Scintillator Pixel Detectors for Measurement of Compton Scattering

Makek, M.; Bosnar, D.; Pavelić, Luka

doi:10.3390/condmat4010024

Cited by 14 publications

(20 citation statements)

References 13 publications

(17 reference statements)

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“…For scattering angles θ > 60 • , there is a possible ambiguity in the determination of the pixel corresponding to the recoil electron and the pixel corresponding to the scattered gamma, since a scattering at a forward angle can result in the same energy responses of the pixels as a scattering at one backward angle. However, the forward scattering is always favored owing to the higher cross-section and the lower absorption probability of the scattered gamma [14]. The azimuthal angle, φ, is reconstructed from the relative position of the two fired pixels in a module.…”

Section: Methodsmentioning

confidence: 99%

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Single-layer Compton detectors for measurement of polarization correlations of annihilation quanta

Makek

Bosnar

Pavelić

et al. 2020

Nuclear Instruments and Methods in Physics Research Section A:

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Measurement of gamma-ray polarization can provide valuable insight in different areas of physics research. One possible application is in Positron Emission Tomography, where the annihilation quanta with orthogonal polarizations are emitted. Since polarization can be measured via Compton scattering, the initial orthogonality of polarizations can be translated to correlation of azimuthal scattering angles, and this correlation may be exploited as an additional handle to identify the true coincidence events. In order to examine the concept of utilizing the polarization correlations in PET, we have used a system of two compact, position and energy-sensitive Compton scattering detectors in coincidence mode. Each consists of a single matrix of scintillation pixels, read-out by a matching array of Silicon photomultipliers on the back side. The Compton events in each module are clearly identified and the scattering angles are reconstructed from the energy deposition and event topology. We have extracted the polarimetric modulation factors from the distributions of the difference of the azimuthal angles of the two Compton-scattered gammas and studied their dependence on Compton scattering angles θ and on azimuthal resolution ∆φ. For scattering angles around θ1,2 = 82 • , where the maximum modulation is expected, the modulation factors from µ = 0.15 ± 0.01 to µ = 0.27 ± 0.02 have been measured, depending on the azimuthal resolution, which is governed by event topology in the detectors. Analogously, for scattering around θ1,2 = 70 • , modulation factors from µ = 0.12 ± 0.01 to µ = 0.21 ± 0.02 have been obtained. The results show that the measurement of the polarization correlations of annihilation quanta are feasible with compact single-layer, single-side read-out detectors, which may be used to build cost-efficient systems for various applications where gamma-ray polarization information is of interest.

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Section: Methodsmentioning

confidence: 99%

“…The azimuthal angle, φ, is reconstructed from the relative position of the two fired pixels in a module. The angular uncertainty is caused by the uncertainty of the interaction position within a pixel, and it depends on the distance, d, of the fired pixels in a module as [14]:…”

Section: Methodsmentioning

confidence: 99%

Single-layer Compton detectors for measurement of polarization correlations of annihilation quanta

Makek

Bosnar

Pavelić

et al. 2020

Nuclear Instruments and Methods in Physics Research Section A:

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“…3-4). Traditionally, Compton detection has been performed using multiple detector layers, but a recent paper outlined the criteria for localizing and decomposing Compton interactions using singleended readout, citing high resolution DOI readout as a key feature for Compton scatter recovery (31). A uniform light guide is not optimal for this task because the SiPM pattern of individual events is random, whereas our Prism-PET modules create a deterministic light sharing pattern regardless of the interaction location inside the primary scintillator column ( Fig.…”

Section: Discussionmentioning

confidence: 99%

High-Resolution Depth-Encoding PET Detector Module with Prismatoid Light-Guide Array

