Compressive effect of the magnetic field on the positron range in commonly used positron emitters simulated using Geant4

Li, Chong; Cao, Xingzhong; Liu, Fuyan; Tang, Haina; Zhang, Zhi Ming; Wang, Boyu; Wei, Long

doi:10.1140/epjp/i2017-11779-x

Cited by 8 publications

(11 citation statements)

References 26 publications

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“…Positron Range Evaluation Using the GATE Model for the GE Signa PET/MR Table 4 shows the comparison of the simulated positron range in soft tissue for different radioisotopes with and without 3T magnetic field with measured values taken from literature (Li et al, 2017;Soultanidis et al, 2011). The simulated mean positron range values for different isotopes in soft tissue, lung and bone are presented on Tables 5, 6 with and without the presence of a 3T magnetic field, with the mean positron range averaged over all directions (Table 5) and the mean positron range calculated for the transversal TABLE 3 | Sensitivity for different isotopes in the presence of 3T magnetic field, presented as the average value of the sensitivity at the center of the FOV and the sensitivity at 10 cm off center.…”

Section: Validation Of the Gate Model For The Ge Signa Pet/mrmentioning

confidence: 99%

“…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%

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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: Validation Of the Gate Model For The Ge Signa Pet/mrmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…These simulation studies deal with various topics, including the effect of magnetic field on the positron ranges of different positron emitters. 14,15 The widely accepted performance measurement standards for PETs, the NEMA NU 2 publication, 16 can be extended to meet the needs for benchmarking the PET performance in PET/MR, 17 and across differ-ent positron emitters. 18 To ensure rigorous comparability and to promote measurement feasibility, the originally recommended methods in NEMA NU 2 use 18 F or 22 Na as the positron source.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the impact of different positron emitters on the performance of a clinical PET/MR system

Meng

Liu

et al. 2022

Medical Physics

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The positron range and prompt gamma emission are distinctive with different positron emitters. The performance assessment of an integrated PET/MR scanner with these positron emitters is required for related applications, as the magnetic field interferes with the positron propagation. Such an assessment is to be performed on the United Imaging uPMR 790-integrated PET/MR system. Methods: The performance measurement methods were modified based on NEMA NU 2-2012, involving 18 F, 64 Cu, 68 Ga, 89 Zr, and 124 I as positron emitters. The NEMA IEC phantom was used for evaluations of image qualities. An agarose cap was wrapped around the point source for tissue-simulating spatial resolution measurement. The count rate performance was assessed with selected positron emitters. Images of a 3D-printed Derenzo phantom and representative patients were also acquired. Results:The image quality measurement showed that all five positron emitters were suitable for the PET/MR system studied. However, due to the magnetic field, the image of the point source showed an elongated comet-tail feature, which could be eliminated by a tissue-simulating cap. This effect is more obvious in 124 I and 68 Ga, due to their long positron ranges. The imaging ability with various positron emitters was further validated with the count rate assessment, the Derenzo phantom, and the clinical images. Conclusions: Different positron emitters could be effectively imaged by the PET/MR system tested. The resolution measurement strategy proposed could be applied to measure PET spatial resolution in the magnetic field.

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“…The imaging error arising from the positron range is a system-independent physical limitation of the spatial resolution and increases with the positron energy (Cal-Gonzalez et al 2013, Carter et al 2020). This effect is normally neglected in studies applying 18 F (the most commonly used positron emitter) since it emits positrons with low average energy (approximately 252 keV) and has a maximum positron range of about 2 mm in water (Sahnoun et al 2020, Li et al 2017.…”

Section: Introductionmentioning

confidence: 99%

“…(Chilra et al 2017). Many of these non-standard radioisotopes emit positrons at energies much higher than 18 F. The average positron energies of 68 Ga and 82 Rb are approximately 840keV and 1550keV, respectively, thus leading to a maximum range in water of approximately 9 mm and 17 mm (Li et al 2017), respectively. Consequently, a significant challenge arises in providing high-quality images when using non-standard positron emitters.…”

Section: Introductionmentioning

confidence: 99%

Accurate 3D Positron Range Correction Method for Heterogeneous Material Densities in PET

Li¹,

Scheins²,

Tellmann³

et al. 2022

Preprint

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Objective: The positron range is a fundamental, detector-independent physical limitation to special resolution in positron emission tomography (PET) as it causes a significant blurring of the reconstructed PET images. A major challenge for positron range correction methods is to provide accurate range kernels that inherently incorporate the generally inhomogeneous stopping power, especially at tissue boundaries. In this work, we propose a novel approach to generate accurate three-dimensional (3-D) blurring kernels both in homogenous and heterogeneous media to improve PET spatial resolution. Approach: In the proposed approach, positron energy deposition was approximately tracked along straight paths, depending on the positron stopping power of the underlying material. The positron stopping power was derived from the attenuation coefficient of 511keV gamma photons according to the available PET attenuation maps. Thus, the history of energy deposition is taken into account within the range of kernels. Special emphasis was placed on facilitating the very fast computation of the positron annihilation probability in each voxel. Results: Positron path distributions of 18F in low-density polyurethane were in high agreement with Geant4 simulation at an annihilation probability larger than 10-2~10-3 of the maximum annihilation probability. The Geant4 simulation was further validated with measured 18F depth profiles in these polyurethane phantoms. The tissue boundary of water with cortical bone and lung was correctly modeled. Residual artifacts from the numerical computations were in the range of 1%. The calculated annihilation probability in voxels shows an overall difference of less than 20% compared to the Geant4 simulation. Significance: The proposed method significantly improves spatial resolution for non-standard isotopes by providing accurate range kernels, even in the case of significant tissue inhomogeneities.

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Compressive effect of the magnetic field on the positron range in commonly used positron emitters simulated using Geant4

Cited by 8 publications

References 26 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

Evaluating the impact of different positron emitters on the performance of a clinical PET/MR system

Accurate 3D Positron Range Correction Method for Heterogeneous Material Densities in PET

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