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Development of simultaneous PET and Compton imaging using GAGG-SiPM based pixel detectors
摘要： Positron emission tomography (PET) is considered an important and powerful tool for molecular imaging and medical diagnosis with its high sensitivity. Further, single-photon emission CT (SPECT) is another important imaging modality providing different types of information in medical diagnosis. On the other hand, Compton imaging is a promising technique for future molecular imaging with multi-nuclides based on Compton scattering kinetics. In this regard, previously, we have developed gadolinium aluminum gallium garnet (GAGG)-scintillation-based PET systems and GAGG-scintillation-based Compton imaging systems for environmental applications. Here, we propose and develop a novel PET–Compton hybrid simultaneous imager based on a two-layer structure using thin scatterers and thick absorbers for multi-nuclide imaging, for e.g., simultaneous imaging of PET and SPECT tracers such as 18F-FDG and 111In, respectively. For achieving good spatial resolution of the Compton imager, the energy resolution of the utilized scintillators forms one of the most important characteristics. In this regard, GAGG is a promising scintillator because of its high light yield of over 50 000 photon/MeV and excellent energy resolution of 4% with no background radiation and moderate decay time. In this study, we present the development of a simultaneous PET–Compton detector that consists of an 8 × 8 multi-pixel photon counter/SiPM (MPPC) array individually coupled with a 2.5 × 2.5 × 9-mm3 Ce:Gd3Ga2.7Al2.3O12 scintillators (absorbers) for proof of concept of simultaneous PET and SPECT imaging. The pixel size of the MPPC is 3 mm × 3 mm, and it is operated at 55 V at room temperature. The signals from the MPPC scintillators are individually amplified and converted with a dynamic time over threshold (dTOT) circuit to record the energy and timing information. In image reconstruction, the data acquired with the use of the developed modules are classified into events of either Compton imaging or PET imaging by coincidence detection between scatterer and absorber or between absorber and absorber, respectively. The coincidence events between absorber and absorber are regarded as PET annihilation-gamma events and those between scatterer and absorber are used as Compton imaging events. In our experiment, images of 111In and 18F-FDG, which are used as multi-nuclide tracers, are acquired simultaneously using the developed detector for Compton imaging and PET imaging. We believe that our approach is a significant step forward for medical imaging and related fields.
关键词： Scintillator,Single-photon emission CT,SiPM,Positron emission tomography,Compton imaging
更新于2025-09-23 15:23:52
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Single-Photon-Emission Computed Tomography with Neutron Activation for Material Inspection
摘要： A single-photon-emission computed tomography (SPECT) system with a lanthanum-bromide (LaBr3:Ce) scintillator was proposed and simulated to detect neutron-activated prompt γ-rays from suspicious materials. The optimized parameters of the SPECT system were calculated to achieve the best performance. Under the optimized conditions, energy spectra, spatial images, and elemental ratios were obtained and employed to identify hidden materials. The carbon-to-oxygen ratios of the materials calculated through the simulations were consistent with the corresponding theoretical values while the calculated nitrogen-to-oxygen ratios were slightly different from the corresponding theoretical values. In the proposed system, not only the energy spectrum of each element but also the characteristic intensity ratios obtained using the reconstructed images were used to identify the unknown elements of hidden materials in the three-dimensional spatial domain. These results demonstrate the feasibility of using the SPECT system in field applications.
关键词： Characteristic elemental intensity ratio,Neutron-activated prompt γ-rays,Single-photon-emission computed tomography
更新于2025-09-23 15:23:52
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Novel SPECT Technologies and Approaches in Cardiac Imaging
摘要： Recent novel approaches in myocardial perfusion single photon emission CT (SPECT) have been facilitated by new dedicated high-efficiency hardware with solid-state detectors and optimized collimators. New protocols include very low-dose (1 mSv) stress-only, two-position imaging to mitigate attenuation artifacts, and simultaneous dual-isotope imaging. Attenuation correction can be performed by specialized low-dose systems or by previously obtained CT coronary calcium scans. Hybrid protocols using CT angiography have been proposed. Image quality improvements have been demonstrated by novel reconstructions and motion correction. Fast SPECT acquisition facilitates dynamic flow and early function measurements. Image processing algorithms have become automated with virtually unsupervised extraction of quantitative imaging variables. This automation facilitates integration with clinical variables derived by machine learning to predict patient outcome or diagnosis. In this review, we describe new imaging protocols made possible by the new hardware developments. We also discuss several novel software approaches for the quantification and interpretation of myocardial perfusion SPECT scans.
