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Pirayesh Islamian J, Ljungberg M. Evaluation of Improved Imaging Properties with Tungsten-Based Parallel-Hole Collimators: A Monte Carlo Study. World J Nucl Med 2024; 23:95-102. [PMID: 38933066 PMCID: PMC11199031 DOI: 10.1055/s-0044-1786165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2024] Open
Abstract
Objectives The purpose of a parallel-hole collimator in a scintillation camera system is to transmit only those photons that have an emission angle close to the direction of the hole. This makes it possible to receive spatial information about the origin of the emission, that is, radioactivity decay. The dimension, shape, and intrahole thickness determine the spatial resolution and, by a tradeoff, sensitivity. The composition of the collimator material also plays an important role in determining a proper collimator. In this study, we compared tungsten alloys as a potential collimator material replacement for the conventional lead antimony material used in most of the current camera systems. Materials and Methods Monte Carlo simulations of a commercial scintillation camera system with low energy high resolution (LEHR), medium-energy (ME), and high-energy (HE) collimators of lead, tungsten, and tungsten-based alloy were simulated for different I-131, Lu-177, I-123, and Tc-99m sources, and a Deluxe rod phantom using the SIMIND Monte Carlo code. Planar images were analyzed regarding spatial resolution, image contrast in a cold source case, and system sensitivity for each collimator configuration. The hole dimensions for the three collimators were those specified in the vendor's datasheet. Results Using Pb, W, and tungsten alloy (Wolfmet) as collimator materials, the full width at half maximum (FWHM) measures for total counts (T) for LEHR with Tc-99m source (6.9, 6.8, and 6.8 mm), for ME with Lu-177 source (11.7, 11.5, and 11.6 mm), and for HE with I-131 (6.2, 13.1, and 13.1 mm) were obtained, and the system sensitivities were calculated as 89.9, 86.1, and 89.8 cps T /MBq with Tc-99m source; 42.7, 17.4, and 20.9 cps T /MBq with Lu-177 source; and 40.1, 69.7, and 77.4 cps T /MBq with I-131 source. The collimators of tungsten and tungsten alloy (97.0% W, 1.5% Fe, 1.5% Ni) provided better spatial resolution and improved image contrast when compared with conventional lead-based collimators. This was due to lower septal penetration. Conclusion The results suggest that development of a new set of ME and HE tungsten and tungsten alloy collimators could improve imaging of I-131, Lu-177, and I-123.
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Affiliation(s)
- Jalil Pirayesh Islamian
- Department of Medical Physics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Michael Ljungberg
- Department of Medical Radiation Physics, Lund, Lund University, Lund, Sweden
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Mandot S, Zannoni EM, Cai L, Nie X, Riviere PJL, Wilson MD, Meng LJ. A High-Sensitivity Benchtop X-Ray Fluorescence Emission Tomography (XFET) System With a Full-Ring of X-Ray Imaging-Spectrometers and a Compound-Eye Collimation Aperture. IEEE TRANSACTIONS ON MEDICAL IMAGING 2024; 43:1782-1791. [PMID: 38696285 PMCID: PMC11129545 DOI: 10.1109/tmi.2023.3348791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2024]
Abstract
The advent of metal-based drugs and metal nanoparticles as therapeutic agents in anti-tumor treatment has motivated the advancement of X-ray fluorescence computed tomography (XFCT) techniques. An XFCT imaging modality can detect, quantify, and image the biodistribution of metal elements using the X-ray fluorescence signal emitted upon X-ray irradiation. However, the majority of XFCT imaging systems and instrumentation developed so far rely on a single or a small number of detectors. This work introduces the first full-ring benchtop X-ray fluorescence emission tomography (XFET) system equipped with 24 solid-state detectors arranged in a hexagonal geometry and a 96-pinhole compound-eye collimator. We experimentally demonstrate the system's sensitivity and its capability of multi-element detection and quantification by performing imaging studies on an animal-sized phantom. In our preliminary studies, the phantom was irradiated with a pencil beam of X-rays produced using a low-powered polychromatic X-ray source (90kVp and 60W max power). This investigation shows a significant enhancement in the detection limit of gadolinium to as low as 0.1 mg/mL concentration. The results also illustrate the unique capabilities of the XFET system to simultaneously determine the spatial distribution and accurately quantify the concentrations of multiple metal elements.
