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. 2024 Jun 28;2(2):3330.
doi: 10.36922/arnm.3330. Epub 2024 Jun 14.

Combining PET and Compton imaging with edge-on CZT detectors for enhanced diagnostic capabilities

Greyson Shoop  1 , Shiva Abbaszadeh  1
Affiliations

Combining PET and Compton imaging with edge-on CZT detectors for enhanced diagnostic capabilities

Greyson Shoop et al. Adv Radiother Nucl Med. .

Abstract

The key metrics for positron emission tomography (PET) imaging devices include the capability to capture the maximum available amount of annihilation photon information while generating high-quality images of the radiation distribution. This capability carries clinical implications by reducing scanning time for imaging, thus reducing radiation exposure for patients. However, imaging quality is degraded by positron range effects and the non-collinearity of positron annihilation photons. Utilizing an edge-on configuration of cadmium zinc telluride (CZT) detector crystals offers a potential solution to increase PET sensitivity. The high cross-section of CZT and its capacity to detect both 511 keV annihilation gammas and high-energy prompt gammas, along with multiple photon interaction events, contribute to this increased sensitivity. In this study, we propose a dual-panel edge-on CZT detector system comprised of 4 × 4 × 0.5 cm3 CZT detectors, with panel dimensions of 20 × 15 cm2 and a thickness of 4 cm. In this study, we demonstrate the increased sensitivity of our imaging system due to the detection of the Compton kinematics of high-energy gammas originating from prompt-gamma-emitting isotopes. This was achieved using Monte Carlo simulations of a prompt-gamma-emitting isotope,72As, with mean positron ranges >3 mm. Our system's dynamic energy range, capable of detecting gammas up to 1.2 MeV, allows it to operate in a dual-mode fashion as both a Compton camera (CC) and standard PET. By presenting reconstructions of 72As, we highlight the absence of positron range effects in CC reconstructions compared to PET reconstructions. In addition, we evaluate the system's increased sensitivity resulting from its ability to detect high-energy prompt gammas.

Keywords: Compton camera; Multi-isotope imaging; Positron emission tomography/computed tomography; Positron range.

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Conflict of interest statement

Conflict of interest The authors declare that they have no competing interests.

Figures

Figure 1.
Figure 1.
Depiction of positron decay for non-pure positron emitters. Annihilation photons represent the position of positron annihilation position and not the radionuclide position.
Figure 2.
Figure 2.
Triple-gamma coincidence techniques for pseudo-time-of-flight image reconstruction Abbreviations: COR: Cone of response; LOR: Line of response.
Figure 3.
Figure 3.
System geometry visualized in Geant4 application for tomography emission. (A) View of dual panel system with dimensions and cartesian coordinate axis. (B) View of dual panel system along y-z plane. (C) View of dual panel system along x-z plane.
Figure 4.
Figure 4.
Experiment visualization. A 0.1 mm radius 72As spherical point source with 2 MBq of activity is placed at the origin within a spherical water phantom of 2 cm diameter. The source is located at (0, 0, 0) mm central to the orientation of the dual panel system.
Figure 5.
Figure 5.
Energy deposition histogram from Geant4 application for tomography emission simulation. Energy deposition spectrum from cadmium zinc telluride detector from simulation of a 2 MBq 72As point source with photoelectric events (phot) and Compton scattering events (compt) plotted separately.
Figure 6.
Figure 6.
Maximum likelihood expectation maximization reconstruction after 20 iterations. (A) Positron emission tomography reconstructions along all imaging planes. (B) Compton camera (CC) reconstructions along all imaging planes were performed with 1 keV of energy blurring. Abbreviation: LOR: Line of response.
Figure 7.
Figure 7.
Maximum likelihood expectation maximization reconstruction after 800 iterations. (A) Positron emission tomography reconstructions along all imaging planes. (B) Compton camera reconstructions along all imaging planes were performed with 51 keV of energy blurring. Abbreviation: LOR: Line of response.
Figure 8.
Figure 8.
Maximum likelihood expectation maximization reconstruction after 3500 iterations. (A) Positron emission tomography (PET) reconstructions along all imaging planes. (B) Compton camera reconstructions along all imaging planes were performed with 51 keV of energy blurring. Abbreviation: LOR: Line of response.
Figure 9.
Figure 9.
Normalized activity profiles of Figure 6 with Gaussian fits after 20 iterations of MLEM. (A) Top row, normalized activity profiles in the x, y, and z directions of positron emission tomography MLEM. (B) Bottom row, normalized activity profiles in the x, y, and z directions of Compton camera MLEM. Abbreviation: MLEM: Maximum likelihood expectation maximization.
Figure 10.
Figure 10.
Normalized activity profiles of Figure 7 with Gaussian fits after 800 iterations of MLEM. (A) Top row, normalized activity profiles in the x, y, and z directions of positron emission tomography MLEM. (B) Bottom row, normalized activity profiles in the x, y, and z directions of Compton camera MLEM. Abbreviation: MLEM: Maximum likelihood expectation maximization.
Figure 11.
Figure 11.
Normalized activity profiles of Figure 8 with Gaussian fits after 3500 iterations of MLEM. (A) Top row, normalized activity profiles in the x, y, and z directions of positron emission tomography MLEM. (B) Bottom row, normalized activity profiles in the x, y, and z directions of Compton camera MLEM. Abbreviation: MLEM: Maximum likelihood expectation maximization.
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References

    1. Dolgin E. Radioactive drugs emerge from the shadows to storm the market. Nat Biotechnol. 2018;36(12):1125–1127. doi: 10.1038/nbt1218-1125 - DOI - PubMed
    1. Bodei L, Herrmann K, Schöder H, Scott AM, Lewis JS. Radiotheranostics in oncology: Current challenges and emerging opportunities. Nat Rev Clin Oncol. 2022;19(8):534–550. doi: 10.1038/s41571-022-00652-y - DOI - PMC - PubMed
    1. Sgouros G, Bodei L, McDevitt MR, Nedrow JR. Radiopharmaceutical therapy in cancer: Clinical advances and challenges. Nat Rev Drug Discov. 2020;19(9):589–608. doi: 10.1038/s41573-020-0073-9 - DOI - PMC - PubMed
    1. Chomet M, Schreurs M, Vos R, et al. Performance of nanoScan PET/CT and PET/MR for quantitative imaging of 18F and 89Zr as compared with ex vivo biodistribution in tumor-bearing mice. EJNMMI Res. 2021;11:57. doi: 10.1186/s13550-021-00799-2 - DOI - PMC - PubMed
    1. Ferguson S, Jans HS, Wuest M, Riauka T, Wuest F. Comparison of scandium-44 g with other PET radionuclides in pre-clinical PET phantom imaging. EJNMMI Phys. 2019;6(1):23. doi: 10.1186/s40658-019-0260-0 - DOI - PMC - PubMed