关键词： fast myocardial perfusion single photon emission computed tomography,quantification,single photon emission computed tomography,low dose,myocardial perfusion imaging,stress only
更新于2025-09-23 15:22:29
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Handbook of Neuro-Oncology Neuroimaging || Positron Emission Tomography (PET) and Single-Photon Emission Computed Tomography (SPECT) Physics
摘要： The purpose of emission tomography is to estimate the distribution of a radiotracer from external measurements of the pattern of photons emerging from the brain. Some of these photons are detected, and certain information about them recorded, by the scanner. These external measurements are termed “projections,” and each measurement in a projection represents, ideally, the sum of radioactivity concentration along a line through the brain. From these measured projection data sets and knowledge of certain aspects of the single-photon emission computed tomography (SPECT) or positron emission tomography (PET) instrument, estimated images of the distribution of radioactivity are mathematically reconstructed. All modern SPECT and PET scanners image the three-dimensional (3D) distribution of radioactivity, either as a stack of two-dimensional (2D) transaxial images or directly as a 3D volume.
关键词： Single-Photon Emission Computed Tomography,Positron Emission Tomography,Image Reconstruction,Radiotracer,SPECT,PET,Radioactivity Distribution,Physics
更新于2025-09-23 15:21:01
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Case Report: SPECT/CT as the New Diagnostic Tool for Specific Wrist Pathology
摘要： Introduction: Single photon emission computed tomography has been introduced as a promising new diagnostic tool in orthopaedic pathology since the early 90'. Computed tomography, the combined with SPECT, gives insight in the specific sight of wrist pathology. Literature already supports introduction of SPECT/CT in wrist pathology, but clinical application is lagging. Case Report: A 40yr old patient reported first in 2004 with persisting pain after a right distal radius fracture. Several diagnostics and operative interventions were performed, all unsuccessful. Because of the persisting pain a SPECT-CT was performed which showed a cyst in the hamate bone, which was successfully enucleated. The patient was finally pain free at recent follow-up. With a QDash-score of 43 and a PRW (H) E-DLV-score of 58/150. Discussion: In this case report, SPECT/CT proved a very sensitive diagnostic tool for specific pathology of the wrist. It offered precise localisation and thereby the clinically suspected diagnosis was confirmed and the patient successfully treated.
关键词： Capitate,Proximal row carpectomy,Wrist,SPECT/CT,Hamate,Single-Photon Emission-Computed Tomography
更新于2025-09-23 15:21:01
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Single-photon emission from single-electron transport in a SAW-driven lateral light-emitting diode
摘要： The long-distance quantum transfer between electron-spin qubits in semiconductors is important for realising large-scale quantum computing circuits. Electron-spin to photon-polarisation conversion is a promising technology for achieving free-space or fibre-coupled quantum transfer. In this work, using only regular lithography techniques on a conventional 15 nm GaAs quantum well, we demonstrate acoustically-driven generation of single photons from single electrons, without the need for a self-assembled quantum dot. In this device, a single electron is carried in a potential minimum of a surface acoustic wave (SAW) and is transported to a region of holes to form an exciton. The exciton then decays and creates a single optical photon within 100 ps. This SAW-driven electroluminescence, without optimisation, yields photon antibunching with g(2)(0) = 0.39 ± 0.05 in the single-electron limit (g(2)(0) = 0.63 ± 0.03 in the raw histogram). Our work marks the first step towards electron-to-photon (spin-to-polarisation) qubit conversion for scaleable quantum computing architectures.
