Radiology Department, New York University School of Medicine, New York, New York, USA.
Magn Reson Med. 2010 Oct;64(4):1098-108. doi: 10.1002/mrm.22510.
There has recently been renewed interest in noncontrast techniques for peripheral MR angiography following the discovery of an association between gadolinium-based contrast agents and nephrogenic systemic fibrosis in patients with renal insufficiency. The "fresh blood imaging" technique proposed by Miyazaki et al. involves the subtraction of two three-dimensional fast spin-echo image sets, one acquired in systole, when the arteries appear dark due to flow-related dephasing, and the other obtained in diastole, when the arteries are brighter. Our goal was to investigate how parameters of the fast spin-echo sequence influence its flow sensitivity, and how that in turn impacts the depiction of large and small arteries. Results from phantom experiments and human studies in the calf suggest that the flow sensitivity is governed largely by the flip angle of the radiofrequency refocusing pulses. The area of the spoiler gradients has a lesser effect, and at low flip angles the echo time plays a role. These parameters can be optimized to obtain good depiction of the calf arteries in healthy subjects. It remains to be seen whether they provide sufficient control over flow sensitivity to achieve diagnostic-quality images in other vascular beds and in the presence of pathology.
最近，人们对肾功能不全患者使用钆基造影剂与肾源性系统纤维化之间的关联发现后，对外周磁共振血管成像的非对比技术重新产生了兴趣。宫崎等人提出的“新血流成像”技术涉及两个三维快速自旋回波图像数据集的减影，一个在收缩期采集，此时由于血流相关失相，动脉显得较暗，另一个在舒张期采集，此时动脉较亮。我们的目标是研究快速自旋回波序列的参数如何影响其对血流的敏感性，以及这种敏感性如何影响大、小动脉的显示。来自人体小腿的仿体实验和研究结果表明，流动敏感性主要由射频重聚焦脉冲的翻转角决定。扰相梯度的面积影响较小，而在低翻转角时，回波时间起作用。可以优化这些参数以获得健康受试者小腿动脉的良好显示。尚不清楚这些参数是否能提供足够的对血流敏感性的控制，以便在其他血管床和存在病变的情况下获得诊断质量的图像。