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Zheng Z, Lai C, Zhou W, Wang Y, Zhang Y, Wang J. Preparation, Mechanical Properties and Strengthening Mechanism of W-Re Alloys: A Review. MATERIALS (BASEL, SWITZERLAND) 2023; 17:102. [PMID: 38203956 PMCID: PMC10779616 DOI: 10.3390/ma17010102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 12/21/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024]
Abstract
W-Re alloys are one of the most important refractory materials with excellent high-temperature performance that were developed to improve the brittleness of tungsten. In the present work, we firstly summarized the research progress on the preparation and strengthening methods of a W-Re alloy. Then, the strengthening mechanisms of the W-Re alloy were discussed, including the influence of Re, solid solution strengthening, second-phase reinforcement and fine-grain strengthening. The results showed that the softening effect of Re was mainly related to the transformation of the preferred slip plane and the introduction of additional d-valence electrons. Some transition elements and refractory metal elements effectively strengthened the W-Re alloy. Carbides can significantly enhance the high-temperature mechanical properties of W-Re alloys, and the reasons are twofold: one is the interaction between carbides and dislocations, and the other is the synergistic strengthening effect between carbides and Re. The objective of this work was to enhance the comprehension on W-Re alloys and provide future research directions for W-Re alloys.
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Affiliation(s)
| | - Chen Lai
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
| | | | | | | | - Jinshu Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
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Lee YC, Zheng J, Kuo J, Acosta-Vélez GF, Linsley CS, Wu BM. Binder Jetting of Custom Silicone Powder for Direct Three-Dimensional Printing of Maxillofacial Prostheses. 3D PRINTING AND ADDITIVE MANUFACTURING 2022; 9:520-534. [PMID: 36660746 PMCID: PMC9831568 DOI: 10.1089/3dp.2021.0019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Recent advances in digital workflow have transformed clinician's ability to offer patient-specific devices for medical and dental applications. However, the digital workflow of patient-specific maxillofacial prostheses (MFP) remains incomplete, and several steps in the manufacturing process are still labor-intensive and are costly in both time and resources. Despite the high demand for direct digital MFP manufacturing, three-dimensional (3D) printing of colored silicone MFP is limited by the processing routes of medical-grade silicones and biocompatible elastomers. In this study, a binder jetting 3D printing process with polyvinyl butyral (PVB)-coated silicone powder was developed for direct 3D printing of MFP. Nanosilica-treated silicone powder was spray dried with PVB by controlling the Ohnesorge number and processing parameters. After printing, the interconnected pores were infused with silicone and hexamethyldisiloxane (HMDS) by pressure-vacuum sequential infiltration to produce the final parts. Particle size, coating composition, surface treatment, and infusion conditions influenced the mechanical properties of the 3D-printed preform, and of the final infiltrated structure. In addition to demonstrating the feasibility of using silicone powder-based 3D printing for MFP, these results can be used to inform the modifications required to accommodate the manufacturing of other biocompatible elastomeric materials.
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Affiliation(s)
- Yun Chang Lee
- Department of Mechanical and Aerospace Engineering, Samueli School of Engineering, University of California, Los Angeles, California, USA
- Weintraub Center for Reconstructive Biotechnology, School of Dentistry, University of California, Los Angeles, USA
- Division of Advanced Prosthodontics, School of Dentistry, University of California, Los Angeles, USA
| | - Jisi Zheng
- Department of Oral Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jonathan Kuo
- Department of Bioengineering, Samueli School of Engineering, University of California, Los Angeles, USA
| | - Giovanny F. Acosta-Vélez
- Weintraub Center for Reconstructive Biotechnology, School of Dentistry, University of California, Los Angeles, USA
- Division of Advanced Prosthodontics, School of Dentistry, University of California, Los Angeles, USA
| | - Chase S. Linsley
- Department of Bioengineering, Samueli School of Engineering, University of California, Los Angeles, USA
| | - Benjamin M. Wu
- Weintraub Center for Reconstructive Biotechnology, School of Dentistry, University of California, Los Angeles, USA
- Division of Advanced Prosthodontics, School of Dentistry, University of California, Los Angeles, USA
- Department of Bioengineering, Samueli School of Engineering, University of California, Los Angeles, USA
- Division of Advanced Prosthodontics, School of Dentistry, University of California, Los Angeles, USA
- Department of Materials Science and Engineering, Samueli School of Engineering, University of California, Los Angeles, USA
- Department of Orthopaedic Surgery, David Geffen School of Medicine, University of California, Los Angeles, USA
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California, USA
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Zhang X, Hou X, Hao Z, Wang P, Shu Y, He J. Research on Spheroidization of Tungsten Powder from Three Different Raw Materials. MATERIALS (BASEL, SWITZERLAND) 2022; 15:8449. [PMID: 36499944 PMCID: PMC9736529 DOI: 10.3390/ma15238449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/11/2022] [Accepted: 11/24/2022] [Indexed: 06/17/2023]
Abstract
In this work, three kinds of tungsten powders with different particle sizes were spheroidized by radio-frequency (RF) inductively coupled plasma spheroidization. The spheroidization behavior of these tungsten powders was investigated and compared. The spheroidization effects of irregular tungsten powder improves with the decrease in degree of agglomeration and increases with primary particle size. Spherical tungsten powder from irregular powder with a primary particle size of 19.9 μm and an agglomeration coefficient of 1.59 had the best spheroidization effect; its apparent density, hall flow time, and spheroidization ratio are 9.36 g/cm3, 6.28 s/50 g, and 98%, respectively. The results show that irregular feedstock tungsten powder with a smaller primary particle size and higher agglomeration degree has a poor spheroidization effect because it is easily affected by the gas flow and deviates from the high temperature zone. On the contrary, irregular feedstock tungsten powder with larger primary particle sizes and lower agglomeration degrees has better spheroidization effects.
