Geometry Optimization of a Dual-Layer Offset Detector for Use in Simultaneous PET/MR Neuroimaging

Teimoorisichani, Mohammadreza; Goertzen, Andrew L.

doi:10.1109/trpms.2018.2864923

Cited by 10 publications

(6 citation statements)

References 22 publications

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“…In the future, we plan to investigate the optimal crystal layer thickness (Teimoorisichani and Goertzen 2019) and the effects of the ICS event recovery (Lee et al 2020) or rejection (Ritzer et al 2017) on the reconstructed PET image quality by using GATE Monte Carlo simulations (Jan et al 2011) and an experimental study.…”

Section: Discussionmentioning

confidence: 99%

A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

Kang¹,

Nishikido²,

Yamaya³

2021

Biomed. Phys. Eng. Express

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The spatial resolution of small animal positron emission tomography (PET) scanners can be improved by the use of crystals with fine pitch and rejection of inter-crystal scattering (ICS) events, which leads to a better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution at the PET field-of-view (FOV) periphery while keeping the sensitivity. In this study we proposed a novel staggered 3-layer DOI detector using BaSO4 reflector material for an enhanced crystal identification performance as well as ICS event rejection capability over those of ESR reflector based DOI detectors. The proposed staggered 3-layer DOI detector had 3-layer staggered LYSO crystal arrays (crystal pitch = 1 mm), an acrylic light guide, and a 4 × 4 SiPM array. The 16 SiPM anode signals were read out by using a resistive network to encode the crystal position and energy information while the timing signal was extracted from the common cathode. The crystal map quality was substantially enhanced by using the BaSO4 reflector material as compared to that of the ESR reflector due to the low optical crosstalk between the LYSO crystals. The ICS events can be rejected with BaSO4 by using simple pulse height discrimination thanks to the light collection efficiency difference that depends on the crystal layers. As a result, the total number of events was decreased around 26% with BaSO4 as compared to that of ESR. The overall energy resolution and coincidence timing resolution with BaSO4 were 19.7 ± 5.6% and 591 ± 160 ps, respectively which were significantly worse than 10.9 ± 2.2% and 308 ± 23 ps values of ESR because of the relatively low light collection efficiency with BaSO4 (1057 ± 308 ADC) compared to that of ESR (1808 ± 118 ADC). In conclusion, we found the proposed staggered 3-layer DOI detector using the BaSO4 reflector material with ICS event rejection capability can be a cost-effective solution for realizing high resolution and highly sensitive small animal PET scanners while minimizing the complexity of the SiPM readout circuit.

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Section: Discussionmentioning

confidence: 99%

A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

Kang¹,

Nishikido²,

Yamaya³

2021

Biomed. Phys. Eng. Express

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“…Despite this, the presented results are equally relevant for other dedicated brain PET devices which have been developed in recent years or are currently under development, e.g. (Gonzalez et al 2018, Jung et al 2015, Nishikido et al 2017, Won et al 2021, Del Guerra et al 2018, Teimoorisichani and Goertzen 2018, Moliner et al 2019, Ahnen et al 2020, Catana 2019, Lerche et al 2020, Carson et al 2021.…”

Section: Discussionmentioning

confidence: 88%

A Detector Block-Pairwise Dead Time Correction Method for Improved Quantitation with a Dedicated BrainPET Scanner

Issa

Scheins

Tellmann

et al. 2022

Preprint

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Dead time correction (DTC) is an important factor in ensuring accurate quantification in PET measurements. This is currently often achieved using a global DTC method, i.e., an average DTC factor is computed. For PET scanners designed to image dedicated organs, e.g., those used in brain imaging or positron emission mammography (PEM), a substantial amount of the administered radioactivity is located outside of the PET field-of-view (FOV). This activity contributes to the dead time (DT) of the scintillation detectors. Moreover, the count rates of the individual scintillation detectors are potentially very inhomogeneous due to the specific irradiation of each detector, especially for combined MR/PET systems, where radiation shields cannot be applied. We have developed a block-pairwise DTC method for our Siemens 3T MR BrainPET insert by extending a previously published method that uses the delayed random coincidence count rate to estimate the DT in the individual scans and planes (i.e., scintillation pixel rings). The method was validated in decay experiments using phantoms with a homogenous activity concentration and with and without out-of-FOV activity. Based on a three-compartment phantom, we compared the accuracy and noise properties of the block-pairwise DTC and the global DTC method. While the currently used global DTC led to a substantial positive bias in regions with high activity, the block-pairwise DTC resulted in substantially less bias. The noise level for the block-pairwise DTC was comparable to the global DTC and image reconstructions without any DTC. Finally, we tested the block-pairwise DTC with a data set obtained from volunteer measurements using the mGlu5R (metabotropic glutamate receptor subtype 5) antagonist [ 11 C]-ABP688, when comparing the time-activity curves (TACs) obtained with the global DTC with the block-pairwise DTC, relative differences in the anterior cingulate cortex (ACC) and the cerebellum of up to 25% were observed during the first 30 minutes of these measurements.

