用于MRI的RF线圈电流双回路H场探针测量的校准

IF 3 Q2 ENGINEERING, ELECTRICAL & ELECTRONIC IEEE Journal of Electromagnetics RF and Microwaves in Medicine and Biology Pub Date : 2023-03-17 DOI:10.1109/JERM.2023.3274742
Wenjun Wang;Juan Diego Sánchez-Heredia;Tom Maurouard;Vitaliy Zhurbenko;Jan Henrik Ardenkjær-Larsen
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引用次数: 0

摘要

目的:在磁共振成像(MRI)中,双环H场探针经常用于测量环形天线上的电流。环路串扰限制了使用这种探针进行直接测量的动态范围。串扰可以通过简单的校准来消除。这项工作分析了探针校准后的定量关系${S}_{21}$与RF线圈电流。方法:RF线圈电流与校准值之间的分析关系${S}_用多端口网络理论建立了探针的{21}$测量值,并通过全波模拟和台式测量进行了验证。通过测量1H陷波频率、有源失谐和前置放大器去耦,证明了校准的效果。结果:校准消除了探针中串扰的影响,并提高了$|的下限{{S}_{21}}|$。校准的${S}_{21}$与线圈电流成比例。在较低的频率范围内,校准的${S}_{21}$到线圈的电流几乎随频率线性变化。影响:校准方法提高了探针测量的灵敏度,并有助于微调电流抑制电路,如有源失谐电路、陷波器、前置放大器去耦。之间的线性频率相关性${S}_{21}$测量值和线圈电流允许对高达128 MHz的线圈电流进行简单、公平的比较,在某些情况下为298 MHz,有助于构建多核线圈。
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Calibrating Double-Loop H-Field Probe Measurements of RF Coil Current for MRI
Objective: Double-loop H-field probes are often used to measure current on loop antennae for magnetic resonance imaging (MRI). Loop crosstalk limits the dynamic range of direct measurements with such probes. The crosstalk can be removed by simple calibration. This work analyses the quantitative relation of a probe's calibrated ${S}_{21}$ with the RF coil current. Method: The analytical relation between RF coil current and calibrated ${S}_{21}$ measurements of a probe is established with the multi-port network theory, and verified by full-wave simulation and benchtop measurements. The effect of calibration is demonstrated by measuring the 1 H trap frequency, the active detuning, and the preamplifier decoupling. Results: The calibration removes the effect of crosstalk in a probe and improves the lower bound of $| {{S}_{21}} |$ . The calibrated ${S}_{21}$ is proportional to coil current. In the lower frequency range, the ratio of calibrated ${S}_{21}$ to coil current changes almost linearly with frequency. Impact : The calibration method improves the sensitivity of probe measurements and facilitates fine-tuning current-suppressing circuits like active detuning circuits, traps, preamplifier decoupling. The linear frequency dependency between ${S}_{21}$ measurements and coil current allows easy, fair comparison of coil current up to 128 MHz, and in some cases 298 MHz, helping build multi-nucleus coils.
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CiteScore
5.80
自引率
9.40%
发文量
58
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Front Cover Table of Contents IEEE Journal of Electromagnetics, RF, and Microwaves in Medicine and Biology About this Journal IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology Publication Information Models of Melanoma Growth for Assessment of Microwave-Based Diagnostic Tools
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