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Jin Y, Meng LJ. Exploration of Coincidence Detection of Cascade Photons to Enhance Preclinical Multi-Radionuclide SPECT Imaging. IEEE Trans Med Imaging 2024; 43:1766-1781. [PMID: 38163304 DOI: 10.1109/tmi.2023.3348756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
We proposed a technique of coincidence detection of cascade photons (CDCP) to enhance preclinical SPECT imaging of therapeutic radionuclides emitting cascade photons, such as Lu-177, Ac-225, Ra-223, and In-111. We have carried out experimental studies to evaluate the proposed CDCP-SPECT imaging of low-activity radionuclides using a prototype coincidence detection system constructed with large-volume cadmium zinc telluride (CZT) imaging spectrometers and a pinhole collimator. With In-111 in experimental studies, the CDCP technique allows us to improve the signal-to-contamination in the projection (Projection-SCR) by ~53 times and reduce ~98% of the normalized contamination. Compared to traditional scatter correction, which achieves a Projection-SCR of 1.00, our CDCP method boosts it to 15.91, showing enhanced efficacy in reducing down-scattered contamination, especially at lower activities. The reconstructed images of a line source demonstrated the dramatic enhancement of the image quality with CDCP-SPECT compared to conventional and triple-energy-window-corrected SPECT data acquisition. We also introduced artificial energy blurring and Monte Carlo simulation to quantify the impact of detector performance, especially its energy resolution and timing resolution, on the enhancement through the CDCP technique. We have further demonstrated the benefits of the CDCP technique with simulation studies, which shows the potential of improving the signal-to-contamination ratio by 300 times with Ac-225, which emits cascade photons with a decay constant of ~0.1 ns. These results have demonstrated the potential of CDCP-enhanced SPECT for imaging a super-low level of therapeutic radionuclides in small animals.
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Yang C, Zannoni EM, Meng LJ. Joint estimation of interaction position and energy deposition in semiconductor SPECT imaging sensors using fully connected neural network. Phys Med Biol 2023; 68:10.1088/1361-6560/aca740. [PMID: 36595331 PMCID: PMC10329845 DOI: 10.1088/1361-6560/aca740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 11/29/2022] [Indexed: 12/02/2022]
Abstract
Objective.Pixelated semiconductor detectors such as CdTe and CZT sensors suffer spatial resolution and spectral performance degradation induced by charge-sharing effects. It is critical to enhance the detector property through recovering the energy-deposition and position estimation.Approach.In this work, we proposed a fully-connected-neural-network-based charge-sharing reconstruction algorithm to correct the charge-loss and estimate the sub-pixel position for every multi-pixel charge-sharing event.Main results.Evident energy resolution improvement can be observed by comparing the spectrum produced by a simple charge-sharing addition method and the proposed energy correction methods. We also demonstrate that sub-pixel resolution can be achieved in projections obtained with a small pinhole collimator and an innovative micro-ring collimator.Significance.These achievements are crucial for multiple-tracer SPECT imaging applications, and for other semiconductor detector-based imaging modalities.
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Affiliation(s)
- Can Yang
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Elena Maria Zannoni
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Ling-Jian Meng
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, United States of America
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, United States of America
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, United States of America
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Jin Y, Streicher M, Yang H, Brown S, He Z, Meng LJ. Experimental Evaluation of a 3-D CZT Imaging Spectrometer for Potential Use in Compton-Enhanced PET Imaging. IEEE Trans Radiat Plasma Med Sci 2023; 7:18-32. [PMID: 38106623 PMCID: PMC10723109 DOI: 10.1109/trpms.2022.3200010] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
We constructed a prototype positron emission tomography (PET) system and experimentally evaluated large-volume 3-D cadmium zinc telluride (CZT) detectors for potential use in Compton-enhanced PET imaging. The CZT spectrometer offers sub-0.5-mm spatial resolution, an ultrahigh energy resolution (~1% @ 511 keV), and the capability of detecting multiple gamma-ray interactions that simultaneously occurred. The system consists of four CZT detector panels with a detection area of around 4.4 cm × 4.4 cm. The distance between the front surfaces of the two opposite CZT detector panels is ~80 mm. This system allows us to detect coincident annihilation photons and Compton interactions inside the detectors and then, exploit Compton kinematics to predict the first Compton interaction site and reject chance coincidences. We have developed a numerical integration technique to model the near-field Compton response that incorporates Doppler broadening, detector's finite resolutions, and the distance between the first and second interactions. This method was used to effectively reject random and scattered coincidence events. In the preliminary imaging studies, we have used point sources, line sources, a custom-designed resolution phantom, and a commercial image quality (IQ) phantom to demonstrate an imaging resolution of approximately 0.75 mm in PET images, and Compton-based enhancement.
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Affiliation(s)
- Yifei Jin
- Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
| | | | - Hao Yang
- H3D, Inc., Ann Arbor, MI 48108 USA
| | | | - Zhong He
- H3D, Inc., Ann Arbor, MI 48108 USA
| | - Ling-Jian Meng
- Department of Nuclear, Plasma and Radiological Engineering, Department of Bioengineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
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Zhao LL, Li YZ, Zhao XM, Dai TA, Li YR, Meng LJ. Dirac-cone-like electronic states on nematic antiferromagnetic FeSe and FeTe. J Phys Condens Matter 2022; 34:325801. [PMID: 35605598 DOI: 10.1088/1361-648x/ac7277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
We investigate the Dirac-cone-like (DCL) topological electronic properties of nematic-like antiferromagnetic (AFM) states of monolayer FeSe and FeTe designed artificially through first-principles calculations and Wannier-function-based tight-binding (WFTB) method. Our calculations reveal most of them have a pair of DCL bands on the Γ-Xline in the Brillouin zone (BZ) near the Fermi level and open a gap of about 20 meV in the absence and presence of spin-orbit coupling (SOC), respectively, similar to the lowest-energy pair-checkerboard AFM FeSe. We further confirm that they are weak topological insulators based on nonzeroZ2and fragile surface states, which are calculated by the WFTB method. For FeSe and FeTe in pair-checkerboard AFM states, we find that the in-plane compression strain in a certain range can give rise to another pair of DCL bands located on the Γ-X' line in the BZ. In addition, the magnetic moments, energies, and Fe-Se/Te distances for various nematic-like AFM configurations are presented. These calculations the combining effect of magnetism and topology in a single material and the understanding of the superconducting phenomena in iron-based FeSe and FeTe.
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Affiliation(s)
- L L Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - Y Z Li
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - X M Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - T A Dai
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - Y R Li
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - L J Meng
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of 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 Trans Radiat Plasma Med Sci 2022. [DOI: 10.1109/trpms.2021.3053592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Li YZ, Zhao LL, Zhao XM, Dai TA, Zhong JX, Meng LJ. Magnetic field effect on topological properties of Dirac semimetals PdTe 2/PtTe 2/PtSe 2. J Phys Condens Matter 2021; 34:085802. [PMID: 34794129 DOI: 10.1088/1361-648x/ac3b28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 11/18/2021] [Indexed: 06/13/2023]
Abstract
We investigated magnetic field effect on the topological properties of transition metal dichalcogenide Dirac semimetals (DSMs) PdTe2/PtTe2/PtSe2based on Wannier-function-based tight-binding (WFTB) model obtained from first-principles calculations. The DSMs PdTe2/PtTe2/PtSe2undergo a transition from DSMs into Weyl semimetals with four pairs of Weyl points (WPs) in the entire Brillouin zone by splitting Dirac points under external magnetic fieldB. The positions and energies of WPs vary linearly with the strength of theBfield under thec-axis magnetic fieldB. Under thea- andb-axisBfield, however, the positions of magnetic-field-inducing WPs deviate slightly from thecaxis, and theirkzcoordinates and energies change in a parabolic-like curve with the increasingBfield. However, the system opens an axial gap on theA-Γ axis, and the gap changes with the direction of theBfield when the out ofc-axisBfield is applied. When we further apply the magnetic field in theac,bc, andabplanes, the results are more diverse compared to the axial magnetic field. Under theacandbcplaneBfield, thekzand energies of WPs within angleθ= [0°, 90°] andθ= [90°, 180°] are mirror symmetrically distributed. The distribution of WPs shows broken rotational symmetry under theabplaneBfield due to the difference of non-diagonal part of Hamiltonian. Our theoretical findings can provide a useful guideline for the applications of DSM materials under external magnetic field in the future topological electronic devices.