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“…is the standard deviation, s is the shift, w is the weighting factor (0 ⩽ w ⩽ 1), and C is a scaling factor normalizing the sum of each GMM to 1. Of course, more elaborate models could be used to parametrize the PSF deformations, such as using more than two Gaussians in the GMM (Teimoorisichani and Goertzen 2019). However, for this work and system, the use of two Gaussians was deemed enough to capture the PSF deformations and thus the shapes for the different PS across the FOV as shown in figure 2 illustrating two extreme cases: two point sources with only minor deformations in the center of FOV, and two point sources with strong deformations located at the edge of FOV.…”

Section: Resolution Degradation and Modelingmentioning

confidence: 99%

Spatially-variant image-based modeling of PSF deformations with application to a limited angle geometry from a dual-panel breast-PET imager

et al. 2019

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Dual-panel PET system configuration can lead to spatially variable point-spread functions (PSF) of considerable deformations due to depth-of-interaction effects and limited angular coverage. If not modelled properly, these effects result in decreased and inconsistent recovery of lesion activity across the field-of-view (FOV), as well as mispositioning of lesions in the reconstructed image caused by strong PSF asymmetries. We implemented and evaluated models of such PSF deformations with spatially-variant image-based resolution modeling (IRM) within reconstruction (varRM) using the Direct Image REConstruction for Time-of-flight (DIRECT) method and within post-reconstruction deconvolution methods. In addition, DIRECT reconstruction was performed with a spatially-invariant IRM (invRM) and without resolution modeling (noRM) for comparison. The methods were evaluated using simulated data for a realistic breast model with a set of 5 mm lesions located throughout the FOV of a dual-panel Breast-PET scanner. We simulated high-count data to focus on the ability of each method to correctly recover the PSF deformations, and a clinically realistic count level to assess the impact of low count data on the quantitative performance of the evaluated techniques. Performance of the methods evaluated herein was assessed by comparing lesion activity recovery (%BIAS), consistency (%SD) across the FOV, overall error (%RMSE), and recovery of each lesion location. As expected, all techniques using IRM provide considerable improvement over the noRM reconstruction. For the high-count cases, the overall quantitative performance of all IRM techniques, whether within reconstruction or within post-reconstruction, is similar if the lesion location misplacements are ignored. However, invRM provides less consistent performance on activity across lesions and is not able to recover accurate lesion locations. For a clinically realistic count level, varRM reconstruction consistently outperforms all compared approaches, while the post-reconstruction IRM approaches exhibit higher %SD and %RMSE values due to being more affected by the data noise than the within-reconstruction IRM approaches.

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Geometry Optimization of a Dual-Layer Offset Detector for Use in Simultaneous PET/MR Neuroimaging

Cited by 10 publications

References 22 publications

A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

A Detector Block-Pairwise Dead Time Correction Method for Improved Quantitation with a Dedicated BrainPET Scanner

Spatially-variant image-based modeling of PSF deformations with application to a limited angle geometry from a dual-panel breast-PET imager

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Geometry Optimization of a Dual-Layer Offset Detector for Use in Simultaneous PET/MR Neuroimaging

Cited by 10 publications

References 22 publications

A staggered 3-layer DOI PET detector using BaSO4 reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

A staggered 3-layer DOI PET detector using BaSO4 reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

A Detector Block-Pairwise Dead Time Correction Method for Improved Quantitation with a Dedicated BrainPET Scanner

Spatially-variant image-based modeling of PSF deformations with application to a limited angle geometry from a dual-panel breast-PET imager

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A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

A staggered 3-layer DOI PET detector using BaSO₄ reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability