Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function.
Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function.
复制标题
使用梯度系统脉冲响应函数对螺旋图像和回波平面图像进行实时失真校正。
DOI：
10.1002/mrm.25788
复制
发表时间：
2016-06
影响因子：
3.3
通讯作者：
Hansen MS
中科院分区：
文献类型：
--
作者：
Campbell-Washburn AE;Xue H;Lederman RJ;Faranesh AZ;Hansen MS
MRI引导的介入需要高帧频成像，这使得螺旋成像和回声平面成像(EPI)等快速成像技术吸引了人们的注意。在这项研究中，我们实现了一个实时失真校正框架，以使这些快速采集能够用于介入性磁共振成像。利用梯度脉冲响应函数(GIRF)校正由梯度波形不准确引起的失真，该函数由标准设备测量并作为校准文件保存在主机上。该文件在运行时被用来计算用于图像重建的预测k空间轨迹。此外，非共振重建频率被实时修改以交互地消除螺旋图像的模糊。在模特儿和健康人志愿者身上实现了对任意图像方向的实时失真校正。GIRF预测的k空间轨迹与测量的k空间轨迹非常接近，用于螺旋成像。使用GIRF预测的轨迹，螺旋和EPI图像失真得到明显改善。GIRF校准文件在4个月内没有系统漂移，并在连续扫描30分钟后被证明在梯度加热的情况下纠正了扭曲。在连续成像过程中，使用交互式非共振重建来锐化解剖边界。这一实时失真校正框架将使这些高帧速率成像方法能够用于MRI引导的干预。
MRI-guided interventions demand high frame-rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real-time to interactively de-blur spiral images. Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 minutes of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. This real-time distortion correction framework will enable the use of these high frame-rate imaging methods for MRI-guided interventions.