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Affiliation(s)
- Y Z Li
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
| | - L L Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
| | - X M Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
| | - T A Dai
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
| | - J X Zhong
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - L J Meng
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
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Zannoni EM, Yang C, Meng LJ. Design Study of an Ultrahigh Resolution Brain SPECT System Using a Synthetic Compound-Eye Camera Design With Micro-Slit and Micro-Ring Apertures. IEEE Trans Med Imaging 2021; 40:3711-3727. [PMID: 34255626 PMCID: PMC8711775 DOI: 10.1109/tmi.2021.3096920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this paper, we discuss the design study for a brain SPECT imaging system, referred to as the HelmetSPECT system, based on a spherical synthetic compound-eye (SCE) gamma camera design. The design utilizes a large number ( ∼ 500 ) of semiconductor detector modules, each coupled to an aperture with a very narrow opening for high-resolution SPECT imaging applications. In this study, we demonstrate that this novel system design could provide an excellent spatial resolution, a very high sensitivity, and a rich angular sampling without scanning motion over a clinically relevant field-of-view (FOV). These properties make the proposed HelmetSPECT system attractive for dynamic imaging of epileptic patients during seizures. In ictal SPECT, there is typically no prior information on where the seizures would happen, and both the imaging resolution and quantitative accuracy of the dynamic SPECT images would provide critical information for staging the seizures outbreak and refining the plans for subsequent surgical intervention.We report the performance evaluation and comparison among similar system geometries using non-conventional apertures, such as micro-ring and micro-slit, and traditional lofthole apertures. We demonstrate that the combination of ultrahigh-resolution imaging detectors, the SCE gamma camera design, and the micro-ring and micro-slit apertures would offer an interesting approach for the future ultrahigh-resolution clinical SPECT imaging systems without sacrificing system sensitivity and FOV.
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Aime S, Amirshaghaghi A, Angel PM, Ardenkjaer-Larsen JH, Atreya R, Awe S, Badea CT, Beekman FJ, Biade S, Borden MA, Brunsing RL, Chandrasekharan P, Chang JB, Chen F, Chen JW, Chen X, Cheng Z, Cheng Z, Cherin E, Clinthorne NH, Cohen J, Colson C, Conolly S, Contag CH, Cutler CS, Dayton PA, Devoogdt N, Dina O, Drake RR, Dubsky S, Ducongé F, Fellows BD, Foster FS, Francis KP, Fung BK, Gambhir SS, Gao R, Giovenzana GB, Goodwill P, Goorden MC, Gorpas D, Grimm J, Groll AN, Hargus S, Harmsen S, He S, Hensley D, Hutton BF, Huynh Q, Iagaru A, Josephson L, Jurisson SS, Keselman P, Kircher MF, Kokate T, Konkle J, Korsen JA, Krasniqi A, Laniyonu A, Levin CS, Lewis MR, Lewis JS, Liu G, Liu Y, Looger LL, Lu K, Lu Y, Lucignani G, Lyons SK, Maina T, Martelli C, Matheson AM, Mempel TR, Meng LJ, Moradi F, Nagle VL, Neurath MF, Nicolson F, Nie L, Ntziachristos V, Orendorff R, Ottobrini L, Ouyang Y, Paez Segala MG, Parraga G, Perez-Liva M, Pratt EC, Rao J, Rath T, Rodriguez E, Rosenthal EL, Ross BD, Saayujya C, Saritas EU, Scott DA, Sheth VR, Slagle C, Tamura R, Tavitian B, Tay ZW, Terreno E, Thakur M, Thompson C, Tian J, Travagin F, Tsourkas A, Tully KM, Usmani SM, VanBrocklin HF, van Keulen S, van Zijl PC, Walmer RW, Wang C, Wang J, Wang LV, Xavier C, Yao J, Yu EY, Zheng X, Zheng B, Zhou XY. Contributors. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.01002-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Meng LJ, Clinthorne NH. Small-Animal SPECT, SPECT/CT, and SPECT/MRI. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00007-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Zannoni EM, Wilson MD, Bolz K, Goede M, Lauba F, Schöne D, Zhang J, Veale MC, Verhoeven M, Meng LJ. Development of a multi-detector readout circuitry for ultrahigh energy resolution single-photon imaging applications. Nucl Instrum Methods Phys Res A 2020; 981:164531. [PMID: 32968332 PMCID: PMC7505227 DOI: 10.1016/j.nima.2020.164531] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this paper, we present the design and preliminary performance evaluation of a novel external multi-channel readout circuitry for small-pixel room-temperature semiconductor detectors, namely CdZnTe (CZT) and CdTe, that provide an excellent intrinsic spatial (250 and 500 μm pixel size) and an ultrahigh energy resolution (~1% at 122 keV) for X-ray and gamma-ray imaging applications. An analog front-end printed circuit board (PCB) was designed and developed for data digitization, data transfer and ASIC control of pixelated CZT or CdTe detectors. Each detector unit is 2 cm × 2 cm in size and 1 or 2 mm in thickness, being bump-bonded onto a HEXITEC ASIC, and wire-bonded to a readout detector module PCB. The detectors' front-end is then connected, through flexible cables of up to 10 m in length, to a remote data acquisition system that interfaces with a PC through USB3.0 connection. We present the design and performance of a prototype multi-channel readout system that can read out up to 24 detector modules synchronously. Our experimental results demonstrated that the readout circuitry offers an ultrahigh spectral resolution (0.8 keV at 60 keV and 1.05 keV at 122 keV) with the Cd(Zn)Te/HEXITEC ASIC modules tested. This architecture was designed to allow easy expansion to accommodate a larger number of detector modules, and the flexibility of arranging the detector modules in a large and deformable detector array without degrading the excellent energy resolution.
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Affiliation(s)
- Elena Maria Zannoni
- Bioengineering, University of Illinois at Urbana-Champaign, United States of America
| | - Matthew D. Wilson
- Science and Technology Facilities Council, Rutherford Appleton Laboratory, United Kingdom
| | - Krystian Bolz
- aSpect Systems GmbH, Eisenbahnstrasse 2, 01097 Dresden, Germany
| | - Mario Goede
- aSpect Systems GmbH, Eisenbahnstrasse 2, 01097 Dresden, Germany
| | - Frank Lauba
- aSpect Systems GmbH, Eisenbahnstrasse 2, 01097 Dresden, Germany
| | - Daniel Schöne
- aSpect Systems GmbH, Eisenbahnstrasse 2, 01097 Dresden, Germany
| | - Jiajin Zhang
- Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, United States of America
| | - Matthew C. Veale
- Science and Technology Facilities Council, Rutherford Appleton Laboratory, United Kingdom
| | | | - Ling-Jian Meng
- Bioengineering, University of Illinois at Urbana-Champaign, United States of America
- Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, United States of America
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Zhou Y, Meng LJ, Wang J. [Changes in serum human cartilage glycoprotein-39 and high-mobility group box 1 in preterm infants with bronchopulmonary dysplasia]. Zhongguo Dang Dai Er Ke Za Zhi 2020; 22:334-338. [PMID: 32312371 PMCID: PMC7389695 DOI: 10.7499/j.issn.1008-8830.2001041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 03/03/2020] [Indexed: 06/11/2023]
Abstract
OBJECTIVE To study the association of the dynamic changes of peripheral blood human cartilage glycoprotein-39 (YKL-40) and high-mobility group box 1 (HMGB1) with bronchopulmonary dysplasia (BPD) in preterm infants. METHODS Preterm infants, with a gestational age of 28-32 weeks and a birth weight of <1 500 g, who were admitted to the neonatal intensive care unit from July 2017 to August 2019 were prospectively selected and divided into a BPD group with 35 infants and a non-BPD group with 51 infants. ELISA was used to measure the serum concentrations of YKL-40 and HMGB1 in preterm infants on days 3, 7, and 14 after birth. RESULTS The BPD group had a significantly lower serum YKL-40 concentration and a significantly higher serum HMGB1 concentration than the non-BPD group on days 3, 7, and 14 (P<0.001). The serum concentrations of YKL-40 and HMGB1 on days 7 and 14 were significantly higher than those on day 3 in both groups (P<0.017). In the BPD group, HMGB1 concentration on day 14 was significantly higher than that on day 7 (P<0.017), while there was no significant change in YKL-40 concentration from day 7 to day 14 (P>0.017). In the non-BPD group, YKL-40 concentration on day 14 was significantly higher than that on day 7 (P<0.017), while there was no significant change in HMGB1 concentration from day 7 to day 14 (P>0.017). CONCLUSIONS There are significant differences in the levels of YKL-40 and HMGB1 in peripheral blood between the preterm infants with BPD and those without BPD on days 3, 7, and 14 after birth, suggesting that YKL-40 and HMGB1 might be associated with the development of BPD.
