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2 Bio-Algorithms and Med-Systems

2 2023

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J-PET application as a Compton camera for proton beam range verification: A preliminary study

Kozani Majid, Rucinski Antoni, Moskal Pawel

Bio-Algorithms and Med-Systems

2023

Vol. 19, no. 1

23--30

Hybrid in-beam PET/Compton camera imaging currently shows a promising approach to use of the quasi-real-time range verification technique in proton therapy. This work aims to assess the capability of utilizing a configuration of the Jagiellonian-positron emission tomography (J-PET) scanner made of plastic scintillator strips, so as to serve as a Compton camera for proton beam range verification. This work reports the production yield results obtained from the GATE/Geant4 simulations, focusing on an energy spectrum (4.2-4.6) MeV of prompt gamma (PG) produced from a clinical proton beam impinging on a water phantom. To investigate the feasibility of J-PET as a Compton camera, a geometrical optimisation was performed. This optimisation was conducted by a point spread function (PSF) study of an isotropic 4.44 MeV gamma source. Realistic statistics of 4.44 MeV PGs obtained from the prior step were employed, simulating interactions with the detector. A sufficient number of detected photons was obtained for the source position reconstruction after performing a geometry optimisation for the proposed J-PET detector. Furthermore, it was demonstrated that more precise calculation of the total deposited energy of coincident events plays a key role in improving the image quality of source distribution determination. A reasonable spatial resolution of 6.5 mm FWHM along the actual proton beam direction was achieved for the first imaging tests. This preliminary study has shown notable potential in using the J-PET application for in-beam PET/Compton camera imaging at quasi-real-time proton range monitoring in future clinical use.

Application of quantum entanglement induced polarization for dual-positron and prompt gamma imaging

Romanchek Gregory, Shoop Greyson, Abbaszadeh Shiva

Bio-Algorithms and Med-Systems

2023

Vol. 19, no. 1

9--16

The intrinsic resolution of Positron Emission Tomography (PET) imaging is bound by positron range effects, wherein the radioactive decay of the imaging tracer occurs at a disjoint location from positron annihilation. Compounding this issue are the variable ranges positrons achieve, depending on tracer species (the energy they are emitted with) and the medium they travel in (bone vs soft tissue, for example) - causing the range to span more than an order of magnitude across various study scenarios (~0.19 mm to ~6.4 mm). Radioisotopes, such as Zr-89, exhibit dual emissions of positron and prompt gammas, offering an opportunity for accurate tracer positioning as prompt gammas originate from the tracer location. These multi-emission radiotracers have historically suffered from increased noise corresponding to the third gamma interfering in annihilation gamma coincidence pairing. Recent advancements, however, have brought to light the unique property of annihilation gammas having scattering kinematics distinct from random gamma pairs. These properties are born from the singular quantum entanglement state available to the gamma pair following para-positronium decay which prescribes linearly orthogonal polarization. Such coherent polarization is not shared by prompt gamma emissions, offering an opportunity for their discrimination. We present an investigation into this technique, comparing the distribution of relevant scattering kinematics of entangled annihilation gammas and corresponding prompt gammas via a Monte Carlo simulation.