Statistical moments of scintillation light distribution analysis with dSiPMs and monolithic crystals

Conde, P.; González, Antonio J.; Hernández, L.; Bellido, P.; Crespo, E.; Iborra, A.; Moliner, L.; Rigla, J. P.; Rodríguez-Álvarez, M. J.; Sánchez, F.; Seimetz, M.; Soriano, Antonio; Vidal, Luis; Benlloch, J.

doi:10.1109/nssmic.2013.6829086

Cited by 2 publications

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References 4 publications

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“…Compared to widely used crystal array PET detectors, the monolithic crystal-based PET detectors have the advantages of high detection efficiency, easy processing, low cost, and 3D position determination with singleended readout. The DOI is determined by the width of the measured scintillation light intensity distribution [1,2]. However, due to the edge effect (escape and reflection of the scintillation light at the edges of crystal) [3][4][5], the spatial resolutions near the edges of the scintillator deteriorate to some extent [6,7].…”

Section: Introductionmentioning

confidence: 99%

Monolithic scintillator PET detector by using light sharing between adjacent detector modules

Sun

Zhang

et al. 2023

J. Inst.

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A monolithic crystal-based positron emission tomography (PET) detector has a low cost and high sensitivity and allows determining 3D positions by scintillation light distribution. However, the edge effect inherent to scintillators deteriorates the position resolution of the detector toward the crystal borders due to the escape and reflection of the scintillation light. An increase in crystal thickness will improve the detection efficiency, but the edge effect becomes severe. To improve the position resolution and detection efficiency of scintillators, the light-sharing technique is developed. Two identical trapezoidal monolithic cerium-doped lutetium yttrium orthosilicate (LYSO) crystals with a bottom size of 25.80 × 25.80 mm2 and a thickness of 20 mm are optically coupled at one lateral face by an optical medium. The scintillation light near the optically coupled interface is jointly collected by two adjacent 8 × 8 SiPM arrays from the bottom faces. The SiPM signals are individually read out and processed by using the multichannel readout application-specific integrated circuits (ASICs) of TOFPET2 to provide a light distribution. The transverse positions and depth of interaction (DOI) are calculated from the measured light distribution. As expected, the optical glue with a refractive index of n = 1.68 shows better light sharing between two LYSO crystals than the coupling media of silicon grease (n = 1.40) and air. For the 20 mm thick monolithic LYSO-based PET detector, the transverse position resolution near the crystal edge is improved by nearly 30% by using the light-sharing method compared with the black-painted treatment. However, the DOI resolution near the edge of the crystal is not significantly improved, which may be attributed to the incomplete collection of scintillation light. The DOI resolution of the detector would be improved by using electronics with lower noise and SiPM arrays with smaller pixel.

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Section: Introductionmentioning

confidence: 99%

Monolithic scintillator PET detector by using light sharing between adjacent detector modules

Sun

Zhang

et al. 2023

J. Inst.

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Performance evaluation of side‐by‐side optically coupled monolithic LYSO crystals

et al. 2022

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Background: Significant interest has been recently shown for using monolithic scintillation crystals in molecular imaging systems, such as positron emission tomography (PET) scanners. Monolithic-based PET scanners result in a lower cost and higher sensitivity, in contrast to systems based on the more conventional pixellated configuration. The monolithic design allows one to retrieve depth-of -interaction information of the impinging 511 keV photons without the need for additional hardware materials or complex positioning algorithms. However, the so-called edge-effect inherent to monolithic-based approaches worsens the detector performance toward the crystal borders due to the truncation of the light distribution, thus decreasing positioning accuracy. Purpose: The main goal of this work is to experimentally demonstrate the detector performance improvement when machine-learning artificial neuralnetwork (NN) techniques are applied for positioning estimation in multiple monolithic scintillators optically coupled side-by-side. Methods: In this work, we show the performance evaluation of two LYSO crystals of 33 × 25.4 × 10 mm 3 optically coupled by means of a high refractive index adhesive compound (Meltmount, refractive index n = 1.70). A 12 × 12 silicon photomultiplier array has been used as photosensor. For comparison, the same detector configuration was tested for two additional coupling cases: (1) optical grease (n = 1.46) in between crystals, and (2) isolated crystals using black paint with an air gap at the interface (named standard configuration). Regarding 2D photon positioning (XY plane), we have tested two different methods: (1) a machine-learning artificial NN algorithm and (2) a squared-charge (SC) centroid technique. Results: At the interface region of the detector, the SC method achieved spatial resolutions of 1.7 ± 0.3, 2.4 ± 0.3, and 2.6 ± 0.4 mm full-width at half -maximum (FWHM) for the Meltmount, grease, and standard configurations, respectively. These values improve to 1.0 ± 0.2, 1.2 ± 0.2, and 1.2 ± 0.3 mm FWHM when the NN algorithm was employed. Regarding energy performance, resolutions of 18 ± 2%, 20 ± 2%, and 23 ± 3% were obtained at the interface region of the detector for Meltmount, grease, and standard configurations, respectively. Conclusions: The results suggest that optically coupling together scintillators with a high refractive index adhesive, in combination with an NN algorithm, reduces edge-effects and makes it possible to build scanners with almost no gaps in between detectors.

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Statistical moments of scintillation light distribution analysis with dSiPMs and monolithic crystals

Cited by 2 publications

References 4 publications

Monolithic scintillator PET detector by using light sharing between adjacent detector modules

Monolithic scintillator PET detector by using light sharing between adjacent detector modules

Performance evaluation of side‐by‐side optically coupled monolithic LYSO crystals

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