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Affiliation(s)
- Xiuqing Zhang
- Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou 450001, China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Xuchu Hou
- Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou 450001, China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Zhenhua Hao
- Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou 450001, China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Pei Wang
- School of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450001, China
| | - Yongchun Shu
- Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou 450001, China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
| | - Jilin He
- Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou 450001, China
- School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
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Lai X, Cai L, Tan JW, Zannoni EM, Odintsov B, Meng LJ. Design, Performance Evaluation, and Modeling of an Ultrahigh Resolution Detector Dedicated for Simultaneous SPECT/MRI. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022. [DOI: 10.1109/trpms.2021.3053592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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SPECT and SPECT/CT. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00008-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Lai X, Zannoni EM, George J, Meng LJ. System Modeling and Evaluation of a Prototype Inverted-Compound Eye Gamma Camera for the Second Generation MR Compatible SPECT. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT 2020; 954:162046. [PMID: 32773914 PMCID: PMC7405694 DOI: 10.1016/j.nima.2019.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We have reported the design of the MRC-SPECT-II system based on the inverted-compound-eye (ICE) gamma camera to offer a > 1% detection efficiency while maintaining a sub-500 μm imaging resolution [1]. One of the key challenges of using the ICE camera for SPECT imaging is whether one could develop an accurate point response function (PRF), given its complex aperture design and low fractionation accuracy of 3D printing. In this work, we will discuss (I) a combined experimental and analytical approach for deriving the precise PRF, and (II) an experimental imaging study to demonstrate the feasibility of using the ICE-camera for acquiring high-quality SPECT images with a sub-500 μm resolution. These studies would help to overcome one of the major hurdles for implement ICE-cameras for practical SPECT imaging.
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Affiliation(s)
- Xiaochun Lai
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign
| | - Elena M Zannoni
- Department of Bioengineering, University of Illinois at Urbana-Champaign
| | - Jonathan George
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign
| | - Ling-Jian Meng
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign
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9
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Densification, Microstructure and Properties of 90W-7Ni-3Fe Fabricated by Selective Laser Melting. METALS 2019. [DOI: 10.3390/met9080884] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The preparation of refractory tungsten and tungsten alloys has always been challenging due to their inherent properties. Selective laser melting (SLM) offers a choice for preparing tungsten and tungsten alloys. In this work, 90W-7Ni-3Fe samples were prepared by selective laser melting and investigated. Different process parameter combinations were designed according to the Taguchi method, and volumetric energy density (VED) was defined. Subsequently, the effects of process parameters on densification, phase composition, microstructure, tensile properties, and microhardness were investigated. Nearly a full densification sample (≥99%) was obtained under optimized process parameters, and the value of VED was no less than 300 J/mm3. Laser power had a dominant influence on densification behavior compared with other parameters. The main phases of 90W-7Ni-3Fe are W and γ-(Ni-Fe), dissolved with partial W. In addition, 90W-7Ni-3Fe showed a high tensile strength (UTS = 1121 MPa) with poor elongation (<1%). A high average microhardness (>400 HV0.3) was obtained, but the microhardness presented a fluctuation along building direction due to the inhomogeneous microstructure.