关键词： quantum computing,GaAs quantum well,electron-spin qubits,surface acoustic wave,single-photon emission
更新于2025-09-23 15:19:57
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Highly indistinguishable single photons from incoherently excited quantum dots
摘要： Semiconductor quantum dots with dimensions exceeding the free-exciton Bohr radius are appealing because of their high oscillator strengths. While this property has received much attention in the context of cavity quantum electrodynamics, little is known about the degree of indistinguishability of single photons consecutively emitted by such dots and on the proper excitation schemes to achieve high indistinguishability. A prominent example is represented by GaAs quantum dots obtained by local droplet etching, which recently outperformed other systems as triggered sources of entangled photon pairs. On these dots, we compare different single-photon excitation mechanisms, and we find (i) poor indistinguishability for conventional excitation via excited states and (ii) photon indistinguishablities above 90% for both strictly resonant and for incoherent phonon-assisted excitation. Among the explored excitation schemes, optical phonon-assisted excitation allows straightforward laser rejection and is thus worth of further investigation and optimization for quantum dots embedded in high-brightness photonic structures.
关键词： quantum dots,indistinguishability,single-photon emission,GaAs,phonon-assisted excitation
更新于2025-09-19 17:13:59
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Brightening and Guiding Single‐Photon Emission by Plasmonic Waveguide–Slit Structures on a Metallic Substrate
摘要： By designing a plasmonic waveguide–slit structure (a nanoslit etched in a silver nanowire) on a silver substrate, an ultrahigh Purcell factor and ultralarge figure of merit (FOM) are numerically predicted. Because of the large field enhancement (>150 times the incident field) and the ultrasmall optical volume (V ≈ 2 × 10?5λ3) of the resonant mode in the metallic nanoslit, the simulations show that the Purcell factor in the system can reach up to FP = 1.68 × 105, which is more than ten times the maximum Purcell factor in previous work (by placing metallic nanoparticles on a metal surface with a nanogap). Because of the utilization of a silver substrate rather than the common dielectric substrate, the mode cutoff of the surface plasmon polariton (SPP) waveguide mode is completely eliminated, which provides a large selection range of the nanowire radii to support the resonant mode in the nanoslit. Moreover, the SPP propagation length is significantly increased by more than 30 times. As a result, an ultralarge FOM of 1.40 × 107 is obtained, which is more than 80 times the maximum FOM in previous work where the metallic nanowire is placed on or surrounded by dielectric materials.
关键词： efficient guiding,long propagation length,bright single-photon emission,metallic substrates,purcell enhancement
更新于2025-09-19 17:13:59
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Single photon emission from top-down etched III-nitride quantum dots
摘要： We report the single photon emission properties of III-nitride quantum dots (QDs) fabricated by electrochemical etching method from an epitaxial wafer. Through such top-down fabrication, QDs with diameters of sub-10 nm are obtained, embedded in GaN nanoneedles. Owing to the size induced quantum con?nement effect, the photoluminescence of the QDs exhibits a 3.35 nm blueshift compared with that of the epitaxial wafer. At low temperature, a second order correlation value down to 0.123 is observed, indicating a high-purity single photon emission. Our QDs manifest single photon emission at a temperature up to 130 K with a high degree of polarization of 0.69, comparable to those QDs synthesized by epitaxial growth. Our work demonstrates single photon emission are viable in top-down QDs by electrochemical etching III-nitride wafers.
关键词： single photon emission,III-nitrides,quantum dot,electrochemical etching
更新于2025-09-16 10:30:52
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Single-Photon Emission Mediated by Single-Electron Tunneling in Plasmonic Nanojunctions
摘要： Recent scanning tunneling microscopy (STM) experiments reported single-molecule fluorescence induced by tunneling currents in the nanoplasmonic cavity formed by the STM tip and the substrate. The electric field of the cavity mode couples with the current-induced charge fluctuations of the molecule, allowing the excitation of photons. We investigate theoretically this system for the experimentally relevant limit of large damping rate κ for the cavity mode and arbitrary coupling strength to a single-electronic level. We find that for bias voltages close to the first inelastic threshold of photon emission, the emitted light displays antibunching behavior with vanishing second-order photon correlation function. At the same time, the current and the intensity of emitted light display Franck-Condon steps at multiples of the cavity frequency ωc with a width controlled by κ rather than the temperature T. For large bias voltages, we predict strong photon bunching of the order of κ=Γ where Γ is the electronic tunneling rate. Our theory thus predicts that strong coupling to a single level allows current-driven nonclassical light emission.
关键词： photon bunching,Franck-Condon steps,photon antibunching,single-photon emission,plasmonic nanojunctions,STM
更新于2025-09-12 10:27:22