Abstract:In gamma-ray astronomy, the 1–10 MeV range is one of the most challenging energy bands to observe owing to low photon signals and a considerable amount of background contamination. This energy band, however, comprises a substantial number of nuclear gamma-ray lines that may hold the key to understanding the nucleosynthesis at the core of stars, spatial distribution of cosmic rays, and interstellar medium. Although several studies have attempted to improve observation of this energy window, development of a det… Show more
“…By revising the structure of the detector, imaging in a wider band can be realized. Particularly, Compton cameras developed for gamma-ray astronomy have realized imaging in high energy bands such as 1–10 MeV 32 . By applying the configuration of the hybrid camera as proposed in this paper, these Compton cameras can perform pinhole imaging without compromising on the performance of the original Compton camera.…”
Section: Discussionmentioning
confidence: 99%
“…By applying the configuration of the hybrid camera as proposed in this paper, these Compton cameras can perform pinhole imaging without compromising on the performance of the original Compton camera. Currently, we are developing a new hybrid camera that covers 20 keV to 5 MeV by adopting the DOI configuration of the scintillator as described in Kishimoto et al (2017) 14 and Hosokoshi et al (2019) 32 . Figure 7 The configuration of the hybrid camera (left).…”
X-ray and gamma-ray imaging are technologies with several applications in nuclear medicine, homeland security, and high-energy astrophysics. However, it is generally difficult to realize simultaneous wide-band imaging ranging from a few tens of keV to MeV because different interactions between photons and the detector material occur, depending on the photon energies. For instance, photoabsorption occurs below 100 keV, whereas Compton scattering dominates above a few hundreds of keV. Moreover, radioactive sources generally emit
both
X-ray and gamma-ray photons. In this study, we develop a “hybrid” Compton camera that can simultaneously achieve X-ray and gamma-ray imaging by combining features of “Compton” and “pinhole” cameras in a single detector system. Similar to conventional Compton cameras, the detector consists of two layers of scintillator arrays with the forward layer acting as a scatterer for high-energy photons (> 200 keV) and an active pinhole for low-energy photons (< 200 keV). The experimental results on the performance of the hybrid camera were consistent with those from the Geant4 simulation. We simultaneously imaged
Am (60 keV) and
Cs (662 keV) in the same field of view, achieving an angular resolution of 10
(FWHM) for both sources. In addition, imaging of
At was conducted for the application in future nuclear medicine, particularly radionuclide therapy. The initial demonstrative images of the
At phantom were reconstructed using the pinhole mode (using 79 keV) and Compton mode (using 570 keV), exhibiting significant similarities in source-position localization. We also verified that a mouse injected with 1 MBq of
At can be imaged via pinhole-mode measurement in an hour.
“…By revising the structure of the detector, imaging in a wider band can be realized. Particularly, Compton cameras developed for gamma-ray astronomy have realized imaging in high energy bands such as 1–10 MeV 32 . By applying the configuration of the hybrid camera as proposed in this paper, these Compton cameras can perform pinhole imaging without compromising on the performance of the original Compton camera.…”
Section: Discussionmentioning
confidence: 99%
“…By applying the configuration of the hybrid camera as proposed in this paper, these Compton cameras can perform pinhole imaging without compromising on the performance of the original Compton camera. Currently, we are developing a new hybrid camera that covers 20 keV to 5 MeV by adopting the DOI configuration of the scintillator as described in Kishimoto et al (2017) 14 and Hosokoshi et al (2019) 32 . Figure 7 The configuration of the hybrid camera (left).…”
X-ray and gamma-ray imaging are technologies with several applications in nuclear medicine, homeland security, and high-energy astrophysics. However, it is generally difficult to realize simultaneous wide-band imaging ranging from a few tens of keV to MeV because different interactions between photons and the detector material occur, depending on the photon energies. For instance, photoabsorption occurs below 100 keV, whereas Compton scattering dominates above a few hundreds of keV. Moreover, radioactive sources generally emit
both
X-ray and gamma-ray photons. In this study, we develop a “hybrid” Compton camera that can simultaneously achieve X-ray and gamma-ray imaging by combining features of “Compton” and “pinhole” cameras in a single detector system. Similar to conventional Compton cameras, the detector consists of two layers of scintillator arrays with the forward layer acting as a scatterer for high-energy photons (> 200 keV) and an active pinhole for low-energy photons (< 200 keV). The experimental results on the performance of the hybrid camera were consistent with those from the Geant4 simulation. We simultaneously imaged
Am (60 keV) and
Cs (662 keV) in the same field of view, achieving an angular resolution of 10
(FWHM) for both sources. In addition, imaging of
At was conducted for the application in future nuclear medicine, particularly radionuclide therapy. The initial demonstrative images of the
At phantom were reconstructed using the pinhole mode (using 79 keV) and Compton mode (using 570 keV), exhibiting significant similarities in source-position localization. We also verified that a mouse injected with 1 MBq of
At can be imaged via pinhole-mode measurement in an hour.