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Affiliation(s)
- Yang Zhou
- Department of Neonatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221002, China.
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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. Nucl Instrum Methods Phys Res A 2020; 954:162046. [PMID: 32773914 DOI: 10.1016/j.nima.2018.09.084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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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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. Nucl Instrum Methods Phys Res A 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] [What about the content of this article? (0)] [Affiliation(s)] [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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George J, Giannoni L, Yoon BH, Meng LJ. Energy-modulated x-ray fluorescence and luminescence emissions from therapeutic nanoparticles. ACTA ACUST UNITED AC 2019; 64:035020. [DOI: 10.1088/1361-6560/aaeec3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Liu WQ, Xu Y, Han AM, Meng LJ, Wang J. [A comparative study of two ventilation modes in the weaning phase of preterm infants with respiratory distress syndrome]. Zhongguo Dang Dai Er Ke Za Zhi 2018; 20:729-733. [PMID: 30210024 PMCID: PMC7389177 DOI: 10.7499/j.issn.1008-8830.2018.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
OBJECTIVE To compare the efficacy between synchronized intermittent mandatory ventilation (SIMV) and pressure support ventilation with volume guarantee (PSV+VG) in the weaning phase of preterm infants with respiratory distress syndrome (RDS). METHODS Forty preterm infants with RDS who were admitted to the neonatal intensive care unit between March 2016 and May 2017 were enrolled as subjects. All infants were born at less than 32 weeks' gestation and received mechanical ventilation. These patients were randomly and equally divided into SIMV group and PSV+VG group in the weaning phase. Ventilator parameters, arterial blood gas, weaning duration (from onset of weaning to extubation), duration of nasal continuous positive airway pressure (NCPAP) after extubation, extubation failure rate, the incidence rates of pneumothorax, patent ductus arteriosus (PDA) and bronchopulmonary dysplasia (BPD), and the mortality rate were compared between the two groups. RESULTS The PSV+VG group had significantly decreased mean airway pressure, weaning duration, duration of NCPAP after extubation, and extubation failure rate compared with the SIMV group (P<0.05). There were no significant differences in arterial blood gas, mortality, or incidence rates of pneumothorax, PDA and BPD between the two groups (P>0.05). CONCLUSIONS For preterm infants with RDS, the PSV+VG mode may be a relatively safe and effective mode in the weaning phase. However, multi-center clinical trials with large sample sizes are needed to confirm the conclusion.
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Affiliation(s)
- Wen-Qiang Liu
- Department of Neonatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221002, China.
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16
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Meng LJ, Tian X, Huang S, Lin RL, Liu XH, Zhu QJ, Tao Z, Liu JX. Solvent- and Heat-Dependent Binding Behaviors of HMeQ[6] with Alkyldiammonium Ions. ChemistrySelect 2018. [DOI: 10.1002/slct.201801062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ling-Jian Meng
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Xiao Tian
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Sai Huang
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Rui-Lian Lin
- College of Chemistry and Chemical Engineering; Anhui University of Technology; Maanshan 243002 China
| | - Xin-Hua Liu
- School of Pharmacy; Anhui Medical University, Hefei; 230032,P. R. China
| | - Qian-Jiang Zhu
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Zhu Tao
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Jing-Xin Liu
- College of Chemistry and Chemical Engineering; Anhui University of Technology; Maanshan 243002 China
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17
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Abstract
Small animal positron emission tomography (PET) imaging often requires high resolution (∼few hundred microns) to enable accurate quantitation in small structures such as animal brains. Recently, we have developed a prototype ultrahigh resolution depth-of-interaction (DOI) PET system that uses CdZnTe detectors with a detector pixel size of 350 μm and eight DOI layers with a 250 μm depth resolution. Due to the large number of line-of-response (LOR) combinations of DOIs, the system matrix for reconstruction is 64 times larger than that without DOI. While a high resolution virtual ring geometry can be employed to simplify the system matrix and create a sinogram, the LORs in such a sinogram tend to be sparse and irregular, leading to potential degradation of the reconstructed image quality. In this paper, we propose a novel high resolution sinogram rebinning method in which a uniform sub-sampling DOI strategy is employed. However, even with the high resolution rebinning strategy, the reconstructed image tends to be very noisy due to insufficient photon counts in many high resolution sinogram pixels. To reduce noise effects, we developed a penalized maximum likelihood reconstruction framework with the Poisson log-likelihood and a non-convex total variation penalty. Here, an ordered subsets separable quadratic surrogate and alternating direction method of multipliers are utilized to solve the optimization. To evaluate the performance of the proposed sub-sampling method and the penalized maximum likelihood reconstruction technique, we perform simulations and preliminary point source experiments. By comparing the reconstructed images and profiles based on sinograms without DOI, with rebinned DOI and with sub-sampled DOI, we demonstrate that the proposed method with sub-sampled DOIs can significantly improve the image quality with lower dose and yield a high resolution of <300 μm.
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Affiliation(s)
- Kyungsang Kim
- Gordon Center for Medical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America
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18
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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19
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Meng LJ, Zhao WX, Chen LX, Sun WQ, Lin RL, Zhu QJ, Tao Z, Liu JX. Single and Double Binding of 1,10-Phenanthroline and 4,7-Dimethyl-1,10-phenanthroline to HMeQ[7]: Contrasting p K
a Shifts Induced by HMeQ[7]. ChemistrySelect 2018. [DOI: 10.1002/slct.201703040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ling-Jian Meng
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Wen-Xuan Zhao
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Li-Xia Chen
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Wen-Qi Sun
- College of Chemistry and Chemical Engineering; Anhui University of Technology; Maanshan 243002 China
| | - Rui-Lian Lin
- College of Chemistry and Chemical Engineering; Anhui University of Technology; Maanshan 243002 China
| | - Qian-Jiang Zhu
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Zhu Tao
- Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province; Guizhou University; Guiyang 550025 China
| | - Jing-Xin Liu
- College of Chemistry and Chemical Engineering; Anhui University of Technology; Maanshan 243002 China
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20
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Groll A, Kim K, Bhatia H, Zhang JC, Wang JH, Shen ZM, Cai L, Dutta J, Li Q, Meng LJ. Hybrid Pixel-Waveform (HPWF) Enabled CdTe Detectors for Small Animal Gamma-Ray Imaging Applications. IEEE Trans Radiat Plasma Med Sci 2017; 1:3-14. [PMID: 28516169 PMCID: PMC5431752 DOI: 10.1109/tns.2016.2623807] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper presents the design and preliminary evaluation of small-pixel CdTe gamma ray detectors equipped with a hybrid pixel-waveform (HPWF) readout system for gamma ray imaging applications with additional discussion on CZT due to its similarity. The HPWF readout system utilizes a pixelated anode readout circuitry which is designed to only provide the pixel address. This readout circuitry works in coincidence with a high-speed digitizer to sample the cathode waveform which provides the energy, timing, and depth-of-interaction (DOI) information. This work focuses on the developed and experimentally evaluated prototype HPWF-CdTe detectors with a custom CMOS pixel-ASIC to readout small anode pixels of 350 μm in size, and a discrete waveform sampling circuitry to digitize the signal waveform induced on the large cathode. The intrinsic timing, energy, and spatial resolution were experimentally evaluated in this paper in conjunction with methods for depth of interaction (DOI) partitioning of the CdTe crystal. While the experimental studies discussed in this paper are primarily for evaluating HPWF detectors for small animal PET imaging, these detectors could find their applications for ultrahigh-resolution SPECT and other imaging modalities.