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Additive manufacturing of pure tungsten by means of selective laser beam melting with substrate preheating temperatures up to 1000 ∘C. NUCLEAR MATERIALS AND ENERGY 2019. [DOI: 10.1016/j.nme.2019.02.034] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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11
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Gear JI, Taprogge J, White O, Flux GD. Characterisation of the attenuation properties of 3D-printed tungsten for use in gamma camera collimation. EJNMMI Phys 2019; 6:1. [PMID: 30617816 PMCID: PMC6323062 DOI: 10.1186/s40658-018-0238-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 12/14/2018] [Indexed: 11/10/2022] Open
Abstract
Background The aim of this work was to characterise the attenuation properties of 3D-printed tungsten and to assess the feasibility for its use in gamma camera collimator manufacture. Method 3D-printed tungsten disks were produced using selective laser melting (SLM). Measurements of attenuation were made through increasing numbers of disks for a Tc-99m (140 keV) and I-131 (364 keV) source. The technique was validated by repeating the measurements with lead samples. Resolution measurements were also made with a SLM tungsten collimator and compared to Monte Carlo simulations of the experimental setup. Different collimator parameters were simulated and compared against the physical measurements to investigate the effect on image quality. Results The measured disk thicknesses were on average 20% above the specified disk thicknesses. The measured attenuation for the tungsten samples were lower than the theoretical value determined from the National Institute of Standards and Technology (NIST) cross-sectional database (Berger and Hubbell, XCOM: photon cross-sections on a personal computer, 1987). The laser scan strategy had a significant influence on material attenuation (up to 40% difference). Results of these attenuation measurements indicate that the density of the SLM material is lower than the raw tungsten density. However, an improved performance compared to a lead collimator was observed. The SLM tungsten collimator was adequately simulated as 80% density and 110% septal thickness. Scatter and septal penetration were 17% less than a similar lead collimator and 33% greater than tungsten at 100% density. Conclusions SLM manufacture of tungsten collimators is feasible. Attenuation properties of SLM tungsten are superior to the lead alternative and the opportunity for bespoke collimator design is appealing.
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Affiliation(s)
- Jonathan I Gear
- Joint Department of Physics, Royal Marsden NHSFT and Institute of Cancer Research, Downs Road, Sutton, SM2 5PT, UK.
| | - Jan Taprogge
- Joint Department of Physics, Royal Marsden NHSFT and Institute of Cancer Research, Downs Road, Sutton, SM2 5PT, UK
| | - Owen White
- Joint Department of Physics, Royal Marsden NHSFT and Institute of Cancer Research, Downs Road, Sutton, SM2 5PT, UK
| | - Glenn D Flux
- Joint Department of Physics, Royal Marsden NHSFT and Institute of Cancer Research, Downs Road, Sutton, SM2 5PT, UK
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Nygren RE, Dehoff RR, Youchison DL, Katoh Y, Wang YM, Spadaccini CM, Henager CH, Schunk PR, Keicher DM, Roach RA, Smith MF, Buchenauer DA. Advanced manufacturing—A transformative enabling capability for fusion. FUSION ENGINEERING AND DESIGN 2018. [DOI: 10.1016/j.fusengdes.2018.04.055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Vrábel J, Pořízka P, Klus J, Prochazka D, Novotný J, Koutný D, Paloušek D, Kaiser J. Classification of materials for selective laser melting by laser-induced breakdown spectroscopy. CHEMICAL PAPERS 2018. [DOI: 10.1007/s11696-018-0609-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Tan C, Zhou K, Ma W, Attard B, Zhang P, Kuang T. Selective laser melting of high-performance pure tungsten: parameter design, densification behavior and mechanical properties. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2018; 19:370-380. [PMID: 29707073 PMCID: PMC5917440 DOI: 10.1080/14686996.2018.1455154] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 03/17/2018] [Accepted: 03/18/2018] [Indexed: 05/24/2023]
Abstract
Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing.