“…To evaluate the impact of the position reconstruction in the final angular resolution of i-TED, we used the Angular Resolution Measure (ARM) [40]. The ARM is defined as the difference between the geometrical scattering angle, determined from the interaction point in the two detection planes and the source position, and the scatter angle calculated using the Compton formula:…”
Section: Impact Of the Intrinsic Spatial Sensitivity On The Compton I...mentioning
We investigate five different models to reconstruct the 3D γ-ray hit coordinates in five large LaCl 3 (Ce) monolithic crystals optically coupled to pixelated silicon photomultipliers. These scintillators have a base surface of 50 × 50 mm 2 and five different thicknesses, from 10 mm to 30 mm. Four of these models are analytical prescriptions and one is based on a Convolutional Neural Network. Average resolutions close to 1-2 mm fwhm are obtained in the transverse crystal plane for crystal thicknesses between 10 mm and 20 mm using analytical models. For thicker crystals average resolutions of about 3-5 mm fwhm are obtained. Depth of interaction resolutions between 1 mm and 4 mm are achieved depending on the distance of the interaction point to the photosensor surface. We propose a Machine Learning algorithm to correct for linearity distortions and pin-cushion effects. The latter allows one to keep a large field of view of about 70-80% of the crystal surface, regardless of crystal thickness. This work is aimed at optimizing the performance of the so-called Total Energy Detector with Compton imaging capability (i-TED) for time-of-flight neutron capture cross-section measurements.
“…In this context, a Compton camera 6 , 7 that can perform imaging in a wide energy band is crucial. Compton cameras are capable of efficiently imaging high-energy photons 8 , 9 , and therefore have been investigated for medical applications, such as visualization of 4.4 MeV prompt gamma rays toward monitoring for proton therapy 10 – 14 . Furthermore, for clinical applications, both scintillator-based and semiconductor-based Compton cameras have been developed 15 – 21 .…”
For radiological diagnosis and radionuclide therapy, X-ray and gamma-ray imaging technologies are essential. Single-photon emission tomography (SPECT) and positron emission tomography (PET) play essential roles in radiological diagnosis, such as the early detection of tumors. Radionuclide therapy is also rapidly developing with the use of these modalities. Nevertheless, a limited number of radioactive tracers are imaged owing to the limitations of the imaging devices. In a previous study, we developed a hybrid Compton camera that conducts simultaneous Compton and pinhole imaging within a single system. In this study, we developed a system that simultaneously realizes three modalities: Compton, pinhole, and PET imaging in 3D space using multiple hybrid Compton cameras. We achieved the simultaneous imaging of Cs-137 (Compton mode targeting 662 keV), Na-22 (PET mode targeting 511 keV), and Am-241 (pinhole mode targeting 60 keV) within the same field of view. In addition, the imaging of Ga-67 and In-111, which are used in various diagnostic scenarios, was conducted. We also verified that the 3D distribution of the At-211 tracer inside a mouse could be imaged using the pinhole mode.
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