Determining positronium lifetimes in uniform samples of aluminum, copper, nickel and quartz using modular J-PET scanner and Biograph Vision Quadra scanner
Author: Gabriela Łapkiewicz
abstract
Defence year: 2024
Positronium imaging is a tool that could raise the specificity of medical imaging. A part of the development of the positronium imaging technique is establishing the method for the assessment of detector imaging precision and comparison of the results obtained between various scanners.
This thesis presents the methods and results of positronium imaging of 4 materials per- formed with modular J-PET and Biograph Vision Quadra PET/CT scanners and compares them with Positronium Annihilation Lifetime Spectroscopy studies of the same samples. The compared materials were disks of quartz glass and 3 metals of high purity: aluminum, nickel and copper. The metal samples spectra are expected to be characterised by short- living components that correspond to positrons directly annihilating in the metal lattice. The mean lifetime of positron in such samples are dependent on the lattice parameters but may be influenced by the lattice defects. The quartz glass is an amorphous substance that is characterised by the ortho-positronium mean lifetime in range representative for biological tissues.
A hypothesis was formulated that that it is possible to obtain the positronium mean lifetime spectra with three detection systems presented in this thesis and analysis of the spectra will yield similar results: the quartz glass will stand out by longer component of ortho-positronium lifetime in comparison with metal samples.
To test the stated hypothesis, the author had performed measurements on PALS system and modular J-PET scanner, preselected the data using dedicated software and analysed the spectra with PALS Avalanche software. Author had also performed analysis of the spectra obtained with Biograph Vision Quadra.
This work have shown that the applied method of measurement and analysis is applica- ble for each of the presented setup. The percentage difference between mean lifetime values obtained with PALS and Biograph Vision Quadra scanner does not exceed 7%. The per- centage difference between mean lifetime values obtained with PALS and modular J-PET scanner does not exceed 30%. The stated hypothesis was proven that in all measurement setups it is possible to differentiate between quartz glass and metal, based on the mean lifetime of ortho-positronium and positron mean lifetime components.
Development of experimental conditions for measuring the ortho-positronium lifetime in extracellular vesicles obtained in vitro
Author: Julia Nizioł
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2023
Investigating the ortho-positronium (o-Ps) lifetime in biological materials holds promise for enhancing our understanding of biological processes and pathologies. This master?s thesis aimed to develop experimental conditions for the measurement of the o-Ps lifetime in extracellular vesicles (EVs) isolated using the low-pressure filtration method. EVs in question were derived from a largescale 2D human pancreatic beta cell culture (1.1B4 cell line) maintained under normoglycemic conditions.
In order to check the effectiveness of the chosen method of isolation, environmental scanning electron microscopy (ESEM) images of the dialysis membrane were taken, which allowed to determine the size of its pores. Fourier transform infrared spectroscopy (FTIR) was employed to characterise the chemical composition of EVs. The qNano device, which operates on the principle of tunable resistive pulse sensing (TRPS), was used to determine the size distribution and concentration of EVs. Transmission electron microscopy (TEM) was employed to visualise the morphological features of EVs and validate their structural integrity. Finally, positron annihilation lifetime spectroscopy (PALS) was used to investigate the o-Ps lifetime in the EV sample. In
addition, the PALS technique was also used to study the lifetime of o-Ps in pancreatic beta cells from which the vesicles were derived, and in PBS buffer in which they were suspended after the isolation. The o-Ps lifetime and intensity for the sample containing EVs measured at 22°C were 1.87 ns and 15.4%. The same sample investigated at 34.2 °C gave results of 1.83 ns and
15.0%, respectively. These results were not significantly different from the results of the PBS measurement.
This study allowed to test several technical solutions to measure the positronium lifetime in EV samples. It underscores the need for continued efforts in exploring EVs with progressive methods such as PALS, as they hold immense potential, for example as carriers of biological cargo or biomarkers.
Wyznaczanie parametrów czułości i swoistości testu dla czasu życia orto-Pozytonium w tkance nowotworowej raka jelita grubego
Author: Agnieszka Babińska
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2023
This master thesis aims to present a study using Positron Annihilation Lifetime Spectroscopy (PALS), which allows the study of matter at the nano- and subnanometer level, to analyze the ortho-Positronium (o-Ps) lifetime and intensity in healthy and cancerous colorectal tissues.
The study presented in this research investigated the possibility of using positronium as a new biomarker in the diagnosis of colorectal cancer. The study aimed to verify the following research hypothesis: in healthy colorectal tissues, the average lifetime of ortho-Positronium (o-Ps) is longer than in cancerous tissues.
The measurements carried out allowed us to determine the average lifetime and average intensity of o-Ps in healthy and cancerous colorectal tissues. The sensitivity and specificity of the diagnostic test showed that 27,3% of colorectal cancer
patients were correctly diagnosed with a positive test result, while 15% of healthy patients (those without colorectal cancer) were correctly diagnosed with a negative test result.
The results do not allow us to indicate clear differences in the o-Ps lifetime and intensity in healthy and cancerous colorectal tissues. In order to confirm the proposed research hypothesis, more measurements of colon sections would be necessary.
Polarization formalisms and quantum entanglement in the positronium system
Author: Mateusz Bała
Supervisor: dr Michał Silarski
abstract
Defence year: 2022
Quantum entanglement of the group of particles, is a fascinating quantum mechanical phenomenon, without the classical analogy, which happens when the system state can be treated only as a whole, and the constituent particles cannot be described separately. The simplest example in which the quantum entanglement can be manifested is the polarized two -photon system.Indeed such a case was analyzed both theoretically and experimentally many times. However, most of the studies were concentrated on the optical photons regime. For higher-energetic photons, the polarization cannot be measured by using standard devices such as polarizers. However, the partial polarization estimation is possible by exploiting the Compton scatterings process. In this work the analysis of high-energetic, polarized two-photon system is considered, probed by the doubly Compton scattering process. The model is described using the quantum information theory formalism. In addition, the model is incorporated to the Monte Carlo C++ library. The simulations of the various quantum states are performed and the results are compared with the expectations from the theory.
Study of the Total Body J-PET sensitivity with the Toy Monte-Carlo model
Author: Szymon Parzych
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2021
The main aim of presented thesis is to investigate sensitivity of the Total Body J-PET scanners as a function of their axial field of view and inner module construction, as well as assessing the influence of the angular acceptance criterion (used for PET performance optimization) on this characteristic. In order to achieve this goal a simulation-based study was carried out with a use of the standard Monte-Carlo simulation software - Geant4 Application for Tomography Emission (GATE). Moreover, a Toy Monte-Carlo model has been developed as a simplified approach to the sensitivity investigation. Its principle of operation, as well as detailed validation by comparison with GATE software is presented in this work. The obtained results demonstrate that the standard imaging total sensitivity achievable with the Total Body J-PET scanners equals to 25.92(05+/-04) [cps/kBq] for the
2 meter long two-layer tomograph and 84.74(0.9+/-1.1) [cps/kBq] for the 2.5 meter long fourlayer tomograph. Such results exceed the conventional PET systems (represented by the Biograph Vision) by a factor of ~4.5 and ~15 respectively. At the same time sensitivity at the center of the tomograph can reach up to 124.1(1.0+/-1.1) [cps/kBq]. Furthermore, due to the possibility of the positronium mean lifetime imaging guaranteed by the J-PET technology, its sensitivity based on the triple coincidence technique has been evaluated. The acquired maximal total sensitivity of 30.63(06+/-31) [cps/kBq] proves to again surpass the traditional crystal-based system up to ~5 times. Ultimately, the sensitivity achieved with the studied Total Body scanners is almost uniform along the whole patient with an additional increase on its sides for both double and triple coincidence imaging. This creates
a possibility for high-quality simultaneous imaging of the whole human body.
System akwizycji danych dla modularnego skanera PET oparty na układach FPGA
Author: Maciej Bakalarek
Supervisor: dr Grzegorz Korcyl
abstract
Defence year: 2020
The aim of the thesis was to design and implement a preprocessing system for tomographic data in FPGA devices. The system has been designed with high parallelism of calculations in mind, thanks to which it works in real-time. Additionally, applications were prepared for live-visualization of the results (i.e. Lines of Response). The paper describes the architecture of the CM-PET scanner (with which the implemented system has been integrated) and the technologies used. In the paper results of tests with the use of four CM-PET?s modules are presented. The estimated maximum system throughput is around 14 MSps.
Study of the ortho-positronium mean lifetime in cancerous and healthy human colon tissues
Author: Zuzanna Bura
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2020
Currently, cancer is the second cause of death worldwide. The most effective method for cancer prevention is early diagnosis. This thesis describes an innovative method for cancer diagnosis that provides not only information about the localization of tumor in the human body but also about its structure. The purpose of this work was to examine the correlation between
orth-positronium (o-Ps) mean lifetime and the degree of malignancy, size, type of cells and other factors which can be associated with colorectal cancer, contemporaneously demonstrate the potential of simultaneous PALS (Positron Annihilation Lifetime Spectroscopy) and PET scan (conduct on Jagiellonian Positron Emission Tomograph, developed at the Jagiellonian University). For this purpose, a series of measurements were performed on normal and cancerous colon tissues. This work also describes details of measurements and their analysis (chapter 4). Chapter 5 shows the results of PALS measurements on living tissues (and fixed in formalin), as well as the impact of environmental factors such as temperature and humidity on the mean lifetime of o-Ps.