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Affiliation(s)
- A Groll
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA (primary: )
| | - K Kim
- Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - H Bhatia
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
| | - J C Zhang
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
| | - J H Wang
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
| | - Z M Shen
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
| | - L Cai
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
| | - J Dutta
- Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - Q Li
- Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - L J Meng
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 USA
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21
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22
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Cai L, Lai X, Shen Z, Chen CT, Meng LJ. MRC-SPECT: A sub-500 μm resolution MR-compatible SPECT system for simultaneous dual-modality study of small animals. Nucl Instrum Methods Phys Res A 2014; 734:147-151. [PMID: 26722136 PMCID: PMC4694628 DOI: 10.1016/j.nima.2013.08.080] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In this paper, we will report the development of an ultrahigh resolution MR-compatible SPECT system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals. This system is constructed with 40 small-pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. We have experimentally demonstrated that this system is capable of providing an imaging resolution of <500 μm when operating inside MR scanners. We will report the design, construction of the MRI-compatible SPECT system, including the detector technology, collimator, system development and so on. The first imaging results obtained with this newly constructed SPECT system will also be reported.
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Affiliation(s)
- Liang Cai
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, Urbana, USA
| | - Xiaochun Lai
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, Urbana, USA
| | - Zengming Shen
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, Urbana, USA
| | - Chin-Tu Chen
- Department of Radiology, University of Chicago, Chicago, USA
| | - Ling-Jian Meng
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, Urbana, USA
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23
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Fu G, Meng LJ, Eng P, Newville M, Vargas P, La Riviere P. Experimental demonstration of novel imaging geometries for x-ray fluorescence computed tomography. Med Phys 2014; 40:061903. [PMID: 23718594 DOI: 10.1118/1.4801907] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
PURPOSE X-ray fluorescence computed tomography (XFCT) is an emerging imaging modality that maps the three-dimensional distribution of elements, generally metals, in ex vivo specimens and potentially in living animals and humans. At present, it is generally performed at synchrotrons, taking advantage of the high flux of monochromatic x rays, but recent work has demonstrated the feasibility of using laboratory-based x-ray tube sources. In this paper, the authors report the development and experimental implementation of two novel imaging geometries for mapping of trace metals in biological samples with ∼50-500 μm spatial resolution. METHODS One of the new imaging approaches involves illuminating and scanning a single slice of the object and imaging each slice's x-ray fluorescent emissions using a position-sensitive detector and a pinhole collimator. The other involves illuminating a single line through the object and imaging the emissions using a position-sensitive detector and a slit collimator. They have implemented both of these using synchrotron radiation at the Advanced Photon Source. RESULTS The authors show that it is possible to achieve 250 eV energy resolution using an electron multiplying CCD operating in a quasiphoton-counting mode. Doing so allowed them to generate elemental images using both of the novel geometries for imaging of phantoms and, for the second geometry, an osmium-stained zebrafish. CONCLUSIONS The authors have demonstrated the feasibility of these two novel approaches to XFCT imaging. While they use synchrotron radiation in this demonstration, the geometries could readily be translated to laboratory systems based on tube sources.
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Affiliation(s)
- Geng Fu
- Department of Nuclear, Plasma, and Radiological Engineering, The University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
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24
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Mejia J, Reis MA, Miranda ACC, Batista IR, Barboza MRF, Shih MC, Fu G, Chen CT, Meng LJ, Bressan RA, Amaro E. Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs. Braz J Med Biol Res 2013; 46:936-942. [PMID: 24270908 PMCID: PMC3854337 DOI: 10.1590/1414-431x20132764] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 08/21/2013] [Indexed: 01/12/2023] Open
Abstract
The single photon emission microscope (SPEM) is an instrument developed to obtain
high spatial resolution single photon emission computed tomography (SPECT) images of
small structures inside the mouse brain. SPEM consists of two independent imaging
devices, which combine a multipinhole collimator, a high-resolution, thallium-doped
cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and
an electron-multiplying charge-coupling device (CCD). Collimators have 300- and
450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes.
Projection data are acquired in a photon-counting strategy, where CCD frames are
stored at 50 frames per second, with a radius of rotation of 35 mm and magnification
factor of one. The image reconstruction software tool is based on the maximum
likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity
attainable with the seven-pinhole imaging device, together with the linearity for
quantification on the tomographic images, and to test the instrument in obtaining
tomographic images of different mouse organs. A spatial resolution better than 500 µm
and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as
well as a correlation coefficient between activity and intensity better than 0.99,
when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones
of mice were registered using 99mTc-labeled radiopharmaceuticals in times
appropriate for routine preclinical experimentation of <1 h per projection data
set. Detailed experimental protocols and images of the aforementioned organs are
shown. We plan to extend the instrument's field of view to fix larger animals and to
combine data from both detectors to reduce the acquisition time or applied
activity.
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Affiliation(s)
- J Mejia
- Hospital Israelita Albert Einstein, Instituto do Cérebro, São Paulo,SP, Brasil
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25
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Abstract
In this paper, we present an analytical approach for optimizing the design of a static SPECT system or optimizing the sampling strategy with a variable/adaptive SPECT imaging hardware against an arbitrarily given set of system parameters. This approach has three key aspects. First, it is designed to operate over a discretized system parameter space. Second, we have introduced an artificial concept of virtual detector as the basic building block of an imaging system. With a SPECT system described as a collection of the virtual detectors, one can convert the task of system optimization into a process of finding the optimum imaging time distribution (ITD) across all virtual detectors. Thirdly, the optimization problem (finding the optimum ITD) could be solved with a block-iterative approach or other nonlinear optimization algorithms. In essence, the resultant optimum ITD could provide a quantitative measure of the relative importance (or effectiveness) of the virtual detectors and help to identify the system configuration or sampling strategy that leads to an optimum imaging performance. Although we are using SPECT imaging as a platform to demonstrate the system optimization strategy, this development also provides a useful framework for system optimization problems in other modalities, such as positron emission tomography and x-ray computed tomography (Moore et al (2009 IEEE Nucl. Sci. Symp. Conf. Rec. pp 4154-7), Freed et al (2008 Med. Phys. 35 1912-25)).
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Affiliation(s)
- L J Meng
- Department of Nuclear, Plasma, and Radiological Engineering, The University of Illinois at Urbana Champaign, Urbana-Champaign, IL 61801, USA.
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26
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Yin Y, Chen X, Wu H, Komarov S, Garson A, Li Q, Guo Q, Krawczynski H, Meng LJ, Tai YC. 3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications. IEEE Trans Nucl Sci 2013; 60:9-15. [PMID: 28250476 PMCID: PMC5328192 DOI: 10.1109/tns.2012.2213611] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μm resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μm pitch pixels (250 μm anode pixels with 100 μm gap) and coplanar cathode. Charge sharing among the pixels of a 350 μm pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μm pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μm pitch detector biased at -1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications.
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Affiliation(s)
- Yongzhi Yin
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 73000, Gansu, China
| | - Ximeng Chen
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 73000, Gansu, China
| | - Heyu Wu
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Sergey Komarov
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Alfred Garson
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63110 USA
| | - Qiang Li
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63110 USA, and also with the State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
| | - Qingzhen Guo
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63110 USA
| | - Henric Krawczynski
- Department of Physics, Washington University in St. Louis, St. Louis, MO 63110 USA
| | - Ling-Jian Meng
- Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61822 USA
| | - Yuan-Chuan Tai
- Department of Radiology, Washington University School of Medicine, St. Louis, MO 63110 USA
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27
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Cai L, Meng LJ. Hybrid pixel-waveform CdTe/CZT detector for use in an ultrahigh resolution MRI compatible SPECT system. Nucl Instrum Methods Phys Res A 2013; 702:10.1016/j.nima.2012.08.069. [PMID: 24371365 PMCID: PMC3872131 DOI: 10.1016/j.nima.2012.08.069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this paper, we will present a new small pixel CdTe/CZT detector for sub-500 μm resolution SPECT imaging application inside MR scanner based on a recently developed hybrid pixel-waveform (HPWF) readout circuitry. The HPWF readout system consists of a 2-D multi-pixel circuitry attached to the anode pixels to provide the X-Y positions of interactions, and a high-speed digitizer to read out the pulse-waveform induced on the cathode. The digitized cathode waveform could provide energy deposition information, precise timing and depth-of-interaction information for gamma ray interactions. Several attractive features with this HPWF detector system will be discussed in this paper. To demonstrate the performance, we constructed several prototype HPWF detectors with pixelated CZT and CdTe detectors of 2-5 mm thicknesses, connected to a prototype readout system consisting of energy-resolved photon-counting ASIC for readout anode pixels and an Agilent high-speed digitizer for digitizing the cathode signals. The performances of these detectors based on HPWF are discussed in this paper.
