CONTRAST-ENHANCED MAGNETIC-RESONANCE ANGIOGRAPHY OF CEREBRAL ARTERIES- A REVIEW

The loss of blood vessel visibility due to the signal saturation of sl ow how can be partially overcome by the T1 reduction that occurs with the use of contrast agents such as Gd-DTPA during magnetic resonance a ngiography (MRA) studies. Dynamic-imaging techniques that have been ap plied successfully in abdominal imaging may also be useful for intracr anial applications, However, the time between arterial and venous enha ncement is very short during intracranial circulation, This limits the spatial resolution that can be obtained between arterial and venous e nhancement, Fortunately, the blood-brain barrier and the relatively lo ng duration of significant decrease in blood T1 has led to the develop ment of very high resolution intracranial MRA techniques. Knowledge of the contrast-agent dilution factors and the ultimate resulting relaxa tion rates can be used to optimize the imaging parameters to maximize vessel signal relative to the background signal (the signal-difference -to-noise ratio). The additional venous vascular detail in the contras t-enhanced study can be spatially resolved in the 3D image data and de termined by incorporating information from both high-resolution precon trast and postcontrast studies. in this article, the history, developm ent and application of contrast agents in MRA are presented.