
abstract
Positronium imaging was recently proposed to image the properties of positronium atoms in the patient body. Positronium properties depend on the size of intramolecular voids and oxygen concentration; therefore, they deliver information different and complementary to the anatomic, morphological, and metabolic images. Thus far, the mean ortho-positronium lifetime imaging has been at the center of research interest. The first ex vivo and in vivo positronium lifetime images of humans have been demonstrated with the dedicated J-PET scanner enabling simultaneous registration of annihilation photons and prompt gamma from beta+gamma emitters. Annihilation photons are used to reconstruct the annihilation place and time while prompt gamma is used to reconstruct the time of positronium formation. This review describes recent achievements in the translation of positronium imaging into clinics. The first measurements of positronium lifetime in humans with commercial PET scanners modernized to register triple coincidences are reported. The in vivo observations of differences in ortho-positronium lifetime between tumor and healthy tissues and between different oxygen concentrations are discussed. So far, the positronium lifetime measurements in humans were completed with clinically available 68Ga, 82Rb, and 124I radionuclides. Status and challenges in developing positronium imaging on a way to a clinically useful procedure are presented and discussed.
Nonmaximal 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, T. Kozik, E. Lisowski, F. Lisowski, W. Mryka, S. Niedzwiecki, S. Parzych, E.P. del Rio, M. Radler, M. Skurzok, E. L. Stepien, P. Tanty, K. Tayefi Ardebili, K. Valsan Eliyan
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.
Development of correction techniques for a J-PET scanner
M. Das, R. Bayerlein, S. Sharma, S. Parzych, S. Niedźwiecki, R. Badawi, E. Yitayew Beyene, N. Chug, C. Curceanu, E. Czerwiński, K. Valsan Eliyan, B. Głowa, A. Hubalewska-Dydejczyk, K. Kacprzak, T. Kaplanoglu, K. Kasperska, G. Korcyl, A. Khreptak, K. Kubat, D. Kumar, E. Lisowski, F. Lisowski, J. Mędrala-Sowa, S. Moyo, W. Mryka, M. Opalińska, P. Pandey, M. Rädler, M. Skurzok, A. Sowa-Staszczak, B. A. Spencer, P. Tanty, K. Tayefi Ardebili, A. Kunimmal Venadan, E. Stępień, P. Moskal
abstract
Objective: Positron Emission Tomography (PET) is a widely used medical imaging technique that allows for non-invasive imaging of metabolic processes. However, traditional PET scanners rely on costly inorganic scintillators, which limit their accessibility ? especially in light of emerging long axial field-of-view devices. The modular J-PET scanner, an innovative alternative, uses 50-cm long plastic scintillator strips, offering a cost-effective and modular solution. In this study, we develop and assess the PET data correction techniques required for quantitative image reconstruction. Methods: We present methods for attenuation correction, random coincidence correction using the Delayed Time Window (DTW) technique, and scatter correction based on Monte Carlo simulations. Phantom studies using the NEMA IQ phantom were performed to qualitatively evaluate these corrections. Results: The results demonstrate that our implemented corrections for attenuation, randoms, and scattered coincidences successfully improve the uniformity of tracer distribution in homogenous volumes and significantly reduce undesired activity in cold regions. Despite limitations in sensitivity and axial resolution, the applied correction techniques effectively enhance image quality, providing promising results for future applications. Conclusions: These findings highlight the potential of the modular J-PET system to offer affordable PET imaging and to pave the way towards a total-body PET scanner based on plastic scintillators. Future work will focus on quantitative validation and the implementation of these corrections for human subject imaging.
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 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.