Adaptation of image reconstruction algorithms with time-of-flight for the J-PET tomography scanner
Author: Kamil Rakoczy
Supervisor: dr Wojciech Krzemień
abstract
Defence year: 2019
The main aim of this thesis is the implementation of various analytic image reconstruction algorithms in the frame of the J-PET Framework analysis package. The implemented algorithms: Kernel Density Estimation, Filtered Back-Projection and Time-Of-Flight-Filtered Back-Projection have been tested both using Monte Carlo simulations and experimental data gathered by the scanner. Obtained results show that the implemented algorithms reconstruct correctly the shape of the phantoms. Comparison studies between implemented algorithms have been performed. In reconstruction of the NEMA phantom, the best results have been obtained using the Shepp-Logan filter with the cut-off parametr equal to 0.75 of Nyquist frequency (corresponding to the Background Variability of 0.13 and the Contrast Recovery Coefficient equal to 1.03 for high activity region of radius 22 mm). For the Time of-Fligth Filtered Back-Projection algorithm, the best reconstruction was obtained using the Hamming filter with the cut-off parameter equal to Nyquist frequency (corresponding to the Background Variability of 0.17 and the Contrast Recovery Coefficient equal to 0.96 for high activity region of radius 22 mm).
Tomographic data processing and visualization on programmable devices
Author: Karol Farbaniec
Supervisor: dr Grzegorz Korcyl
abstract
Defence year: 2019
The aim of this work is to implement selected data processing stages for Digital J-PET detector readout and explore feasibility of hardware acceleration of image reconstruction. Moreover this work covers main aspects of FPGA design process. First chapter contains introduction to PET tomography, data processing followed by image reconstruction. Second chapter present fundamentals of digital electronics in reference to FPGA technology. Later Digital J-PET detecting system is described with system architecture and readout procedure. In fourth chapter implementation details are presented on data processing for detecting module and image reconstruction kernel. Next chapter contains results of implemented components.
Feasibility studies of measurements of annihilation photons polarization with the J-PET detector
Author: Nikodem Krawczyk
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2016
Development and implementation of Electronic Logbook for J-PET research groupusing Symfony2 framework
Author: Mateusz Haber
Supervisor: dr Marcin Zieliński
abstract
Defence year: 2015
The main aim of this thesis was to develop and implement an interactive ElectronicLogbook for Jagiellonian Positron Emission Tomography research group. Using the modernand innovative Symfony2 framework, Bootstrap, jQuery and Angular.js technologies we havecreated a fully working client-server web application based on the Model-View-Controllerarchitecture. The data storage was organized using two database engines: MySQL, andPostgreSQL, served in back-end by the Doctrine package. Application was designed in theResponsive Web Design (RWD) approach, making it possible to use it on the any portabledevices (e.g. like tablets and smartphones).Application was prepared according to the functional requirements provided by the J-PET group. The main functionality of the application is a multifunctional and intuitiveactivity logging system, which allows to register and further monitor the situation of theexperimental work. Secondly the application allows to associate the laboratory work infor-mation with the experimental parameters available from external database. Furthermore,we have implemented the error and warning handling system, allowing to monitor and reportall the custom situations encountered during the laboratory work. Application was supple-mented with the Shift Management module, allowing to organize weekly laboratory work ofthe research group.
Studies of changes of signals shapes in plastic scintillator strips
Author: Monika Pawlik-Niedźwiecka
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
The main aim of this master thesis was to study properties of signals in plastic
scintillator detectors with different shapes. The scintillators with the length
of 500 mm and cross sections of square (14 mm side), hexagonal (9 mm side),
triangular (17 mm side) and circular (16 mm and 10mm dia.) were studied.
A series of measurements were done with 68Ge radioactive source placed in lead
collimator. 500 mm long scintillator connected to two photomultipliers by optical
gel and reference detector were used to make an experimental setup.
Measurements were performed at 5 positions across each strip. It was observed
that the rise time increases and the fall time decreases with the distance between
the irradiation place and photomultiplier.
The impact of a patient's size on a spatial resolution of PET scanner constructed of polymer scintillators
Author: Ewelina Kubicz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
The aim of this thesis is to determine how size of a patient influences the
temporal and spatial resolution of a double module of Strip PET prototype
based on polymer scintillators. Such a scanner is currently being developed
at Jagiellonian University by the J-PET collaboration. All measurements
were conducted using a double module of a Strip PET prototype with a 22Na
source. Four different sizes of phantoms filled with water or ethyl alcohol
were used as a simulation of a patient?s body. The achieved time resolution
along Line-of-Response is around 146 ps, and it is the same for all tested
phantoms within the uncertainty range and as a result spatial resolution
along Line-of-Response is equal to about 22 mm. Both these values are two
times better than in currently used PET scanners.
Reconstruction of hit position of gamma quanta in scintillators based on sampling of signals in voltage and fraction domains
Author: Natalia Zoń
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
With the ongoing development of novel Positron Emission Tomography solutions, there exists a demand for researching methods of processing data allowing for the reconstruction of 3D human body images from signals gathered by the device?s detectors.
This thesis describes a method of reconstructing the position of gamma quanta hit along a single polymer scintillator based on the calculation of similarity of signals incoming from a PET device with respect to signals in a previously created database.
The similarity of two signals is computed using either a set of times corresponding to a set of voltage thresholds common for the two compared signals (Chi-square method) or two sets of points designating two curves representing the signals (Frechet distance method). The theoretical basis of the concept and its general idea as well as individual steps of the proposed algorithm are explained in detail in the next chapters of this thesis.
The realization of the method in form of a computer program was implemented in Python (version 2.7), a high-level, general purpose programming language which allows for employing multiple programing paradigms including object-oriented, functional, procedural or imperative programming.
This thesis is supplemented with Appendix containing the source code of the computer program.
Synteza scyntylatorów polimerowych
Author: Anna Wieczorek
Supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2013
Scyntylatory to substancje, których cząsteczki ulegają jonizacji lub wzbudzeniu pod wpływem oddziaływania z promieniowaniem jonizującym, a powracając do stanu podstawowego, emitują fotony.
Przedmiotem badań prezentowanych w niniejszej pracy są scyntylatory polimerowe. Ich głównym składnikiem jest polimer ? poliwinylotoluen lub polistyren, który samodzielnie nie może być efektywnym scyntylatorem, gdyż średnia droga emitowanych przez niego fotonów jest zbyt krótka. Niezbędne jest stosowanie dodatków fluorescencyjnych.
Zadaniem pierwszego z nich jest odbiór energii z polimeru
i emisja światła z zakresu UV. Następnie promieniowanie to jest pochłaniane przez drugi dodatek fluorescencyjny ? wavelength shifter, który emituje falę świetlną z zakresu widzialnego, a więc taką, której długość dopasowana jest do elementów układu detekcyjnego.
Celem pracy magisterskiej było otrzymanie w warunkach laboratoryjnych efektywnego scyntylatora. Aby tego dokonać należało zoptymalizować warunki procesu polimeryzacji, takie jak przedział temperaturowy prowadzenia procesu czy dobór stężenia dodatków fluorescencyjnych. Dokonano pomiaru krystaliczności metodą XRD, wykonano analizę termograwimetryczną, potwierdzającą wysoki stopień konwersji monomeru do polimeru oraz określono ich właściwości scyntylacyjne.
Otrzymywane scyntylatory mają być wykorzystane, jako detektory promieniowania gamma w Pozytonowej Emisyjnej Tomografii Komputerowej.
Studies of detection of gamma radiation with use of organic scintillator detectors in view of positron emission tomography
Author: Szymon Niedzwiecki
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2011
Positron emission tomography (PET) is experiencing nowadays a lot
of interest. PET scanner measures density distribution of radiopharmaceuticals
with radioactive isotopes emitting positrons in human body.
annihilation of positrons with electrons from the body of the patient
results in emission of two gamma quanta, going back to back which are
then measured in detectors surrounding the patient. After applying
reconstruction algorithms density distribution of annihilations is determined.
PET modalities can eectively vizualize metabolic processes
inside examined patient, unlike other kind of scans like Computer Tomography
or Nuclear Magnetic Resonance, which tell us only about
anatomy of the patients body.
In recent times even more sophisticated method of scan was introduced
- the Time-Of-Flight PET. TOF PET measures time dierence
between arrival of gamma quanta in two detectors. Hovewer due to lack
of fast scintillaton materials this method weren't applied in practice.
