Modeling of active shimming of metallic needles for interventional MRI.
Modeling of active shimming of metallic needles for interventional MRI.
复制标题
用于介入 MRI 的金属针主动匀场建模。
DOI：
10.1002/mrm.28320
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发表时间：
2020
影响因子：
3.3
通讯作者：
Sengupta,Saikat
中科院分区：
文献类型：
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作者：
Sengupta,Saikat
目的在许多介入性磁共振成像应用中，金属针和组织之间的巨大磁化率差异引起的伪影是一个长期存在的问题。针头造成的信号空洞可能会隐藏程序目标，并阻碍基于图像的准确监控。本文提出了一种主动垫片的形式来解决这一问题，该垫片的设计灵感来自于海军舰艇上使用的消磁线圈，该垫片是为了纠正针引起的磁场干扰(ΔB0)而设计的。方法对3T时10号中空单斜面钛针诱导的ΔB0进行不同方向的建模。对63对具有独特尖端路径的正交线圈对的垫片性能进行了评估，并选择了最佳线圈对。结果使用一个扁平的无环线圈和一个与大多数方向成斜角的正交1.5圈线圈相结合，每个线圈的电流远低于1安培，可以预测钛针引起的ΔB0的锈蚀校正。填隙的ΔB0标准偏差减少了约49%至~10%，具体取决于针的方向，随着针更多地沿B0对齐，性能会变差。结论模拟预测，在许多介入性磁共振应用中，使用外部提供的任意方向的直流垫片线圈可以最大限度地减少金属探头引起的ΔB0和信号损失，这是潜在的好处。
PurposeArtifacts caused by large magnetic susceptibility differences between metallic needles and tissue are a persistent problem in many interventional MRI applications. The signal void caused by the needle can hide procedure targets and prevent accurate image‐based monitoring. In this paper, a solution to this problem is presented in the form of an active shim insert inspired from degaussing coils used in naval vessels, that is designed to correct the field disturbance (ΔB0) caused by the needle.MethodsThe ΔB0induced by a 10 gauge hollow single‐beveled titanium needle at 3T is modeled in different orientations. A set of 63 orthogonal coil pairs with unique tip paths are evaluated for shimming performance, and an optimal coil pair is chosen. Shimming performance and current demands are evaluated over a range of needle orientations.ResultsRobust correction of the titanium needle induced ΔB0is predicted using a flat no‐loop coil combined with an orthogonal 1½ turn loop coil angled at the bevel angle for most orientations, with currents well below 1 amp per coil. Reductions in ΔB0standard deviations with shimming ranged from ~49% to ~10% depending on needle orientation, with performance worsening as the needle is aligned more along B0.ConclusionSimulations predict that it is possible to minimize metallic probe induced ΔB0and signal losses using externally supplied direct current shim coil inserts in arbitrary orientations for potential benefits in many interventional MRI applications.