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Affiliation(s)
- Chaolin Tan
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, China
- National Engineering Laboratory for Modern Materials Surface Engineering Technology, Guangdong Institute of New Materials, Guangzhou, China
- School of Metallurgy & Materials, University of Birmingham, Birmingham, UK
| | - Kesong Zhou
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, China
- National Engineering Laboratory for Modern Materials Surface Engineering Technology, Guangdong Institute of New Materials, Guangzhou, China
| | - Wenyou Ma
- National Engineering Laboratory for Modern Materials Surface Engineering Technology, Guangdong Institute of New Materials, Guangzhou, China
| | - Bonnie Attard
- School of Metallurgy & Materials, University of Birmingham, Birmingham, UK
| | - Panpan Zhang
- National Engineering Laboratory for Modern Materials Surface Engineering Technology, Guangdong Institute of New Materials, Guangzhou, China
| | - Tongchun Kuang
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, China
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Lai X, Meng LJ. Simulation study of the second-generation MR-compatible SPECT system based on the inverted compound-eye gamma camera design. Phys Med Biol 2018; 63:045008. [PMID: 29298960 DOI: 10.1088/1361-6560/aaa4fb] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this paper, we present simulation studies for the second-generation MRI compatible SPECT system, MRC-SPECT-II, based on an inverted compound eye (ICE) gamma camera concept. The MRC-SPECT-II system consists of a total of 1536 independent micro-pinhole-camera-elements (MCEs) distributed in a ring with an inner diameter of 6 cm. This system provides a FOV of 1 cm diameter and a peak geometrical efficiency of approximately 1.3% (the typical levels of 0.1%-0.01% found in modern pre-clinical SPECT instrumentations), while maintaining a sub-500 μm spatial resolution. Compared to the first-generation MRC-SPECT system (MRC-SPECT-I) (Cai 2014 Nucl. Instrum. Methods Phys. Res. A 734 147-51) developed in our lab, the MRC-SPECT-II system offers a similar resolution with dramatically improved sensitivity and greatly reduced physical dimension. The latter should allow the system to be placed inside most clinical and pre-clinical MRI scanners for high-performance simultaneous MRI and SPECT imaging.
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Affiliation(s)
- Xiaochun Lai
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 S Wright St, Urbana, IL 61801, United States of America
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DiFilippo FP. Design of a Tri-PET collimator for high-resolution whole-body mouse imaging. Med Phys 2017; 44:4230-4238. [PMID: 28556264 DOI: 10.1002/mp.12379] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/30/2017] [Accepted: 05/22/2017] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Tri-PET refers to high-resolution 511-keV emission tomography using a multipinhole collimator in conjunction with lower resolution PET detectors operating in coincidence mode. Tri-PET is unique in that three spatial locations are associated with each event (two detector coordinates and one pinhole location). Spatial resolution and sensitivity are similar to that of 511-keV SPECT and are governed mainly by the collimator design. However because of a third spatial location in Tri-PET, the line-of-response is overdetermined. This feature permits new opportunities in data processing which impact collimator design. In particular, multiplexing can be avoided since the coincidence data identify the pinhole through which the photon passed. In this paper, the principles of Tri-PET collimator design are reviewed and then applied to the case of high-resolution imaging of a small animal in a clinical PET scanner. METHODS The design of a 148-pinhole collimator for whole-body imaging of a mouse is presented. Two pinhole designs were investigated: knife-edge pinholes with 1.1 mm aperture and novel hyperboloidal pinholes with 1.2 mm aperture, both having 18° cone angle. The pinhole configuration is unfocused, covering a whole-body mouse field of view with nearly uniform sensitivity. Computer simulations were performed of a micro hot rods phantom imaged with this collimator in a clinical PET scanner. Sensitivity was estimated by simulating a point source centered on-axis at locations spanning a 70-mm axial range, similar to the NEMA NU-4 standard for whole-body mouse imaging. RESULTS Reconstructed images of the hot rods phantom demonstrated the ability to resolve 1.1 mm structures with the knife-edge pinholes and 1.0 mm structures with the hyperboloidal pinholes. Sensitivity was found to be 0.093% and 0.054% for the knife-edge and hyperboloidal pinholes, respectively. CONCLUSIONS With a properly designed multipinhole collimator, high-resolution and acceptable sensitivity are achievable with Tri-PET using ordinary clinical PET detectors.
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Affiliation(s)
- Frank P DiFilippo
- Department of Nuclear Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA
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Hutton BF, Occhipinti M, Kuehne A, Máthé D, Kovács N, Waiczies H, Erlandsson K, Salvado D, Carminati M, Montagnani GL, Short SC, Ottobrini L, van Mullekom P, Piemonte C, Bukki T, Nyitrai Z, Papp Z, Nagy K, Niendorf T, de Francesco I, Fiorini C. Development of clinical simultaneous SPECT/MRI. Br J Radiol 2017; 91:20160690. [PMID: 28008775 PMCID: PMC5966197 DOI: 10.1259/bjr.20160690] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There is increasing clinical use of combined positron emission tomography and MRI, but to date there has been no clinical system developed capable of simultaneous single-photon emission computed tomography (SPECT) and MRI. There has been development of preclinical systems, but there are several challenges faced by researchers who are developing a clinical prototype including the need for the system to be compact and stationary with MRI-compatible components. The limited work in this area is described with specific reference to the Integrated SPECT/MRI for Enhanced stratification in Radio-chemo Therapy (INSERT) project, which is at an advanced stage of developing a clinical prototype. Issues of SPECT/MRI compatibility are outlined and the clinical appeal of such a system is discussed, especially in the management of brain tumour treatment.