Availability of new, faster scintillators and cost-eective photomultipliers,
as well as improvements in eld of electronics enabled usage
of TOF PET modalities. Resolution of measuring time dierence in-
uences spatial resolution of reconstruction thus making this quantity
most important when designing TOF PET scanner. One of the best
presently available scanner achieved time resolution of about 550 ps.
In this thesis feasibility study of using plastic scintillators in TOF
PET reconstruction is tested. At present TOF PET scanners are based
on crystal scintillators, which compared to plastic scintillators are much
slower and more expensive to manufacture. Measurements of amplitude
spectra of polymer scintillators, which were irradiated by gamma
quanta from annihilation, made by dr A. Kochanowski and mgr .
Kap?on in Chemistry Department of Jagiellonian University, allowed
for determining best composition of base, primary and secondary additive.
As a result of the test performed in the framework of this thesis a
PVT+PPO+POPOP was found as the best combination out of eight
examined. Experimental measurement of distrubution of time dierence
between signals from both sides of RP422 scintillator strip has
been also performed with result of 680 ps. This result can be further
improved by upgrading electronic components of experimental setup.
Bulk polymerization of styrene and its derivatives as material for construction of scintillators
Author: Łukasz Kapłon
Supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2011
The purpose of this study was to produce a plastic scintillator, i.e. material which exhibits scintillation ? the act of luminescence when excited by ionizing radiation. Synthesis of this material is based on dissolving scintillation additives in the monomer (styrene or vinyltoluene) and bulk polymerization by free radical mechanism. Several series of samples were prepared with different content of scintillation additives and polymerization conditions. Afterwards they were submitted for testing at the Division of Nuclear Physics, Jagiellonian University. The results confirm the effectiveness in the detection of gamma radiation. The resulting plastic scintillators, due to its advantages such as short response time, low production cost and the ability to produce samples of different shapes and sizes, will be used to build ionizing radiation detectors, for example in positron emission tomography (PET).
Liniowy model pozytonowego tomagrafu emisyjnego
Author: Ewelina Czaicka
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2008
Celem niniejszej pracy było opracowanie nowego ćwiczenia na II pracownie
fizyczną Instytutu Fizyki Uniwersytetu Jagiellońskiego. Ćwiczenie to ma na celu
zaprezentowanie zasady działania pozytonowego tomografu emisyjnego.
Evaluation of the NEMA characteristics for the Modular J-PET scanner
Author: Faranak Tayefi Ardebili
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2024
This study aim is to evaluate the performance characteristics of the Modular Jagiellonian Positron Emission Tomograph (Modular J-PET) in accordance with the recognized standards established by the National Electrical Manufacturers Association (NEMA) for Positron Emission Tomography (PET) scanners. The Modular J-PET represents the lat-est prototype within the Jagiellonian-PET group, distinguished by its utilization of plastic scintillator strips optimized for the precise detection of back-to-back gamma quanta arising from electron-positron annihilations. The Modular J-PET comprises 24 individual mod-ules arranged in a symmetrical 24-sided polygon circumscribing a circular configuration with a diameter of 73.9 cm. Each module is constructed from 13 scintillator strips, aligned adjacently, each measuring 50 cm in length and possessing a cross-sectional dimension of 6 mm × 24 mm. Dual-ended scintillation light readout is accomplished through analog Silicon Photomultipliers (SiPMs).Data collected during the experimentation phase were subjected to analysis employing software known as the J-PET Framework. The average system sensitivity of the ModularJ-PET was determined to be 0.768?0.003 cps/kBq in the center with the peak sensitivity of 2.1 cps/kBq. The system sensitivity has improved by sixfold compared to the first generation of the J-PET prototype with 192 strips.Radial spatial resolution for TOF image reconstruction methods was found to be 4.92?0.56 mm,7.38?0.49 mm, and 6.94?0.38 mm at positions 1 cm, 10 cm, and 20 cm from the detector center, respectively. Tangential spatial resolution for TOF image reconstruction methods was determined as 7.38?0.51 mm,7.37?0.10 mm, and 14.67?0.31 mm at the same positions, while axial spatial resolution was calculated as 30.73?0.52 mm,30.73?0.64 mm, and 31.96?0.29 mm. It is worth noting that the tangential and radial spatial resolution values of the Modular J-PET detector align closely with those of commercialPET devices. Future enhancements are anticipated in axial spatial resolution through anextended axial field of view scanner and the application of wavelength shifting (WLS)techniques. The determination of the scattered fraction based on single-scatter randoms background (SSRB) algorithms yielded a value of 41.68?0.19 [%], which is consistent with that observed in commercial PET devices. To validate the experimental findings,GATE simulations were conducted.The simulations included spatial resolution assessments using a sodium source, as wellas evaluations of sensitivity and scatter fraction involving a phantom conforming to NEMA standards. The simulations indicated that the Modular J-PET achieves a system sensitivity of 1.324?0.032 cps/kBq at the center of the detector?s field of view and 1.313?0.001 cps/kBq at a 10 cm offset from the tomograph center. The peak sensitivity at the center of the detector?s filed of view to be 2.9 cps/kBq across various multiplicity cuts. Fur-thermore, the scatter fraction, computed utilizing SSRB algorithms, was established at(40.25?2.3)%. Radial spatial resolution for TOF image reconstruction methods was found to be 4.80?0.59 mm,7.26?0.55 mm, and 6.67?0.42 mm at positions 1 cm, 10 cm, and 20 cm from the detector center, respectively. Tangential spatial resolution for TOF image reconstruction methods was determined as 7.27?0.47 mm ,7.27?0.59 mm, and 15.1?0.4 mm at the same positions, while axial spatial resolution was calculated as 29.97?0.49 mm,30.53?0.74 mm, and 31.78?0.11 mm.The Modular J-PET, characterized by its single-layer configuration with 50 cm scintillator strips, exhibits the potential for extension to an extended axial field-of-view through multi-layer arrangements. Consequently, the presented Modular J-PET prototype holds promise for the cost-effective development of a total-body J-PET system constructed from plastic scintillators.
Evaluation of Positron Emission Mammography using plastic scintillator and wavelength shifters
Author: Shivani Shivani
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2023
The thesis focuses on the design and fabrication of a specialized detector system called J-PEM (Jagiellonian Positron Emission Mammography) optimized for breast imaging. This system utilizes plastic scintillators, wavelength shifters, and photodetectors to improve spatial resolution and detection of annihilation photons.
The prototype system consists of a single module comprising two layers of plastic scintillators and one layer of wavelength shifters. Silicon Photomultipliers are used for signal readout. The use of plastic scintillators and wavelength shifters enables the achievement of a spatial resolution of approximately 5 mm, as validated by simulation studies and experimental analyses.
Despite being a single-head module, the J-PEM system demonstrates spatial resolution comparable to established imaging modalities, making it a cost-effective tool for breast cancer detection. Comparisons between different configurations suggest that employing wavelength shifters without optical separation yields superior resolution.
The J-PEM system incorporates DOI (depth of interaction) sensitivity, which indicates the potential for further enhancements through narrower wavelength shifters in future advancements. Overall, the research findings highlight the effectiveness, efficiency, and potential of the J-PEM system for improving breast cancer detection with enhanced spatial resolution.
Determination of performance characteristics of the J-PET tomograph
Author: Monika Pawlik-Niedźwiecka
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Michał Silarski
abstract
Defence year: 2023
The aim of this work was to determine the performance characteristics of the Jagiellonian Positron Emission Tomography (J-PET) detector according to the worldwide NEMA norm for PET scanners. J-PET scanner was built out of three layers of axially arranged organic scintillators and it was optimized for detection of back-to-back gamma quanta from electron-positron annihilations.
Sensitivity of the J-PET detector is equal to 0.130 ? 0.014cps/kBq and 0.0789 ? 0.0061 cps/kBq for 0 and 10 cm radial offset, respectively. Low sensitivity value comes from the sparse detector geometry.
Tangential spatial resolution is equal to 0.635 ? 0.092 cm, 0.715 ? 0.092 cm and 0.630 ? 0.092 cm for position 1, 10 and 20 cm from the detector center, respectively. Radial spatial resolution is equal to 0.280 ? 0.092 cm, 0.500 ? 0.092 cm and 0.445 ? 0.092 cm, respectively, and the axial spatial resolution is equal to 3.850 ? 0.028 cm, 3.667 ? 0.048 cm and 3.788 ? 0.053 cm. Tangential and radial spatial resolution values of the J-PET detector are of the same order as for commercial PET devices. Axial spatial resolution will be improved in the future by application of the WLS.
Obtained value of scattered fraction on the level of 35.41 ? 0.19 [%] is comparable to the commercial PET devices.
Feasibility study of lesion detection by means of Total-Body Jagiellonian Positron Emission Tomography scanner
Author: Meysam Dadgar
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2022
Metastasis as the major reason for 90 % of cancer-related deaths, occurs when cancerous cells detach from their primary tissue and spread to the other part of the body through blood vessels or the lymphatic system. Detection of these malignant lesions in their early stages can increase the patient?s survival rate by taking proper treatment strategies. Due to their low sensitivity, conventional PET scanners cannot detect metastatic lesions in the early stages.