Estimating influence of positron range in proton-therapy-beam monitoring with PET
W. Mryka, M. Das, E.Y. Beyene, P. Moskal, E. Stępień
abstract
The application of PET scanners to proton-beam-therapy monitoring is a promising solution to obtain the range of the beam and hence the positions of a Bragg peak - maximum dose deposition point. A proton beam induces nuclear reactions in the tissue, leading to the production of isotopes that emit beta+ radiation. This enables the imaging of the density distribution of beta+ isotopes produced in the body, allowing the reconstruction of the proton beam range. Moreover, PET detectors may open the possibility for in-beam monitoring, which would offer an opportunity to verify the range during irradiation. PET detectors may also allow positronium imaging, which would be the indicator of the tissue conditions. However, the image of annihilation points does not represent the range of the proton beam. There are several factors influencing the translation from annihilation points to obtain the Bragg peak position. One of them is the kinetic energy of the positron. This energy corresponds to some range of the positron within the tissue. In this manuscript we estimate positron energy and its range and discuss its influence on proton therapy monitoring.
Exploration of simultaneous dual-isotope imaging with multi-photon modular J-PET scanner
Ermias Yitayew Beyene, Manish Das, Martyna Durak-Kozica, Grzegorz Korcyl, Wiktor Mryka, Szymon Niedźwiecki, Szymon Parzych, Keyvan Tayefi Ardebili, Rafał Walczak, Kamil Wawrowicz, Ewa Stępień, Paweł Moskal
abstract
The modular J-PET scanner, comprising 24 compact and versatile modules, each consisting of 13 plastic strips with four SiPM detectors at the ends, represents a powerful tool for clinical applications in nuclear medical imaging. This study presents preliminary results from the exploration of simultaneous dual-isotope imaging using the modular J-PET system. Our approach involved two isotopes: 68Ge, characterized by a ringlike shape, and 22Na, exhibiting a point-like shape. The imaging was based on double-coincidence and triple-coincidence events. In the double coincidence case, both isotopes contributed comparably, whereas in the triple coincidence case 22Na dominated due to the prompt gamma being emitted with 100% of positron emissions, unlike 68Ga, where the prompt gamma was emitted in only 1.3% of cases after positron emission. In this work we present direct 2? images determined for two-signal events and images for three-signal events, with two signals from annihilation photons and one from a prompt gamma. These results showcase the preliminary findings from simultaneous dual-isotope imaging of 68Ga and 22Na isotopes using the modular J-PET scanner, which will be presented and discussed.
Estimating the efficiency and purity for detecting annihilation and prompt photons for positronium imaging with J-PET using toy Monte Carlo simulation
M. Das, W. Mryka, E.Y. Beyene, S. Parzych, S. Sharma, E. Stępień, P. Moskal
abstract
The positronium imaging technique represents a potential enhancement of the PET imaging method. Its core principle involves employing a beta+ radiation source that emits additional gamma quanta referred to as prompt gamma. Our aim is to evaluate the capability to differentiate between annihilation and prompt gamma emissions, a vital aspect of positronium imaging. For this purpose, the selected isotopes should enable high efficiency and purity in detecting both prompt gamma and annihilation gamma. The assessment of the efficiency in identifying prompt and annihilation photons for various isotopes, which are potentially superior candidates for beta++ gamma emitters, is conducted through toy Monte-Carlo simulation utilizing the cross-section formula for photon-electron scattering. In this article, we have performed calculations for efficiency and purity values across different isotopes under ideal conditions and examined how these values evolve as we incorporate the fractional energy resolution into the analysis. Ultimately, the primary goal is to determine the energy threshold that optimizes both efficiency and purity, striking a balance between accurately identifying and recording events of interest while minimizing contamination from undesired events.
Positronium as a biomarker for Neuroendocrine tumour
Manish Das, Sushil Sharma, Ewa Stępień, Pawel Moskal
abstract
Ex-Vivo Positronium Lifetime Imaging with 44Sc using J-PET Scanner
Karol Kubat, Manish Das, Sushil Sharma, Bartosz Leszczyński, Ewa Ł. Stępień, and Pawel Moskal
abstract
Positronium Lifetime Imaging (PLI), an advanced extension of Positronium Emission
Tomography (PET), is an emerging diagnostic modality [1,2,3]. It has potential to probe
nano-scale environmental properties such as hypoxia, tumour microenvironment
pathology by mapping the spatial distribution of Ps lifetime in biological tissues [4, 5, 6].
