3D CE MRA技术是一项较为复杂的成像过程，其扫描方法也很重要，先谈一下造影剂到达时扫描时机的选择方法。
  造影剂到达时扫描时机的选择方法：
  从开始注射造影剂至3D CE MRA采集数据之间的延迟时间，可以用下面的公式计算：
  延迟时间＝预计循环时间 +（注射时间÷2）－（扫描时间÷2）。
  这样，采用相位编码顺序采集数据时，灌注中心时间点就可以与采集的中心时间点一致，从而也可以保证至少在采集K-空间中心时动脉内造影剂的浓度保持在最高水平。
  利用三维追踪法（3D TRICKS）血管造影技术时，还可以在邻近血管强化前对血管进行短期重复成像，而此时造影剂到达时间的估计则显得不太重要，而且还可以连续地检查多个部位。
  Methods to time image acquisition with bolus arrival:
  The delay between start of contrast material infusion and of 3D CE MRA acquisition can be calculated as follows:
  scan delay＝estimated circulation time + (infusion time÷2) － (scan time ÷2).
  The middle of a bolus contrast infusion can then be expected to reach the arteries during acquisition midpoint when a sequential phase-encoding order is used. This provides maximal arterial gadolinium concentration during acquisition of at least the central half of K-space.
  Using 3D TRICKS angiography, issues of bolus timing assume less importance, vessels can be repeatedly imaged in the short interval before adjacent venous enhancement occurs, and multiple locations can be studied consecutively.