In 2019, a new Total-Body PET (TB PET) scanner called uEXPLORER with higher sensitivity thanks to the full detector coverage along the patient?s body was constructed. The main obstacle in the worldwide utilization of this generation of scanners is their higher construction and maintenance price. Since 2013, there has been continuous research to develop a novel economic type of PET scanner named Jagiellonian Positron Emission Tomography (J-PET) based on plastic scintillators. This technology, by providing a cost-efficient solution in the construction of the Total-Body PET scanners opens possibilities for worldwide utilization of these systems and improves the survival rate of patients significantly with precise diagnosis. The research presented in this thesis evaluated the lesion detectability of Total-Body J-PET scanners by accomplishing the GATE simulation from XCAT anthropomorphic digital phantoms.
This thesis?s main aim is to investigate the lesion detectability of the Total-Body J-PET scanner and improve this feature by optimizing event selection criteria and the spatial resolution of the tomograph. The liver is the organ under study to determine the lesion detectability of Total-Body J-PET.
For the case of the presented thesis, a series of simulations with point sources and cylindrical phantoms has been performed for the determination of optimum characteristics of Total-Body J-PET. The second group of the simulations has been performed by utilization of human-grade XCAT anthropomorphic phantoms. The results of the simulations have been analyzed by Gate Output J-PET Analyzer (Goja) which has been developed by the J-PET collaboration. Due to the unique configuration of the J-PET-based scanners and their special detection principle, conventional image reconstruction software could not be compatible. In the case of the image reconstruction Quantitative Emission Tomography Iterative Reconstruction (QETIR) in collaboration with the Medisip research group from Gent, Belgium has been used.
The results showed that the Total-Body J-PET tomograph can detect centimeter-grade lesions in the various ranges of the XCAT phantoms with different body mass index (BMI). However applying acceptance angle criteria to remove the contribution of the most oblique coincidences in the image reconstruction, provided the possibility of detecting sub-centimeter (5mm) lesions in a higher number of the iterations of image reconstruction.
Test of T, P and CP Symmetry in the decay of ortho-Positronium using the J-PET detector
Author: Juhi Raj
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2022
Conservation of discrete symmetries plays a fundamental role in the exploration of physics laws in the area of elementary particle physics. CP symmetry violation in the weak interaction was one of the first intriguing discoveries to the particle physics community in this domain. So far, there has not been any experimental evidence of violating discrete symmetries in the charged leptonic sector. This Ph.D. thesis reports the explored sensitivity of testing the T, P and CP symmetries in the charged leptonic sector using the versatile and novel detector, Jagiellonian- Positron Emission Tomograph (J-PET), in the decay of ortho-Positronium. A distinctive research methodology to test T, P and CP discrete symmetries in the decay of ortho-Positronium was formulated from four experiments conducted through 2017-2020 for 122 days. The achieved result showed no asymmetry within the achieved sensitivity of 7 × 10^?4.
Development of positronium imaging with the 192-strip J-PET detector
Author: Kamil Dulski
Supervisor: prof. Paweł Moskal, prof. Bożena Jasińska
abstract
Defence year: 2022
The thesis describes the basics of a new imaging technique - positronium imaging. Positronium imaging is a technique that combines the metabolic information obtained in a standard Positron Emission Tomography (PET) scan with the structural indices examined by the Positron Annihilation Lifetime Spectroscopy (PALS) technique. In particular, proof of concept of the positronium imaging, by means of the 192-strip J-PET detector is presented.
A research hypothesis was formulated which stated that it is possible to simultaneously measure the distribution of the radioisotope inside the sample and to determine the structural index (mean ortho-positronium lifetime) in each part of the sample. According to this hypothesis, it is possible to distinguish samples with a di erent structure. Therefore, positronium imaging can nd application not only in PET scans by delivering additional information, potentially improving PET diagnosis e ectiveness, but also in material research as a technique to characterize the nanostructure in every part of the large sample. In order to demonstrate that positronium imaging can be an important technique and prove the research hypothesis, comprehensive studies were carried out using the 192-strip J-PET detector. To ensure the high quality of the collected data, the J-PET detector was calibrated for time and position reconstruction, and a set of data selection conditions was developed. It was also checked how developed selection criteria and dedicated measurement simulations re ect the measurement conditions and at the same time maintain high purity of the data sample. In order to check how well the J-PET detector is able to examine the properties of positronium, an additional analysis was carried out in terms of the separation of various states and types of positronium decay. The results of the analysis shows the possibilities of the J-PET detector in the context of fundamental studies, on the example of the precise determination of the ortho-positronium decay constant.
The main part of the work focuses on testing the research hypothesis on two systems that covered two potential applications of positronium imaging - material and medical studies. The positronium image of a system composed of samples of di erent porosity shows that it is possible to distinguish the samples in terms of structure, despite the lack of visible di erences on the analogue to the standard image of annihilation density distribution. The developed method of estimating the mean o-Ps lifetime for single voxels allows to obtain quite good agreement, even for voxels with a relatively low o-Ps intensity. A clear separation in terms of structure is also presented in the positronium image from the in-vitro measurement of the human tissues. Measurement setup consisted of four samples of two types of tissue - cardiac myxoma and adipose tissue. Despite relatively low di erences in the mean lifetime of o-Ps, the positronium image of these samples also con rms the research hypothesis, successfully separating di erent types of tissues, with quite good compatibility of tissues of the same type.
Characterization of melanoma cell spheroids by means of imaging techniques and positron annihilation lifetime spectroscopy
Author: Hanieh Karimi
Supervisor: prof. Paweł Moskal, prof. Ewa Stępień
abstract
Defence year: 2022
The presented thesis is devoted to evaluating the three-dimensional (3D) spheroid characteristics using imaging techniques and examining the positron annihilation lifetime spectroscopy (PALS) as a novel biomedical approach to identify the cancer malignancy level. A 3D spheroid mimics important properties of a real tumor and may soon become a reasonable substitute for animal models and human tissue. In this thesis, the morphological analysis of spheroid cell cultures was conducted using micro-CT and compared to that of confocal microscopy. An approach is proposed that can potentially open new diagnostic opportunities to determine the characteristics of cancer cells cultured in 3D structures instead of using actual tumors. Micro-CT analysis of a spheroid showed that the spheroid size and shape differed depending on the cell line, initial cell number, and duration of culture. The micro-CT allows for high-resolution visualization of the spheroids? structure.
In this study, it was hypothesized whether the difference between the grade of malignancy of cancer cell lines can be probed by positronium biomarker. The hypothesis was tested on the 3D spheroid model. Positron annihilation lifetime spectroscopy is known as an appropriate technique to evaluate the properties of different organic and inorganic materials based on the determination of the void size within and between molecules.
To test the proposed hypothesis, the lifetime of ortho-Positronium (o-Ps) was evaluated in 3D melanoma spheroids from two melanoma cell lines differing in the stage of malignancy. Obtained results show that the o-Ps lifetime and intensity are different between 3D melanoma spheroids with different malignancy level. The presented method paves the way for the application of the
3D spheroids for the in-vitro tests of positronium biomarker. The result of the method applied to studies of positronium in melanoma cancer cells revealed that positronium is a promising biomarker that may be applied in PET diagnostics for the assessment of the degree of cancer malignancy.
Design and optimization of the strip PET scanner based on plastic scintillators
Author: Paweł Kowalski
Supervisor: prof. Wojciech Wiślicki, prof. Paweł Moskal
abstract
Defence year: 2021
The novel whole-body PET system is developed by the J-PET Collaboration. It is built of relatively cheap plastic scintillator strips arranged axially in the form of a cylinder. Usage of plastic scintillators opens perspective for the cost-effective construction of the total-body PET. In order to determine properties of the scanner prototype and optimize its geometry, advanced computer simulations using the GATE software were performed.
Firstly, simulations were verified with experimental results for laboratory prototype. After that, the simulations were used to calculate the NEMA characteristics and maps of efficiency. The spatial resolution, the sensitivity, the scatter fraction and the NECR were estimated according to the NEMA norm as a function of the length of the tomograph, number of the detection layers, diameter of the tomographic chamber and for various types of the applied readout.
Simulations results were used to optimize geometry and working parameters of the JPET scanner. They were also used to compare the J-PET solution with current commercial technology.
Biomedical applications of Positron Annihilation Lifetime Spectroscopy: nanostructural characterization of normal and cancer cells and tissues
Author: Ewelina Kubicz
Supervisor: prof. Paweł Moskal, prof. Ewa Stępień
abstract
Defence year: 2020
This thesis is devoted to examining a possible biomedical application of Positron Annihilation Lifetime Spectroscopy (PALS), for the characterisation of normal and cancer cells and tissues. PALS allows to study molecular structure at the nano- and subnanometer levels, by measurement of positronium properties in intra-molecular voids.