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Affiliation(s)
- Liang Cai
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, 216 Talbot Laboratory, 104 S Wrig, Urbana, Urbana, Illinois 61801, USA
| | - Ling-Jian Meng
- Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign, 216 Talbot Laboratory, 104 S Wrig, Urbana, Urbana, Illinois 61801, USA
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28
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Komarov S, Yin Y, Wu H, Wen J, Krawczynski H, Meng LJ, Tai YC. Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications. Phys Med Biol 2012; 57:7355-80. [PMID: 23079763 DOI: 10.1088/0031-9155/57/22/7355] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 µm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 µm in x,y-plane and ∼0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 µm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 µm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of the inherent limitations of MC methods.
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Affiliation(s)
- Sergey Komarov
- Department of Radiology, Washington University, St. Louis, MO 63110, USA.
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29
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Cai L, Shen ZM, Zhang JC, Chen CT, Meng LJ. First imaging result with an ultrahigh resolution stationary MR compatible SPECT system. IEEE Nucl Sci Symp Conf Rec (1997) 2012; 2012:3568-3571. [PMID: 26692275 PMCID: PMC4682676 DOI: 10.1109/nssmic.2012.6551817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this paper, we will present the design and preliminary performance of an ultrahigh resolution stationary MR compatible SPECT (MRC-SPECT) system that is developed in our lab. The MRC-SPECT system is based on the second-generation energy-resolved photon-counting (ERPC) CdTe detectors and there are several key features associated with this system. Firstly, up to a total of twenty ERPC detectors will be assembled as a very compact ring, which provides an adequate angular sampling capability and a relatively high detection efficiency. The detectors are supported on a gantry made of high strength polyamide structure constructed using 3-D printing. This compact system can be directly operated inside an MR scanner. The detector module used in this system offers an intrinsic resolution of 350μm and an excellent energy resolution of around 3~4kev. Each ERPC detector module consists of four pixelated CdTe detectors with a total dimension of 4.5cm×2.25cm. Secondly, a die-cast platinum pinhole inserts and cast lead apertures are developed for this stationary SPECT system. Four 300/500μm diameter pinholes are used for each detector and all pinholes are mounted around a casted cylinder lead aperture tube. The inner diameter of the lead aperture tube is 6cm and the lead tube thickness is 16mm. The opposite detectors are placed 15.6cm apart and the magnification factor of this SPECT system is about 1.2. Thirdly, a comprehensive charge collection model inside strong magnetic field has been developed to account for the magnetic field induced distortion in the SPECT image. This model can accurately predict the detector's energy and spatial response to gamma ray incident events and then help to compensate for the event position recording error due to the strong magnetic field. In this development, we have made an effort to minimize the amount of magnetic materials in the system to alleviate potential interference to magnetic field inhomogeneity.
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Affiliation(s)
- L Cai
- Nuclear, Plasma and Radiological Engineering in University of Illinois at Urbana-Champaign
| | - Z M Shen
- Nuclear, Plasma and Radiological Engineering in University of Illinois at Urbana-Champaign
| | - J C Zhang
- Nuclear, Plasma and Radiological Engineering in University of Illinois at Urbana-Champaign
| | - C T Chen
- Nuclear, Plasma and Radiological Engineering in University of Illinois at Urbana-Champaign
| | - L J Meng
- Nuclear, Plasma and Radiological Engineering in University of Illinois at Urbana-Champaign
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30
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Meng LJ, Li N, La Riviere PJ. X-ray Fluorescence Emission Tomography (XFET) with Novel Imaging Geometries - A Monte Carlo Study. IEEE Trans Nucl Sci 2011; 58:3359-3369. [PMID: 22228913 PMCID: PMC3251222 DOI: 10.1109/tns.2011.2167632] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This paper presents a feasibility study for using two new imaging geometries for synchrotron X-ray fluorescence emission tomography (XFET) applications. In the proposed approaches, the object is illuminated with synchrotron X-ray beams of various cross-sectional dimensions. The resultant fluorescence photons are detected by high-resolution imaging-spectrometers coupled to collimation apertures. To verify the performance benefits of the proposed methods over the conventional line-by-line scanning approach, we have used both Monte Carlo simulations and an analytical system performance index to compare several different imaging geometries. This study has demonstrated that the proposed XFET approach could lead to a greatly improved imaging speed, which is critical for making XFET a practical imaging modality for a wide range of applications.
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Affiliation(s)
- L J Meng
- Department of Nuclear Plasma and radiological Engineering, University of Illinois at Urbana-Champaign
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31
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Abstract
This paper presents an analytical approach for performing adaptive angular sampling in single photon emission computed tomography (SPECT) imaging. It allows for a rapid determination of the optimum sampling strategy that minimizes image variance in regions-of-interest (ROIs). The proposed method consists of three key components: (a) a set of close-form equations for evaluating image variance and resolution attainable with a given sampling strategy, (b) a gradient-based algorithm for searching through the parameter space to find the optimum sampling strategy and (c) an efficient computation approach for speeding up the search process. In this paper, we have demonstrated the use of the proposed analytical approach with a single-head SPECT system for finding the optimum distribution of imaging time across all possible sampling angles. Compared to the conventional uniform angular sampling approach, adaptive angular sampling allows the camera to spend larger fractions of imaging time at angles that are more efficient in acquiring useful imaging information. This leads to a significantly lowered image variance. In general, the analytical approach developed in this study could be used with many nuclear imaging systems (such as SPECT, PET and X-ray CT) equipped with adaptive hardware. This strategy could provide an optimized sampling efficiency and therefore an improved image quality.
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Li XX, Yang XG, Lu YQ, Lu SS, Zhang M, Yao HI, Meng LJ, Lu KH. Protective effects of melatonin against oxidative stress in flow cytometry-sorted buffalo sperm. Reprod Domest Anim 2011; 47:299-307. [PMID: 21790800 DOI: 10.1111/j.1439-0531.2011.01858.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Previous reports of the ability of melatonin to scavenge a variety of toxic oxygen and nitrogen-based reactants suggest that melatonin could be an effective antioxidant for protecting sperm. In this study, flow cytometry and laser tweezers Raman spectroscopy were used to evaluate the effect of melatonin on buffalo sperm quality to optimize sperm sex-sorting procedures. In fresh sperm incubated in the presence or absence of melatonin (10(-4) m) for 1, 24, 48 h or 72 h at 27°C, the mitochondrial activity was significantly higher than in a non-melatonin control (p < 0.05). Also, during the flow-sorting process, sperm in melatonin-supplemented groups had higher (p < 0.05) mitochondrial activity than the control. The intensity of Raman spectra from sperm frozen in media supplemented with melatonin was significantly weaker than that for non-melatonin-treated groups, except for a band at 1302 per cm. Thus, melatonin helps to protect buffalo sperm from reactive oxygen species induced by staining, sorting and freezing and increases semen quality after the freezing-thawing processes. Furthermore, the results indicate the high potential of the laser tweezers Raman spectroscopy technique for rapid, effective and non-invasive assessment of the quality of sperm cells.
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Affiliation(s)
- X X Li
- Animal Reproduction Institute, Guangxi University, Nanning, China
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Abstract
This paper presents new approaches to accelerating X-ray fluorescence tomography (XFCT) that are grounded in both novel image acquisition strategies that improve the quality of the data acquired and in image reconstruction strategies that reduce the amount of data acquired. First, we introduce an alternative imaging scheme that uses an emission tomography (ET) system to collect the fluorescence photons representing an entire 2D slice or volumetric projection of the object at one time. Preliminary results indicate that this could achieve a ten to hundredfold improvement in imaging speed. Secondly, novel image reconstruction algorithms are introduced that allow for improved quantitative accuracy as well as for imaging of regions of interest, which will lead to further reduction in data-acquisition time.
