Performance of three-photon PET imaging: Monte Carlo simulations

Kacperski, Krzysztof; Spyrou, N. M.

doi:10.1088/0031-9155/50/23/019

Cited by 22 publications

(14 citation statements)

References 21 publications

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“…15 Finally, there are other processes which can also yield tri-ple coincidences, like random triple events caused by three different decays, or positron annihilations generating three γ-rays via the formation of orthopositronium. 16 These events do not provide information about the LORs in which a decay occur, but as they are typically one or two orders of magnitude less frequent 8,17 than the aforementioned triple coincidences, we did not consider them in this work.…”

Section: Introductionmentioning

confidence: 99%

Recovery and normalization of triple coincidences in PET

et al. 2015

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Purpose: Triple coincidences in positron emission tomography (PET) are events in which three γ-rays are detected simultaneously. These events, though potentially useful for enhancing the sensitivity of PET scanners, are discarded or processed without special consideration in current systems, because there is not a clear criterion for assigning them to a unique line-of-response (LOR). Methods proposed for recovering such events usually rely on the use of highly specialized detection systems, hampering general adoption, and/or are based on Compton-scatter kinematics and, consequently, are limited in accuracy by the energy resolution of standard PET detectors. In this work, the authors propose a simple and general solution for recovering triple coincidences, which does not require specialized detectors or additional energy resolution requirements. Methods: To recover triple coincidences, the authors' method distributes such events among their possible LORs using the relative proportions of double coincidences in these LORs. The authors show analytically that this assignment scheme represents the maximum-likelihood solution for the triple-coincidence distribution problem. The PET component of a preclinical PET/CT scanner was adapted to enable the acquisition and processing of triple coincidences. Since the efficiencies for detecting double and triple events were found to be different throughout the scanner field-of-view, a normalization procedure specific for triple coincidences was also developed. The effect of including triple coincidences using their method was compared against the cases of equally weighting the triples among their possible LORs and discarding all the triple events. The authors used as figures of merit for this comparison sensitivity, noise-equivalent count (NEC) rates and image quality calculated as described in the NEMA NU-4 protocol for the assessment of preclinical PET scanners. Results: The addition of triple-coincidence events with the authors' method increased peak NEC rates of the scanner by 26.6% and 32% for mouse-and rat-sized objects, respectively. This increase in NEC-rate performance was also reflected in the image-quality metrics. Images reconstructed using double and triple coincidences recovered using their method had better signal-to-noise ratio than those obtained using only double coincidences, while preserving spatial resolution and contrast. Distribution of triple coincidences using an equal-weighting scheme increased apparent system sensitivity but degraded image quality. The performance boost provided by the inclusion of triple coincidences using their method allowed to reduce the acquisition time of standard imaging procedures by up to ∼25%. parameters like spatial resolution or contrast.

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Section: Introductionmentioning

confidence: 99%

Recovery and normalization of triple coincidences in PET

et al. 2015

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“…Furthermore, the random counts recorded by the scanner for [Fe] = 3 mM is within 0.05% of the counts expected for a 6% increase in count rate relative to the [Fe] = 0 measurement. Furthermore, scintillators currently used in PET scanners, with an energy resolution that is typically worse than 15% at 662 keV and 35% at 340 keV, have low efficiency and sensitivity for detecting three annihilation photons (with a continuum spectrum) 31 . Nevertheless, triple coincidences may be identified by operating the scanner in LIST mode 32 .…”

Section: Phantom Numbermentioning

confidence: 99%

Positron annihilation localization by nanoscale magnetization

Gholami

Yuan

Wilks

et al. 2020

Sci Rep

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In positron emission tomography (PET), the finite range over which positrons travel before annihilating with an electron places a fundamental physical limit on the spatial resolution of PET images. After annihilation, the photon pair detected by the PET instrumentation is emitted from a location that is different from the positron-emitting source, resulting in image blurring. Here, we report on the localization of positron range, and hence annihilation quanta, by strong nanoscale magnetization of superparamagnetic iron oxide nanoparticles (SPIONs) in PET-MRI. We found that positron annihilations localize within a region of interest by up to 60% more when SPIONs are present (with [Fe] = 3 mM) compared to when they are not. The resulting full width at half maximum of the PET scans showed the spatial resolution improved by up to $$\approx$$ ≈ 30%. We also found evidence suggesting that the radiolabeled SPIONs produced up to a six-fold increase in ortho-positronium. These results may also have implications for emerging cancer theranostic strategies, where charged particles are used as therapeutic as well as diagnostic agents and improved dose localization within a tumor is a determinant of better treatment outcomes.

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“…In this work, time windowing, signal processing and readout electronics were not simulated. Only annihilation into two photons were simulated; that of other numbers has been presented elsewhere [14].…”

Section: Annihilation Under Pet Conditionsmentioning

confidence: 99%