Positron range in tissue-equivalent materials: experimental microPET studies

Alva‐Sánchez, Héctor; Quintana-Bautista, Christian; Martínez‐Dávalos, A.; Ávila‐Rodríguez, Miguel A.; Rodríguez‐Villafuerte, M.

doi:10.1088/0031-9155/61/17/6307

Cited by 19 publications

(50 citation statements)

References 21 publications

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“…This dependency is clearly demonstrated at the interface between different tissues as shown in Figure 6. These findings are in agreement with previous studies on the positron range (Rickey et al, 1992;Cal-González et al, 2009;Shah et al, 2014;Alva-Sánchez et al, 2016;Huang et al, 2016;Caribé et al, 2017), and confirm a reduced positron range in the perpendicular direction of a magnetic field. Moreover, studies have also indicated (Iida et al, 1986;Wirrwar et al, 1997;Soultanidis et al, 2011;Kraus et al, 2012) that a higher magnetic field will also induce a greater reduction of the positron range.…”

Section: Discussionsupporting

confidence: 93%

“…Furthermore, the positron range relates directly to the energy of the positron (Kemerink et al, 2011;Emond et al, 2019). Studies with various PET radioisotopes have reported a larger reduction of the positron range for isotopes emitting positrons with a higher energy such as 120 I (Herzog et al, 2010), 82 Rb (Rahmim et al, 2008); or 68 Rb (Wirrwar et al, 1997;Cal-González et al, 2009;Soultanidis et al, 2011;Alva-Sánchez et al, 2016;Li et al, 2017). In order to reduce the blurring effect of the positron range, it can be modeled as part of Point Spread Function (PSF), used in the reconstruction algorithm to model the PET system response.…”

Section: Introductionmentioning

confidence: 99%

“…Visualization of the GATE model of the GE Signa PET/MR system including the NEMA NECR (right) and sensitivity (left) phantom with a 70-cm-line activity source (red). The PET system consists of 5 rings of 28 detector blocks (25 mm × 4.0 mm × 5.3 mm) based on lutetium-yttrium-oxyorthosilicate (LYSO) crystals with MR-compatible SiPM technology(Alva-Sánchez et al, 2016). This results in an axial and transaxial FOV of 25 and 60 cm, respectively.…”

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confidence: 99%

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Monte Carlo Simulations of the GE Signa PET/MR for Different Radioisotopes

et al. 2020

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NEMA characterization of PET systems is generally based on 18 F because it is the most relevant radioisotope for the clinical use of PET. 18 F has a half-life of 109.7 min and decays into stable 18 O via β+ emission with a probability of over 96% and a maximum positron energy of 0.633 MeV. Other commercially available PET radioisotopes, such as 82 Rb and 68 Ga have more complex decay schemes with a variety of prompt gammas, which can directly fall into the energy window and induce false coincidence detections by the PET scanner. Methods: Aim of this work was threefold: (A) Develop a GATE model of the GE Signa PET/MR to perform realistic and relevant Monte Carlo simulations (B) Validate this model with published sensitivity and Noise Equivalent Count Rate (NECR) data for 18 F and 68 Ga (C) Use the validated GATE-model to predict the system performance for other PET isotopes including 11 C, 15 O, 13 N, 82 Rb, and 68 Ga and to evaluate the effect of a 3T magnetic field on the positron range. Results: Simulated sensitivity and NECR tests performed with the GATE-model for different radioisotopes were in line with literature values. Simulated sensitivities for 18 F and 68 Ga were 21.2 and 19.0 /kBq, respectively, for the center position and 21.1 and 19.0 cps/kBq, respectively, for the 10 cm off-center position compared to the corresponding measured values of 21.8 and 20.0 cps/kBq for the center position and 21.1 and 19.6 cps/kBq for the 10 cm off-center position. In terms of NECR, the simulated peak NECR was 216.8 kcps at 17.40 kBq/ml for 18 F and 207.1 kcps at 20.10 kBq/ml for 68 Ga compared to the measured peak NECR of 216.8 kcps at 18.60 kBq/ml and 205.6 kcps at 20.40 kBq/ml for 18 F and 68 Ga, respectively. For 11 C, 13 N, and 15 O, results confirmed a peak NECR similar to 18 F with the effective activity concentration scaled by the inverse of the positron fraction. For 82 Rb, and 68 Ga, the peak NECR was lower than for 18 F while the corresponding activity concentrations were higher. For the higher energy positron emitters, the positron range was confirmed to be