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Affiliation(s)
- P J La Riviere
- Department of Radiology, University of Chicago, Chicago, IL, USA
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Meng LJ, Li N. Non-Uniform Object-Space Pixelation (NUOP) for Penalized Maximum-Likelihood Image Reconstruction for a Single Photon Emission Microscope System. IEEE Trans Nucl Sci 2009; 5:2777-2788. [PMID: 28255178 PMCID: PMC5330327 DOI: 10.1109/tns.2009.2024677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper presents a non-uniform object-space pixelation (NUOP) approach for image reconstruction using the penalized maximum likelihood methods. This method was developed for use with a single photon emission microscope (SPEM) system that offers an ultrahigh spatial resolution for a targeted local region inside mouse brain. In this approach, the object-space is divided with non-uniform pixel sizes, which are chosen adaptively based on object-dependent criteria. These include (a) some known characteristics of a target-region, (b) the associated Fisher Information that measures the weighted correlation between the responses of the system to gamma ray emissions occurred at different spatial locations, and (c) the linear distance from a given location to the target-region. In order to quantify the impact of this non-uniform pixelation approach on image quality, we used the Modified Uniform Cramer-Rao bound (MUCRB) to evaluate the local resolution-variance and bias-variance tradeoffs achievable with different pixelation strategies. As demonstrated in this paper, an efficient object-space pixelation could improve the speed of computation by 1-2 orders of magnitude, whilst maintaining an excellent reconstruction for the target-region. This improvement is crucial for making the SPEM system a practical imaging tool for mouse brain studies. The proposed method also allows rapid computation of the first and second order statistics of reconstructed images using analytical approximations, which is the key for the evaluation of several analytical system performance indices for system design and optimization.
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Affiliation(s)
- L J Meng
- Department of Nuclear, Plasma, and Radiological Engineering, the University of Illinois at Urbana Champaign, Urbana-Champaign, IL 61801 USA
| | - Nan Li
- Department of Nuclear, Plasma, and Radiological Engineering, the University of Illinois at Urbana Champaign, Urbana-Champaign, IL 61801 USA
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Meng LJ, Ma X, Liu HP, Yang XD, Xia JW, Xu HS, Hu ZG, Zhu XL, Wang M, Mao RS, Zhang DC, Mao LJ, Li J, Li GH, Liu Y, Yang JC, Yuan YJ, Zheng JH, Yang XT, Xiao GQ, Zhan WL. The first test experiment performed at the electron cooler of storage rings in Lanzhou. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/163/1/012031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Meng LJ, Fu G, Roy EJ, Suppe B, Chen CT. An Ultrahigh Resolution SPECT System for I-125 Mouse Brain Imaging Studies. Nucl Instrum Methods Phys Res A 2009; 600:498-505. [PMID: 20161174 PMCID: PMC2723829 DOI: 10.1016/j.nima.2008.11.149] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper presents some initial experimental results obtained with a dual-head prototype single photon emission microscope system (SPEM) that is dedicated to mouse brain studies using I-125 labeled radiotracers. In particular, this system will be used for in vivo tacking of radiolabeled T cells in mouse brain. This system is based on the use of the intensified electron multiplying charge-coupled device (I-EMCCD) camera that offers the combination of an excellent intrinsic spatial resolution, a good signal-to-noise ratio, a large active area and a reasonable detection efficiency over an energy range between 27-140keV. In this study, the dual-head SPEM system was evaluated using both resolution phantoms and a mouse with locally injected T cells labelled with I-125. It was demonstrated that for a relatively concentrated source object, the current dual-head SPEM system is capable of visualizing the tiny amount of radioactivity (~12 nCi) carried by a very small number (<1000) of T cells. The current SPEM system design allows four or six camera heads to be installed in a stationary system configuration that offers a doubled or tripled sensitivity at a spatial resolution similar to that obtained with the dualhead system. This development would provide a powerful tool for in vivo and non-invasive tracking of radiolabeled T cells in mouse brain and potentially for other rodent brain imaging studies.
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Affiliation(s)
- L J Meng
- Department of Nuclear, Plasma and Radiological Engineering, the University of Illinois at Urbana Champaign
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Abstract
In this paper, we present the use of modified uniform Cramer-Rao type bounds (MUCRB) for the design of single photon emission tomography (SPECT) systems. The MUCRB is the lowest attainable total variance using any estimator of an unknown vector parameter, whose mean gradient matrix satisfies a given constraint. Since the mean gradient is closely related to local impulse function, the MUCRB approach can be used to evaluate the fundamental tradeoffs between spatial resolution and variance that are achievable with a given SPECT system design. As a possible application, this approach allows one to compare different SPECT system designs based on the optimum average resolution-variance tradeoffs that can be achieved across multiple control-points inside a region-of-interest. The formulation of the MUCRB allows detailed modelling of physical aspects of practical SPECT systems and requests only a modest computation load. It can be used as an analytical performance index for comparing different SPECT system or aperture designs.
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Affiliation(s)
- Ling-Jian Meng
- Nuclear, Plasma, and Radiological Sciences, University of Illinois, Urbana-Champaign, Urbana, IL 61801 USA
| | - Nan Li
- Nuclear, Plasma, and Radiological Sciences, University of Illinois, Urbana-Champaign, Urbana, IL 61801 USA
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Abstract
This paper presents the design and feasibility study of a very-high resolution gamma camera for detecting 27-35 keV X and gamma rays emitted by I-125 labelled radiotracers. This detector consists of a newly developed Electron-multiplying CCD (EMCCD) sensor and a de-magnifier tube coupled to a thin layer of scintillator. A prototype detector was developed and experimentally evaluated. This detector has a detection area of ~ 5 cm2. It provided an intrinsic spatial resolution of < 60 µm FWHM and a high signal-to-noise ratio for detecting the 27-35 keV photons, which ensures an excellent counting efficiency. This detector will be used as the key component for a single photon emission microscope (SPEM) system that is under development.
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Affiliation(s)
- L J Meng
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 USA
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Abstract
This paper presents the spectroscopic performance of two newly developed pixelated HgI2 detectors. These detectors are 1 × 1 × 0.814 cm3 and 1 × 1 × 1.016 cm3 in size. Each detector has four closely packed 1 × mm2 anode pixels at the center of one of the 1 × 1 cm2 surfaces. These anode pixels are surrounded by a large anode. All results presented here are based on events from a sub-volume underneath the anode pixels. In these detectors, signals were read out by a discrete electronics based on multiple A-250 pre-amplifiers and a digital oscilloscope for sampling pulse waveforms. Depth sensing technique was used to correct the depth-dependent variation in photopeak amplitude. Main results presented are: (1) energy resolutions of 0.85 ~ 1.3% have been achieved on these detectors; (2) the electron mobility-lifetime product was measured to be ~1 × 10-2 cm2/V and the measured electron lifetime was ~200 μs and (3) variation in electron drifting properties under different anode pixels were observed. Significant non-uniformity in internal electric field strength was also experimentally demonstrated.
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Affiliation(s)
- L J Meng
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 USA
| | - Z He
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 USA
| | - B Alexander
- Constellation Technology Corporation, Largo, FL 33777 USA
| | - J Sandoval
- Constellation Technology Corporation, Largo, FL 33777 USA
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Meng LJ, Clinthorne NH, Skinner S, Hay RV, Gross M. Design and Feasibility Study of a Single Photon Emission Microscope System for Small Animal I-125 Imaging. IEEE Trans Nucl Sci 2006; 53:1168-1178. [PMID: 28255179 PMCID: PMC5330363 DOI: 10.1109/tns.2006.871405] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper presents a design study of a single photon emission microscope (SPEM) system for small animal imaging using I-125 labelled radiotracers. This system is based on the use of a very-high resolution gamma camera coupled to a converging non-multiplexing multiple pinhole collimator. This enables one to "zoom" into a small local region inside the object to extract imaging information with a very high spatial resolution and a reasonable sensitivity for gamma rays emitted from this local region. The SPEM system also includes a pinhole (or multiple pinhole) gamma camera that has a full angular coverage of the entire object. The designed imaging spatial resolution for the SPEM system is between 250 μm to 500 μm FWHM.