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Affiliation(s)
- Brian F Hutton
- 1 Institute of Nuclear Medicine, University College London (UCL), London, UK
| | - Michele Occhipinti
- 2 Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano and Instituto Nacionale di Fisica Nucleare (INFN), Milan, Italy
| | | | - Domokos Máthé
- 4 CROmed Ltd, Budapest, Hungary.,5 Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | | | | | - Kjell Erlandsson
- 1 Institute of Nuclear Medicine, University College London (UCL), London, UK
| | - Debora Salvado
- 1 Institute of Nuclear Medicine, University College London (UCL), London, UK
| | - Marco Carminati
- 2 Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano and Instituto Nacionale di Fisica Nucleare (INFN), Milan, Italy
| | - Giovanni L Montagnani
- 2 Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano and Instituto Nacionale di Fisica Nucleare (INFN), Milan, Italy
| | - Susan C Short
- 6 Faculty of Medicine and Health, University of Leeds, Leeds, UK
| | - Luisa Ottobrini
- 7 Department of Medical-Surgical Pathophysiology and Transplants, University of Milan, Italy.,8 Institute for Molecular Bioimaging and Physiology (IBFM), National Council of Research (CNR), Milan, Italy
| | | | | | | | | | | | | | | | - Irene de Francesco
- 12 Department of Oncology, University College London Hospitals NHS Foundation Trust, London
| | - Carlo Fiorini
- 2 Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano and Instituto Nacionale di Fisica Nucleare (INFN), Milan, Italy
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19
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Pato LRV, Vandenberghe S, Zedda T, Van Holen R. Parallel-hole collimator concept for stationary SPECT imaging. Phys Med Biol 2015; 60:8791-807. [DOI: 10.1088/0031-9155/60/22/8791] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Van Audenhaege K, Van Holen R, Vanhove C, Vandenberghe S. Collimator design for a multipinhole brain SPECT insert for MRI. Med Phys 2015; 42:667989. [PMID: 26520758 DOI: 10.1118/1.4934371] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Brain single photon emission computed tomography (SPECT) imaging is an important clinical tool, with unique tracers for studying neurological diseases. Nowadays, most commercial SPECT systems are combined with x-ray computed tomography (CT) in so-called SPECT/CT systems to obtain an anatomical background for the functional information. However, while CT images have a high spatial resolution, they have a low soft-tissue contrast, which is an important disadvantage for brain imaging. Magnetic resonance imaging (MRI), on the other hand, has a very high soft-tissue contrast and does not involve extra ionizing radiation. Therefore, the authors designed a brain SPECT insert that can operate inside a clinical MRI. METHODS The authors designed and simulated a compact stationary multipinhole SPECT insert based on digital silicon photomultiplier detector modules, which have shown to be MR-compatible and have an excellent intrinsic resolution (0.5 mm) when combined with a monolithic 2 mm thick LYSO crystal. First, the authors optimized the different parameters of the SPECT system to maximize sensitivity for a given target resolution of 7.2 mm in the center of the field-of-view, given the spatial constraints of the MR system. Second, the authors performed noiseless simulations of two multipinhole configurations to evaluate sampling and reconstructed resolution. Finally, the authors performed Monte Carlo simulations and compared the SPECT insert with a clinical system with ultrahigh-resolution (UHR) fan beam collimators, based on contrast-to-noise ratio and a visual comparison of a Hoffman phantom with a 9 mm cold lesion. RESULTS The optimization resulted in a stationary multipinhole system with a collimator radius of 150.2 mm and a detector radius of 172.67 mm, which corresponds to four rings of 34 diSPM detector modules. This allows the authors to include eight rings of 24 pinholes, which results in a system volume sensitivity of 395 cps/MBq. Noiseless simulations show sufficient axial sampling (in a Defrise phantom) and a reconstructed resolution of 5.0 mm (in a cold-rod phantom). The authors compared the 24-pinhole setup with a 34-pinhole system (with the same detector radius but a collimator radius of 156.63 mm) and found that 34 pinholes result in better uniformity but a worse reconstruction of the cold-rod phantom. The authors also compared the 24-pinhole system with a clinical triple-head UHR fan beam system based on contrast-to-noise ratio and found that the 24-pinhole setup performs better for the 6 mm hot and the 16 mm cold lesions and worse for the 8 and 10 mm hot lesions. Finally, the authors reconstructed noisy projection data of a Hoffman phantom with a 9 mm cold lesion and found that the lesion was slightly better visible on the multipinhole image compared to the fan beam image. CONCLUSIONS The authors have optimized a stationary multipinhole SPECT insert for MRI and showed the feasibility of doing brain SPECT imaging inside a MRI with an image quality similar to the best clinical SPECT systems available.
