Principles of magnetic resonance angiography.

It has been a decade since it was realized that MR could image blood flow. In this period of time, the technique of imaging vascular structures has improved significantly and has developed into a new area: vascular magnetic resonance imaging or magnetic resonance angiography (MRA). MRA is not simply a single new MR imaging technique, rather, it consist of an entire family of new pulse sequences. Each one of these pulse sequences requires careful consideration for optimal visualization of the vascular structures of interest. Recent development in MRA produced not only anatomical information but also physiologic data such as flow velocity and flow rates. The intent of this review is the summarize the basic principles of neuro MRA techniques currently in use. Terms like: time-of flight, phase contrast, signal loss in MRA will be discussed.