Marian Smoluchowski
Institute of Physics

Jagiellonian University in Kraków

Bachelor thesis

Application of XAD4 water solutions for positronium imaging phantom

Supervisor: dr Szymon Niedźwiecki

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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.

CONFERENCE PROCEEDINGS POSTERS

1. Feasibility study of positronium imaging with Biograph Vision Quadra and Modular J-PET
   S. Parzych, J. Baran, E. Yitayew Beyene, M. Conti, A. Coussat, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Valsan Eliyan, A. Gajos, B. Hiesmayr, A. Jędruszczak, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Łapkiewicz, L. Mercolli, W. Migdał, S. Moyo, W. Mryka, S. Niedźwiecki, E. Pérez Del Río, L. Raczyński, A. Rominger, H. Sari, S. Sharma, K. Shi, S. Shivani, R. Shopa, M. Skurzok, W.M. Steinberger, E. Stępień, P. Tanty, F. Tayefi, K. Tayefi Ardebili, W. Wiślicki, P. Moskal
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   published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
   Positronium Imaging is gaining interest as a new promising method that may improve the diagnostic specificity of Positron Emission Tomography. Recently, the first ex-vivo and in-vivo positronium lifetime images were demonstrated by means of the dedicated multi-photon J-PET system. The latest upgrades of the Biograph Vision Quadra (Siemens Healthineers) to the singles mode acquisition open the possibility of multi-photon imaging. In this simulation-based work, sensitivity of both systems has been assessed as a function of the energy window applied for registration of the prompt photon. The research was conducted using four radioisotopes: 124 I, 68 Ga, 44 Sc, 22 Na, which were chosen due to their medical or laboratory utilization. Simulations were performed with the GATE software. The result indicates that Biograph Vision Quadra provides about 400 times higher sensitivity with respect to the modular J-PET prototype used to demonstrate the first positronium images, assuming full energy acquisition of the prompt photon.
2. Performance of NEMA characteristics of Modular J-PET
   F. Tayefi Ardebili, S. Niedźwiecki, J. Baran, E. Beyene, D. Borys, K. Brzezinski, N. Chug, A. Coussat, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Eliyan, J. Gajewski, A. Gajos, B. Hiesmayr, A. Jędruszczak, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Łapkiewicz, W. Migdał, S. Moyo, W. Mryka, S. Parzych, E. Pérez del Río, L. Raczyński, S. Sharma, S. Shivani, R. Shopa, M. Skurzok, P. Tanty, K. Tayefi Ardebili, W. Wislicki, E. Stępień, P. Moskal
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   published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
   The Modular J-PET scanner, developed by the J-PET collaboration, is a new prototype PET scanner developed based on axially arranged plastic scintillators as a large axial field of view (50cm) affordable tomograph. In this study, the performance characteristics of the scanner were evaluated according to NEMA NU2-2018 standards using Monte Carlo simulation. In order to ensure the selection of true coincidence events, certain criteria were established. Specifically, each photon emitting from a single annihilation must deposit at least 200 keV within 4 ns of a coincidence time window. The preliminary results showed that the sensitivity profile peak was 4 cps/kBq at the center of the detector, While the scatter fraction was estimated to be 39% using the single slice rebinning algorithm. Spatial resolution was estimated around 4.5 mm in the radial and tangential direction and 18 mm in the axial direction.
3. Normalization and scatter corrections for the J-PET scanner
   A. Coussat, W. Krzemień, J. Baran, S. Parzych, L. Raczyński, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, J. Gajewski, B. Hiesmayr, K. Valsan Eliyan, A. Jędruszczak, K. Kacprzak, A. Gajos, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, T. Kozik, G. Łapkiewicz, G. Korcyl, S. Moyo, D. Kumar, W. Mryka, S. Niedźwiecki, S. Sharma, E. Pérez Del Río, S. Shivani, R. Shopa, P. Tanty, M. Skurzok, K. Tayefi, F. Tayefi, E. Stępień, W. Wiślicki, P. Moskal
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   published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
   The Jagiellonian PET scanner is a cost-effective large axial FOV Positron Emission Tomography technology that enables multi-photon imaging and is currently under development at the Jagiellonian University. The current 50 cm prototype, named Modular J-PET, is being investigated for various applications. It is well known that PET data can be affected by several effects during acquisition, such as scattered gamma photons or variations in detection efficiency. Consequently, achieving the reconstruction of images of satisfactory quality requires a set of corrections to be applied to each line-of-response. This summary discusses the implementation and performance of scatter and normalization corrections for the Modular J-PET, and their extension prior to the assembly of a total-body Jagiellonian PET scanner. Normalization correction is achieved using component-based normalization, a method particularly suitable for large scanners with a high number of lines-of-response. Scatter correction is achieved using an extension of the single scatter simulation technique that incorporates time-of-flight information. Reconstruction of reference phantoms based on Monte Carlo simulations highlight improvements in image quality. The application of normalization reduces the non-uniformity in the reconstructed image by a factor of 10 in the axial direction and 2 in the radial direction.
4. Positronium Lifetime Measurements using 82Rb in a Long-Axial FOV PET/CT Scanner
   W.M. Steinberger, H. Sari, L. Mercolli, S. Parzych, S. Niedźwiecki, G. Łapkiewicz, P. Moskal, E. Stępień, A. Rominger, K. Shi, M. Conti
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   published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors
   This work details results from two positronium (Ps) lifetime measurements performed in a long-axial FOV PET/CT scanner using 82 Rb. Ps lifetime measurements are of interest for PET because they can yield additional diagnostic information. The first measurement placed drops of a 82 Rb solution in between aluminum disks, quartz disks, and into a gelatin mixture. The extracted ortho-Ps (o-Ps) lifetime for the quartz sample was measured to be 1.53+/-0.04 ns, which agrees well with the previously published value of 1.56+/-0.08 ns. The lifetime of the aluminum is also compared with previous results, however, the lifetime exhibits a longer o-Ps lifetime due to positrons leaking into the surrounding plastic holder. The second measurement performed assessed the uniformity of the extracted lifetimes across a uniform cylinder (20?×30 cm3 ) filled with water and an activity of approximately 73.3 MBq. The resulting histo-image was sliced into 1.25 cm thick cross sections, which resulted in lifetime distributions containing on average 1.98×10 5 +/-1.06×10 4 counts. These lifetime distributions were integral normalized and compared to an averaged lifetime across the uniform cylinder. Overall average deviation in the lifetime measured across the cylinder was determined to be -0.015+/-1.53%.
5. Developing a phantom for the positronium imaging evaluation
   G. Łapkiewicz, S. Niedźwiecki, P. Moskal
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   published in: Acta Phys. Polon. B Proc. Suppl. 15 (2022) 4-A4
   In this contribution, a concept for a new phantom for positronium imaging with PET scanners is described. The proposed phantom is based on the NEMA IEC phantom in which six high-activity spheres are filled with solutions characterized by a different mean ortho-positronium lifetime. A method for controlling ortho-positronium lifetime is discussed along with preliminary results. The XAD4 suspended in various fractions of water was tested as a potential model of a sample with a controlled mean lifetime of ortho-positronium. The mean lifetime of ortho-positronium for six samples was estimated by means of the Positronium Annihilation Lifetime Spectroscopy (PALS). Obtained spectra were fitted with the PALS Avalanche analysis program and components corresponding to the ortho-positronium annihilation in the XAD4 pores were established. As a result, the correlations between the lifetime and production intensity of ortho-positronium and the concentration of XAD4 in water were determined.