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Affiliation(s)
- Karen Van Audenhaege
- Department of Electronics and Information Systems, Ghent University-iMinds Medical IT, MEDISIP-IBiTech, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Roel Van Holen
- Department of Electronics and Information Systems, Ghent University-iMinds Medical IT, MEDISIP-IBiTech, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Christian Vanhove
- Department of Electronics and Information Systems, Ghent University-iMinds Medical IT, MEDISIP-IBiTech, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Stefaan Vandenberghe
- Department of Electronics and Information Systems, Ghent University-iMinds Medical IT, MEDISIP-IBiTech, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
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21
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Van Audenhaege K, Van Holen R, Vandenberghe S, Vanhove C, Metzler SD, Moore SC. Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging. Med Phys 2015; 42:4796-813. [PMID: 26233207 PMCID: PMC5148182 DOI: 10.1118/1.4927061] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/07/2015] [Accepted: 07/08/2015] [Indexed: 01/23/2023] Open
Abstract
In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new collimator-production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole collimator for different applications.
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Affiliation(s)
- Karen Van Audenhaege
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Roel Van Holen
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Stefaan Vandenberghe
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Christian Vanhove
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Scott D Metzler
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Stephen C Moore
- Division of Nuclear Medicine, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115
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22
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Bouckaert C, Vandenberghe S, Van Holen R. Evaluation of a compact, high-resolution SPECT detector based on digital silicon photomultipliers. Phys Med Biol 2014; 59:7521-39. [PMID: 25401505 DOI: 10.1088/0031-9155/59/23/7521] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
MicroSPECT is one of the main functional imaging techniques used in the preclinical setting. Even though high-resolution images can be obtained with currently available systems, their sensitivity is often quite low due to the use of multi-pinhole collimation. This results in long acquisition times and hampers dynamic imaging. However, it has already been shown that this limited sensitivity can be overcome using high-resolution detectors. In this article, we therefore investigated the use of a digital photon counter (DPC) in combination with a 2 mm thick monolithic LYSO crystal for SPECT imaging. These light sensors contain arrays of avalanche photodiodes whose signals are directly digitised. The DPCs have the advantage that they are very compact, have a high intrinsic resolution, are MR compatible and allow disabling cells with a high dark count rate. In order to investigate the influence of the temperature dependent dark count rate on the detector performance, we compared it at 3 °C and 18 °C. At 3 °C, we observed an energy resolution of 28.8% and an intrinsic spatial resolution of 0.48 mm. Furthermore, the count rate at 10% loss is 60 kcps. Next, we looked at the event loss at 18 °C caused by the higher dark count rate and found a 5% loss compared to the 3 °C measurements. At this higher temperature the energy resolution becomes 29.2% and the intrinsic spatial resolution decreases to 0.52 mm. Due to the 5% count loss, the count rate at 10% loss increases to 63 kcps. A small degradation of the detector performance is thus observed at 18 °C.These results show the usefulness of this detector for SPECT imaging together with its excellent intrinsic spatial resolution. A drawback of the detector is its low, spatially varying energy resolution. Even though the detection efficiency and intrinsic spatial resolution are better at 3 °C, results are still acceptable at 18 °C.
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Affiliation(s)
- Carmen Bouckaert
- MEDISIP, Department of Electronics and Information Systems, Ghent University, iMinds Medical IT-IBiTech, Ghent, Belgium
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23
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Dold P, Bone MC, Flohr M, Preuss R, Joyce TJ, Deehan D, Holland J. Validation of an optical system to measure acetabular shell deformation in cadavers. Proc Inst Mech Eng H 2014; 228:781-6. [DOI: 10.1177/0954411914546562] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Deformation of the acetabular shell at the time of surgery can result in poor performance and early failure of the hip replacement. The study aim was to validate an ATOS III Triple Scan optical measurement system against a co-ordinate measuring machine using in vitro testing and to check repeatability under cadaver laboratory conditions. Two sizes of custom-made acetabular shells were deformed using a uniaxial/two-point loading frame and measured at different loads. Roundness measurements were performed using both the ATOS III Triple Scan optical system and a co-ordinate measuring machine and then compared. The repeatability was also tested by measuring shells pre- and post-insertion in a cadaver laboratory multiple times. The in vitro comparison with the co-ordinate measuring machine demonstrated a maximum difference of 5 µm at the rim and 9 µm at the measurement closest to the pole of the shell. Maximum repeatability was below 1 µm for the co-ordinate measuring machine and 3 µm for the ATOS III Triple Scan optical system. Repeatability was comparable between the pre-insertion (below 2 µm) and post-insertion (below 3 µm) measurements in the cadaver laboratory. This study supports the view that the ATOS III Triple Scan optical system fulfils the necessary requirements to accurately measure shell deformation in cadavers.
