MAGNETIC RESONANCE FLUOROSCOPY TRIGGERING FOR HIGH RESOL

我们建议进一步发展在前一个资金周期中开发的实时磁共振成像(MRI)技术，以实现高分辨率磁共振血管成像。具体的假设是，与目前的透视触发椭圆中心对比度增强3D MRA相比，在许多血管区域的成像中，可以获得30%的空间分辨率和40%的信号改善。尽管人们对增强磁共振血管成像的兴趣与日俱增，但增强磁共振血管成像仍然受到空间分辨率的限制。在前一个资金周期中，我们开发了透视触发的对比增强MRA技术，并表明它可以可靠地在从颈动脉分叉到骨盆(冠状动脉除外)的几乎所有动脉区域提供高空间分辨率、静脉抑制的血管成像。我们还从理论上确定了3DCE-MRA的空间分辨率与MR采集参数和对比剂特性的依赖关系。我们希望进一步应用这种实时MRI能力、临床经验和理论发展来生成分辨率和信号水平更高的图像。具体要研究的项目有：1.k空间信号增强方法。分辨率改进的一般策略是在外围k空间视图处获得更高的信号电平。这将通过减少TR、降低视野、延长对比剂和选择扫描时间来实现。2.实时MRA序列修改。为了利用到达对比剂的上升时间，MRA采集的中心向内部分将先于标准的椭圆中心-(向外)序列。观察顺序的特征将响应于瞬时测量的进药通过时间而实时修改。读数的翻转角度将动态改变，以匹配与时间相关的eRnsT角度。3.嵌入式透视/3DMRA。用于2D透视成像的重复间隔将被插入到椭圆中心3D MRA序列中。这些将在3D采集期间被分类、重建和显示，从而允许操作员观察对比行为并进行干预，例如通过触发另一个时间帧或推进表格。

We propose to further develop real-time magnetic resonance imaging (MRI) techniques developed in the previous funding cycle toward high resolution MR angiographic imaging. The specific hypothesis is that compared to the current performance level of fluoroscopically-triggered elliptical-centric contrast-enhanced 3D MRA 30 percent improved spatial resolution and 40 percent improved signal can be obtained in imaging many vascular areas. Despite increased interest, contrast-enhanced MRA continues to be limited by spatial resolution. In the previous funding cycle we developed the technique of fluoroscopically-triggered contrast- enhanced MRA and showed that it can reliably provide high spatial resolution, venous-suppressed angiograms in virtually all arterial areas from the carotid bifurcation to the pelvis (with the exception of the coronary arteries). We have also theoretically determined the dependence of spatial resolution in 3D CE-MRA on MR acquisition parameters and contrast bolus characteristics. We wish to further apply this real-time MRI capability, clinical experience, and theoretical development to generate images with an improved level of resolution and signal. Specific projects to be studied are: 1. k-Space Signal Enhancement Methods. The general strategy for resolution improvement is to obtain increased signal level at the peripheral k-space views. This will be done by TR reduction, FOV reduction, prolongation of the contrast bolus, and selection of scan time. 2. Real-Time MRA Sequence Modification. In order to exploit the risetime of the arriving contrast bolus, a centric-in portion of the MRA acquisition will precede the standard elliptical centric- (out) sequence. The characteristics of the view order will be modified in real time in response to the instantaneously measured bolus transit time. The flip angle of the readout will be altered dynamically to match the time-dependent Ernst angle. 3. Embedded Fluoroscopic/3D MRA. Repetition intervals devoted to 2D fluoroscopic imaging will be inserted into the elliptical centric 3D MRA sequence. These will be sorted, reconstructed and displayed during the 3D acquisition allowing he operator to observe contrast behavior and intervene, such as by triggering another temporal frame or advancing the table.