We report a study of the original image reconstruction algorithm based on the time-of-flight maximum-likelihood expectation-maximization (TOF MLEM), developed for the total-body (TB) Jagiellonian PET ...(J-PET) scanners. The method is applicable to generic cylindrical or modular multilayer layouts and is extendable to multiphoton imaging. The system response matrix (SRM) is represented as a set of analytical functions, uniquely defined for each pair of plastic scintillator strips used for the detection. A realistic resolution model (RM) in detector space is derived from fitting the Monte Carlo simulated emissions and detections of annihilation photons on oblique transverse planes. Additional kernels embedded in SRM account for time-of-flight (TOF), parallax effect, and axial smearing. The algorithm was tested on datasets, simulated in GATE for the NEMA IEC and static extended cardiac-torso phantoms inside a 24-module 2-layer TB J-PET. Compared to the reference TOF MLEM with none or a shift-invariant RM, an improvement was observed, as evaluated by the analysis of image quality, difference images, and ground-truth metrics. We also reconstructed the data with additive contributions, prefiltered geometrically and with non-TOF scatter correction applied. Despite some deterioration, the obtained results still capitalize on the realistic RM with better edge preservation and superior ground-truth metrics. The envisioned prospects of the TOF MLEM with analytical SRM include its application in multiphoton imaging and further upgrade to account for the noncollinearity, positron range, and other factors.
J-PET is the first positron-emission tomograph (PET) constructed from plastic scintillators. It was optimized for the detection of photons from electron-positron annihilation. Such photons, having an ...energy of 511 keV, interact with electrons in plastic scintillators predominantly via the Compton effect. Compton scattering is at most probable at an angle orthogonal to the electric field vector of the interacting photon. Thus registration of multiple photon scatterings with J-PET enables to determine the polarization of the annihilation photons. In this contribution we present estimates on the physical limitation in the accuracy of the polarization determination of 511 keV photons with the J-PET detector.
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The Jagiellonian Positron Emission Tomograph (J-PET) is a novel device being developed at Jagiellonian University in Krakow, Poland based on organic scintillators. J-PET is an axially symmetric (M. ...Mohammed) has been affiliated to affiliation 6. Please check if correct, otherwise, provide the correct affiliation.and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pursue tests of discrete symmetries in decays of positronium in addition to medical imaging. J-PET enables the measurement of both momenta and the polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows the study of time reversal symmetry violation operator which can be constructed solely from the annihilation photons momenta before and after the scattering in the detector.
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We present new Fe and Si isotope ratio data for the Torres del Paine igneous complex in southern Chile. The multi-composition pluton consists of an approximately 1 km vertical exposure of homogenous ...granite overlying a contemporaneous 250-m-thick mafic gabbro suite. This first-of-its-kind spatially dependent Fe and Si isotope investigation of a convergent margin-related pluton aims to understand the nature of granite and silicic igneous rock formation. Results collected by MC-ICP-MS show a trend of increasing δ
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Fe and δ
30
Si with increasing silica content as well as a systematic increase in δ
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Fe away from the mafic base of the pluton. The marginal Torres del Paine granites have heavier Fe isotope signatures (δ
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Fe = +0.25 ± 0.02 2se) compared to granites found in the interior pluton (δ
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Fe = +0.17 ± 0.02 2se). Cerro Toro country rock values are isotopically light in both Fe and Si isotopic systems (δ
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Fe = +0.05 ± 0.02 ‰; δ
30
Si = −0.38 ± 0.07 ‰). The variations in the Fe and Si isotopic data cannot be accounted for by local assimilation of the wall rocks, in situ fractional crystallization, late-stage fluid exsolution or some combination of these processes. Instead, we conclude that thermal diffusion or source magma variation is the most likely process producing Fe isotope ratio variations in the Torres del Paine pluton.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Müntener and Baumgartner (Contrib Mineral Petrol,
2019
) comment on our interpretations of the petrogenetic processes operating within the Torres del Paine Intrusive complex (Gajos et al., in Contrib ...Mineral Petrol 171(11):93,
2016
). The issues raised reflect either points that are subject to interpretation or misrepresentations of the data we provided. We dispute field observations and counter that their model reflects over-interpretation due to limited age dating. We provide new geothermometry data indicating that marginal granites formed in a cold environment, consistent with our original model. The Fe and Sr data are not consistent with their two endmember mixing argument. We conclude by reaffirming our position that the thermal migration zone refining process provides a viable explanation for the isotopic variation and construction of the Torres del Paine pluton.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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