Studies conducted in the framework of this thesis aim to test the research hypothesis that positronium can be used as a novel biomarker for cancer diagnostics. The working hypothesis assumes that cancer cells differ from normal ones, in their nanostructure and molecular interactions. These changes are significant enough to affect positronium properties to a degree observable with the PALS technique. Correlations between the cellular organisation, its relation to the cell morphology and
signalling with positronium are examined in connection with positronium properties to carcinogenesis and metastatic processes.
The proposed hypothesis is tested in two models: benign cardiac myxoma specimens and malignant melanoma cultured cell lines. In both cases, positronium properties are compared to an appropriate normal tissue and cell line. Studies are performed
for both fixed and living cells and tissues to investigate the influence of water and cell viability on the PALS signal.
Obtained results show significant differences in positronium lifetime and its production intensity between cancer and normal cells and tissues in all studied cases, regardless of hydration and fixation of specimens. Therefore, obtained results validate
the working hypothesis that positronium can be applied as a novel biomarker in cancer diagnostics.
Study of angular correlations in the ortho-positronium annihilation with the J-PET detector for the search of CPT symmetry violation
Author: Muhsin Mohammed
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Aleksander Gajos
abstract
Defence year: 2020
Testing the conservation of the CPT symmetry is one of the most important issues for modern physical science. CPT is the only combination of charge conjugation, parity, and time-reversal that is observed to be an exact symmetry of nature at the fundamental level. Several experiments are currently performed to test the symmetry in the leptonic sector, e.g. in neutrino oscillations. CPT can be tested also by using charged leptons by searching for the electric dipole moment, e.g. of the electron. In this thesis, we present a test of CPT invariance in the decays of positronium as the lightest purely leptonic bound system.
Positronium is a viable system for the investigation of possible violations of the discrete symmetries in the leptonic sector. We search for CPT-violating decay processes of positronium atoms by the Jagiellonian Positron Emission Tomograph (J-PET), using the angular correlation of S ⋅ (k1 × k2), where S is the positronium spin and k1, k2 are the momenta of the most energetic positronium decay photons. A non zero expectation value of CPT-odd angular correlation would give rise to an up/down asymmetry of the decay plane with respect to the spin orientation of the ortho-positronium atom. In the previous similar experiments, the precision of determining this kind of correlation has been limited to about 3‰. The precise experimental CPT symmetry tests with J-PET are possible thanks to a dedicated reconstruction technique of the ortho-positronium (o-Ps) into 3γ decays. The reconstruction of the o-Ps decay into three photons was used in order to determine the spin direction of the positronium atoms. Also, the identification of o-Ps decay into 3γ events as well as the reconstruction of their annihilation points was achieved using a large decay chamber with a layer of a highly porous material target silica (R60G) on its inner wall, whose setup allows for determining the o-Ps spin linear polarization without the use of external magnetic field. The measurements were performed with the J-PET by using two radioactive sources with different activities and two different kinds of annihilation chambers. We have measured the angular distribution of gamma quanta emitted in three-photons annihilation as a result of o-Ps decay.
The test of the CPT symmetry with J-PET detector resulted in the mean value of the CPT-sensitive angular correlation operator OCPT=(-5.5 ± 3.7) × 10-4, which corresponds to the CPT violation coefficient of CCPT=(-13.6 ± 9.2) × 10-4, therefore no violation has been found at the precision level of 9.2 × 10-4, which is factor of 3 better than the previous experimental results.
Double-strip prototype of polymer time-of-flight positron emission tomograph based on multi-level analog electronics
Author: Szymon Niedźwiecki
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2019
The aim of this work was to construct and perform tests of a proto-
type Positron Emission Tomography (PET) scanner consisting of two
detection modules. Each module consisted of a long plastic scintil-
lator strip and was read-out from both sides by fast vacuum tube
photomultipliers. Two dimensions of strips were tested: 5 x 19 x 300
mm 3 and 7 x 19 x 500 mm 3 . It was shown, that one can successfully
utilise plastic scintillators for 511 keV gamma quanta registration and
determination of e + e ? annihilation position.
The research presented in this thesis was conducted in the frame-
work of the J-PET collaboration, whose aim is the elaboration of the
cost-effective method for construction of total-body PET.
In the course of this work a R9800 Hamamatsu photomultiplier is
selected for the first prototype of the total-body J-PET scanner and
a multi-threshold constant threshold board design is decided to be
used for time of interaction and energy loss measurement. An opti-
misation method of detector parameters: voltage supplied and thresh-
old for front end-boards is provided.
The main comparison with commercial scanners was performed
for a 30 cm long prototype. The fractional energy resolution is deter-
mined to be 9% at 340 keV - which is equal to the Compton edge for
511 keV gamma quanta. The Coincidence Resolving Time (CRT) is
determined to be 280 ps and Point Spread Function (PSF) at 1 cm off
the center of tested prototype was equal to 9.8 mm and 6.7 mm for
transaxial and axial resolutions, respectively.
Result of this thesis constituted the basis for the project of the full
scale prototype with diamater of 85 cm and axial field of view of 50
cm. The author of this thesis was taking part in the costruction of the
first full scale whole-body prototype from the stage of mechanical
assembly to assistance in performing measurements similiar to the
ones as described in the thesis.
Synthesis and characterization of polystyrene scintillators and their application in positron emission tomography
Author: Łukasz Kapłon
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2018
The aim of the thesis was to develop polystyrene scintillator for use in the novel time of flight Jagiellonian Positron Emission Tomography (J-PET) scanner being elaborated for the whole-body imaging. To achieve this goal, polystyrene based plastic scintillators with the different chemical compositions were produced and characterized. Spectroscopic and optical properties of these polystyrene scintillators were measured. Structure of manufactured plastic scintillators were studied using two methods: powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC).
Optimization of the conditions of styrene polymerization for the production of gamma radiation detectors was conducted. As a result of the work presented in this thesis the time-temperature cycles were established: (i) for polymerization in small cylinders as well as (ii) for polymerization in the glass mold allowing to manufacture long plastic scintillator strips. This thesis presents also a new method developed for the fast quality control of plastic scintillator strips. The method was successfully applied during J-PET prototype building.
Light output, decay time, emission spectra and technical attenuation length were measured to develop best composition of polystyrene scintillator. Among the polystyrene scintillators synthesized in the framework of this thesis it was established that:
(i) polystyrene scintillator with 2% BPBD primary solute and 0.06% POPOP wavelength shifter possess the best timing properties with decay time of 1.51 ns that is in the range of the decay time of the best commercial scintillators as e.g. BC-420 (1.5 ns), BC-404 (1.8 ns) and EJ-230 (1.5 ns) used in the J-PET tomograph;
(ii) polystyrene scintillator with 2% PPO primary solute and 0.03% bis-MSB and 0.03% POPOP wavelength shifters is characterized by the best light output of over 11200 photons per megaelectronvolt (MeV) which is comparable with light output of BC-420 with value 10240 photons per MeV.
Investigations of fundamental symmetries with the electron-positron systems
Author: Aleksander Gajos
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2018
This work concerned two experimental searches for the violation of fundamental discrete symmetries in physical systems originating from electron-positron interactions. The first study was a direct test of the symmetry under reversal in time in transitions of neutral K mesons, performed with quantum-entangled neutral kaon pairs produced in the e+e->KsKl process. Data collected by the KLOE experiment operating at the DAFNE collider in 2004-2005 were studied to select events of the KsKl->pi e nu 3pi0 and KsKl->pi+pi- pi e nu processes and compare their rates. For the Kl->3pi0 decay involving only neutral particles, a dedicated reconstruction technique based on trilateration was devised. Rates of each process identified by two time-ordered neutral kaon decays, determined as a function of a difference between kaon decays, were used to measure the asymptotic level of two T-violation sensitive ratios of double kaon decay rates, yielding the values of R2 = 1.020 +/- 0.017stat +/- 0.035syst and R4 = 0.990 +/- 0.017stat +/- 0.039syst. In agreement with expectation based on the size of the the dataset used, these results do not reach the sensitivity needed to probe T violation. However, this measurement proves that the required reconstruction and analysis of the data is feasible and prospects exist for a statistically significant test of the T symmetry with a larger dataset collected by the KLOE-2 experiment is certain systematic effects are eliminated.
The second part of this work comprised a demonstration of the feasibility of using the J-PET detector to search for non-vanishing angular correlations in the decays of ortho-positronium atoms, the lightest purely leptonic systems decaying into photons. The trilateration based reconstruction method prepared for Kl->3pi0 decay at KLOE was adapted to the ortho-positronium annihilations into three photons. Its performance was validated using Monte Carlo simulations proving it may be applied to determination of spin direction of positrons forming the positronium atoms, thus allowing for control of their polarization in the experiment. Moreover, the feasibility of identification of 3gamma events as well as reconstruction of their origin points was demonstrated using a test measurement performed with the J-PET detector.
