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Targeted principle component analysis:A new motion artifact correction approach for near-infrared spectroscopy

Journal of Innovative Optical Health Sciences 2014年第2期7卷 98-105页

作者： Meryen A.Yücel Julitte Selb Robert J.C.ooper David A.Boas Athinoula A.Martinos Center for Biomedical imaging Department of Radiology Massachusetts General Hospital Haruard Medical SchoolCharlestownMAUSA Department of medical physics and Bioengineering University College London LondonUK

As near-infrared spectroscopy(NIRS)broadens its application area to diferent age and diseasegroups,motion artifacts in the NIRS signal due to subject movement is becoming an *** artifacts generally produce signal fiuctuations that are larger than physio-logical NIRS signals,thus it is cruciai to corect for them before obtaining an cstimate ofstimulusevoked hemodynamic responses.,There are various methods for correction such as principlecomponent analy sis(P CA),wavelet-based filt ering and spline int ***,we introduce anew approach to motion artifact correction,targeted principle component analysis(PCA),which incorporates a PCA filter only on the segments of data identified as motion *** expected that this will overcome the issues of filtering desired signals that plagues standardPCA fitering of entire data *** compared the new approach with the most efiective motionartifact correction algorithms on a set of data acquired simultaneously with a collodion-fixedprobe(low motion artifact content)and a standard Velcro probe(high motion artifact content).Our results show that tPCA gives statistically better results in recovering hemodynamic responsefunction(HRF)as compared to wavelet-based fltering and spline interpolation for the *** resulis in a significant reduction in mean-squauared'error(MSE)and significant en-hancement in Pearson's correlation coeficient to the true HRF,The collodion-fixed fiber probewith no motion correction performed better than the Velcro probe corrected for motion artifactsin terms of MSE and Pearson's correlation ***,if the experimental study permits,the use of a collodion-fixed fiber probe may be desirable.I the use of a collodion-fixed probe is notfeasible,then we suggest the use of tP CA in the processing of motion artifact contaminated data.

关键词： Wavelet spline collodion-fixed fiber.

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Active ferromagnetic shimming of the permanent magnet for magnetic resonance imaging scanner

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Chinese physics B 2010年第7期19卷 603-610页

作者：唐昕洪礼明俎栋林 Institute of Heavy Ion physics Beijing Key Laboratory of Medical Physics and EngineeringSchool of PhysicsPeking University

This paper presents an approach of active ferromagnetic shimming for C-type permanent magnetic resonance imaging （MRI） magnet. It is designed to reduce inhomogeneity of magnetostatic field of C-type permanent magnet to meet the stringent requirement for MRI applications. An optimal configuration （locations and thicknesses） of active ferromagnetic pieces is generated through calculation according to the initial field map and the demanded final homo- geneity specifications. This approach uses a minimisation technique which makes the sum of squared magnetic moment minimum to restrict the amount of the active ferromagnetic material used and the maximal thickness of pieces stacked at each hole location in the shimming hoards. Simulation and experimental results verify that the method is valid and efficient.

关键词： magnetic resonance imaging active ferromagnetic shimming permanent magnet NdFeB pieces

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Magnetic-mediated hyperthermia for cancer treatment:Research progress and clinical trials

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Chinese physics B 2013年第10期22卷 32-45页

作者：赵凌云刘嘉毅欧阳伟炜李丹叶李立李利亚唐劲天 Institute of medical physics and Engineering Department of Engineering PhysicsKey Laboratory of Particle & Radiation ImagingMinistry of EducationTsinghua University Affiliated Ruikang Hospital Guangxi University of Traditional Chinese Medicine The Affiliated Hospital to Guiyang medical University China–Japan Friendship Hospital Zhongnan Hospital of Wuhan University

Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanopa... 详细信息

关键词： aagnetic-mediated hyperthermia magnetic nanoparticles alternative magnetic field magneticLanoparticle hyperthermia thermochemotherapy

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Phase-sensitive fat suppression steady-state free procession sequence with phase correction

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Chinese physics B 2008年第1期17卷 328-334页

作者：俎中良周堃张仕刚高篙包尚联 Beijing City Key Laboratory of medical physics and Engineering Peking University Siemens Mindit MRI Center medical physics Department Health Science Center of Peking University

Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.

