Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering最新文献_第6页

Optimization magnetic resonance imaging shim coil using second derivative discretized stream function 利用二阶导数离散流函数优化磁共振成像垫片线圈

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-07-21 DOI: 10.1002/cmr.b.21352

Yang Hu, Qiuliang Wang, Xuchen Zhu, Chaoqun Niu, Yaohui Wang

{"title":"Optimization magnetic resonance imaging shim coil using second derivative discretized stream function","authors":"Yang Hu, Qiuliang Wang, Xuchen Zhu, Chaoqun Niu, Yaohui Wang","doi":"10.1002/cmr.b.21352","DOIUrl":"10.1002/cmr.b.21352","url":null,"abstract":"<div>\u0000 \u0000 In Magnetic Resonance Imaging (MRI) equipment, a set of shim coils are designed to generate specific magnetic fields, thus eliminating harmonic components of magnetic field to obtain a high level homogeneous magnetic field within the region of interesting (ROI). In the electromagnetic design process, in order to produce the desired magnetic field, the deviation between the calculated magnetic field of shim coil and the theoretical magnetic field is treated as a kind of traditional objective functions to optimize the distribution of current density on the surface of shim coil skeleton. However, such function is ill-posed because of the overdetermined or underdetermined system of equations. The regularization method is commonly used to solve such problem by constructing the regularization term. This article proposes a new iterative optimization method for the design of shim coils in MRI. Based on the boundary element method (BEM), the discretized stream functions can be obtained by discretizing the surface of coil skeleton using a set of triangular elements. As the regularization term, the second derivative stream function is included in the minimization of the deviation between calculated magnetic fields and target magnetic fields. The distribution of coil which meets the design requirements can be obtained by using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. At last, the cubic spline interpolation is used to make lines as smooth as possible to be processed. In this article, the proposed method was employed to design two kinds of room temperature shim coils for cylindrical and/or biplanar MRI shim coil system. The simulation results demonstrate that the proposed method is effective and practical.\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2017-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21352","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80864441","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 : 2017-07-21 DOI: 10.1002/cmr.b.21330

引用次数: 0

DVD Review DVD的评论

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-07-21 DOI: 10.1002/cmr.b.21331

引用次数: 0

Fault detection method for magnetic resonance imaging spectrometer based on the acquisition and analysis of its output waveforms 基于输出波形采集与分析的磁共振成像光谱仪故障检测方法

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-06-27 DOI: 10.1002/cmr.b.21353

Liang Xiao, Shanmei Ouyang, Yuwei Li, Hongjie Wang

{"title":"Fault detection method for magnetic resonance imaging spectrometer based on the acquisition and analysis of its output waveforms","authors":"Liang Xiao, Shanmei Ouyang, Yuwei Li, Hongjie Wang","doi":"10.1002/cmr.b.21353","DOIUrl":"10.1002/cmr.b.21353","url":null,"abstract":"<div>\u0000 \u0000 In the development of a magnetic resonance imaging spectrometer, the equipment fault detection methods are mainly reliant on visual inspection of reconstructed images or k-space data, combined with observation of the output waveforms via an oscilloscope. However, when using the above methods, it may be quite difficult to determine minor design flaws that would produce image ghost or other problems. This article presents a fault detection method that is based on acquisition and analysis of the output waveforms from the spectrometer. While a sequence is running, the spectrometer outputs, including the digital gate and the gradients, are sampled using a data acquisition card. The acquired data is then processed using a high-performance graphic processing unit to allow the feature points, which are the endpoints of the waveform segments in this design, to be extracted. The processing operation is composed of data filtering, differencing, and clustering. Finally, the extracted feature points are compared with the predefined feature points of the sequence to determine any design errors. This method has been used to solve image ghost problems in our home-built spectrometer.\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2017-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21353","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87313052","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: 0

An MRI scanner-independent radiofrequency dosimeter for the estimation of RF power deposition with a human torso phantom 一种独立于MRI扫描仪的射频剂量计，用于估计人体躯干幻影的射频功率沉积

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-05-29 DOI: 10.1002/cmr.b.21351

Youngseob Seo

{"title":"An MRI scanner-independent radiofrequency dosimeter for the estimation of RF power deposition with a human torso phantom","authors":"Youngseob Seo","doi":"10.1002/cmr.b.21351","DOIUrl":"10.1002/cmr.b.21351","url":null,"abstract":"<div>\u0000 \u0000 An assessment of radiofrequency (RF) power deposition independent of the information provided by MRI scanners is thus desirable. We developed a novel scanner-independent RF dosimeter based on measurements of the resistance of a thermistor that dissipates the RF power during scanning. With the RF dosimeter, the RF power deposition for four MRI sequences with specific absorption rate (SAR) values (0.1-3.3 W/kg) was measured on five different scanners and the correlation between the RF dosimeter reading and the SAR levels calculated by the scanners was investigated. The novel RF dosimeter showed a linear relationship between the RF power deposition and the scanner-reported whole-body averaged SAR for each scanner. However, there was a variability in the reading among different scanners. The RF dosimeter readings were 9.7 and 9.5 mW on GE 1.5 T (SAR=2.6 W/kg), 3.6 and 3.7 mW on Philips 1.5 T (SAR=3.3 W/kg), 9.5 and 8.6 mW on Siemens 3 T (SAR=3.0 W/kg), and 4.7 and 3.9 mW on Philips 3 T (SAR=2.6 W/kg), respectively. The scanner-independent RF dosimeter developed in this study can play a significant role in checking the accuracy of scanners’ SAR values as a standardized method for measuring the RF power deposition for MR safety.\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2017-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21351","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75611596","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: 1