Despite the common consensus on its advantages and ongoing progress in adaptation of
reconstruction algorithms and detector technology, PLI faces slow translation in clinical
applications mainly due to two reasons: (1) measurement of nano-second positronium
lifetimes requires fast gamma-ray detectors, and (2) new radioisotopes that provide both
medically suitable half-life and high positron yield accompanying a prompt gamma signal
for Ps lifetime estimation. The first in-vivo results on PLI of human brain was reported
by J-PET collaboration using 68Ga radioisotope [7]. However, the low prompt gamma
yield of 68Ga, only a ~1.34% prompt?? branching ratio, poses challenges for accurate
lifetime estimation due to limited statistics [8].
To address this, 44Sc has emerged as a highly promising isotope for PLI [9], boasting an
optimal decay profile: a clinically suitable half-life of 4.04 hours, an ultrashort deexcitation delay of 2.61 ps, and a 100% decay probability producing a single, high-energy
(1157 keV) prompt gamma following positron emission [8].
In this work, we report the successful application of PLI using 44Sc, performed with the
state-of-the-art Modular J-PET tomograph, featuring triggerless data acquisition enabling
simultaneous multiphoton detection [7].
For this study 44Sc was produced at the Heavy Ion Laboratory in Warsaw and transported
to Jagiellonian University in Kraków. Four phantoms containing cardiac myxoma tissue,
blood thrombi, adipose tissue, and Fused Silica were used, where the Fused Silica serving
as the certified material with a known o-Ps lifetime for quality control. Event selection
was based on the simultaneous detection of two 511 keV photons and one de-excitation
photon, enabling the reconstruction of positronium lifetime images. The reconstructed
annihilation positions, obtained using the two 511 keV photons along with the positron
lifetime, was used to identify regions of interest (ROIs) in image samples. Whereas the oPs lifetime was estimated utilizing the registration time of an additional prompt gamma
as the o-Ps formation time. The obtained o-Ps lifetime shows good agreement with
previously reported values for biological tissues [3, 10].
In this presentation, we will show the first-ever demonstration of ex-vivo PLI with 44Sc,
marking a significant advancement and opening new possibilities for developing PLI for
clinical applications.
Acknowledgments
This work was supported by the National Science Centre of Poland (Grants:
2021/42/A/ST2/00423, 2021/43/B/ST2/02150, 2022/47/I/NZ7/03112), SciMat and
qLife under the Excellence Initiative at Jagiellonian University, and PLGrid (ACK
Cyfronet AGH, PLG/2024/017688).
Reference
[1] P. Moskal, Proc. 2019 IEEE Nucl. Sci. Symp. Med. Imaging Conf. (NSS MIC), Manchester (2019)
1-3, DOI: 10.1109/NSS/MIC42101.2019.9059856
[2] P. Moskal et al., IEEE Transactions on Radiation and Plasma Medical Sciences Early access
(2025), DOI: 10.1109/TRPMS.2025.3583554
[3] P. Moskal et al., Science Advances 7 (2021) eabh439
[4] P. Moskal et al., EJNMMI Physics 10 (2023) 22
[5] P. Moskal et. al., Bio-Algorithms and Med-Systems 17(4) (2021) 311-319
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Towards the Development of an Iterative Algorithm for Positronium Lifetime Imaging Using 44Sc with the Modular J-PET
Anand Pandey, Sushil Sharma, Manish Das, Hsin-Hsiung Huang, Berkin Uluutku, Giulianno Gasparato, Chien-Min Kao, Ewa Stepien, Pawel Moskal
abstract
2nd Symposium on new trends in nuclear and medical physics