Hit-time and hit-position reconstruction of gamma quanta in the J-PET tomography system based on a library of model signals
Author: Neha Gupta-Sharma
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Michał Silarski
abstract
Defence year: 2018
Positron Emission Tomography (PET) is an advanced nuclear medicine imaging modal-
ity. It enables to determine the diseases (like cancer, heart diseases etc) in vivo in their
earliest stage which significantly influence the health-care resources provided to the pa-
tient. However, high cost of PET scanners construction has limited their availability.
J-PET (Jagiellonian-PET) is one of the project started with the aim to build a more
economical PET modality. It is an assemble of plastic scintillators in a cylindrical fash-
ion with large longitudinal field-of-view (FOV). In the plastic scintillators gamma quanta
emitted from the patient?s body interact via Compton scattering. Therefore, amplitudes
of processed signals strongly depend not only on the hit-position but also on the energy
deposition which demands for a new reconstruction method.
The aim of this work is to develop a new reconstruction method for hit-time and
hit-position of the registered gamma quanta. The developed method is based on the eval-
uation of degree of similarity between the registered signals and model signals stored in
a database. The compared signals are expressed in the form of an array including times
determined when sampling the signal in voltage domain. As a measure of similarity the
Mahalanobis distance between the examined and model signals is used. The model signal
is referred to as a signal which shape is determined from the measured experimental data.
The hit-position and hit-time are defined as the time and position of the model signal at
most similar to the registered one. The method is optimized for number of threshold levels
with different combinations, energy loss regions and number of parameters included to
calculate the value of Mahalanobis distance. Time-of-flight resolution is used as a criterion
of optimization. The final conclusion is that the reconstruction of image will be performed
on the two-threshold levels followed by the bisection of energy region from 0.2 MeV to
0.38 MeV in two parts using Mahalanobis distance as a function of position (z) and time
shift (?t).
The method was validated on the J-PET two-strips prototype, for two sets of strips
modules: one with dimensions 5x19x300 mm3 and the second with dimensions 7x19x500 mm3 .
As a result the obtained time-of-flight resolutions for the annihilation point in the center
of the detector are equal to 325 ps (FWHM) and 414 ps (FWHM) for the modules with
dimensions of 5x19x300 mm3 and 7x19x500 mm3 , respectively. Spatial resolutions when
gamma was hitting at the center of the scintillator for module with dimensions 5x19x300
mm3 and 7x19x500 mm3 are equal to 25.2 mm (FWHM) and 32.3 mm (FWHM), respec-
tively. Spatial transverse and axial resolutions obtained from the image reconstructed by
the J-PET two-strips prototype for point-like source placed at the center of the detector
with maximum likelihood expectation maximization algorithm using two-strip module
with dimension 5x19x300 mm3 are equal to FWHM = 7.7 mm and FWHM = 20.2 mm,
respectively.
Development of novel plastic scintillators based on polyvinyltoluene for the hybrid J-PET/MR tomograph
Author: Anna Wieczorek
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2017
Kalibracja energetyczna i synchronizacja czasowa modularnego scyntylacyjnego systemu detekcyjnego do tomografii TOF-PET
Author: Tomasz Bednarski
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2016
Celem tej pracy było skonstruowanie i uruchomienie pierwszego prototypu urzadzenia
do tomografii pozytonowej wykorzystujacego scyntylatory plastikowe. Wykonany
został 24-modułowy detektor, w którym scyntylatory o wymiarach
5 × 19 × 300 mm3 sa ułozone na pobocznicy walca o srednicy 360 mm. W stosunku
do obecnie dostepnych, komercyjnych skanerów, uruchomiony prototyp tomografu
PET ma około dwa razy wieksze osiowe pole widzenia i jednoczesnie o około 50 ps
(FWHM) lepsza rozdzielczosc czasowa. Dodatkowo w ramach tej pracy zostały przygotowane
i przetestowane metody synchronizacji czasowej i kalibracji energetycznej
detektora.
Uzyskana rozdzielczosc czasowa koincydencji pomiedzy modułami detekcyjnymi
dla anihilacji elektronu z pozytonem w srodku detektora to sigma = 208 ? 4 ps
(FWHM = 490 ps). Natomiast rozdzielczosc przestrzenna uproszczonej rekonstrukcji
(Rozdział 9.1) dla punktowego zródła waha sie od sigma = 26.9 ? 0.2 mm
(FWHM = 63.3 mm) do sigma = 39.6 ? 0.9 mm (FWHM = 93.3 mm) w obszarze od
centrum tomografu do 100 mm od jego osi. Wykonanie rekonstrukcji obrazu metoda
najwiekszej wiarygodnosci MLEM (z ang. Maximum Likelihood Expectation Maximization)
po dziesieciu iteracjach pozwala na otrzymanie poprzecznej rozdzielczosci
przestrzennej FWHM = 18 ? 2 mm (odpowiednio sigma = 7.6 mm) oraz rozdzielczosci
wzdłuz osi detektora FWHM = 27 ? 2 mm (odpowiednio sigma = 11.5 mm).
Osiagniete wyniki były podstawa projektu konstrukcji tomografu w pełnej skali,
tj. o srednicy wewnetrznej 800 mm, osiowym polu widzenia 500 mm i składajacego
sie ze 192 modułów detekcyjnych.
W pracy, potwierdzono, ze mozliwa jest pozytonowa tomografia emisyjna wykorzystujaca
scyntylatory plastikowe, wbrew opiniom uznanym przez prawie 40 lat.
A novel data acquisition system based on fast optical links and universal readout boards
Author: Grzegorz Korcyl
Supervisor: prof. Piotr Salabura
abstract
Defence year: 2015
Various scale measurement systems are composed of the sensors providing data through the data acquisition system to the archiving facility. The scale of such systems is determined by the number of sensors that require processing and can vary from few up to hundreds of thousands. The number and the type of sensors impose several requirements on the data acquisition system like readout frequency, measurement precision and online analysis algorithms. The most challenging applications are the large scale experiments in nuclear and particle physics.
This thesis presents a concept, construction and tests of a modular and scalable, tree-structured architecture of a data acquisition system. The system is composed out of two logical elements: endpoints which are the modules providing data and hubs that concentrate the data streams from the endpoints and provide connectivity with the rest of the system. Those two logical functions are realised by the base modules called Trigger Readout Board (abbr. TRB) which feature basic functionality: digitization of the signals, communication with other modules and external networks, control and monitoring mechanisms. This set of functions can be extended on the modules via a system of Add-on boards that introduce new features and allows to adapt the platform for various applications.
The key characteristics of TRB based system are: scalable, flexible, extensible and reconfigurable. The scalability of the platform is realized by the hub components, which allow to create tree structures with many layers, each opening new ports for additional endpoints, without reducing the performance of the entire system. The TRB boards are based on FPGAs, which are reconfigurable, programmable logic devices. This approach results in a possible use of the same hardware module for different functions with just a change of the firmware. It also allows to introduce new functionalities over time. Together with the Add-on system, the platform can be relatively easily adapted to various applications and extended with new elements.
The platform was developed inside the HADES Collaboration with significant contribution from the author. The HADES detector was also the largest target application and was used for extensive tests of the system. Several conducted experiments and laboratory tests described in this thesis confirm the design and allow to evaluate the system performance. The platform has also found application in various other systems, one of them being the J-PET medical imaging project also described in this thesis.
Badanie zależności wzmocnienia fotopowielaczy krzemowych w funkcji temperatury
Author: Eryk Bluj
abstract
Defence year: 2024
Positron emission tomograph (PET) is a device widely used in medical diagnostics. It is used both to detect the location of tumors in the patient's body and to monitor the treatment process. It is used, for example, in combination with proton therapy. The principle of operation of this device is based on the detection of radiation from the annihilation of positrons created in the process of ?+ decay, which occurs in the patient's body after the injection of a radiopharmaceutical into the body. All PET scanners currently produced are made using crystal scintillators, which are significant in mass and have high production costs. The J-PET group led by prof. dr hab. Paweł Moskal set the goal of constructing a PET scanner using plastic scintillators, which are much lighter than crystal scintillators. A scanner made in this way will be much more mobile and low-cost compared to classic tomographs of this type. In addition to the aforementioned scintillators, a very important element of the PET scanner are also photomultipliers, which together with scintillators are used to convert the aforementioned radiation into a measurable electrical signal. Due to the desire to create a mobile tomograph, photomultipliers should also be as small as possible and at the same time as accurate as possible. For this reason, it was decided to use sillicon photomultipliers (SiPM), which are the main focus of the work. Many parameters characterizing SiPM significantly depend on temperature. The following work focuses on examining one of such dependencies, in order to exclude potential errors related to temperature changes in the PET scanner being created at the Jagiellonian University. The work presents the results of measurements carried out in a narrow temperature range (17?C ? 23?C) for two Hamamatsu S14160-6050HS and two Onsemi MICROFJ-60035-TSV SiPM photomultipliers. An analysis of the signals collected during the measurements was carried out. Using the author's program, histograms of quantities calculated based on the above-mentioned signals (amplitude and total charge) were created, which are a estimate of the energy of the ? quantum on the scintillator. Then the Compton edges appearing in the above-mentioned histograms were determined. The final result of the work is the obtained temperature dependencies of the determined Compton edges. They show a significant decrease in the Compton edge position values with increasing temperature. For Onsemi photomultipliers the temperature changes were ?1.61mV/K and ?1.22mV/K for the amplitude case and ?0.96pC/K and ?0.481pC/K for the charge case, respectively. For the Hamamatsu photomultipliers, these values were ?0.845mV/K and -0.56mV/K for the amplitude case and ?0.340pC/K and ?0.406pC/K for the charge case, respectively. These mean a jump in the Compton edge value by a few percent with a temperature drop of 1?C.