DVD Review DVD的评论

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-04-10 DOI: 10.1002/cmr.b.21308

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 : 2017-04-10 DOI: 10.1002/cmr.b.21307

引用次数: 0

Characterization of a PXIe based low-field digital NMR spectrometer 基于PXIe的低场数字核磁共振谱仪的表征

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-03-29 DOI: 10.1002/cmr.b.21350

Joshua R. Biller, Karl F. Stupic, Anthony B. Kos, Tim Weilert, George A. Rinard, Yoshihiro Nakishima, John Moreland

{"title":"Characterization of a PXIe based low-field digital NMR spectrometer","authors":"Joshua R. Biller, Karl F. Stupic, Anthony B. Kos, Tim Weilert, George A. Rinard, Yoshihiro Nakishima, John Moreland","doi":"10.1002/cmr.b.21350","DOIUrl":"10.1002/cmr.b.21350","url":null,"abstract":"<div>\u0000 \u0000 A low-field nuclear magnetic resonance (NMR) instrument is an important tool for investigating a wide variety of samples under different conditions. In this paper, we describe a system constructed primarily with commercially available hardware and control software, capable of single-pulse NMR experiments. Details of the construction of the main B0 magnet are also included. The operating frequency for demonstration is 460 kHz (10 mT), however, the range of the hardware spans 700 Hz (16 μT) to 25 MHz (0.6 T). Tip angle optimizations are used to find the most narrow usable pulse width for this configuration, and the T1 of water is measured by single-pulse-saturation-recovery (SPSR) to demonstrate the potential for this system as a relaxometer. Discussions of resonator construction and efficiency, power requirements and programming strategies that would increase the utility of this system are also included. Construction of any low-field NMR system will depend on experimental interests, budget and engineering resources. A survey of other low-field NMR systems from the literature is included to aid the novice or experienced magnetic resonance scientist in consideration of how a low-field spectrometer could be constructed and used in the lab.\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2017-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21350","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84591359","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: 6

Digital filters for low-field NMR 低场核磁共振数字滤波器

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-02-08 DOI: 10.1002/cmr.b.21346

Andrea Valori, Jonathan Mitchell, Edmund J. Fordham

{"title":"Digital filters for low-field NMR","authors":"Andrea Valori, Jonathan Mitchell, Edmund J. Fordham","doi":"10.1002/cmr.b.21346","DOIUrl":"10.1002/cmr.b.21346","url":null,"abstract":"We review the theory and operation of digital filters in modern nuclear magnetic resonance (NMR) spectrometers with fully digital receivers. Custom digital filters tailored for particular experimental requirements offer substantial improvements in signal-to-noise ratio (SNR), sensitivity, pulse sequence timing, and rejection of heteronuclear contamination. Pass-band filters are designed and applied in the frequency domain. In high-field imaging and spectroscopy, the impact of the filter is straight forward to visualize. However, low-field NMR data acquired on bench-top magnets are typically analyzed in the time-domain where the influence of a frequency-domain filter is not obvious and largely overlooked by end-users. We provide practical guidance on the design and implementation of digital filters for bench-top NMR applications, with examples of data acquired at 2.4 and 12.9 MHz. We discuss the compromise between speed (filter settling time) and noise rejection, and consider the special case of 19F signal contamination in 1H measurements. We suggest filter designs for narrow-line liquid samples, broad-line samples, and imaging.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 4","pages":"202-220"},"PeriodicalIF":0.9,"publicationDate":"2017-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21346","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80970854","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: 3

Synchronous radial 1H and 23Na dual-nuclear MRI on a clinical MRI system, equipped with a broadband transmit channel 临床MRI系统上的同步径向1H和23Na双核MRI，配备宽带传输通道

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-02-03 DOI: 10.1002/cmr.b.21347

Joshua D. Kaggie, Nabraj Sapkota, Bijaya Thapa, Kyle Jeong, Xianfeng Shi, Glen Morrell, Neal K. Bangerter, Eun-Kee Jeong

{"title":"Synchronous radial 1H and 23Na dual-nuclear MRI on a clinical MRI system, equipped with a broadband transmit channel","authors":"Joshua D. Kaggie, Nabraj Sapkota, Bijaya Thapa, Kyle Jeong, Xianfeng Shi, Glen Morrell, Neal K. Bangerter, Eun-Kee Jeong","doi":"10.1002/cmr.b.21347","DOIUrl":"https://doi.org/10.1002/cmr.b.21347","url":null,"abstract":"The purpose of this work was to synchronously acquire proton (1H) and sodium (23Na) image data on a 3T clinical MRI system within the same sequence, without internal modification of the clinical hardware, and to demonstrate synchronous acquisition with 1H/23Na-GRE imaging with Cartesian and radial k-space sampling. Synchronous dual-nuclear imaging was implemented by: mixing down the 1H signal so that both the 23Na and 1H signal were acquired at 23Na frequency by the conventional MRI system; interleaving 1H/23Na transmit pulses in both Cartesian and radial sequences; and using phase stabilization on the 1H signal to remove mixing effects. The synchronous 1H/23Na setup obtained images in half the time necessary to sequentially acquire the same 1H and 23Na images with the given setup and parameters. Dual-nuclear hardware and sequence modifications were used to acquire 23Na images within the same sequence as 1H images, without increases to the 1H acquisition time. This work demonstrates a viable technique to acquire 23Na image data without increasing 1H acquisition time using minor additional custom hardware, without requiring modification of a commercial scanner with multinuclear capability.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"46B 4","pages":"191-201"},"PeriodicalIF":0.9,"publicationDate":"2017-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21347","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92192907","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: 13