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Monte Carlo Simulations of the GE Signa PET/MR for Different Radioisotopes

et al. 2020

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“…In that study using imaging plates similar to that in our study (BAS-SR 2025), the spatial resolution of 18 F (E max 0.63 MeV) was 339 ± 24 μm (FWHM) and that of 15 O (E max 1.73 MeV), which is close to that of 68 Ga (E max 1.899 MeV), was 420 ± 72 μm (FWHM). Thus, the differences may partly be explained by the lower spatial resolution when using 68 Ga. For micro-PET, the spatial resolution for 18 F in water is 2.0 mm (FWHM) versus 2.8 mm for 68 Ga leading to similar effects [ 37 ].…”

Section: Discussionmentioning

confidence: 99%

High uptake of 68Ga-PSMA and 18F-DCFPyL in the peritumoral area of rat gliomas due to activated astrocytes

et al. 2020

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Background: Recent studies reported on high uptake of the PSMA ligands [ 68 Ga]HBED-CC (68 Ga-PSMA) and 18 F-DCFPyL in cerebral gliomas. This study explores the regional uptake and cellular targets of 68 Ga-PSMA and 18 F-DCFPyL in three different rat glioma models. Methods: F98, 9 L, or U87 rat gliomas were implanted into the brains of 38 rats. After 13 days of tumor growth, 68 Ga-PSMA (n = 21) or 18 F-DCFPyL (n = 17) was injected intravenously, and animals were sacrificed 40 min later. Five animals for each tracer and tumor model were additionally investigated by micro-PET at 20-40 min post injection. Cryosections of the tumor bearing brains were analyzed by ex vivo autoradiography and immunofluorescence staining for blood vessels, microglia, astrocytes, and presence of PSMA. Blood-brain barrier (BBB) permeability was tested by coinjection of Evans blue dye (EBD). 68 Ga-PSMA uptake after restoration of BBB integrity by treatment with dexamethasone (Dex) was evaluated in four animals with U87 gliomas. Competition experiments using the PSMA-receptor inhibitor 2-(phosphonomethyl)pentane-1,5-dioic acid (PMPA) were performed for both tracers in two animals each. Results: Autoradiography demonstrated a strong 68 Ga-PSMA and 18 F-DCFPyL binding in the peritumoral area and moderate binding in the center of the tumors. PMPA administration led to complete inhibition of 68 Ga-PSMA and 18 F-DCFPyL binding in the peritumoral region. Restoration of BBB by Dex treatment reduced EBD extravasation but 68 Ga-PSMA binding remained unchanged. Expression of activated microglia (CD11b) was low in the intra-and peritumoral area but GFAP staining revealed strong activation of astrocytes in congruency to the tracer binding in the peritumoral area. All tumors were visualized in micro PET, showing a lower tumor/brain contrast with 68 Ga-PSMA than with 18 F-DCFPyL. Conclusions: High uptake of 68 Ga-PSMA and 18 F-DCFPyL in the peritumoral area of all glioma models is presumably caused by activated astrocytes. This may represent a limitation for the clinical application of PSMA ligands in gliomas.

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“…Historically, the most often-cited distribution utilized for Monte Carlo-based comparisons of positron range blurring effects arising from different radionuclides has not been the density of positron annihilations (aPSF) itself, but rather its projection into a single dimension [3][4][5][6][7]18] (see Fig. 3), viz…”

Section: Kernel Characterization and Notationmentioning

confidence: 99%

The Impact of Positron Range on PET Resolution, Evaluated with Phantoms and PHITS Monte Carlo Simulations for Conventional and Non-conventional Radionuclides

et al. 2019

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Purpose: The increasing interest and availability of non-standard positron-emitting radionuclides has heightened the relevance of radionuclide choice in the development and optimization of new positron emission tomography (PET) imaging procedures, both in preclinical research and clinical practice. Differences in achievable resolution arising from positron range can largely influence application suitability of each radionuclide, especially in small-ring preclinical PET where system blurring factors due to annihilation photon acollinearity and detector geometry are less significant. Some resolution degradation can be mitigated with appropriate range corrections implemented during image reconstruction, the quality of which is contingent on an accurate characterization of positron range. Procedures: To address this need, we have characterized the positron range of several standard and non-standard PET radionuclides (As-72, F-18, Ga-68, Mn-52, Y-86, and Zr-89) through imaging of small-animal quality control phantoms on a benchmark preclinical PET scanner. Further, the Particle and Heavy Ion Transport code System (PHITS v3.02) code was utilized for Monte Carlo modeling of positron range-dependent blurring effects.

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Positron range in tissue-equivalent materials: experimental microPET studies

Cited by 19 publications

References 21 publications

Monte Carlo Simulations of the GE Signa PET/MR for Different Radioisotopes

Monte Carlo Simulations of the GE Signa PET/MR for Different Radioisotopes

High uptake of 68Ga-PSMA and 18F-DCFPyL in the peritumoral area of rat gliomas due to activated astrocytes

The Impact of Positron Range on PET Resolution, Evaluated with Phantoms and PHITS Monte Carlo Simulations for Conventional and Non-conventional Radionuclides

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