Wyznaczanie optymalnego modelu określającego obszar naświetlania wiązką protonową fantomu PMMA lub wodnego
Author: Mateusz Janus
abstract
Defence year: 2024
In this thesis an analysis of emission profiles obtained after irradiating the PMMA and water phantoms with pencil beam and PBS method, respectively, was performed. The analysis was done by the use of self-made computer program, which can be accessed through the link https://github.com/emdzejski/MJ_praca_licencjacka_kod.git, in order to determine an optimal way of finding an ending point of emission profiles. Profiles were obtained after selection, reconstruction and analysis performed by the team taking part in the experiment examining the use of modular J-PET detector in range monitoring of a proton beam. Time needed for this preliminary work with data exceeds the scope of a bachelor thesis, thus the analysis in this paper began with complete profiles. 5 PMMA phantom (irradiated with a 16 Gy dose) profiles and 7 water phantom (irradiated with a 286 Gy dose) profiles corresponding to each of the irradiation fields were examined. The model was supposed to be a function with a shape of a sigmoid curve. This particular shape was desired, so that the function would resemble the decreasing edge occuring in the profiles. Five such functions were analysed by means of fitting them to each of examined profiles. The ultimate criterion of utility of a given function was the chi-squared test for the water phantom and differences between shifts between fit parameters and referential beam ranges for PMMA phantom. Functions with best results were logistic function, dose-response curve, Hill equation and logistic dose-response curve. Considering relatively simple form of equations for logistic function and dose-response curve, these two functions were chosen as an optimal model of irradiation. The logistic dose-response curve was selected as an optimal model of pencil beam irradiation, because of simpler implementation without any loss of fitting precision.
Study of high-energy photons polarization in Compton scattering using the J-PET detector system
Author: Kamila Kasperska
Supervisor: dr Magdalena Skurzok
abstract
Defence year: 2023
The purpose of this work is the study of the high-energy photons polarization in Compton scattering using the Jagiellonian Positron Emission Tomography scanner (J-PET), more specifically finding the distribution of an angle between incoming and scattered photons polarization planes which opens the door for the polarization studies. Although polarization itself is a well studied phenomenon, until now it was only possible to investigate it in a narrow range of energies, using optical methods. J-PET detector, due to its unique construction, allows the registration of high-energetic gamma quanta emitted by the radioactive source and
coming from the electron-positron annihilation and also their multiple scatterings. It enables to determine the direction of photons momentum vectors, thus the directions of their polarization. In this work three main types of analysis were performed, differing in the energy and origin of the incoming photons: (i) electron-positron annihilation photons, with the energy of 511 keV, (ii) already scattered photons, found between two interactions in the detector with an unknown energy, (iii) 22Ne de-excitation photons, with the energy of 1275 keV. Future measurements of the polarization will allow deeper understanding of the other phenomena,
such as quantum entanglement or testing discrete symmetries in the leptonic sector.
Application of XAD4 water solutions for positronium imaging phantom
Author: Gabriela Łapkiewicz
Supervisor: dr Szymon Niedźwiecki
abstract
Defence year: 2022
Positron Emission Tomography (PET) is a non-invasive method of medical examina- tion, that allows for early diagnosis of diseases (such as cancer) and therapeutic process monitoring. At the heart of this method is registration of gamma quanta sourcing from the direct annihilation of positron originating from ?+ decay and electron from surrounding matter.
Positrons from Beta+ decay can also bond with electrons and create a meta-stable atom called positronium. Positronium exists for a limited period of time dependent on medium properties. Measurement of lifetime of positronium is the subject matter of Positronium Annihilation Lifetime Spectroscopy (PALS).
Positronium Annihilation Lifetime Spectroscopy (PALS) is a research method that uses dependency of the lifetime of positronium on free volume sizes for examining properties and structure of the matter. New PET imaging method developed at Jagiellonian University enables measurement and imaging of the lifetime of ortho-positronium. Research conducted at Jagiellonian University shows that the ortho-positronium lifetime measurement can be applied for medical diagnostics purposes to improve specificity of PET imaging. To assess the accuracy of this new method it is essential to develop a phantom that will allow for measurement of the lifetime of ortho-positronium alongside activity concentration.
Presented in this thesis is a method for assessing mean lifetime of ortho-positronium dependency on concentration of XAD4 and water mixture using PALS technique. Within this dissertation hypothesis was tested, that adding water to XAD4 polymer will result in gradual filling of pores, with increase of water concentration in a mixture and with electron free volume decrease, mean lifetime of ortho-positronium is expected to shorten accordingly. A total of 6 samples were measured: dry XAD4, distilled water and 4 mixtures of XAD4 and water in different concentrations. Acquired lifetime spectra were analysed using PALS Avalanche program. The results of the measurements show dependency of mean lifetime of ortho-positronium on XAD4 mass percentage in water.
The presented method of controlling mean lifetime of ortho-positronium in XAD4 pores will serve in the future to prepare a phantom for assessment of precision of the positronium imaging method developed at Jagiellonian University.
Opracowanie metody oznaczania czasu życia pozytonium w mikropęcherzykach pochodzących z hodowli komórek prawidłowych beta-trzustki
Author: Julia Nizioł
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2021
The phenomenon of positronium formation in biological material brings new possibilities formedical diagnostics. This thesis presents a method for determining mean positronium lifetme in microvesicles isolated from the culture of beta-pancreatic cells using low-vacuum filtration technique combined with the ultracentrifugation. The concentration of microvesicles in the prepared samples was tested with qNano particle analyzer, the operation of which is based on the TRPS (Tunable Resistive Pulse Sensing) technology. Before starting the actual measurements, Positron Annihilation Lifetime Spectrometer was adjusted accordingly, e.g. by equipping it with a thermostat which allows to precisely control the temperature in the system. A series of measurements was performed to check the temperature stability and a calibration curve was obtained, on the basis of which it is possible to accurately determine the temperature of the sample during the measurement. The positron source was additionally secured against leakage, which may occur when testing with liquid samples. Parafilm was used for this purpose, the positronium lifetime in it changes with temperature, what was taken into account in data analysis. The positronium lifetime in microvesicles cultured under normoglycemic and hyperglycemic conditions was investigated. The values were 1.80 ns and 1.77 ns respectively, thus not significantly different from the lifetime determined in the PBS buffer in which microvesicles were suspended (g = 1.80 ns). On the basis of the obtained results, it can be concluded that to conduct research with microvesicles using the presented method, it is necessary that the samples have a higher concentration of vesicles.
Simulations of absorption in the brain of gamma quanta from positronium atoms
Author: Agata Jędruszczak
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2021
Positronium imaging is a new method that can be used for PET scanning. This method allows not only to determine the location of the tumor, but also to analyze the structure of the tissue. What is important is how many gamma quanta from a positronium atom reach the detector. The main goal of this work is to study the absorption in the brain of gamma quanta from a positronium atom. The brain in this study is approximated by a sphere with water. The 3 gamma / 2 gamma ratio, a parameter that reflects the tissue structure, is determined. For this purpose, Monte Carlo simulations of positron decays into 2 gamma and 3 gamma and photon absorption in the brain and skull were performed. The simulation results were compared with theoretical calculations. The results of the percent events for which none of photons scattered in the head are as follows: 26.10 +/- 0.05% for para-positronium and 8.40 +/- 0.03% for ortho-positronium (absorption in the brain), 20.84 +/- 0.05% for para-positronium, 5.46 +/- 0,02% for ortho-positronium (absorption in the brain and in skull). The values of the 3 gamma / 2 gamma ratio from the simulation are: 0.322 +/- 0.002 for absorption in the brain and 0.262 +/- 0.002 for absorption in the brain and skull. The dependence of absorption probability of photons in the head on the location of positronium atom decay in the brain is determined.
Analiza pochodnych steroli i prenoli w próbkach pęcherzyków zewnątrzkomórkowych metodą spektrometrii masowej TOF-SIMS
Author: Agnieszka Babińska
Supervisor: prof. Ewa Stępień
Auxilliary supervisor: dr inż. Magdalena Marzec
abstract
Defence year: 2021
Niniejsza praca ma na celu przedstawienie wyników wykorzystujących spektrometrię masową jonów wtórnych z analizatorem czasu przelotu (ToF-SIMS) do analizy składu lipidowego pęcherzyków zewnątrzkomórkowych, pochodzących z ludzkich komórek beta trzustki hodowanych w warunkach hiperglikemii. ToF-SIMS jest czułą metodą spektrometryczną, stosowaną do jakościowego określania składu powierzchni. Dzięki jej zaawansowanemu rozwojowi, została zaadoptowana do badań biologicznych, gdzie wykorzystywana jest przede wszystkim do analizy lipidów oraz protein.
