Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering最新文献_第7页

Finite element method-based approach for radiofrequency magnetic resonance coil losses estimation 基于有限元法的射频磁共振线圈损耗估算方法

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-01-31 DOI: 10.1002/cmr.b.21348

Giulio Giovannetti, Gianluigi Tiberi, Michela Tosetti

{"title":"Finite element method-based approach for radiofrequency magnetic resonance coil losses estimation","authors":"Giulio Giovannetti, Gianluigi Tiberi, Michela Tosetti","doi":"10.1002/cmr.b.21348","DOIUrl":"10.1002/cmr.b.21348","url":null,"abstract":"<p>The simulation and the design of radiofrequency (RF) coils are fundamental tasks to maximize Signal-to-Noise Ratio (SNR) in Magnetic Resonance (MR) applications. The estimation of coil resistance, that is, the losses within the coil conductors, which depends on tuning frequency, allows the prediction of coil performance and data SNR. At RF, the conductor resistance is increased due to the skin effect, which distributes the current primarily near the conductor surface instead of uniformly over the cross section. Moreover, the radiative losses estimation as a function of tuning frequency permits a total coil performance characterization, especially for high-frequency tuned coils when this loss mechanism could be the dominant one. In this work we compared Finite Element Method (FEM) simulations with analytical calculations performed in wire loop RF coils for MR applications. Our results showed that FEM can predict the losses within the coil conductors at 5.7 MHz with a relative difference of <3% compared to analytical calculation, while the relative difference increased to 58% at 127.8 MHz. Concerning the radiative losses, the relative difference between analytical formulation and FEM was lower than 3% at 5.7 MHz, and increasing to 44% at 127.8 MHz. Experimental measurements on a circular coil prototype were also performed at 85.2 MHz and 127.8 MHz, showing a better agreement with FEM simulations than with analytical calculations.</p>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 4","pages":"186-190"},"PeriodicalIF":0.9,"publicationDate":"2017-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21348","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85906435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Approaches to designing micro-solenoidal RF probes for 14 T MRI studies of millimeter-range sized objects 用于毫米尺度物体的14t MRI研究的微螺线管射频探针的设计方法

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-01-24 DOI: 10.1002/cmr.b.21349

Bahram Seifi, Elena Semouchkina, Michael Lanagan, Thomas Neuberger

引用次数: 2

Pole plate effected gradient coils design in permanent magnet MRI system 永磁磁共振成像系统中极板对梯度线圈设计的影响

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-11-19 DOI: 10.1002/cmr.b.21344

Yajie Xu, Hector Sanchez Lopez, Qiaoyan Chen, Xiaodong Yang

引用次数: 1

Trap design and construction for high-power multinuclear magnetic resonance experiments 大功率多核磁共振实验陷阱设计与构建

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-11-17 DOI: 10.1002/cmr.b.21345

Joseph V. Rispoli, Ivan E. Dimitrov, Sergey Cheshkov, Craig Malloy, Steven M. Wright, Mary P. McDougall

{"title":"Trap design and construction for high-power multinuclear magnetic resonance experiments","authors":"Joseph V. Rispoli, Ivan E. Dimitrov, Sergey Cheshkov, Craig Malloy, Steven M. Wright, Mary P. McDougall","doi":"10.1002/cmr.b.21345","DOIUrl":"10.1002/cmr.b.21345","url":null,"abstract":"<p>Performing multinuclear experiments requires one or more radiofrequency (RF) coils operating at both the proton and second-nucleus frequencies; however, inductive coupling between coils must be mitigated to retain proton sensitivity and coil tuning stability. The inclusion of trap circuits simplifies placement of multinuclear RF coils while maintaining inter-element isolation. Of the commonly investigated non-proton nuclei, perhaps the most technically demanding is carbon-13, particularly when applying a proton decoupling scheme to improve the resulting spectra. This work presents experimental data for trap circuits withstanding high-power broadband proton decoupling of carbon-13 at 7 T. The advantages and challenges of building trap circuits with various inductor and capacitor components are discussed. Multiple trap designs are evaluated on the bench and utilized on an RF coil at 7 T to detect broadband proton-decoupled carbon-13 spectra from a lipid phantom. A particular trap design, built from a coaxial stub inductor and high-voltage ceramic chip capacitors, is highlighted owing to both its performance and adaptability for planar array coil elements with diverse spatial orientations.</p>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 4","pages":"162-168"},"PeriodicalIF":0.9,"publicationDate":"2016-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21345","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"35015267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

