Concepts in Magnetic Resonance Part A最新文献_第5页

Diffusion measurements using the second echo 利用二次回波进行扩散测量

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21462

Hilary T. Fabich, Partha Nandi, Hans Thomann, Mark S. Conradi

引用次数: 4

Sensitivity estimation in circular and square loops 圆形和方形回路的灵敏度估计

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21461

Giulio Giovannetti

{"title":"Sensitivity estimation in circular and square loops","authors":"Giulio Giovannetti","doi":"10.1002/cmr.a.21461","DOIUrl":"10.1002/cmr.a.21461","url":null,"abstract":"Circular and square loops are the simplest design employed as radiofrequency coils for magnetic resonance applications. Being usually much smaller than the volume coils, these loop coils have higher signal-to-noise ratio (SNR) because they receive noises only from nearby regions. However, they have a relatively poor field homogeneity and, thus, are mainly used as receive coils. In this work, author describes a coil sensitivity estimation method based on a simulator which permits the characterization of loop coils performance, in terms of magnetic field patterns and coil losses, where this last term including conductor, sample, capacitor, radiative and soldering losses. The evaluation of coil sensitivity for circular and square loops was performed at different tuning frequencies usually used in clinical scanner (21, 64, and 128 MHz) and at different distances respect to the coil plane. Simulation data were acquired for circular loop radius between 0.5 and 4 cm and for square loop side sizes between 1 and 8 cm, with the scope of evaluating the loop sizes which maximize the sensitivity in dependence of the penetration depth in the sample region and therefore to design optimized coils for maximizing SNR in MR applications.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"47A 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21461","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79573666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Aspects of NMR reciprocity and applications in highly conductive media 核磁共振互易性及其在高导电介质中的应用

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21466

Andrew J. Ilott, Alexej Jerschow

{"title":"Aspects of NMR reciprocity and applications in highly conductive media","authors":"Andrew J. Ilott, Alexej Jerschow","doi":"10.1002/cmr.a.21466","DOIUrl":"10.1002/cmr.a.21466","url":null,"abstract":"In the context of NMR spectroscopy and MRI, the principle of reciprocity provides a convenient method for determining the reception sensitivity from the transmitted rf field pattern. The reciprocity principle for NMR was originally described by Hoult et al (J Magn Reson. 1976;24:71) and is related to the broader Lorentz reciprocity principle and similar theorems from antenna theory. One frequent application of the reciprocity principle is that for a single coil used for both transmission and detection, the transmit and receive fields can be assumed to be equal. This aspect is also where some of the conceptual difficulty of applying the theorem may be encountered. For example, the questions of whether one should use the complex conjugate field for detection or whether one should apply the theorem in the rotating frame or in the laboratory frame may give rise to considerable confusion. We attempt here to provide a helpful discussion of the application of the reciprocity principle in such a way as to clarify some of the confounding questions. In particular, we avoid the use of the “negatively rotating frame,” which is frequently mentioned in this context, since we consider it to unnecessarily complicate the matter. In addition, we also discuss the implications of the theorem for magnetic resonance experiments on conducting samples, and metals, in particular.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"47A 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21466","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73503767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Magnetic resonance data modeling: The Bayesian analysis toolbox 磁共振数据建模:贝叶斯分析工具箱

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21467

James D. Quirk, G. Larry Bretthorst, Joel R. Garbow, Joseph J. H. Ackerman

引用次数: 10

The past, present, and future of 1.26T2 1.26T2的过去、现在和未来

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21473

David Rovnyak

引用次数: 4

Foodomics and storage monitoring of three meat cuts by 1H NMR 三种肉块的食物组学及1H NMR储存监测

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-04-26 DOI: 10.1002/cmr.a.21474

José Eraldo do Nascimento Fontes, Magdevis Yanet Rodriguez-Caturla, Anderson S. Sant'Ana, Thiago Inácio Barros Lopes, Anita Jocelyne Marsaioli

引用次数: 3

Guide to simulating complex NMR probe circuits 指南模拟复杂的核磁共振探针电路

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2019-03-29 DOI: 10.1002/cmr.a.21463