1. Feasibility study of positronium imaging with Biograph Vision Quadra and Modular J-PET
   S. Parzych, J. Baran, E. Y. Beyene, M. Conti, A. Coussat, N. Chug, C. Curceanu, E. Czerwiński, M. Dadgar, K. Dulski, K. Valsan Eliyan, A. Gajos, B. Hiesmayr, A. Jedruszczak, K. Kacprzak, M. Kajetanowicz, T. Kaplanoglu, Ł. Kapłon, K. Klimaszewski, G. Korcyl, T. Kozik, W. Krzemień, D. Kumar, G. Łapkiewicz, L. Mercolli, W. Migdał, S. Moyo, W. Mryka, S. Niedźwiecki, E. Perez del Rio, L. Raczyński, A. Rominger, H. Sari, S. Sharma, K. Shi, Shivani, R. Y. Shopa, M. Skurzok, W. M. Steinberger, E. Ł. Stępień, P. Tanty, F. Tayefi, K. Tayefi, W. Wiślicki, P. Moskal
   2023 IEEE Nuclear Science Symposium and Medical Imaging Conference
2. Developing a phantom for the positronium imaging evaluation
   G. Łapkiewicz, S. Niedźwiecki, P. Moskal
   4th Jagiellonian Symposium on Advances in Particle Physics and Medicine, Cracow, Poland, July 2022

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