DVD Review DVD的评论

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-11-14 DOI: 10.1002/cmr.b.21305

引用次数: 0

NMR Concepts 核磁共振的概念

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-11-14 DOI: 10.1002/cmr.b.21304

引用次数: 0

UHF EPR spectrometer operating at frequencies between 400 MHz and 1 GHz 工作频率在400兆赫和1千兆赫之间的超高频EPR光谱仪

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-10-31 DOI: 10.1002/cmr.b.21328

Richard W. Quine, George A. Rinard, Yilin Shi, Laura Buchanan, Joshua R. Biller, Sandra S. Eaton, Gareth R. Eaton

引用次数: 7

Comparison between circular and square loops for low-frequency magnetic resonance applications: theoretical performance estimation 圆形和方形环在低频磁共振应用中的比较:理论性能估计

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-10-18 DOI: 10.1002/cmr.b.21343

Giulio Giovannetti

{"title":"Comparison between circular and square loops for low-frequency magnetic resonance applications: theoretical performance estimation","authors":"Giulio Giovannetti","doi":"10.1002/cmr.b.21343","DOIUrl":"10.1002/cmr.b.21343","url":null,"abstract":"<p>Radiofrequency receiver coils in magnetic resonance (MR) systems are used to pick up the signals emitted by the nuclei with high signal-to-noise ratio (SNR) in a small region of sensitivity. The quality of obtained images strongly depends upon the correct choice of the coils geometry and size. The simplest design of such coils is circular and square loops, both producing in the central region-of-interest a magnetic field perpendicular to the coil plane, with an amplitude that decreases along the coil axis. This work reviews a method for coil SNR model development employing an equivalent electric circuit and applies it for circular and square loop design. Coil inductance and resistance were analitically calculated by taking into account for the conductors cross-geometry and the magnetic field pattern was estimated using Biot–Savart law, while the sample-induced resistance was calculated with a method employing a quasi-static approach. Coil performance prediction permitted to compare circular and square loops and demonstrated that when a simple relationship between loops size is satisfied, the performance of both coils resulted to be very similar in terms of SNR. Since the theoretical approach formulation is largely detailed, this article could be interesting for graduate students and researchers working in the field of MR coil design and development.</p>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 3","pages":"146-155"},"PeriodicalIF":0.9,"publicationDate":"2016-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21343","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81197074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 21

A new fully integrated multichannel receiver design for magnetic resonance imaging 一种全新的全集成多通道磁共振成像接收机设计

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-10-17 DOI: 10.1002/cmr.b.21341

Mazin Jouda, Oliver G. Gruschke, Jan G. Korvink

{"title":"A new fully integrated multichannel receiver design for magnetic resonance imaging","authors":"Mazin Jouda, Oliver G. Gruschke, Jan G. Korvink","doi":"10.1002/cmr.b.21341","DOIUrl":"10.1002/cmr.b.21341","url":null,"abstract":"<div>\u0000 \u0000 <p>In this contribution, we introduce a new fully integrated receiver architecture for magnetic resonance imaging (MRI), based on CMOS technology. The design is conceived to be an excellent solution to the size, cost, and complexity problems associated with multiple MRI channels, and potentially removes a technical barrier when implementing arrays of massive numbers of coils. In contrast to conventional MRI receivers, the CMOS integrated solution allows to perform all the required signal processing within a single chip. This includes low-noise pre-amplification, frequency down-conversion, filtering, and analog-to-digital conversion. The CMOS chip is designed to be mounted in close proximity to the MR receive coils so as to avoid both signal attenuation as well as the use of bulky coaxial cables which are normally employed to transfer the MRI signals to the spectrometer. The output MR signals from the chip are digital and therefore relatively immune to noise. Operation in the digital domain allows to perform time-domain multiplexing on the data streams, and to replace the electrical coaxial cables with optical fibers. The simulation results of both the system-level and the circuit-level realizations of the new receiver showed successful reconstruction of the MR image with very minimal SNR degradation and no remarkable distortion or artifacts.</p>\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 3","pages":"134-145"},"PeriodicalIF":0.9,"publicationDate":"2016-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21341","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84652292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

NMR Concepts 核磁共振的概念

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2016-09-23 DOI: 10.1002/cmr.b.21301

引用次数: 0