Positronium imaging was recently proposed to image the properties of positronium atoms in the patient’s body. Positronium properties depend on the size of intramolecular voids and oxygen concentration; therefore, they deliver information different from 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 β+γ 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 have been 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.

Objectives: This paper presents the prospects for increasing the availability of PET diagnostics by combining low-cost, lightweight and easily portable modular J-PET with the 44Ti/44Sc generator. Methods: J-PET is constructed based on the low-cost axially arranged plastic scintillators that may enable the construction of PET scanners 5 to 10 times less expensive compared to current PET systems, which are based on crystal scintillators. Development of the radionuclide 44Ti/44Sc generator with the 60-year half-lifetime would enable long-term onsite production of 44Sc labelled radiopharmaceuticals, eliminating the need for extensive and costly infrastructure typically associated with nuclear medicine. Presently applied 68Ge/68Ga generators with the 270 days half-lifetime require renewal every year. The 44Ti/44Sc generator could, in principle, be purchased once every half century. Results: The lightweight and portable J-PET scanner, combined with the 44Ti/44Sc generator, can be deployed in remote and underserved regions, thus democratising access to advanced medical-imaging techniques. Conclusions: This novel concept shows the transformative potential of combining innovative J-PET technology with the 44Ti/44Sc generator to make advanced diagnostics more accessible and affordable worldwide, especially benefiting millions of patients in low- and medium-income countries, and driving further innovations in medical imaging.

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 that 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 and random 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 for 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 Lifetime Imaging (PLI), an emerging extension of conventional positron emission tomography (PET) imaging, offers a novel window for probing the submolecular properties of biological tissues by imaging the mean lifetime of the positronium atom. Currently, the method is under rapid development in terms of reconstruction and detection systems. Recently, the first in vivo PLI of the human brain was performed using the J-PET scanner utilizing the 68Ga isotope. However, this isotope has limitations due to its comparatively low prompt gamma yields, which is crucial for positronium lifetime measurement. Among alternative radionuclides, 44Sc stands out as a promising isotope for PLI, characterized by a clinically suitable half-life (4.04 hours) emitting 1157 keV prompt gamma in 100% cases after the emission of the positron. This study reports the first experimental demonstration of PLI with 44Sc, carried out on a NEMA-Image Quality (IQ) phantom using the Modular J-PET tomograph–the first plastic scintillators-based PET scanner.

Silicon drift detectors (SDDs) stand as a groundbreaking technology with a diverse range of applications, particularly in the fields of physics and medical imaging. This paper provides an analysis of the performance of SDDs as detectors for X-ray radiation measurement, shedding light on their exceptional capabilities and potential in medical imaging. Compared to conventional detectors, SDDs have several notable advantages. Their high efficiency in capturing X-rays allows them to provide outstanding sensitivity and accuracy in detecting even low-energy X-rays. In addition, SDDs exhibit significantly low electronic-noise levels, contributing to better signal-to-noise ratio and better data quality. Furthermore, their high resolution enables exact spatial localization of radiation sources, which is essential for accurate diagnosis. This research is devoted to the evaluation of efficiency and potential application of SDDs in X-ray spectroscopy, with particular emphasis on their application in medical imaging. We focus on evaluating the performance characteristics of SDDs, such as their linearity, stability and sensitivity in detecting X-rays. The aim is to highlight the suitability of SDDs for a wide range of applications.