Time-Resolved Lower Extremity MR Angiography using HighlY Constrained Back PRojec

描述（由申请人提供）：我们建议使用我们最近构思的HYPR方法来开发一种易于实施、时间分辨、多站、对比度增强的外周MR血管造影方案，该方案可提供高空间分辨率血管造影片，其时间分辨率明显高于当前MR技术。HYPR方法允许通过仅使用满足奈奎斯特准则所需的径向k空间线总数的非常小的子集来产生时间帧，从而极大地改善径向k空间采集中的时间分辨率。条纹伪影，通常会导致从构建图像使用严重减少数量的投影，通过约束未过滤的反投影数据的区域，其中对象，在这种情况下，血管，是已知存在的。为了确定血管的位置，使用来自多个时间帧的数据产生血管图或合成图像。这是可能的，因为每个时间帧的数据都是从以略有不同的角度采集的径向k空间线产生的。合成图像中的高SNR决定了各个时间帧中的SNR，从而相对于仅基于欠采样的加速方法提供了改进的图像质量。初步模拟表明，即使使用大于100的欠采样因子，也可以实现良好的图像质量。为了实现我们的目标，我们建议开发三种MRA技术- 3D混合HYPR，3D HYPR TRICKs和3D HYPR VIPR -并使用一系列模拟，幻影和志愿者研究来评估和优化这些技术的性能。随后，将在一组患者中将最成功的HYPR外周血管协议与传统的X射线DSA进行比较。我们的中心假设是，HYPR将允许采集非常高的时间分辨率对比增强多站外周MR血管造影片，其中空间分辨率，SNR和图像质量保持在高水平。

DESCRIPTION (provided by applicant): We propose to use our recently-conceived HYPR method to develop an easy-to-implement, time-resolved, multi-station, contrast-enhanced peripheral MR angiography protocol that provides high spatial resolution angiograms with dramatically higher temporal resolution than is possible with current MR techniques. The HYPR method permits great improvements to temporal resolution in radial k-space acquisitions by producing time frames using only a very small subset of the total number of radial k-space lines necessary to satisfy the Nyquist criterion. Streak artifacts that would ordinarily result from constructing images using a severely reduced number of projections are ameliorated by constraining unfiltered back projected data to regions in which objects, in this case vessels, are known to exist. In order to determine the location of the vessels, a vessel map, or composite image, is produced using data from multiple time frames. This is possible because the data for each of the time frames is produced from radial k-space lines that are acquired at slightly different angles. The high SNR in the composite images dictates the SNR in the individual time frames, providing improved image quality relative to accelerated methods that are based solely on undersampling. Preliminary simulations suggest that good image quality may be achieved even when undersampling factors greater than 100 are used. In order to achieve our goal, we propose to develop three MRA techniques - 3D hybrid HYPR, 3D HYPR TRICKs, and 3D HYPR VIPR - and to evaluate and optimize the performance of these techniques using a series of simulation, phantom, and volunteer studies. Following this, the most successful HYPR peripheral vascular protocol will be compared with conventional x-ray DSA in a cohort of patients. Our central hypothesis is that HYPR will permit acquisition of very high temporal resolution contrast-enhanced multi-station peripheral MR angiograms, in which spatial resolution, SNR, and image quality are maintained at high levels.