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Reduced aliasing artifacts using shaking projection k-space sampling trajectory

Chinese physics B 2014年第3期23卷 656-662页

作者：朱艳春杜江杨文超段侪杰王浩宇高嵩包尚联 Beijing Key Laboratory of medical physics and Engineering School of Physics Peking University Department of Radiology University of California Institute of Computational physics and Complex Systems Lanzhou University Shenzhen Key Laboratory for Minimal Invasive medical Technologies Tsinghua University medical imaging physics Laboratory Health Science Center of Peking University

Radial imaging techniques, such as projection-reconstruction （PR）, are used in magnetic resonance imaging （MRI） for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function （PSF）. In this paper, a shaking projection （SP） k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. ASP trajectory has the same aliasing character when using half sampling frequency （or half data） for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling recon- struction. Furthermore, this method can be applied to three-dimensional （3D） hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts.

关键词： shaking projection radial sampling gridding reconstruction point spread function

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A necessary and sufficient condition for transforming autonomous systems into linear autonomous Birkhoffian systems

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Chinese physics B 2013年第10期22卷 349-353页

作者：崔金超刘世兴宋端 School of Aerospace Engineering Beijing Institute of Technology College of physics Liaoning University physics of medical imaging Department Eastern Liaoning University

The problem of transforming autonomous systems into Birkhoffian systems is studied. A reasonable form of linear autonomous Birkhoff equations is given. By combining them with the undetermined tensor method, a necessary and sufficient condition for an autonomous system to have a representation in terms of linear autonomous Birkhoff equations is obtained. The methods of constructing Birkhoffian dynamical functions are given. Two examples are given to illustrate the application of the results.

关键词： autonomous systems linear autonomous Birkhoff's equations non-Hamiltonian systems Whit-taker's equations

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Toxicity of superparamagnetic iron oxide nanoparticles: Research strategies and implications for nanomedicine

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Chinese physics B 2013年第12期22卷 24-33页

作者：李蕾江玲玲曾云刘刚 Center for Molecular imaging and Translational Medicine School of Public Health Xiamen University Sichuan Key Laboratory of medical imaging North Sichuan Medical College

Superparamagnetic iron oxide nanoparticles （SPIONs） are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to investigate the potential adverse biological effects and safety issues associated with SPIONs, which is essential for the development of next-generation SPIONs and for continued progress in translational research. In this mini review, we summarize recent developments in toxicity studies on SPIONs, focusing on the relationship between the physicochemical properties of SPIONs and their induced toxic biological responses for a better toxicological understanding of SPIONs.

关键词： superparamagnetic iron oxide nanoparticle nanotoxicity cytotoxicity oxidative stress reactive oxygen species

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A new Monte Carlo code for absorption simulation of laser-skin tissue interaction

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Chinese Optics Letters 2007年第4期5卷 238-240页

作者： Afshan Shirklvand Saeed Sarlcar Marjaneh Hejazi Leila Ataie-Fashtami Mohammad Reza Alinaghizadeh medical physics & Biomedical Engineering Department Tehran University of medical Sciences Tehran Iran medical physics & Biomedical Engineering Department Tehran University of medical Sciences Tehran Iran Research Center for Science and Technology in Medicine Tehran Iran Iranian Academic Center for Education Culture and Research Tehran Iran Iranian Center for medical Laser Tehran Iran NOOR medical imaging Center Tehran Iran

In laser clinical applications, the process of photon absorption and thermal energy diffusion in the target tissue and its surrounding tissue during laser irradiation are crucial. Such information allows the selection of proper operating parameters such as laser power, and exposure time for optimal therapeutic. The Monte Carlo method is a useful tool for studying laser-tissue interaction and simulation of energy absorption in tissue during laser irradiation. We use the principles of this technique and write a new code with MATLAB 6.5, and then validate it against Monte Carlo multi layer （MCML） code. The new code is proved to be with good accuracy. It can be used to calculate the total power absorbed in the region of interest. This can be combined for heat modelling with other computerized programs.

关键词： Laser beams Laser irradiation medical imaging Multilayers Photon migration Tissue

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Blue LED-pumped efficient NIR luminescence in Sb3+-doped lead-free metal halides

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Science China Materials 2025年

作者： Xiaoyong Huang College of physics and Optoelectronics Taiyuan University of Technology

Broadband near-infrared （NIR） light sources hold promise for some important NIR spectroscopy applications such as night vision,plant growths,optical communications,remote sensing,biomedical imaging and other noninvasive and nondestructive detections[1–4].Recently,the phosphors-converted NIR lightemitting diodes （LEDs） based on“blue LED chips+broadband NIR phosphors”are widely developed for next-generation costeffective NIR light *** this respect,the performance of NIR phosphors directly determines the overall quality of phosphors-converted NIR LEDs.

