Boos M, Scheffler K, Ott H W, Radü E W, Bongartz G
Institut für Diagnostische Radiologie, Universitätskliniken, Kantonspital, Basel.
Radiologe. 1997 Jul;37(7):515-28. doi: 10.1007/s001170050249.
The introduction of fast gradient systems allows a reliable visualization of the extracranial carotid vessels by the magnetic resonance angiography (MRA) which meanwhile is implemented into clinical routine. By the mainly applied time-of-flight (TOF) technique, vessels can be imaged without contrast agent (CA). Due to the application of ultra-fast gradient-echo-sequences, the first-pass evaluation of an intravenous bolus-injection of Gadolinium in the carotids from the aortic arch up to the skull base can be performed in less than 30 s. In this study. Advantages and disadvantages of both techniques are discussed. For a qualitatively optimal contrast enhanced MRA (CE-MRA) timing parameters like injection delay, flow rate and the adjustment of sequence parameters have to be considered in relation to the fast venous return from the sinus to the jugular veins. First, the optimal time point of the data acquisition have been determined at a model and with a computer simulation in reference to the presence of CA in the arteries. As a result, 90% of the contrast contribution is defined by 16% of the symmetrically acquired central k-space lines. A measuring protocol for clinical use was obtained by a gradual variation of spacial resolution, measuring time and CA-injection parameters and was proved in normal volunteers and patients. An exact determination of the bolus-arrival-time by means of a test-bolus injection was acquired. The best qualitative results were achieved by a double-dose- injection at 2 ml/s injection rate. The temporal reserves of ultra-fast sequences should be invested in the improvement of the spatial resolution. To date, further investigations related to the problem of optimal CA-application may improve the potentials of CE-MRA procedures.
快速梯度系统的引入使得通过磁共振血管造影（MRA）能够可靠地显示颅外颈动脉血管，同时该技术已应用于临床常规检查。通过主要应用的时间飞跃（TOF）技术，可以在不使用造影剂（CA）的情况下对血管进行成像。由于应用了超快速梯度回波序列，从主动脉弓到颅底的颈动脉内静脉团注钆的首次通过评估可在不到30秒内完成。在本研究中，讨论了这两种技术的优缺点。对于定性优化的对比增强MRA（CE-MRA），必须考虑诸如注射延迟、流速等时间参数以及序列参数的调整，以应对从窦到颈静脉的快速静脉回流。首先，已在模型上并通过计算机模拟，参照动脉中CA的存在情况确定了数据采集的最佳时间点。结果表明，90%的对比贡献由对称采集的中央k空间线的16%所定义。通过逐步改变空间分辨率、测量时间和CA注射参数获得了临床使用的测量方案，并在正常志愿者和患者中得到了验证。通过试验团注注射精确确定了团注到达时间。以2 ml/s的注射速率进行双剂量注射可获得最佳的定性结果。超快速序列的时间储备应投入到提高空间分辨率上。迄今为止，与最佳CA应用问题相关的进一步研究可能会提高CE-MRA程序的潜力。
