Real Time Motion correction for Brain MRI

描述(申请人提供)：头部和大脑的磁共振成像(MRI)是研究和诊断的强大工具。在核磁共振扫描中，患者被要求保持头部非常静止，因为轻微的运动会破坏核磁共振数据，但这对幼儿、老年人以及患有帕金森氏症、精神分裂症、癫痫和痴呆症的人来说可能很困难。我们的研究将使MRI能够更好地服务于这些患者，因为即使在扫描过程中发生头部移动，也可以收集准确的数据。在磁共振成像中，纠正运动伪影的标准方法是基于回溯图像的运动检测和校正，如SPM和AIR等流行的分析程序包中实现的那样。这种方法非常适合于成像平面内的运动，但不能处理不能用单一的旋转/平移来描述的实质性的穿过平面的运动，并且改变成像视场(FOV)中组织的自旋磁化历史。实时测量头部位置并在数据采集之前调整视场的预期运动校正技术因此为穿透平面运动提供了引人注目的优势。然而，现有的导航回波和PACE等预期技术会导致数据采集速率的延迟。我们的目标是实现和验证一种新的方案，用于前瞻性校正MRI运动伪影，该方案与成像数据的获取并行操作，防止时间延迟。我们开发了一种跟踪装置，用于实时监测头部位置的三维变化，使用三个射频跟踪线圈进行空间定位，同时通过标准磁头线圈获取图像数据。我们的第一个具体目标是使用我们的跟踪设备实现动态运动检测，并预期在飞利浦Achieva扫描仪上重新对准成像平面。我们的第二个具体目标是根据幻影在MRI数据中创建逼真的运动伪像。将使用四个指标来评估校正算法的成功。我们的第三个专题将研究12名志愿者，他们被指示转过头来追踪移动的视觉刺激。用于评估该算法的度量包括a)与使用空气的标准回溯运动校正的比较，b)在使用运动校正方案和不使用运动校正方案的情况下收集的图像中存在的高空间频率的评估，c)通过校正的图像与未校正的图像的线条轮廓的比较，以及d)测量其中一个模型中的小圆柱体的宽度=高度。我们预计，我们的方案将能够更好地解决患者群体中常见的运动程度。

DESCRIPTION (provided by applicant): Magnetic resonance imaging (MRI) of the head and brain is a powerful tool for research and diagnosis. During a MRI scan patients are asked to keep their head very still because slight movements can spoil the MRI data, but this can be difficult for young children, elderly people, and those who suffer from Parkinson's disease, schizophrenia, epilepsy, and dementia. Our research will let MRI better serve these patients by allowing accurate data to be collected even when head movements occur during scanning. The standard approach to correct motion artifacts in MRI is retrospective image-based motion detection and correction as implemented in popular analysis packages such as SPM and AIR. This approach is well suited to motion within the imaging plane, but cannot handle substantial through-plane motion which both cannot be described by a single rotation/translation and alters the spin magnetization history of the tissue in the imaging field of view (FOV). Prospective motion correction techniques which measure head position in real time and adjust the FOV prior to data acquisition thus offer a compelling advantage for through-plane motion. However, existing 'prospective techniques such as navigator echoes and PACE impose a delay in data acquisition rates. Our objective is to implement and validate a novel scheme for prospective correction of MRI motion artifact that operates in parallel with the acquisition of imaging data, preventing temporal delay. We have developed a tracking device for real-time monitoring of three- dimensional changes in head position using three RF tracking coils for spatial localization simultaneous with image data acquisition via a standard head coil. Our first specific aim is to implement dynamic motion detection using our tracking device and prospective re-alignment of the imaging plane on a Philips Achieva scanner. Our second specific aim is to create realistic motion artifacts in MRI data from phantoms. Four metrics will be used to evaluate the success of the correction algorithm. Our third specific will study twelve volunteers who have been instructed to turn their heads to track a moving visual stimulus. The metrics used to evaluate the algorithm consist of a) comparison with standard retrospective motion correction using AIR, b) evaluation of the high spatial frequencies present in the images collected with and without the motion correction scheme, c) comparison of line profiles through the images of corrected vs. uncorrected images and d) measurement of the width at = height of small cylinders in one of the phantoms. We expect that our scheme will be better able to address the degree of motion typically seen in patient populations.