观察超声电机引起的磁共振成像（MRI）伪影的研究。

A study on observed ultrasonic motor-induced magnetic resonance imaging (MRI) artifacts.

机构信息

Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada; Division of Neurosurgery, The Hospital for Sick Children, Toronto, Canada.

出版信息

Biomed J. 2019 Apr;42(2):116-123. doi: 10.1016/j.bj.2018.12.007. Epub 2019 May 6.

DOI:10.1016/j.bj.2018.12.007

PMID:31130247

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC6541879/

Abstract

BACKGROUND

The safe performance of magnetic resonance imaging (MRI)-guided robot-assisted interventions requires full control and high precision of assistive devices. Because many currently available tools are not MRI-compatible, the characterization of existing tools and development of new ones are necessary. The purpose of this research is to identify and minimize the image artifacts generated by a USM in MR images.

METHODS

The behavior of an ultrasonic motor (USM), the most common MRI-safe actuator, in a high-field scanner was investigated. The motor was located in three orientations with respect to the bore axis with the power on or off. The induced image artifacts were compared across four sequences. Three artifact reduction methods (employing ultrashort sequences, slice thickness reductions, and bandwidth increments) were tested.

RESULTS

Signal voids, pileups, and geometric distortions were observed when the motor was off. The artifact size was minimal when the motor shaft was aligned with the bore axis. In addition to the above artifacts, zipper and motion artifacts were noted when the motor was running, and these artifacts increased with increasing motor speed. Increasing the bandwidth slightly reduced the artifacts. However, decreasing the slice thickness from 5 mm to 3 mm and from 5 mm to 1 mm reduced artifact size from 30% to 40% and from 60% to 75%, respectively.

CONCLUSION

The image artifacts were due to the non-homogenous nature of the static and gradient fields caused by the motor structure. The operating motor interferes with the RF field, causing zipper and motion artifacts.

摘要

背景

磁共振成像（MRI）引导机器人辅助介入的安全性能需要充分控制和高精度的辅助设备。由于许多现有的工具都不兼容 MRI，因此需要对现有的工具进行特性描述和开发新的工具。本研究的目的是识别和最小化超声马达（USM）在 MRI 图像中产生的图像伪影。

方法

研究了高场扫描仪中常用的 MRI 安全致动器 - 超声马达（USM）的行为。将电机分别以三种相对于孔轴的取向放置，开启或关闭电源。在四个序列中比较了感应图像伪影。测试了三种减少伪影的方法（采用超短序列、减少切片厚度和增加带宽）。

结果

当电机关闭时，会观察到信号缺失、堆积和几何变形。当电机轴与孔轴对齐时，伪影尺寸最小。当电机运行时，除了上述伪影外，还会注意到拉链和运动伪影，并且这些伪影随着电机速度的增加而增加。略微增加带宽会稍微减少伪影。但是，将切片厚度从 5mm 减少到 3mm 和从 5mm 减少到 1mm 分别将伪影尺寸从 30%减少到 40%和从 60%减少到 75%。