et al. 2020

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Depth-encoding detectors with single-ended readout provide a practical, cost-effective approach for constructing high resolution and high sensitivity PET scanners. However, the current iteration of such detectors utilizes a uniform glass light guide to achieve depth-encoding, resulting in non-uniform performance throughout the detector array due to suboptimal intercrystal light sharing. We introduce Prism-PET, a singleended readout PET detector module with a segmented light guide composed of an array of prismatoids that introduces enhanced, deterministic light sharing. Methods: High resolution PET detector modules were fabricated with single-ended readout of polished multicrystal lutetium yttrium orthosilicate (LYSO) scintillator arrays directly coupled 4-to-1 and 9-to-1 to arrays of 3.2 × 3.2 mm 2 silicon photomultiplier pixels. Each scintillator array was coupled at the non-readout side to a light guide (one 4-to-1 module with a uniform glass light guide, one 4-to-1 Prism-PET module and one 9-to-1 Prism-PET module) to introduce intercrystal light sharing, which closely mimics the behavior of dual-ended readout with the additional benefit of improved crystal identification. Flood histogram data was acquired using a 3 MBq Na-22 source to characterize crystal identification and energy resolution. Lead collimation was used to acquire data at specific depths to determine depth-of-interaction (DOI) resolution. Results: The flood histogram measurements showed excellent and uniform crystal separation throughout the Prism-PET modules while the uniform glass light guide module had performance degradation at the edges and corners. A DOI resolution of 5.0 mm full width at half maximum (FWHM) and energy resolution of 13% were obtained in the uniform glass light guide module. By comparison, the 4-to-1 coupled Prism-PET module achieved 2.5 mm FWHM DOI resolution and 9% energy resolution. Conclusions: PET scanners based on our Prism-PET modules with segmented prismatoid light guide arrays can achieve high and uniform spatial resolution (9-to-1 coupling with ~ 1 mm crystals), high sensitivity, good energy and timing resolutions (using polished crystals and after applying DOI-correction), and compact size (depth-encoding eliminates parallax error and permits smaller ring-diameter).

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“…In addition, the framework for performing accurate Compton localization using single-ended readout depthencoding modules was laid out in a recent paper, demonstrating that high DOI resolution is a critical component in determining the primary interaction site [48]. Based on the existing literature and our CNN results, we expect that our neural network approach for DOI estimation may be translatable to perform…”

Section: Accepted Articlementioning

confidence: 93%

Sub‐2 mm depth of interaction localization in PET detectors with prismatoid light guide arrays and single‐ended readout using convolutional neural networks

et al. 2021

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Purpose Depth of interaction (DOI) readout in PET imaging has been researched in efforts to mitigate parallax error, which would enable the development of small diameter, high‐resolution PET scanners. However, DOI PET has not yet been commercialized due to the lack of practical, cost‐effective, and data efficient DOI readout methods. The rationale for this study was to develop a supervised machine learning algorithm for DOI estimation in PET that can be trained and deployed on unique sets of crystals. Methods Depth collimated flood data was experimentally acquired using a Na‐22 source with a depth‐encoding single‐ended readout Prism‐PET module consisting of lutetium yttrium orthosilicate (LYSO) crystals coupled 4‐to‐1 to 3×3 mm2 silicon photomultiplier (SiPM) pixels on one end and a segmented prismatoid light guide array on the other end. A convolutional neural network (CNN) was trained to perform DOI estimation on data from center, edge and corner crystals in the Prism‐PET module using (a) all non‐zero readout pixels and (b) only the 4 highest readout signals per event. CNN testing was performed on data from crystals not included in CNN training. Results An average DOI resolution of 1.84 mm full width at half maximum (FWHM) across all crystals was achieved when using all readout signals per event with the CNN compared to 3.04 mm FWHM DOI resolution using classical estimation. When using only the 4 highest signals per event, an average DOI resolution of 1.92 mm FWHM was achieved, representing only a 4% dropoff in CNN performance compared to using all non‐zero pixels per event. Conclusions Our CNN‐based DOI estimation algorithm provides the best reported DOI resolution in a single‐ended readout module and can be readily deployed on crystals not used for model training.

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Scintillator Pixel Detectors for Measurement of Compton Scattering

Cited by 14 publications

References 13 publications

Single-layer Compton detectors for measurement of polarization correlations of annihilation quanta

Single-layer Compton detectors for measurement of polarization correlations of annihilation quanta

High-Resolution Depth-Encoding PET Detector Module with Prismatoid Light-Guide Array

Sub‐2 mm depth of interaction localization in PET detectors with prismatoid light guide arrays and single‐ended readout using convolutional neural networks

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