Zawartość prenoli i steroli w pęcherzykach zewnątrzkomórkowych komórek beta trzustki jest regulowana wieloma czynnikami środowiskowymi, jak i genetycznymi. W części eksperymentalnej, czynnikiem wywołującym widoczne zmiany składu lipidowego były warunki hiperglikemiczne.
Z przeprowadzonej jednoczynnikowej analizy wariancji ANOVA oraz testu Tukey?a wynika, iż dla wszystkich wybranych jonów dla prenoli i steroli występują istotne różnice statystyczne pomiędzy średnimi wartościami intensywności dla warunków normalnych oraz hiperglikemicznych przy p?0,05.
Przeprowadzona analiza potwierdziła, iż wykorzystana technika ToF-SIMS jest skuteczna, zaś jej zaawansowany rozwój sprawił, iż jest coraz częściej stosowana do badań biologicznych, gdzie wykorzystywana jest przede wszystkim do analizy lipidów oraz protein.
Zastosowanie promieniowania kosmicznego do kalibracji czasowej detektora J-PET
Author: Magdalena Styczeń
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2018
The aim of the study was to simulate the passage of cosmic radiation through
the J-PET detection system in order to determine the multiplicity of events with
individual scintillators depending on their orientation.
Results obtained for 10^6 generated events show double and triple multiplicity as
most common ones. Higher multiples were noted in scintillators oriented more
horizontally. Assuming a 100% probability of the reaction of the cosmic radiation
with the scintillator, it has been shown that for multiples greater than one, there
are scintillators through which up to 0.61% of the recorded cosmic radiation
passes.
The obtained results will help in the time calibration of the J-PET detector,
enabling a more accurate estimation of the probability of a given coincidence
occurring.
Badanie czasu życia pozytonium pod kątem diagnostyki nowotworowej za pomocą tomografu J-PET
Author: Zuzanna Bura
Supervisor: dr Michał Silarski
abstract
Defence year: 2018
Celem niniejszej pracy była demonstracja potencjału wykorzystania metody PALS w diagnostyce nowotworowej z wykorzystaniem nowoczesnego pozytonowego tomografu emisyjnego, rozwijanego w Instytucie Fizyki UJ. W tym celu przeprowadzono szereg pomiarów czasów życia orto-pozytonium w materiałach o różnej porowatości, za pomocą skanera J-PET, jako wstęp do dalszych badań nad wykorzystaniem PALS w diagnostyce. Metoda pozytonowej tomografii emisyjnej pozwala nie tylko na wyznaczenie lokalizacji nowotworu, ale również otwiera nowe możliwości w rozpoznawaniu ich rodzajów. Opis podstaw fizycznych tomografii PET znajduje się w rozdziale 1. W rozdziale 2 opisano ogólnie budowę skanera J-PET. Sposób pomiaru i analizy danych został przedstawiony w rozdziale 3, a podsumowanie wykonanych badań znajduje się w ostatnim rozdziale, oznaczonym jako 4.
Feasibility study of proton beam therapy range monitoring by means of the J-PET tomograph
Author: Maria Kawula
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2017
The aim of this work was to determine amount of positron emitters produced in block made of poly methyl methacrylate (PMMA) during proton beam irradiation, check detection efficiency for registartion of annihilation gamma quanta with the plastic J-PET (Jagiellonian Positron Emission Tomography) tomograph and to find spatial resolution of such a scanner. Simulations were prepared using emph{GATE} software.\Obtained numbers of most significant for imaging isotopes: $^{15}$O, $^{11}$C and $^{10}$C for proton beam with energy 175 MeV that consists of 10$^6$ protons, are respectively 1.84 $cdot 10^4$, 4.47$cdot 10^4$, 4.69$cdot 10^3$. Efficiency for registration of gamma quanta by 2.5 cm thick layer of scintilation material used in J-PET scanner is at the level of 22.7\%. Spatial resolution of point source, that emits pairs of gamma quanta with energy 511 keV and is placed at the centre of two modules system (one module consists of ten plastic strips), was defined by point spread function (PSF) in three dimensions: $z$- along detector, $x$,$y$- transve$^3$rsal to detector. For a strip size $0.6cross 2.5cross 50$ cm and the distance between modules of 20 cm results are: PSF$_{z}=1.2$ cm, PSF$_{y}=3.7$ cm, PSF$_{x}=0.1$ cm and for a strip size $0.3cross 1cross 50$ cm and distance between modules of 20 cm results are: PSF$_{z}=1$ cm, PSF$_{y}=3.1$ cm, PSF$_{x}=0.1$ cm.
Plastic scintillators as an alternative for crystals in PET - determination of the counting efficiency
Author: Julia Gnatek
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2017
The aim of this work was to experimentally check the theoretical predictions of plastic scintillators? efficiency. The BC?420 scintillators have been used in the prototype of the J-PET detector. The measurement system consisted of two BaF_2 detectors, a plastic detector, an oscilloscope, 4 photomultipliers and a sodium isotope 22Na (as a source of positrons). The assessment of the plastic scintillators? efficiency was conducted by counting the number of registered and unregistered events from 511 keV gamma ray beam.
The efficiency was determined for 6 detector depths, in particular for 1.9 cm, which is the thickness of plastic scintillators used in the J-PET system. The obtained efficiency for this setup is (11.1 +- 0.3stat +- 3.0syst)%, for events with energy deposited greater than 100 keV, while theoretical prediction is 11.6 % with negligible error.
Badania możliwości jednoczesnego dokonywania pomiarów za pomocą tomografu Jagiellonian-PET oraz tomografu komputerowego.
Author: Nikodem Krawczyk
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2015
Test of Lightguides for the J-PET Detector
Author: Dominika Alfs
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2015
The aim of this work was to test the impact of the lightguides insertion in the J-PET detection system and to choose the best of available solutions. At the two strip J-PET test system a series of measurements was performed with different combinations concerning the length of the lightguides (3 mm and 3 cm) and scintillators (3, 15 and 30 cm), shape of lightguides (trapezoidal and cylindrical, with and without a cut matching the scintillator size) and optical connection between elements (optical gel and glue). It was proven that the insertion of the thin lightguide does not spoil the time resolution and the light output. Additionally, the correlation between the time resolution and the light output was confirmed.
Wyznaczanie miejsca i czasu interakcji kwantu gamma w paskach styntylacyjnych przy użyciu metody największej wiarygodności
Author: Krzysztof Giergiel
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Badanie właściwości detektorów scyntylacyjnych otoczonych lustrami pod kątem zastosowania w Pozytonowej Emisyjnej Tomografii
Author: Adam Ciesielski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Synteza scyntylatorów polimerowych i ich badanie pod kątem zastosowania w obrazowaniu PET
Author: Kamil Dulski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Nieorganiczne scyntylatory używane komercyjnie w Pozytonowej Emisyjnej Tomografii (PET) pomimo dobrych właściwości detekcyjnych posiadają stosunkowo wysoką cenę produkcji. Materiały polimerowe w większości są znacznie tańsze i dlatego warto rozważyć ich użycie w tomografii PET. Znalezienie materiału polimerowego, lub polimeru odpowiednio domieszkowanego, zdolnego zastąpić komercyjne scyntylatory, bez wielkiej straty na dokładności pomiaru, pozwoliłoby na zredukowanie kosztów diagnostyki PET. W tej pracy skupiono się na sprawdzeniu czy związki polimerowe domieszkowane dodatkami luminescencyjnymi, zdołają osiągnąć parametry detekcyjne porównywalne z szeroko stosowanymi materiałami scyntylacyjnymi. Ograniczono się do testów polimerów pod kątem rejestrowania promieniowania o energii zbliżonej do energii promieniowania anihilacyjnego używanego w tomografii PET.
Synteza scyntylatorów polimerowych domieszkowanych ciężkimi atomami
Author: Arkadiusz Janas
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2013
Celem niniejszej pracy jest wprowadzenie ciężkich atomów do scyntylatorów polimerowych w celu maksymalnego zwiększenia prawdopodobieństwa wystąpienia efektu fotoelektrycznego co wiąże się z zwiększeniem wydajności świetlnej scyntylatora a tym samym możliwością detekcji promieniowania jonizującego. Synteza polega na sporządzeniu roztworów o odpowiedniej ilości monomeru, inicjatora oraz związków zawierających ciężkie atomy w tym wypadku jest są to atomy ołowiu w postaci dimetakrylanu ołowiu. Przygotowany roztwór polimeryzuje poprzez polimeryzację rodnikową w masie. Scyntylatory polimerowe są najczęściej używane do celów diagnostycznych w pozytonowej emisyjnej tomografii komputerowej.