关键词： steady-state free precession fat suppression phase-sensitive phase correction

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Interleaving Gradient Magnetic Field Method for Diffusion Weighted Spectroscopy

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Chinese physics Letters 2008年第1期25卷 325-328页

作者：高嵩俎中良包尚联 Department of medical physics Health Science Center Peking University Beijing 100083 Beijing City Key Lab of medical physics and Engineering School of Physics Peking University Beijing 100871

Diffusion-weighted magnetic resonance spectroscopy （DWS） has considerable potential in clinical and research applications. However, it is seldom implemented in conventional magnetic resonance imaging （MRI） scanners due to the strict hardware requirements. We propose an interleaving gradient magnetic field （IGMF） method based on point resolved spectroscopy （PRESS）. Four interlaced powerful diffusion sensitive gradient magnetic fields are positioned around the two π refocusing rf pulses in the PRESS sequence. This method utilizes the interval time in the PRESS pulse sequence, doubles the duration time of the diffusion sensitive gradient magnetic field and decreases the detrimental effect of the induced eddy current. The results of theoretical analysis and experimental observation demonstrate that the IGMF method is suitable for conventional MRI scanners.

关键词： pulsars x-ray spectra relativity and gravitation redshift

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Local adaptive segmentation algorithm for 3-D medical image based on robust feature statistics

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Science China(Information Sciences) 2014年第10期57卷 158-169页

作者： ZHUO ZiHan ZHAI WeiMing LI Xin LIU LingLing TANG JinTian Key Laboratory Particle & Radiation imaging Ministry of Education Department of Engineering PhysicsTsinghua University State Key Laboratory of Intelligent Technology and Systems National Laboratory for Information Science and Technology Department of Computer Science and Technology Tsinghua University Department of medical imaging Tianjin Medical University

medical image segmentation is of pivotal importance in computer-aided clinical diagnosis. Many factors, including noises, bias field effect, local volume effect, as well as tissue movement may affect the medical image, thus causing blurring or uneven characteristics when forming a picture. Such quality defects will inevitably impair the gray-scale difference between adjacent tissues and lead to insufficient segmentation or even leakage during tissue or organ segmentation. In the present investigation, a local adaptive segmentation algorithm for 3-D medical image based on robust feature statistics(LARFS) was proposed. By combining segmentation algorithm principles for traditional region growing(RG) and robust feature statistics(RFS), the location and neighborhood image information of input seed point can be comprehensively analyzed by *** show that, for different segmentation objects, under controlling the input parameter of growing factor within certain range, LARFS segmentation algorithm can adapt well to the regional geometric shape. And because the robust feature statistics is applied in the contour evolution process, LARFS algorithm is not sensitive to noises and not easily influenced by image contrast and object topology. Hence, the leakage and excessive segmentation effects are ameliorated with a smooth edge, and the accuracy can be controlled within the effective error range.

关键词： medical image adaptive segmentation region growing robust feature statistics contour evolution

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How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

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Nuclear Science and Techniques 2017年第4期28卷 24-30页

作者： Hojjat Mahani Gholamreza Raisali Alireza Kamali-Asl Mohammad Reza Ay Radiation Application Research School Nuclear Science and Technology Research Institute Tehran Iran Research Center for Molecular and Cellular imaging Tehran University of Medical Science Tehran Iran Radiation Medicine Department Shahid Beheshti UniversityTehran Iran Department of medical physics and Biomedical Engineering Tehran University of Medical Science Tehran Iran

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated *** this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ^(99m)Tc pencil-beam toward central crystal element was *** incident angle was assumed to vary from 0° to 45° in 5° *** effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were *** influence of photon energy on the crystal identification(CI) was also *** detection accuracy(PDA) was defined as a factor indicating performance of the ***,a set of ^(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each *** results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the *** a crystal-dependent critical angle,the PDA monotonically *** PDA reaches 0.44 for the CsI(Na) at 45° beam *** PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam *** addition,the PVRs derived from flood images linearly correlate their corresponding *** conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.

关键词： Monte Carlo GATE Molecular SPECT Position detection accuracy Pixelated crystal

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Radiation-induced inflammation and autoimmune diseases

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Military medical Research 2018年第1期5卷 62-71页

作者： Rasoul Yahyapour Peyman Amini Saeed Rezapour Mohsen Cheki Abolhasan Rezaeyan Bagher Farhood Dheyauldeen Shabeeb Ahmed Eleojo Musa Hengameh Fallah Masoud Najafi School of Medicine Jiroft University of Medical Sciences Department of Radiology Faculty of ParamedicalTehran University of Medical Sciences Department of Radiologic Technology Faculty of ParamedicineAhvaz Jundishapur University of Medical Sciences Department of medical physics School of MedicineIran University of Medical Sciences Departments of medical physics and Radiology Faculty of Paramedical SciencesKashan University of Medical Sciences Department of medical physics and Biomedical Engineering Faculty of MedicineTehran University of Medical Sciences (International Campus) Department of Physiology College of MedicineUniversity of Misan Research center for molecular and cellular imaging Tehran University of Medical Sciences Department of Chemistry Faculty of ScienceIslamic Azad University Radiology and Nuclear Medicine Department School of Paramedical Sciences Kermanshah University of Medical Science

Currently,ionizing radiation(IR)plays a key role in the agricultural and medical industry,while accidental exposure resulting from leakage of radioactive sources or radiological terrorism is a serious *** to IR has various detrimental effects on normal *** an increased risk of carcinogenesis is the best-known long-term consequence of IR,evidence has shown that other diseases,particularly diseases related to inflammation,are common disorders among irradiated *** disorders are among the various types of immune diseases that have been investigated among exposed *** diseases and diabetes are two autoimmune diseases potentially induced by ***,the precise mechanisms of IR-induced thyroid diseases and diabetes remain to be elucidated,and several studies have shown that chronic increased levels of inflammatory cytokines after exposure play a pivotal ***,cytokines,including interleukin-1(IL-1),tumor necrosis factor(TNF-α)and interferon gamma(IFN-α),play a key role in chronic oxidative damage following exposure to ***,these cytokines change the secretion of insulin and thyroid-stimulating hormone(TSH).It is likely that the management of inflammation and oxidative damage is one of the best strategies for the amelioration of these diseases after a radiological or nuclear *** the present study,we reviewed the evidence of radiation-induced diabetes and thyroid diseases,as well as the potential roles of inflammatory *** addition,we proposed that the mitigation of inflammatory and oxidative damage markers after exposure to IR may reduce the incidence of these diseases among individuals exposed to radiation.

关键词： Radiation Inflammation Autoimmune diseases Thyroid Diabetes

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Quantification of the impact of TOF and PSF on PET images using the noise-matching concept: clinical and phantom study

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Nuclear Science and Techniques 2017年第11期28卷 258-265页

作者： M. Shekari P. Ghafarian S. Ahangari M. R. Ay Department of medical physics and Biomedical Engineering Tehran University of Medical Sciences Tehran Iran Research Center for Molecular and Cellular imaging Tehran University of Medical Sciences Tehran Iran Chronic Respiratory Diseases Research Center National Research Institute of Tuberculosis and Lung Diseases(NRITLD) Shahid Beheshti University of Medical SciencesTehran Iran PET/CT and Cyclotron Center Masih Daneshvari HospitalShahid Beheshti University of Medical Sciences Tehran Iran

This study was to assess quantitatively the accuracy of ^(18)F-FDG PET/CT images reconstructed by TOF+PSF and TOF only, considering the noise-matching concept to minimize probable bias in evaluating algorithm performance caused by noise. PET images of similar noise level were considered. Measurements were made on an inhouse phantom with hot inserts of Φ10–37 mm, and oncological images of 14 patients were analyzed. The PET images were reconstructed using the OSEM, OSEM+TOF and OSEM+TOF+PSF algorithms. Optimal reconstruction parameters including iteration, subset, and FWHM of post-smoothing filter were chosen for both the phantom and patient data. In terms of quantitative accuracy, the recovery coefficient(RC) was calculated for the phantom PET images. The signal-to-noise ratio(SNR),lesion-to-background ratio(LBR), and SUV_(max)were evaluated from the phantom and clinical data. The smallest hot insert(Ф10 mm) with 2:1 activity concentration ratio could be detected in the PET image reconstructed using the TOF and TOF+PSF algorithms, but not the OSEM algorithm. The relative difference for SNR between the TOF+PSF and OSEM showed significantly higher values for smaller sizes, while SNR change was smaller for Ф22–37 mm inserts both 2:1 and 4:1 activity concentration ratio. In the clinical study, SNR gains were 1.6 ± 0.53 and 2.7 ± 0.74 for the TOF and TOF+PSF, while the relative difference of contrast was 17 ± 1.05 and 41.5 ± 1.85% for the TOF only and TOF+PSF, respectively. The impact of TOF+PSF is more significant than that of TOF reconstruction, in smaller inserts with low activity concentration ratio. In the clinical PET/CT images, the use of the TOF+PSF algorithm resulted in better SNR and contrast for lesions, and the highest SUV_(max)was also seen for images reconstructed with the TOF+PSF algorithm.

关键词： Time of flight (TOF) Point spread function(PSF) Lesion detectability PET Quantification Image reconstruction SUV

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Accuracy and effectiveness of self-gating signals in free-breathing three-dimensional cardiac cine magnetic resonance imaging

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Chinese physics B 2016年第12期25卷 543-548页

作者：李硕王磊朱艳春杨洁谢耀钦付楠王乙高嵩 medical imaging physics Laboratory Health Science CenterPeking University Institute of Biomedical and Health Engineering Shenzhen Institutes of Advanced TechnologyChinese Academy of Sciences Department of Orthopedic Surgery People's Hospital of LuohuShenzhen University Department of Radiology Weill Cornell Medical CollegeCornell University

Conventional multiple breath-hold two-dimensional （2D） balanced steady-state free precession （SSFP） presents many difficulties in cardiac cine magnetic resonance imaging （MRI）. Recently, a self-gated free-breathing three-dimensional （3D） SSFP technique has been proposed as an alternative in many studies. However, the accuracy and effectiveness of selfgating signals have been barely studied before. Since self-gating signals are crucially important in image reconstruction, a systematic study of self-gating signals and comparison with external monitored signals are needed. Previously developed self-gated free-breathing 3D SSFP techniques are used on twenty-eight healthy volunteers. Both electrocardiographic （ECG） and respiratory bellow signals are also acquired during the scan as external signals. Self-gating signal and external signal are compared by trigger and gating window. Gating window is proposed to evaluate the accuracy and effectiveness of respiratory self-gating signal. Relative deviation of the trigger and root-mean-square-deviation of the cycle duration are calculated. A two-tailed paired t-test is used to identify the difference between self-gating and external signals. A Wilcoxon signed rank test is used to identify the difference between peak and valley self-gating triggers. The results demonstrate an excellent correlation （P = 0, R 〉 0.99） between self-gating and external triggers. Wilcoxon signed rank test shows that there is no significant difference between peak and valley self-gating triggers for both cardiac （H = 0, P 〉 0.10） and respiratory （H = 0, P 〉 0.44） motions. The difference between self-gating and externally monitored signals is not significant （two-tailed paired-sample t-test： H = 0, P 〉 0.90）. The self-gating signals could demonstrate cardiac and respiratory motion accurately and effectively as ECG and respiratory bellow. The difference between the two methods is not significant and can be explained. Furthermore, few ECG trigger error

关键词： self-gating free-breathing cine MRI effectiveness accuracy

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