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Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

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Nuclear Science and Techniques 2023年第12期34卷 40-52页

作者： Mahak Osouli Alamdari Pardis Ghafarian Arman Rahmim Mehrdad Bakhshayesh‑Karam Mohammad Reza Ay Department of medical physics Iran University of Medical SciencesTehranIran Chronic Respiratory Diseases Research Center National Research Institute of Tuberculosis and Lung Diseases(NRITLD)Shahid Beheshti University of Medical SciencesTehranIran PET/CT and Cyclotron Center Masih Daneshvari HospitalShahid Beheshti University of Medical SciencesTehranIran Departments of Radiology and physics University of British ColumbiaVancouverBCCanada Research Center for Molecular and Cellular imaging Advanced Medical Technologies and Equipment InstituteTehran University of Medical SciencesTehranIran Department of medical physics and Biomedical Engineering Tehran University of Medical SciencesTehranIran

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction *** this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction *** was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:*** NEMA phantom(phantom I)was scanned separately in a one-bed *** simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different *** image quality parameters were evaluated by both *** in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)*** and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere *** reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

关键词： Positron emission tomography/computed tomography(PET/CT) Random coincidences Scatter coincidences·Time of flight(TOF) Point spread function(PSF) Field of view(FOV) Noise equivalent count rate(NECR) Signal-toNoise ratio(SNR)

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Negative refractions by triangular lattice sonic crystals in partial band gaps

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Chinese physics B 2015年第4期24卷 310-321页

作者： S.Alagoz B.B.Alagoz A.Sahin S.Nur Department of physics Inonu University Department of Electrical and Electronics Engineering Inonu University Vocational School of Health Services Medical Imaging Techniques Inonu University

This study numerically demonstrates the effects of partial band gaps on the negative refraction properties of sonic crystal. The partial band gap appearing at the second band edge leads to the efficient transmissions of scattered wave envelopes in the transverse directions inside triangular lattice sonic crystal, and therefore enhances the refraction property of sonic crystal. Numerical simulation results indicate a diagonal guidance of coupled scattered wave envelopes inside crystal structure at the partial band gap frequencies and then output waves are restored in the vicinity of the output interface of sonic crystal by combining phase coherent scattered waves according to Huygens＇ principles. This mechanism leads to two operations for wavefront engineering： one is spatial wavefront shifting operation and the other is convex-concave wavefront inversion operation. The effects of this mechanism on the negative refraction and wave focalization are investigated by using the finite difference time domain （FDTD） simulations. This study contributes to a better understanding of negative refraction and wave focusing mechanisms at the band edge frequencies, and shows the applications of the slab comer beam splitting and SC-air multilayer acoustic system.

关键词： sonic crystal negative refraction wave focusing partial band gap

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Polynomial curve fitting method for refraction-angle extraction in diffraction enhanced imaging

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Chinese physics C 2009年第11期33卷 969-974页

作者：陈志强丁飞黄志峰张丽尹红霞王振常朱佩平 Department of Engineering physics Tsinghua University Key Laboratory of Particle & Radiation imaging(Tsinghua University)Ministry of Education medical imaging Center Beijing Tongren Hospital Capital Medical University Beijing Synchrotron Radiation Facility Institute of High Energy Physics Chinese Academy of Sciences

X-ray diffraction sorbing low-Z sample. How enhanced imaging （DEI） is applied to extract phase information from to inspect internal structures of weakly abraw images measured in different positions of rocking curve is the key problem of DEI. In this paper, we present an effective extraction method called polynomial curve fitting method, in order to extract accurate information angular in a fast speed. It is compared with the existing methods such as multiple-images statistical method and Gaussian curve fitting method. The experiments results on a plastic cylinder and a black ant at the Beijing Synchrotron Radiation Facility prove that the polynomial curve fitting method can obtain most approximate refraction-angle values and its computation speed is 10 times faster than the Gaussian curve fitting method.

关键词： diffraction enhanced imaging synchrotron radiation polynomial curve fitting

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Au modified BiVO_(4) microparticles for photocatalytic N_(2) fixation

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Optoelectronics Letters 2022年第1期18卷 24-28页

作者： SUI Meirong GU Xiuquan School of medical imaging Xuzhou Medical UniversityXuzhou 221004China School of Materials Science and physics China University of Mining and TechnologyXuzhou 221116China

In this work,a visible light photocatalyst based on Au modified BiVO_(4)microspheres was synthesized successfully through using a facile photodeposition method for visible light N_(2)*** with pure BiVO_(4)microparticles(MPs),the obtained Au/BiVO_(4)MPs show superior N_(2)photofixation performance to BiVO_(4),owing to the enhancements of both the visible light absorption and charge carrier *** optimization,the actual NH_(4)^(+)generation rate of Au/BiVO_(4)reaches 0.419 mg·L^(-1),which is approximately 2 times higher than that of the pure BiVO_(4)*** results presented herein provide new insights into rational design of highly active catalysts with Au NPs toward efficient,stable,and sustainable visible light N_(2)fixation in mild conditions.

关键词： visible pure modified

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A novel approach to designing cylindrical-surface shim coils for a superconducting magnet of magnetic resonance imaging

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Chinese physics B 2010年第1期19卷 563-574页

作者：刘文韬俎栋林唐昕 Beijing Key Laboratory of medical physics and Engineering IHIP of Physics SchoolPeking University

For a superconducting magnet of magnetic resonance imaging （MRI）, the novel approach presented in this paper allows the design of cylindrical gradient and shim coils of finite length. The method is based on identification of the weighting of harmonic components in the current distribution that will generate a magnetic field whose z-component follows a chosen spherical harmonic function. Mathematical expressions which relate the harmonic terms in the cylin- drical current distribution to spherical harmonic terms in the field expansion are established. Thus a simple matrix inversion approach can be used to design a shim coil of any order pure harmonic. The expressions providing a spherical harmonic decomposition of the field components produced by a particular cylindrical current distribution are novel. A stream function was applied to obtain the discrete wire distribution on the cylindrical-surface. This method does not require the setting of the target-field points. The discussion referring to matrix equations in terms of condition numbers proves that this novel approach has no ill-conditioned problems. The results also indicate that it can be used to design cylindrical-surface shim coils of finite length that will generate a field variation which follows a particular spherical harmonic over a reasonably large-sized volume.

关键词： active shimming superconducting MRI magnet target-field approach harmonic coils

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