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Affiliation(s)
- Philipp Dold
- Medical Products Division, CeramTec GmbH, Plochingen, Germany
| | - Martin C Bone
- School of Mechanical Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Markus Flohr
- Medical Products Division, CeramTec GmbH, Plochingen, Germany
| | - Roman Preuss
- Medical Products Division, CeramTec GmbH, Plochingen, Germany
| | - Tom J Joyce
- School of Mechanical Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - David Deehan
- Newcastle Surgical Training Centre, Freeman Hospital, Newcastle upon Tyne, UK
| | - James Holland
- Newcastle Surgical Training Centre, Freeman Hospital, Newcastle upon Tyne, UK
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24
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Deprez K, Van Holen R, Vandenberghe S. A high resolution SPECT detector based on thin continuous LYSO. Phys Med Biol 2013; 59:153-71. [PMID: 24334315 DOI: 10.1088/0031-9155/59/1/153] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Single-photon emission computed tomography (SPECT) detectors with improved spatial resolution can be used to build multi-pinhole SPECT systems that have a higher sensitivity or a higher spatial resolution. In order to improve the spatial resolution we investigate the performance of a 2 mm thick continuous Lutetium Yttrium Orthosilicate (LYSO) scintillator and compare it to the performance of a 5 mm thick continuous NaI(Tl) scintillator. The advantages of LYSO are its high stopping power and its non-hygroscopicity. Drawbacks are the lower light output and the intrinsic radioactivity. The hypothesis of this study is that such a thin LYSO scintillator will have a small light spread and, as a consequence, will also have an improved spatial resolution when coupled to a Hamamatsu H8500 position sensitive photomultiplier tube. To optimize the spatial resolution and the useful detector area we used a mean nearest neighbor event-positioning method. Beam source measurements ((99m)Tc, 140 keV) were done to investigate the energy resolution and the spatial resolution of both detectors. The effect of the intrinsic radioactivity of the LYSO scintillator in the energy window was quantified. The mean energy resolution is 9.3% for the NaI(Tl) scintillator and 21.3% for the LYSO scintillator. The LYSO spectrum shows an X-ray escape peak which decreases the detection efficiency with 9.1%. The spatial resolution of the LYSO detector (0.93 mm full width at half maximum (FWHM)) is superior to the spatial resolution of the NaI(Tl) detector (1.37 mm FWHM). The intrinsic radioactivity in the energy window (42% window centered at 140 keV) is low (125.6 cps, 0.024 cps mm(-3)). LYSO is a promising scintillator for small-animal SPECT imaging, where spatial resolution is more important than energy resolution.
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Affiliation(s)
- Karel Deprez
- ELIS Department, MEDISIP - iMinds, Ghent University, Ghent, Belgium
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25
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Chaix C, Kovalsky S, Kosmider M, Barrett HH, Furenlid LR. Integration of AdaptiSPECT, a small-animal adaptive SPECT imaging system. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2013; 8853. [PMID: 26347197 DOI: 10.1117/12.2029768] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AdaptiSPECT is a pre-clinical adaptive SPECT imaging system under final development at the Center for Gamma-ray Imaging. The system incorporates multiple adaptive features: an adaptive aperture, 16 detectors mounted on translational stages, and the ability to switch between a non-multiplexed and a multiplexed imaging configuration. In this paper, we review the design of AdaptiSPECT and its adaptive features. We then describe the on-going integration of the imaging system.
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Affiliation(s)
- Cécile Chaix
- Center for Gamma-ray Imaging, University of Arizona, Tucson, AZ 85724
| | - Stephen Kovalsky
- Center for Gamma-ray Imaging, University of Arizona, Tucson, AZ 85724
| | - Matthew Kosmider
- Center for Gamma-ray Imaging, University of Arizona, Tucson, AZ 85724
| | | | - Lars R Furenlid
- Center for Gamma-ray Imaging, University of Arizona, Tucson, AZ 85724
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26
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Deprez K, Pato LRV, Vandenberghe S, Van Holen R. Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole). Phys Med Biol 2013; 58:859-85. [DOI: 10.1088/0031-9155/58/4/859] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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