B1+ Phase mapping at 7 T and its application for in vivo electrical conductivity mapping
B1+ Phase mapping at 7 T and its application for in vivo electrical conductivity mapping
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DOI：
10.1002/mrm.22995
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发表时间：
2012-02-01
影响因子：
3.3
通讯作者：
van den Berg, Cornelis A. T.
中科院分区：
文献类型：
--
作者：
van Lier, Astrid L. H. M. W.;Brunner, David O.;van den Berg, Cornelis A. T.
在本研究中，提出了一种基于B？1+相和齐次亥姆霍兹方程。这项新的MRI技术可能为基于电导率差异的肿瘤和病变特征开辟未来的机会，同时它也可能在射频安全评估中得到应用。仅使用B？1+相(而不是络合物B？+1字段)被寻址。此外，还发现B？1+相位可以直接从可测量的收发器相位arg(B？+ 1 B ?1)在头上。通过模拟和测量，对7 t型鸟笼线圈激发的人头进行验证，表明可以使用B？只有1+相位信息。不同脑组织间电导率对比清晰可见。白质、灰质和脑脊液的测量平均值分别与文献值相差54%、26%和-13%。B？1+相位测量非常适合体内应用，因为测量时间很短（每个成像切片不到一分钟），并且与先前提出的方法相反，将患者暴露在低射频功率下。《理性医学杂志》，2012。(C) 2011 Wiley期刊公司
In this study, a new approach to measure local electrical conductivity in tissue is presented, which is based on the propagating B?1+ phase and the homogeneous Helmholtz equation. This new MRI technique might open future opportunities for tumor and lesion characterization based on conductivity differences, while it may also find application in radio frequency safety assessment. Prerequisites for conductivity mapping using only the B?1+ phase (instead of the complex B?+1 field) are addressed. Furthermore it was found that the B?1+ phase can be derived directly from the measurable transceive phase arg(B?+1 B?-1) in the head. Validation for a human head excited by a 7 T-birdcage coil using simulations and measurements showed that it is possible to measure in vivo conductivity patterns in the brain using B?1+ phase information only. Conductivity contrast between different brain tissues is clearly observed. The measured mean values for white matter, gray matter and cerebrospinal fluid differed 54%, 26%, and -13% respectively from literature values. The proposed method for B?1+ phase measurements is very suited for in vivo applications, as the measurement is short (less than a minute per imaged slice) and exposes the patient to low RF power, contrary to earlier proposed approaches. Magn Reson Med, 2012. (C) 2011 Wiley Periodicals, Inc.