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Affiliation(s)
- L J Meng
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 USA
| | - N H Clinthorne
- Department of Radiology, University of Michigan, Ann Arbor, MI 48109 USA
| | - S Skinner
- VA Medical Center, Ann Arbor, MI 48109 USA
| | - R V Hay
- Van Vandel Research Institute, Grand Rapids, MI 49503 USA
| | - M Gross
- VA Medical Center, Ann Arbor, MI 48109 USA
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41
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Abstract
This paper presents a modified Uniform Cramer-Rao bound (UCRB) for studying estimator spatial resolution and variance tradeoffs. We proposed to use a resolution constraint that is imposed on mean gradient vectors of achieved estimators and derived the minimum achievable variance for any estimator satisfies this resolution constraint. This approach partially overcomes the limitations of the former UCRB approach based on a bias-gradient norm constraint. We applied this method in a feasibility study of using multiple pinhole apertures for small animal SPECT imaging applications. The SPECT system studied was based on an existing gamma camera. The achievable spatial resolution and variance tradeoffs for systems with different design parameters, such as number of pinholes and pinhole size, were studied.
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Affiliation(s)
- L J Meng
- Department of Radiology, University of Michigan, 1906 Cooley Bldg., 2355 Bonisteel Blvd., Ann Arbor, MI 48109, USA
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Abstract
This paper presents a feasibility of a gamma ray imager using combined electronic and mechanical collimation methods. This detector is based on the use of a multiple pinhole collimator, a position sensitive scintillation detector with Anger logic readout. A pixelated semiconductor detector, located between the collimator and the scintillation detector, is used as a scattering detector. For gamma rays scattered in the first detector and then stopped in the second detector, an image can also be built up based on the joint probability of their passing through the collimator and falling into a broadened conical surface, defined by the detected Compton scattering event. Since these events have a much smaller angular uncertainty, they provide more information content per photon compared with using solely the mechanical or electronic collimation. Therefore, the overall image quality can be improved. This feasibility study adapted a theoretical approach, based on analysing the resolution-variance trade-off in images reconstructed using Maximum a priori (MAP) algorithm. The effect of factors such as the detector configuration, Doppler broadening and collimator configuration are studied. The results showed that the combined collimation leads to a significant improvement in image quality at energy range below 300keV. However, due to the mask penetration, the performance of such a detector configuration is worse than a standard Compton camera at above this energy.
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Affiliation(s)
- L J Meng
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan
| | - D K Wehe
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan
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Meng LJ, Rogers WL, Clinthorne NH. Feasibility Study of Compton Scattering Enhanced Multiple Pinhole Imager for Nuclear Medicine. IEEE Trans Nucl Sci 2002; 2:1258-1262. [PMID: 28250473 PMCID: PMC5328635 DOI: 10.1109/nssmic.2002.1239548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper presents a feasibility study of a Compton scattering enhanced (CSE) multiple pinhole imaging system for gamma rays with energy of 140keV or higher. This system consists of a multiple-pinhole collimator, a position sensitive scintillation detector as used in standard Gamma camera, and a Silicon pad detector array, inserted between the collimator and the scintillation detector. The problem of multiplexing, normally associated with multiple pinhole system, is reduced by using the extra information from the detected Compton scattering events. In order to compensate for the sensitivity loss, due to the low probability of detecting Compton scattered events, the proposed detector is designed to collect both Compton scattering and Non-Compton events. It has been shown that with properly selected pinhole spacing, the proposed detector design leads to an improved image quality.
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Affiliation(s)
- L J Meng
- Department of Radiology, University of Michigan
| | - W L Rogers
- Department of Radiology, University of Michigan
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Qin K, Yang DS, Yang Y, Chishti MA, Meng LJ, Kretzschmar HA, Yip CM, Fraser PE, Westaway D. Copper(II)-induced conformational changes and protease resistance in recombinant and cellular PrP. Effect of protein age and deamidation. J Biol Chem 2000; 275:19121-31. [PMID: 10858456 DOI: 10.1074/jbc.275.25.19121] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
While PrP(C) rearranges in the area of codons 104-113 to form PrP(Sc) during prion infections, the events that initiate sporadic Creutzfeldt-Jakob disease are undefined. As Cu(II) is a putative ligand for PrP(C) and has been implicated in the pathogenesis of Creutzfeldt-Jakob disease and other neurodegenerative diseases, we investigated the structural effects of binding. Incubation of brain microsomes with Cu(II) generated approximately 30-kDa proteinase K-resistant PrP. Cu(II) had little effect on fresh recombinant PrP23-231, but aged protein characterized by conversion of Asn-107 to Asp decreased alpha-helical content by approximately 30%, increased beta-sheet content 100%, formed aggregates, and acquired proteinase K resistance in the presence of Cu(II). These transitions took place without need for acid pH, organic solvents, denaturants, or reducing agents. Since conversion of Asn to Asp proceeds by a spontaneous pathway involving deamidation, our data suggest that covalent variants of PrP(C) arising in this manner may, in concert with Cu(II), generate PrP(Sc)-like species capable of initiating sporadic prion disease.
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Affiliation(s)
- K Qin
- Centre for Research in Neurodegenerative Diseases, Department of Medical Biophysics, Mass Spectrometry Laboratory, Modern Medicine Research Centre, Toronto, Ontario M 5S 3HS, Canada
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Meng LJ, Reyes H, Axelson M, Palma J, Hernandez I, Ribalta J, Sjövall J. Progesterone metabolites and bile acids in serum of patients with intrahepatic cholestasis of pregnancy: effect of ursodeoxycholic acid therapy. Hepatology 1997; 26:1573-9. [PMID: 9398000 DOI: 10.1002/hep.510260627] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The concentrations in serum of sulfated metabolites of progesterone are known to be elevated in patients with intrahepatic cholestasis of pregnancy (ICP). The profiles of these metabolites and conjugated bile acids were analyzed in serum from 11 patients with ICP before and during administration of ursodeoxycholic acid (UDCA) (8 patients) or placebo (3 patients). The clinical condition of 7 of the patients given UDCA improved markedly, and 1 patient given placebo had a spontaneous remission of the disease. The total concentration of conjugated bile acids in the 11 patients was 25 +/- 6 micromol/L (mean +/- SEM) and decreased to 6.3 +/- 3.5 micromol/L in the 7 patients responding to treatment with UDCA. The level of 7alpha-hydroxy-4-cholesten-3-one was significantly lower (7.2 +/- 2.2 ng/mL) in patients with ICP than in healthy pregnancy (18 +/- 4.6 ng/mL) (P < .05). The concentrations of 5alpha-pregnane-3alpha,20alpha-diol mono- and disulfates decreased by 52% +/- 7.9% and 68% +/- 5.5%, respectively, in the patients responding to treatment. Similar decreases were observed for the mono- and disulfates of 5alpha-pregnane-3alpha,20alpha,21-triol and 5beta-pregnane-3alpha,20alpha-diol. The disulfate of 5alpha-pregnane-3beta,20alpha-diol showed a smaller decrease, while glucuronidated steroids were not affected. The 3alpha-/3beta-hydroxysteroid ratio and di-/monosulfate ratio decreased significantly during UDCA. The magnitudes of the changes of bile acid and steroid concentrations during UDCA were not correlated to each other. The results suggest that UDCA stimulates the biliary excretion of steroids with a 3alpha-sulfoxy group and disulfates. This effect seems to be independent of the effect on bile acid excretion, indicating the use of different transport proteins. The possibility of an effect of UDCA on the formation of the steroid sulfates cannot be excluded.
