Minimal artifact actively shimmed metallic needles in MRI.
Minimal artifact actively shimmed metallic needles in MRI.
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DOI：
10.1002/mrm.28977
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发表时间：
2022-01
影响因子：
3.3
通讯作者：
Chen Y
中科院分区：
文献类型：
--
作者：
Sengupta S;Yan X;Hoyt TL;Drake G;Gunderman A;Chen Y
金属针引起的信号空洞给许多 MRI 应用中的可视化和监测带来了挑战。在这项工作中，我们探索了解决此问题的方法，即采用主动垫片插入件的形式，该垫片插入件安装在针内并校正由针在其外部引起的场干扰 (ΔB0)。对 4mm OD 钛针在 3 特斯拉下引起的 ΔB0 进行了建模，并设计和制造了 2 线圈正交匀场组来对 ΔB0 进行匀场。在具有四种不同脉冲序列的水体模中以多个方向评估针周围的信号恢复。在有和没有匀场的离体猪组织动态梯度回波实验中评估针周围的相位稳定性。此外，在 1A 电流和并发成像的连续操作 8 分钟下评估垫片插入件的加热情况。使用最大电流为 1.172 A 的主动匀场显示，针周围丢失信号的平均恢复量约为 63%，最大电流为 1.172 A。信号恢复和底层 ΔB0 的校正与成像序列无关。通过主动匀场，还可最大限度地减少可感知信号空洞之外的针引起的相位梯度。在连续 1A 主动匀场操作 8 分钟内，温度升高高达 0.9°C。提出了一种使用有源垫片插入件来最小化金属针引起的信号损失的与序列无关的方法。该方法在一系列定性和定量介入 MRI 应用中具有潜在的优势。
Signal voids caused by metallic needles pose visualization and monitoring challenges in many MRI applications. In this work we explore a solution to this problem in the form of an active shim insert that fits inside a needle and corrects the field disturbance (ΔB0) caused by the needle outside of it. The ΔB0 induced by a 4mm OD Titanium needle at 3 Tesla is modeled and a 2-coil orthogonal shim set is designed and fabricated to shim the ΔB0. Signal recovery around the needle is assessed in multiple orientations in a water phantom with four different pulse sequences. Phase stability around the needle is assessed in an ex-vivo porcine tissue dynamic gradient echo experiment with and without shimming. Additionally, heating of the shim insert is assessed under 8 minutes of continuous operation with 1A current and concurrent imaging. An average recovery of ~63% of lost signal around the needle across orientations is shown with active shimming with a maximum current of 1.172 A. Signal recovery and correction of the underlying ΔB0 is shown to be independent of imaging sequence. Needle-induced phase gradients outside the perceptible signal void are also minimized with active shimming. Temperature rise of up to 0.9° Celsius is noted over 8 minutes of continuous 1A active shimming operation. A sequence independent method for minimization of metallic needle induced signal loss using an active shim insert is presented. The method has potential benefits in a range of qualitative and quantitative interventional MRI applications.
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