Actively Shimmed Needles for Interventional MRI

项目总结/摘要 针伪影一直是介入性MRI领域长期未解决的挑战。差异较大 MR兼容金属针或管心针与周围水之间的磁化率 包含组织的针在针附近引起显著的场扰动，这导致信号损失 由于体素内失相、图像失真和由于体素错误映射而导致的信号堆积。这些文物限制了 在不同程度上，几乎每个介入性MRI程序都通过模糊和扭曲目标， 妨碍了感兴趣区域的精确成像。这导致瞄准精度降低， 手术时间、无法监测治疗以及最终MRI引导手术的有效性降低。 因此，本提案的目标是为这个问题引入一个概念验证解决方案，其灵感来自于 舰船和潜艇防御磁场敏感海域的消磁线圈技术 地雷我们建议开发一种有源消磁或垫片插入物，用于补偿针感应Δ B 0 并证明了在3特斯拉的离体组织实验中对磁化率伪影的校正。AIM 1A这 工作致力于模拟3特斯拉下的针和探针感应场偏差，包括 针材料、尖端形状和方向的影响。目标1b将侧重于匀场的模拟 以及将补偿目标1a中估计的场变化的有源匀场线圈的建模。目标在Aim 2将是针和针垫片插入件的实际制造和测试，沿着适当的 用于在成像期间操作DC匀场线圈的电子器件。扫描仪内校准和体模测试将 遵循垫片插入线圈的台架测试。不锈钢、钛、镍钛诺和钛合金引起的伪影缓解 将在凝胶体模中以任意方向展示黄铜针和探针。最后，在Aim 3将在两个不同的离体MR引导研究中演示针伪影补偿， 活检靶向研究和MR测温精度实验。第一阶段的目标是展示 改进了针周围组织的定性和定量成像，第二种方法将显示 通过基于图像相位差的方法提高了温度测量的精度。如果成功， 所提出的工作可以刺激针和管心针设计，其对于感应场进行自补偿， 在高场的广泛介入性MRI应用。

PROJECT SUMMARY / ABSTRACT Needle artifacts have been a long unsolved challenge in the field of Interventional MRI. The large difference in magnetic susceptibilities between an MR compatible metallic needle or stylet and the surrounding water containing tissue induces significant field perturbations in the vicinity of the needle, which results in signal loss due intra-voxel dephasing, image distortions and signal pileups due to voxel mismapping. These artifacts limit to various extents almost every interventional MRI procedure by obscuring and distorting targets and preventing accurate imaging of the region of interest. This results in reduced targeting accuracies, increased procedure times, inability to monitor therapy and ultimately, reduction in the efficacy of MRI guided procedures. The goal of this proposal is to therefore introduce a proof-of-concept solution for this problem that is inspired by degaussing coil technology used in ships and submarines for defense against magnetic field sensitive sea mines. We propose to develop an active degaussing or shim insert for compensation of needle induced ΔB0 and demonstrate correction of susceptibility artifacts in ex-vivo tissue experiments at 3 Tesla. Aim1a of this work is dedicated to the simulation of needle and stylet induced field deviations at 3 Tesla that will include the influence of needle material, tip shape and orientation. Aim 1b will be focused on the simulation of shim fields and modeling of active shim coils that will compensate the field variations estimated in Aim 1a. The goal in Aim 2 will be the actual fabrication and testing of the needle and needle shim inserts, along with the appropriate electronics for operation of the DC shim coils during imaging. In-scanner calibration and phantom tests will follow bench testing for shim insert coils. Mitigation of artifacts induced by Stainless Steel, Titanium, Nitinol and Brass needles and stylets will be demonstrated in gel phantoms at arbitrary orientations. Finally the goal in Aim 3 will be the demonstration of needle artifact compensation in two different ex-vivo MR guided studies, a biopsy targeting study and an MR thermometry precision experiment. The goal in the first will be to show improved qualitative and quantitative imaging of tissue around the needle and in the second will be to show improved precision of temperature measurements by image phase difference based methods. If successful, the proposed work can spur needle and stylet designs that are self compensated for induced fields for use in a wide spectrum of interventional MRI applications at high field.