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Affiliation(s)
- L J Meng
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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Meng LJ, Reyes H, Palma J, Hernandez I, Ribalta J, Sjövall J. Effects of ursodeoxycholic acid on conjugated bile acids and progesterone metabolites in serum and urine of patients with intrahepatic cholestasis of pregnancy. J Hepatol 1997; 27:1029-40. [PMID: 9453429 DOI: 10.1016/s0168-8278(97)80147-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND/AIMS AND METHODS The mechanism(s) behind the effects of ursodeoxycholic acid on serum steroid sulphate profiles in patients with intrahepatic cholestasis of pregnancy is not clear. Conjugated progesterone metabolites and bile acids have therefore been analysed in serum and urine of patients with intrahepatic cholestasis of pregnancy before and during treatment with ursodeoxycholic acid using chromatographic and mass spectrometric methods. RESULTS The concentration of glycine-/taurine-conjugated bile acids decreased from 8.9+/-3 micromol/l (mean+/-SEM) before treatment to 1.8+/-0.6 micromol/l during treatment with ursodeoxycholic acid. The total bile acid excretion in urine decreased from 56+/-14 to 32+/-5.6 micromol/g creatinine. The proportion of cholic acid in serum and urine, and of 1beta-, 2beta- and 6alpha-hydroxylated cholic acids in urine decreased markedly during ursodeoxycholic acid while the percentages of 3alpha,12alpha-dihydroxy-3-oxo-4-cholenoic acid and chenodeoxycholic acid were unchanged. The levels in serum and excretion in urine of sulphated steroids decreased during ursodeoxycholic acid, by 45-49% for disulphates and 33-35% for monosulphates. The ratios of 3alpha- to 3beta-hydroxysteroid disulphates were lowered by ursodeoxycholic acid from 1.1 (mean) to 0.68 in serum, and from 1.2 to 0.70 in urine. The corresponding ratios for monosulphates before and during ursodeoxycholic acid were 6.9 and 4.5, respectively, in serum, and 21 and 5.2, respectively, in urine. The major monosulphates in urine, dominated by 5alpha-pregnane-3alpha, 20alpha-diol, were also conjugated with N-acetylglucosamine. The excretion of these double conjugates decreased from 27+/-8.4 to 15+/-5.3 micromol/g creatinine during ursodeoxycholic acid. In contrast to sulphated steroids, the concentrations of glucuronides were unchanged in serum and their excretion in urine tended to increase during ursodeoxycholic acid. The metabolism of ursodeoxycholic acid was similar to that described in nonpregnant subjects. In addition to metabolites hydroxylated in the 1beta-, 5beta-, 6alpha/beta and 22-positions, a 4-hydroxy-ursodeoxycholic acid was tentatively identified. This occurred predominantly as a double conjugate with glycine/taurine and glucuronic acid, as did other 4-hydroxylated bile acids of probable foetal origin. CONCLUSIONS The results are compatible with the contention that ursodeoxycholic acid stimulates the biliary excretion of sulphated progesterone metabolites, particularly those with a 3alpha-hydroxy-5alpha(H) configuration and disulphates. The effect(s) appears to be independent of the stimulation of bile acid secretion. An effect of ursodeoxycholic acid on the reductive metabolism of progesterone cannot be excluded.
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Affiliation(s)
- L J Meng
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
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Meng LJ, Reyes H, Palma J, Hernandez I, Ribalta J, Sjövall J. Profiles of bile acids and progesterone metabolites in the urine and serum of women with intrahepatic cholestasis of pregnancy. J Hepatol 1997; 27:346-57. [PMID: 9288610 DOI: 10.1016/s0168-8278(97)80181-x] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND/AIMS AND METHODS The etiology of intrahepatic cholestasis of pregnancy (JCP) is unknown. We have performed comprehensive chromatographic and mass spectrometric analyses of progesterone metabolites and bile acids in serum and urine of six patients in order to characterize changes that might be of importance for the development of the disease. RESULTS Conjugated bile acids were increased in serum and urine of patients with ICP while the levels of unconjugated bile acids were similar in healthy pregnancies and ICP. Unconjugated and conjugated 7 alpha, 12 alpha-dihydroxy-3-oxo-4-cholenoic acid was excreted in urine both in healthy pregnancies and in ICP, possibly indicating a rate limitation of 3-oxo-delta 4-steroid 5 beta-reductase in pregnancy. The serum levels and urinary excretion of total sulfated progesterone metabolites were increased in ICP while the glucuronides were unchanged or low. Confirming previous results, the fraction of metabolites with 3 alpha-hydroxy-5 alpha(H) configuration was increased. The urinary excretion of 5 alpha-pregnane-3 alpha, 20 alpha-diol 3-sulfate, 20-N-acetylglucosaminide was greatly increased in ICP, as was that of 3 alpha-hydroxy-5 alpha-androstane-17 beta-carboxylic acid, assumed to be a progesterone metabolite. CONCLUSIONS The combined results of this and previous studies are compatible with a primary change in the reductive metabolism of progesterone in ICP, resulting in increased formation of metabolites with a 3 alpha-hydroxy-5 alpha(H) configuration and a larger fraction of sulfates. There also seems to be a selective defect in the biliary secretion of sulfated metabolites, particularly disulfates.
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Affiliation(s)
- L J Meng
- Department of Medical Biochemistry and Biophysics, Karolinska Instituter, Stockholm, Sweden
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Meng LJ, Griffiths WJ, Nazer H, Yang Y, Sjövall J. High levels of (24S)-24-hydroxycholesterol 3-sulfate, 24-glucuronide in the serum and urine of children with severe cholestatic liver disease. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)37217-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Meng LJ, Griffiths WJ, Nazer H, Yang Y, Sjövall J. High levels of (24S)-24-hydroxycholesterol 3-sulfate, 24-glucuronide in the serum and urine of children with severe cholestatic liver disease. J Lipid Res 1997; 38:926-34. [PMID: 9186910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Extracts of urine and serum from children with cholestatic liver disease were analyzed by fast atom bombardment (FAB) mass spectrometry. About half of all spectra showed a peak at m/z 657, compatible with the presence of a glucuronidated cholestenediol sulfate. Separation by ion exchange chromatography before and after solvolysis and treatment with beta-glucuronidase, combined with analyses by gas chromatography-mass spectrometry and FAB mass spectrometry with collision-induced dissociation, showed that the major compound responsible for the peak at m/z 657 was (24S)-24-hydroxycholesterol 3-sulfate, 24-glucuronide. The double conjugate of 27-hydroxycholesterol was also identified and double conjugates of cholestene- and cholestanetriols were also present. Semiquantitative analyses of the double conjugate of 24-hydroxycholesterol in patients whose FAB spectra showed a peak at m/z 657 indicated serum levels of 2-18 microM and a daily urinary excretion of 0.1-2.7 mumol/24 h. Eleven of 13 studied patients with a prominent peak at m/z 657 in the FAB spectra of their serum or urine either underwent liver transplantation or died. It is concluded that double conjugation of hydroxysterols with sulfuric and glucuronic acids can be an important metabolic pathway, particularly for (24S)-24-hydroxycholesterol. It is speculated that serious cholestatic liver disease may induce an increased formation and release of (24S)-24-hydroxycholesterol from brain (Lütjohann et al. 1996, Proc. Nutl. Acad. Sci. USA. 93: 9799-9804) with subsequent extracerebral conjugation with sulfuric and glucuronic acids.
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Affiliation(s)
- L J Meng
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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Meng LJ, Sjövall J. Method for combined analysis of profiles of conjugated progesterone metabolites and bile acids in serum and urine of pregnant women. J Chromatogr B Biomed Sci Appl 1997; 688:11-26. [PMID: 9029309 DOI: 10.1016/s0378-4347(97)88051-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A method for analysis of profiles of conjugated progesterone metabolites and bile acids in 10 ml of urine and 1-4 ml of serum from pregnant women is described. Total bile acids and neutral steroids from serum and urine were extracted with octadecylsilane-bonded silica. Groups of conjugates were separated on the lipophilic ion-exchanger triethylaminohydroxypropyl Sephadex LH-20 (TEAP-LH-20). Fractions were divided for steroid or bile acid analyses. Sequences of hydrolysis/solvolysis and separations on TEAP-LH-20 permitted separate analyses of steroid glucuronides, monosulfates and disulfates and bile acid aminoacyl amidates, sulfates, glucuronides and sulfate-glucuronides. Radiolabelled compounds were added at different steps to monitor recoveries and completeness of separation, and hydrolysis/solvolysis of conjugates was monitored by fast-atom bombardment mass spectrometry. The extraction and solvolysis of steroid disulfates in urine were studied in detail, and extraction recoveries were found to be pH-dependent. Following methylation of bile acids, all compounds were analysed by capillary gas chromatography and gas chromatography-mass spectrometry of their trimethylsilyl ether derivatives. Semiquantification of individual compounds in each profile by gas-liquid chromatography had a coefficient of variation of less than 30%. The total analysis required 3 days for serum and 4 days for urine.
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Affiliation(s)
- L J Meng
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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