Francis David Doty

{"title":"Guide to simulating complex NMR probe circuits","authors":"Francis David Doty","doi":"10.1002/cmr.a.21463","DOIUrl":"10.1002/cmr.a.21463","url":null,"abstract":"S-parameter-based circuit simulators are well suited to obtaining accurate solutions of even the most complex rf probe circuits. The basic theory necessary for determining the relative S/N of the probe circuit, based on B1/P0.5, from the voltage, current, impedance, and S-parameter data that come from circuit simulators, is presented. Examples of simulator applications to circuits of increasing complexity are presented. A key requirement for effective utilization of circuit simulators in probe circuit optimizations is constructing an approximate analytical solution of the circuit, or an inverse simulation program, to accompany the direct circuit simulation, that calculates all the needed circuit component values based on minimal input data, such as B0, desired nuclides, sample coil description, and hardware options and details such as characteristics of various leads. A method of developing the needed inverse simulation program is presented for a simplified single-coil HXY probe circuit. The inverse program is validated by the direct simulation itself. The methods are then applied to a detailed circuit that includes all significant leads, stray capacitances, couplings, and losses for a NB 28.2-T 1-mm HXYZ MAS probe. Similar HXY circuit models were validated by NMR experiments with rotor sizes from 0.75 mm to 3.2 mm at fields from 11.7 T to 21 T. Detailed HXYZ circuit model results at 11.7 T, including pulse widths, component values, voltages, and port isolations, agreed with experimental results within a few per cent. The 1200-MHz HXYZ simulation predicted a 1H π/2 pulse of 1.3 μs at 25 W.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"47A 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2019-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21463","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37317155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

NMR Concepts 核磁共振的概念

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-10-07 DOI: 10.1002/cmr.a.21372

引用次数: 0

DVD Review DVD的评论

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-10-07 DOI: 10.1002/cmr.a.21374

引用次数: 0

Illustration of inversion-recovery and Carr-Purcell-Meiboom-Gill sequences by the determination of ethanol content in alcoholic beverages 倒置-恢复和Carr-Purcell-Meiboom-Gill序列测定酒精饮料中乙醇含量的说明

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-09-30 DOI: 10.1002/cmr.a.21460

Yves Gossuin, Quoc L. Vuong, Leonid Grunin, Laurence Van Nedervelde, Anne Pietercelie

{"title":"Illustration of inversion-recovery and Carr-Purcell-Meiboom-Gill sequences by the determination of ethanol content in alcoholic beverages","authors":"Yves Gossuin, Quoc L. Vuong, Leonid Grunin, Laurence Van Nedervelde, Anne Pietercelie","doi":"10.1002/cmr.a.21460","DOIUrl":"https://doi.org/10.1002/cmr.a.21460","url":null,"abstract":"In Nuclear Magnetic Resonance (NMR) education, the introduction of the relaxation phenomenon and the relaxation times (T1 and T2) is an important and compulsory step, as is the description of the Carr-Purcell-Meiboom-Gill (CPMG) and inversion-recovery (IR) measurement sequences. Indeed those sequences are still used nowadays for, respectively, the measurement of T2 and T1 but also in Magnetic Resonance Imaging (MRI) and NMR spectroscopy. Practical works with the students, performed for example with water, allow to illustrate this part of the teaching. In this work we propose an alternative and funny way to introduce these important topics. With a few microliters of a concentrated Gd3+ solution, a few milliliters of an alcoholic beverage and a low resolution and low field NMR device, it is possible, thanks to the relaxation phenomenon and using CPMG and IR sequences, to measure the alcohol content of the beverage provided that the alcohol proton exchange with water protons is taken into account. First the method is validated with synthetic water-ethanol mixtures, then it is used to study nine different alcoholic beverages. The correlation of the ethanol volume fractions determined by NMR with the actual ethanol content of the beverages is rather good, especially for the method based on T2 relaxation, with a correlation coefficient r2 = 0.994. However, it seems that the method developed in this work always underestimates the ethanol volume fraction at high ethanol content for a reason which remains to be found.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"46A 3","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21460","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91571105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0